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The surface chemistry of flotation Bennett, Robert Lougheed 1938

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h%% fly THE SURFACE CHEMISTRY OF FLOTATION by '. • Robert Lougheed Bennett A-.Thesis-submitted-for the Degree of MASTER OF APPLIED SCIENCE i n the Department ' : " .of CHEMISTRY The University of. B r i t i s h Columbia September 1938 THE SURFACE CHEMISTRY OF FLOTATION PART 1. BIBLIOGRAPHY 1. THE SURFACE CHEMISTRY OF FLOTATION PART 1. BIBLIOGRAPHY CONTENTS Chapter 1. Page HISTORICAL AND INTRODUCTORY 1 : .Chapter 2. . AN ANNOTATED BIBLIOGRAPHY OF  EXPERIMENTAL AND THEORETICAL INVESTIGATIONS IN THE PHYSICAL CHEMISTRY OF FLOTATION 6 I . INTRODUCTORY 6 I I . FROTH FORMATION 8 I I I . COLLECTION 11 1 . C o l l e c t o r s 11 D e f i n i t i o n of a C o l l e c t o r 1 1 Examples of C o l l e c t o r s 11 • 'Structure of C o l l e c t o r s 11 P r e p a r a t i o n and P u r i f i c a t i o n of C o l l e c t o r s and t h e i r Compounds 12 Chemical Reactions of Co l l e c t o r s - 12 P h y s i c a l P r o p e r t i e s of C o l l e c t o r s and t h e i r -Compounds 14 2. E f f e c t - o f Various Reagents on Recovery i n 'F l o t a t i o n Tests and P r a c t i c e ~~ ~ •' 16 Small Scale F l o t a t i o n Tests . 16 F l o a t a M l I t y of Pure M i n e r a l s (Inherent F l o a t -: . a b i l i t y ) . . 17 1 1 . Page E f f e c t of Various Reagents on the Recovery of '-*-,' : M i n e r a l s i n the Presence of a C o l l e c t o r , (Galena - P y r i t e - S p h a l e r i t e - Chalco-c£te' - C h a l c o p y r l t e - Miscellaneous S u l -f i d e M i n e r a l s - O x i d i z e d M i n e r a l s - Won-' m e t a l l i c M i n e r a l s ) 18 S p e c i f i c E f f e c t s of C o l l e c t o r s on M i n e r a l s 24 Infl u e n c e of Temperature on F l o a t a b i l i t y 25 3. Experimental Evidence f o r the Reaction of C o l l e c -~ "~ " t o r s with' M i n e r a l s : ~ ' ~ : : ~r~~ 26 Changes i n a C o l l e c t o r S o l u t i o n i n Contact w i t h a M i n e r a l ( A b s t r a c t i o n : I n general = by galena - p y r i t e - s p h a l e r i t e - c h a l c o c i t e -c h a l c o p y r l t e - s u l f u r and gr a p h i t e - m i s c e l -laneous m i n e r a l s ) 26 Changes i n a M i n e r a l i n Contact w i t h a C o l l e c t o r S o l u t i o n . • • • ( P h y s i c a l nature of coa t i n g - A n a l y s i s of coatings on galena - p y r i t e - c h a l c o c i t e -miscellaneous minerals) 32 4. Contact Angles as a Measure of F l o a t a b i l i t y 56 The Contact Angle 36 "S i g n i f i c a n c e of the Contact Angle ; as a Measure of F l o at a b i l i t y . 37. E f f e c t of va r i o u s F a c t o r s on the Contact Angle 38 H y s t e r e s i s of Contact Angle- 40 Time t o Develop Contact 40 Miscellaneous Contact Angle I n v e s t i g a t i o n s 41 5. E l e c t r i c a l j a f f e c t s i n F l o t a t i o n 43 Charge : "on M i n e r a l s , A i r - B u b b l e s , and O i l Particles.'.. 43 P o t e n t i a l of M i n e r a l E l e c t r o d e s 43 E f f e c t of Reagents on M i n e r a l Charge 43 6. Thermodynamics of F l o t a t i o n 45 Heat of Wetting 45 . H i . Page - Surf ace. Energy : • . ' 45 Displacement Pressure and Adhesion Tension 45 Contact Angle as a Thermodynamic Quantity 47 7. ^ Miscellaneous Studies of Wetting 48 8. Theories of (Jollector A c t i o n 49 I n t r o d u c t o r y 49 Chemical Theory 49 Ads o r p t i o n xheory 51 Ostwald 1s Theory 53 E l e c t r i c a l Theories 54 Miscellaneous Theories, 56 IV. DEPRESSION 57 1. Evidence of Depression Obtained from F l o t a t i o n ~~ ~ Tests and P r a c t i c e (Depression of galena - p y r i t e - s p h a l e r i t e -c h a l c o c i t e - c h a l c o p y r i t e - miscellaneous m i n e r a l s ) 57 2. Experimental Evidence f o r the Reaction of ~" Depressors w i t h M i n e r a l s ~ 63 Changes i n a S o l u t i o n of Depressor i n Contact w i t h a M i n e r a l ( A b s t r a c t i o n of Depressor by galena - p y r i t e - c h a l c o p y r i t e « s p h a l -e r i t e ) 63 Changes i n a M i n e r a l i n Contact w i t h a Depressor S o l u t i o n - 64 5. Contact Angle Studies of Depression 65 Depression by Cyanide (Galena - p y r i t e - s p h a l e r i t e - chalco-p y r i t e - miscellaneous m i n e r a l s ) 65 Depression by sodium s u l f i d e 69 Depression by other reagents 69 Depression i n General 70 A. Theorles of Depressor A c t i o n Page 71 Depression by Cyanide 71 Depression by Reagents other than Cyanide (Chromates - Lime - S u l f i t e s - ' M i s c e l l a n -eous Reagents) 73 •V. ACTIVATION 1. Evidence of A c t i v a t i o n Obtained f r o m ' F l o t a t i o n .. ™* ' Tests and Pr a c t i c e ' '• ' ~ ~~"~ ( P y r i t e -.-sphalerite- - miscellaneous s u l f i d e minerals - o x i d i z e d minerals - n o n - m e t a l l i c m i n e r a l s ) , - ' ' " - . 75 2. Experimental Evidence f o r the Reaction of A c t i -' v a t o r s w i t h M i n e r a l s ' ~ ! : ~ 78 Changes i n a S o l u t i o n of A c t i v a t o r i n Contact-w i t h a M i n e r a l ( A b s t r a c t i o n of A c t i v a t o r ) 78 Changes i n a M i n e r a l i n Contact w i t h an A c t i -v a t o r S o l u t i o n 78 5s Contact Angle Studies of A c t i v a t i o n 81 4. Theories, of A c t i v a t o r A c t i o n . 83 REFERENCES FOR BIBLIOGRAPHY 85 1 THE SURFACE CHEMISTRY OF FLOTATION CHAPTER I HISTORICAL AND INTRODUCTORY Flotation is a process of ore concentration in which the ore minerals are separated into two or more products. One product, usually containing worthless minerals, is termed tailings; the other products,, containing the valuable minerals in a more concentrated state, are termed concen-trates. In modern flotation, air is generated i n , or introduced into a pulp of finely-ground ore suspended in water, which contains small amounts of various reagents. Because of the presence of froth-forming reagents, a zone of rising froth forms at the upper surface of the pulp, and flows over the l i p of the containing vessel. The minerals in the ore-pulp, are mechanically carried into this froth zone to a greater or less extent. Certain minerals show a greater tendency than others to b e carried into the froth by the air bubbles rising through the pulp; and, once in the froth, to rise with i t , These minerals eventually reach the upper surface of the froth, overflow with i t , and are removed as concentrate. Other minerals either do not enter the froth; or, i f they do enter, tend to settle out and f a l l back into the pulp. To do this, their effective downward velocity in the froth must b e greater than the effective upward velocity with which the froth is rising. T h e s e minerals eventually remain 2 suspended i n the pulp and are removed as t a i l i n g s . The d e n s i t y of a given m i n e r a l does not determine whether the mineral w i l l become concenti-ate or t a i l i n g . E a r l y f l o t a t i o n processes, which have become ob s o l e t e , are b u l k - o i l f l o t a t i o n , and s k i n - f l o t a t i o n . The f i r s t p r a c t i c a l process of f l o t a t i o n was the bulk-o i l process, introduced by W i l l i a m Haynes i n 1860 ( B r i t . P a t. 488/1860) and m o d i f i e d by C a r r i e J . Everson (U.S.Pat. 348,157 --1885). The Elmore process, t y p i c a l of b u l k - o i l f l o t a t i o n , c o n s i s t e d i n t r e a t i n g ore w i t h water and l a r g e q u a n t i t i e s of o i l j s e l e c t i v e adsorption of c e r t a i n minerals i n the o i l phase, or at the o i l - w a t e r i n t e r f a c e ; and removal of the m i n e r a l - c o n t a i n i n g o i l a f t e r i t had r i s e n t o the surface of the water. S k i n - f l o t a t i o n c o n s i s t e d of r e t e n t i o n of s e l e c t e d min-e r a l p a r t i c l e s i n a t h i n l a y e r at a f r e e water s u r f a c e . Apparatus f o r t h i s process i s described by Macquisten (U.S.Pat. 865,194-5/1907) and Wood (U.S.Pat. 1,088,050/1915) (28.6.1) Gas as a buoyant medium was introduced by D e l p r a t i n 1902 (U.S.Pat 735,071/1903; B r i t . P a t . 26,279/1902) and by P o t t e r i n 1904 (U.S.Pat. 776,145/1904). The p o t t e r - D e l p r a t Process i n v o l v e d chemical generation of gas by the r e a c t i o n of a c i d w i t h s u l f i d e s and carbonates contained i n the ore. This process marks the beginning of f r o t h f l o t a t i o n as now p r a c t i c e d . A i r was f i r s t introduced d i r e c t l y i n t o the pulp by Sulman, P i c a r d and b a l l o t i n 1906 (U.S.Pat. 835,120/1906). With".the use of a i r Instead of o i l as a buoyant medium, i t was found t h a t the q u a n t i t y of o i l could be m a t e r i a l l y r e -duced without a f f e c t i n g performance. I n 1909 Greenway, Sulman and Higgins (U.S.Pat. 962,678/ 1909) recommended the use of s o l u b l e f r o t h i n g agents, such as pine o i l . The q u a n t i t i e s of such agents which were r e -q u i r e d , were of the order of l e s s than one pound per ton of ore. This patent marks the r e c o g n i t i o n of f r o t h i n g agentsj although the f r o t h e r s used a l s o had c o l l e c t i n g power, as defin e d below. During the p e r i o d from 1915 t o 1922, c e r t a i n n o n - f r o t h i n g reagents, having the p r o p e r t y of c o l l e c t i n g d e s i r e d m i n e r a l s i n t o the f r o t h , were introduced.. I n 1921, P e r k i n s (U.S.Pat 1,364,304/1921) d i f f e r e n t i a t e d between the f r o t h i n g and the c o l l e c t i n g f u n c t i o n s of a r e -agent, he showed that c e r t a i n non-oleaginous organic com-pounds, c o n t a i n i n g t r i v a l e n t n i t r o g e n or d i v a l e n t s u l f u r , s p e c i f i c a l l y t h i o c a r b a n i l l d , or other thioamido, or t h i o u r e a compounds, had the property of i n c r e a s i n g the tendency of a m i n e r a l t o adhere to the a i r phase, and be c o l l e c t e d i n the f r o t h . Compounds which have t h i s p r o p e r t y are now termed c o l l e c t o r s . The a c t i o n by which the a i r - a d h e r i n g tendency Is i n c r e a s e d , i s termed c o l l e c t i o n . The compounds i n t r o -duced by P e r k i n s had no f r o t h i n g p r o p e r t i e s , and were de-signed to be used i n conjunction w i t h known reagents which would cause a f r o t h to form. 4 Jianthates as c o l l e c t o r s were patented In 1925 "by K e l l e r (U.S.Pat. 1,554,216/1925; Can.Pat. 247,547/1925), and d i -thiophosphates of the type formula: /0R S-P-OR R= hydrocarbon group NSH prepared from phosphorus p e n t a s u l f i d e and c r e s y l i c a c i d , were patented i n 1926 by Whitworth (U.S.Pat. 1,593,232/1926) The patent of Pe r k i n s i n 1921 marks the beginning of a new f l o t a t i o n technique, which has been termed "chemical f l o t a t i o n " , i n c o n t r a s t to the o l d e r " o i l f l o t a t i o n " . This b r i e f survey has i n d i c a t e d the stages i n the development of f r o t h i n g and c o l l e c t i o n , as p r a c t i c e d i n modern f l o t a t i o n . Mention must be made, a l s o , of the de-velopment of two other phases of f l o t a t i o n . These are a c t i v a t i o n and depression. A c t i v a t i o n of a s p e c i f i c m i n e r a l , or m i n e r a l s , i s accomplished by adding to the ore-pulp a reagent, termed an a c t i v a t o r , which w i l l cause the m i n e r a l , otherwise un-a f f e c t e d by a c o l l e c t o r , to be c o l l e c t e d i n t o the f r o t h . Depression i s accompli^fed by adding a reagent, termed a depressor, which w i l l cause the m i n e r a l , normally c o l l e c t e d , to be depressed; that i s , u n a f f e c t e d by the c o l l e c t o r . achwarz i n 1906 (U.S.Pat 807,501/1906) introduced a l k a l i s u l f i d e s or p o l y s u l f i d e s as a c t i v a t o r s f o r o x i d i z e d ores. Uopper s u l f a t e , the most common a c t i v a t o r f o r s p h a l -e r i t e , was discovered by Bradford i n 1913. 5 Bichromates, as depressors f o r galena, were suggested by Lowry and Greenway i n 1912 ( A u s t r a l . Pat. 5,065/1912) O i l f l o t a t i o n was u s u a l l y c a r r i e d out In an a c i d c i r -c u i t , but w i t h the advent of chemical f l o t a t i o n about 1921, a l k a l i n e c i r c u i t s soon became common p r a c t i c e . The use of a l k a l i n e c i r c u i t s l e d t o the di s c o v e r y of the depressing e f f e c t of lime on p y r i t e , and of cyanide on s p h a l e r i t e by Sheridan and G r i s w o l d (U.S.Pats. 1,421,585/1922; 1,427,235/ 1922) 6 CHAPTER I I AM ANNOTATED BIBLIOGRAPHY OF  EXPERIMENTAL AND THEORETICAL INVESTIGATIONS IN  THE PHYSICAL CHEMISTRY OF FLOTATION INTRODUCTORY F l o t a t i o n has developed l a r g e l y as an a r t . D i s c o v e r i e s , i n many cases, have been the r e s u l t of t r i a l and e r r o r , u n t i l about 1928, very l i t t l e fundamental experimental work was done, although.several t h e o r i e s were advanced. Much of the experimental work c a r r i e d on s i n c e has d e a l t w i t h the extremely complex systems e x i s t i n g i n a f l o t a t i o n c e l l t r e a t i n g n a t u r a l ores. While such work has given d e f i n i t e i n f o r m a t i o n regarding treatment methods f o r a s p e c i f i c ore, i t has thrown l i t t l e l i g h t on the fundamental r e a c t i o n s taking p l a c e . E a r l y experimenters o f t e n f a i l e d t o r e a l i z e the d e l i c a t e nature of the r e a c t i o n s they d e a l t w i t h , and the profound e f f e c t on f l o t a t i o n performance of almost i n -t a n g i b l e amounts of reagents. The f a c t t h a t as sm a l l a quan t i t y as 0.002 mgm. of potassium cyanide i s s u f f i c i e n t to prevent a 6 sq. cm. area of p y r i t e from being f l o a t e d ; and a comparable amount of copper s u l f a t e w i l l cause s p h a l -e r i t e , otherwise u n f l o a t a b l e , t o be f l o a t e d ; emphasize the n e c e s s i t y f o r extreme care i n i n v e s t i g a t i n g the phenomena of f l o t a t i o n . These facts must he carried in mind when considering the ..following experimental work, and the conclusions based upon i t . This work is considered as i t relates to the study of four fundamental chemical operationst froth formation, collection, depression, and activation. 8 FROTH FORMATION A f r o t h i s a d i s p e r s i o n of a gas i n a l i q u i d , which forms when the gas-bubble w a l l s are made capable of w i t h -standing s t r e s s e s o They are i n t h i s c o n d i t i o n when the su r f a c e - t e n s i o n of the l i q u i d - g a s I n t e r f a c e , forming the bubble w a l l i s capable of r a p i d change. I f a c a p i l l a r y a c t i v e substance i s dissolved, i n water i t w i l l tend to con-centrate i n the f r o t h (03.8.1) at the air - w a t e r i n t e r f a c e , i n agreement w i t h the fribb's equation r e l a t i n g the amount of adsorption of a substance at an i n t e r f a c e to i t s e f f e c t on surface t e n s i o n . I f a f i l m of such a s o l u t i o n i s s t r e t c h -ed, the concent r a t i o n of the substance i n the surface i s decreased, and the surface t e n s i o n of the f i l m n e c e s s a r i l y i n c r e a s e s ; thus s e t t i n g up a fo r c e which w i l l oppose the s t r e t c h i n g f o r c e . F r o t h i n g agents, as used i n f l o t a t i o n , are c a p i l l a r y a c t i v e substances which s t a b i l i z e a f r o t h i n t h i s way. Langmuir 1 s work (16 .25 .2) (17.25 ) suggests t h a t o r i e n t e d adsorption of a monomolecular f i l m of a hetero-p o l a r f r o t h e r such as amyl a l c o h o l , w i l l occur at the a i r -water I n t e r f a c e , i n such a way that the non-polar hydro-carbon group Is o r i e n t e d towards the gas phase. Taggart and Oaudin (22.3.1) note the h e t e r o p o l a r character of molecules of the f r o t h e r s used In f l o t a t i o n . Bartsch (24.25.1)(24.25.2) f i n d s that hydrocarbons, c h l o r o -form, carbon t e t r a c h l o r i d e and carbon d i s u l f i d e have l i t t l e 9 or no f r o t h i n g , or foam s t a b i l i z i n g a b i l i t y ; but o r g a n i c a c i d s , ; a l c o h o l s , amines, aldehydes, ketones, e t c . a i d i n the p r o d u c t i o n and s t a b i l i t y of foams. Each reagent has an optimum c o n c e n t r a t i o n f o r g r e a t e s t foam s t a b i l i t y , , He notes t h a t m i n e r a l s a l s o exert a s t a b i l i z i n g e f f e c t . As a r e s u l t of a s t a t i s t i c a l study of a l a r g e number of o r g a n i c compounds, i n which b o t h the f r o t h i n g e f f e c t , measured by a s p e c i a l apparatus, and f l o t a t i o n performance, are c o r r e l a t e d t o s t r u c t u r e , Taggart, T a y l o r and i n c e (30.3.3) s t a t e that the molecule of a n o n - c o l l e c t i n g f r o t h e r s h o u l d c o n t a i n one (and p r e f e r a b l y one only) oxygen-bearing,.water-a v i d group, such as: *0 -OH -C-OH =0=0 at l e a s t a s i x carbon-atom c h a i n , a t t a c h e d t o the above group; and t h a t the compound s h o u l d have a s o l u b i l i t y i n water of about 1 gm. per l i t r e . Because the s o l u b i l i t y of the compounds s t u d i e d decreases w i t h 'hydrocarbon l o a d i n g ' , they suggest the hydrocarbon group i s hydrophobic, w h i l e the r e s t o f the molecule i s h y d r o p h i l i c , i n l i n e w i t h Langmuir's treatment of p a r t i a l s o l u b i l i t y . r'rothing of s o l u t i o n s of an homologous s e r i e s i n c r e a s e s to a c e r t a i n p o i n t , then decreases w i t h i n c r e a s i n g molec-u l a r weight; presumably because of the d e c r e a s i n g s o l u b i l i t y of the h i g h e r members. G-audin (32.25.5) s t a t e s t h a t the presence i n a f r o t h e r of i o n i z a b l e p o l a r groups such as -COOH or -NHg w i l l 10 cause I t to have c o l l e c t i n g tendencies. -' i h e modern conceptions of f r o t h i n g have been summar-i s e d by d e l (iiuSIce (34.6.3) A device f o r t e s t i n g the f r o t h i n g p r o p e r t i e s of f l o t -a t i o n reagents i s described by uhristmann (U.S.Pat. 1,866,296) 1932). I n p r a c t i c e , pine o i l or c r e s y l i c a c i d are almost ex-c l u s i v e l y used as f r o t h i n g agents. L i t t l e a t t e n t i o n was p a i d to the development of new f r o t h e r s u n t i l the work of jjean and Hersberger (35.3.1). They s t a t e t h a t the i d e a l f r o t h e r , In low c o n c e n t r a t i o n s , Should form a copious, but not too p e r s i s t e n t f r o t h ; the f r o t h should be independent of ph, added s a l t s , and added c o l l e c t o r s ; and the f r o t h e r should be n o n - c o l l e c t i n g , but should e m u l s i f y and d i s p e r s e i n s o l u b l e c o l l e c t i n g agents. By b a l a n c i n g p o l a r and non-p o l a r groups, and making use of the f a c t t h a t a complex p o l a r group w i l l a l l o w long chain hydrocarbon groups to be used without decreasing the s o l u b i l i t y of the compound too g r e a t l y , they propose a l i s t of compounds which should conform to the s p e c i f i e d c h a r a c t e r i s t i c s . Kecent f r o t h e r patents are reviewed by Bassett (38.4.1) 11 COLLECTION ' D e f i n i t i o n of a C o l l e c t o r C o l l e c t o r s are r e a g e n t s , i n v a r i a b l y o r g a n i c , which r e a c t w i t h a m i n e r a l i n such a way t h a t i t s tendency t o adhere t o a i r , i n p r e f e r e n c e to water; hence i t s tendency to f l o a t , i s i n c r e a s e d . iiixamples of ( J o l l e c t o r s examples of such r e a g e n t s , commonly used, are: 0 H n u s u a l l y = u 2 t i 5 , C 3 H 7 , C 4 H g , etc, Xanthates S s C S s x i s Ba or K Dithiophosphates * i s u s u a l l y C 6H 4.CH 3 X5X T h i o c a r b a n i l i d i>:Cs^"26^5 N i l - G 6 H 5 Diazoaminobenzene OgHgNrN .Nil .CgJig ^^3s /C H T r i m e t h y l c e t y l ammonium bromide CH3- Cgi® 33 S t r u c t u r e of C o l l e c t o r s xhe h e t e r o p o l a r nature of c o l l e c t o r molecules was e a r l y r e c o g n i z e d (24.3.1)(28.3.1). Taggart, T a y l o r and Ince (30.3.3), from a s t a t i s t i c a l study of the c o l l e c t i n g index (an a r b i t r a r y measure of c o l l e c t i n g e f f e c t , dependent-., on contact angle measurements) f o r a l a r g e number of o r g a n i c compounds, reach the c o n c l u s i o n t h a t the e f f e c t i v e n e s s of 12 a compound aa a c o l l e c t o r depends on the hydrocarbon group present, i n the molecule, i'rom s t u d i e s of the a b s t r a c t i o n of a c o l l e c t o r from* s o l u t i o n by a m i n e r a l , they show t h a t a b s t r a c t i o n i s dependent on the presence of a :S or s i m i l a r group. They s t a t e t h a t n o n - f r o t h i n g c o l l e c t o r molecules must con t a i n d i v a l e n t s u l f u r , t r i v a l e n t n i t r o g e n , or other m u l t i -v a l e n t negative element i n the low v a i e n t s t a t e , and must have a hydrocarbon complex w i t h 8 or more carbon atoms. The compound should have a s o l u b i l i t y of 200 to 300 mgm. per l i t r e i n water, and probably possess the a b i l i t y t o form r e l a t i v e l y i n s o l u b l e base metal s a l t s . P r e p a r a t i o n and P u r i f i c a t i o n of U o l l e c t o r s  and t h e i r Compounds The methods of r o s t e r (28.19.2) f o r the p r e p a r a t i o n of xanthates and other t r i t h i o c a r b o n a t e s have been quoted by u-audin (32.25.5). Poster's method has been m o d i f i e d by De W i t t and Roper (32.1.1) i n t h e i r p r e p a r a t i o n of a h i g h l y p u r i f i e d potassium e t h y l xanthate. Gaudin and Schumann (36.8.3) give methods f o r the p r e p a r a t i o n and p u r i f i c a t i o n of potassium n-amyl xanthate and cuprous n-amyl xanthate. Chemical Reactions of C o l l e c t o r s A study of the s o l u b i l i t y and k i n e t i c s of decomposition of x a n t h i c acids i n water shows t h a t decomposition i s a c c e l -erated by hydrogen i o n s , and r e t a r d e d by s u l f a t e ions (18.25.1) 13 The k i n e t i c s of decomposition i n organic l i q u i d s has al s o been s t u d i e d (13.25.1).. The decomposition i s a c c e l e r -ated i n l i q u i d s * c o n t a i n i n g -OH groups. A l k a l i xanthates decompose i n a c i d s o l u t i o n to form carbon d i s u l f i d e and a l c o h o l . I f , however, the pH i s not below 5, and the temperature i s l e s s than 5° 0. (13.25.1;, the s t a b l e , w a t e r - i n s o l u b l e x a n t h i c a c i d i s formed. In 1 to 2 normal a l k a l i n e s o l u t i o n , xanthate i o n i s decomposed (08.25.1), as evidenced by the composition of the i n s o l u b l e cuprous s a l t s p r e c i p i t a t e d from such a s o l -u t i o n . I t i s probable t h a t mono-, d i - , or t r i t h i o c a r b o n a t e s are formed. Taylor and K n o l l (34.3.7) consider the most probable decomposition products of an aqueous s o l u t i o n of an a l k a l i xanthate are e i t h e r dixanthogen- 1-, or carbon d i s u l f i d e and a l c o h o l . De Witt and Koper (32.1.1) s t a t e that the hydroxy! i o n d e r i v e d from h y d r o l y s i s cannot account f o r the observed pH change i n s o l u t i o n s of potassium e t h y l xanthate. Schaum, S i e d l e r and Wagner (32.12.3) note very s l i g h t h y d r o l y s i s of 0.01 normal xanthate s o l u t i o n s at room temperature. The h y d r o l y s i s increases a u t o c a t a l y t i c a l l y a f t e r 20 hours. They consider xanthates, at the concentrations used i n f l o t a t i o n , are completely d i s s o c i a t e d . Taylor and K n o l l i n v e s t i g a t e d the s t a b i l i t y of potas-sium e t h y l xanthate s o l u t i o n s (34.3.7), and f i n d t h a t a 1. 14 water s o l u t i o n has a pH of 7.2. C o n d u c t i v i t y measurements i n d i c a t e e t h y l x a n t h i c a c i d i s a stro n g a c i d . Sodium or potassium e t h y l xanthate, from a s o l u t i o n c o n t a i n i n g c u p r i c i o n s , p r e c i p i t a t e s y e l l o w cuprous xanthate (1855.25.1)(08.25.2)(10.25.1J(31.1.1), and from a s o l u t i o n c o n t a i n i n g l e a d i o n s , p r e c i p i t a t e s white l e a d xanthate (34.3.7) as .determined by an a l y z i n g the p r e c i p i t a t e s f o r base metals. Taggart, d e l Giudice and Z i e h l (34.3.6) s t a t e t h a t f e r r o u s s a l t s , w i t h xanthate i o n , on o x i d a t i o n , form a pre-c i p i t a t e which i s probably dixanthogen and f e r r i c xanthate; tha t f e r r i c s a l t s , w i t h e t h y l xanthate i o n , form f e r r i c e t h y l xanthate, as determined by a n a l y s i s . They give a t a b l e of the r e a c t i o n s of c o l l e c t o r s w i t h heavy metal i o n s . P h y s i c a l P r o p e r t i e s of C o l l e c t o r s and t h e i r Compounds The s o l u b i l i t y i n water at 0° C. of sodium methyl and e t h y l xanthates i s reported to be 0.05 and 0.02 mol. per l i t r e , r e s p e c t i v e l y (18.25.1) The surface t e n s i o n of aqueous s o l u t i o n s of potassium e t h y l xanthate has been measured by De W i t t and ass o c i a t e s (32.1.1)(35.1.1) who note that s o l u t i o n s of the iso m e r i c forms of potassium e t h y l xanthate have d i f f e r e n t s u r f a c e t e n s i o n s . Taggart and co-workers mention the s o l u b i l i t y of z i n c e t h y l xanthate i s about 335 mgm. per l i t r e (30.3.1); that of 2. S O u ^ 4 ( S - . C C°=2 H s ) " - » S : < ° f 5 * (s = < C * H 15 l e a d e t h y l xanthate i s 0,2 mgm. per l i t r e (32.8.1). ,: Weinlg and Palmer (29.25.4) s t a t e t h a t xanthates are more s o l u b l e than the corresponding s u l f i d e s . B r i g h t o n , Burgener and Gross (32.6.2) f i n d t h a t the s o l u b i l i t y of c u p r i c and z i n c n-amyl, and c u p r i c e t h y l xanthates i s i n c r e a s e d by i n c r e a s e i n sodium cyanide con-c e n t r a t i o n . They r e p o r t the s o l u b i l i t y i n water of z i n c n-amyl xanthate as 80 mgm, per l i t r e ; l e a d n-amyl xanthate as 50 mgm. per l i t r e . They were unable, u s i n g c o l o r i m e t r i c methods, to determine copper xanthates i n water, or l e a d xanthate i n sodium cyanide s o l u t i o n . i h e r e l a t i v e s o l u b i l i t i e s of v a r i o u s m e t a l l i c xan-thates i n water have been determined by Warren (33.5.1). Gaudin (34.3.5A) g i v e s s o l u b i l i t i e s f o r cuprous n-amyl xanthate i n v a r i o u s o r g a n i c s o l v e n t s , as f o l l o w s : acetone 16, d i e t h y l e t h e r 15, carbon d i s u l f i d e 7.3, benzene 388, petroleum e t h e r l e s s than 1 mgm. per l i t r e . EFFECT OF VARIOUS REAGENTS ON KECOVEKY  IN FLOTATION TESTS AMD PRACTICE s m a l l s c a l e F l o t a t i o n Tests •The small s c a l e f l o t a t i o n t e s t i s probably the o l d e s t experimental technique used In studying f l o t a t i o n phenomena. Various devices have been described f o r t h i s work; many manufacturers market m i n i a t u r e c e l l s , t a k i n g a charge of 500 or 1000 grams, which are miniatures of t h e i r p l a n t u n i t s A 50 gram a g i t a t i o n type c e l l , w i t h automatic f r o t h overflow i s d e s cribed by Gates and Jacobs en • | ), and has been modified by Hansen . This c e l l has r e c e i v e d wide acceptance f o r use i n experimental work. A f l o t a t i o n t e s t i s u s u a l l y c a r r i e d out as f o l l o w s : A weighed amount of ore i s crushed t o 4 to 20 mesh, and ground w i t h water and c e r t a i n reagents i n a l a b o r a t o r y b a l l m i l l . The pulp i s then t r a n s f e r r e d ' t o the f l o t a t i o n c e l l , and water i s added t o give the d e s i r e d r a t i o of ore to water F r o t h i n g and other reagents may now be added, and the c e l l set i n o p eration. The m i n e r a l r i s i n g i n t o the f r o t h i s scraped o f f , or overflows, and Is recovered as concentrate. T a i l i n g s and. concentrate pulps are f i l t e r e d , and t h e i r s o l i d content d r i e d , weighed, and assayed f o r v s r i o u s metals. jhe recovery of a given metal i s reported as the percentage of that metal present i n the charge, which i s recovered i n the concentrate. -17 More complete d e t a i l s of f l o t a t i o n t e s t i n g methods and apparatus are d e s c r i b e d by D i e t r i c h , Engel and Guggenheim (37.13.2). F o r the r e s u l t s of f l o t a t i o n t e s t s on a wide v a r i e t y of n a t u r a l o r e s , r e f e r e n c e should be made to the p u b l i c a t i o n s " I n v e s t i g a t i o n s i n Ore D r e s s i n g and M e t a l l u r g y " p u b l i s h e d a n n u a l l y by the Department Of Mines, Ottawa, Canada. -F l o a t a b i l i t y of l u r e M i n e r a l s (Inherent F l o a t a b i l i t y ) Although i t has been shown r e p e a t e d l y t h a t c l e a n m i n e r a l s do not make contact w i t h an a i r bubble u n d e r . s t a t i c c o n d i t i o n s , i t has not been c o n c l u s i v e l y demonstrated t h a t m i n e r a l s , under a c t u a l f l o t a t i o n c o n d i t i o n s , have no i n h e r e n t f l o a t a b i l i t y . ±h.e c o n f l i c t i n g c o n c l u s i o n s reached by v a r i o u s workers depend, i n p a r t , t h e r e f o r e , upon t h e i r experimental approach t o the s u b j e c t of i n h e r e n t f l o a t a b i l i t y . I n v e s t i g a t o r s who have measured the contact angles developed by an a i r bubble on a m i n e r a l s u r f a c e (30.3.1) (33 ..8 .2)( 34.3 .2) (34.3.6 ; agree t h a t no contact Is developed i f the m i n e r a l s u r f a c e i s c l e a n . G-audin, (32.25.5), summing up the r e s u l t s a t t a i n e d In a c t u a l f l o t a t i o n p r a c t i c e , and i n s m a l l s c a l e t e s t s , g i v e s a t a b l e of i n h e r e n t f l o a t a b i l i t i e s of pure m i n e r a l s , ne considers" t h a t metals are the most f l o a t a b l e ; then, i n order of d e c r e a s i n g f l o a t a b i l i t y : i n t e r m e t a l l i c compoundsj s u l f i d e s o f metals n e a r e s t s u l f u r i n the p e r i o d i c t a b l e ; s u l f i d e s of metals f u r t h e s t from s u l f u r i n the p e r i o d i c t a b l e ; n o n - a c i d — . . 18 forming oxides of the metals nearest t o the d i v i d i n g l i n e between metals and m e t a l l o i d s i n the p e r i o d i c t a b l e ; and t h a t the l e a s t f l o a t a b l e compounds are compound o x i d e s , and oxides of the metals f a r removed from the d i v i d i n g l i n e bet ween metals and non-metals In the p e r i o d i c t a b l e . Me s t a t e t h a t g r a p h i t e and s u l f u r have i n h e r e n t f l o a t a b i l i t y , and xanthates do not f u n c t i o n as c o l l e c t o r s w i t h these m i n e r a l s Rey (35.17.1; s u b s t a n t i a l l y agrees w i t h G-audin i n contendin t h a t s u l f u r , g r a p h i t e , t a l c , and molybdenite w i l l a t t a c h to an a i r bubble i n the absence of any o r g a n i c reagent. R a v i t z and P o r t e r (34.3.1) r e p o r t that they were able to f l o a t pure, u n o x i d i z e d g a l e n a i n a n i t r o g e n atmosphere, i n the absence of r e a g e n t s , thus s u p p o r t i n g the i d e a of I n -herent f l o a t a b i l i t y . They s t a t e t h a t a i r w i l l d i s p l a c e water from a pure g a l e n a s u r f a c e , i n d.irect c o n t r a d i c t i o n t the work of Taggart (30.3.1) and Wark and Oox (34.3.2) E f f e c t of Various Reagents on the r e c o v e r y  of M i n e r a l s i n the Presence of a C o l l e c t o r Galena Galena, when pure and u n o x i d i z e d , a c c o r d i n g to Gaudin, (32.25.5) f l o a t s r e a d i l y without a c o l l e c t o r ; a f r o t h e r only b e i n g r e q u i r e d . I f the galena Is o x i d i z e d , i n c r e a s i n g amounts of c o l l e c t o r are r e q u i r e d t o produce the same r e -covery, depending on the extent of o x i d a t i o n . These ob-s e r v a t i o n s are confirmed by other workers (34.3.1) Kellermann and. Bender (30.12.2) note t h a t f r e s h xan-19 thate s o l u t i o n b a r e l y f l o a t s g a l e n a , but becomes e f f e c t i v e on s t a n d i n g , or on treatment w i t h s u l f u r i c a c i d , and conclude t h a t f l o t a t i o n i s e f f e c t e d by xanthate h y d r o l y s i s p r o d u c t s . F l o t a t i o n t e s t s made i n a 50 gram c e l l (25.6.1) i n the l a b o r a t o r i e s of the American Cyanamid uompany (27.2.1) showed t h a t pure, dry-ground g a l e n a gave equal r e c o v e r i e s w i t h p i n e - o i l and potassium e t h y l xanthate; and w i t h phospho-1 c r e s y l i c reagent, but p o o r e r r e c o v e r i e s w i t h t h i o c a r b a n i l i d o - t o l u i d i n e mixture (TT m i x t u r e ) , f o r the same reagent con-c e n t r a t i o n . P y r i t e Equal r e c o v e r i e s of pure p y r i t e are o b t a i n e d w i t h p i n e -o i l - p o t a s s i u m e t h y l xanthate, p h o s p h o c r e s y l i c reagent, and TT m i x t u r e , i n the ph range 5.0 to 5.2 (27.2.1). Gaudin (32.25.5) notes a poor r e c o v e r y of pure p y r i t e w i t h methyl q u i n o l i n e , but: b e t t e r r e c o v e r y of p y r i t e than c h a l c o c i t e , when both minerals; are p r e s e n t ; due presumably to the a c t i v a t i o n of p y r i t e by copper ions d e r i v e d from the c h a l c o c i t e . Pure, c l e a n p y r i t e i s e a s i l y f l o a t e d , and o x i d a t i o n i n h i b i t s f l o t a t i o n , a c c o r d i n g to Gaudin et a l (28.19.1--P a r t 2 ) . Gaudin n o t e s , f u r t h e r (32.25.5) t h a t p y r i t e i s , f l o a t e d more r e a d i l y by h i g h e r xanthates than.by lower; and more r e a d i l y by xanthates than by mercaptans. using amyl xanthate as c o l l e c t o r , Gaudin (29.10.1) found t h a t the r e -.0.CpH/ .GEU 1. p r o b a b l y s:P~0.OgH^.CH^ 20 covery of p y r i t e was zero i f the pn was above a c r i t i c a l v a l u e between 6,4 and 7.0. S p h a l e r i t e Most workers agree t h a t potassium e t h y l xanthate does not c o l l e c t s p h a l e r i t e u n t i l the m i n e r a l has been a c t i v a t e d , by copper s u l f a t e , f o r example (28.19.1)(30 .3.5). R e s u l t s of Buchanan and Christmann (27.2.1), who f i n d h i g h r e c o v e r i e s of pure s p h a l e r i t e w i t h v a r i o u s c o l l e c t o r s , i n c l u d i n g p o t a s -sium e t h y l xanthate, are e x p l a i n e d by assuming t r a c e s of copper s u l f a t e were p r e s e n t w h i l e the t e s t s were made. Gaudin (32.25.5) c o n s i d e r s pure s p h a l e r i t e i s one of the most d i f f i c u l t s u l f i d e s to f l o a t , and s t a t e s t h a t c o l -l e c t o r s w i t h l e s s than f i v e carbon atoms i n t h e i r h y d r o c a r -bon chain do not c o l l e c t s p h a l e r i t e , u n l e s s used i n l a r g e amounts. The f o l l o w i n g l i s t of c o l l e c t o r s f o r pure s p h a l -e r i t e i s g i v e n : d i - i s o - a m y l ammonium d i - i s o amyl d i t h i o -carbamate; xanthates h i g h e r than h e x y l xanthate; t r i t h i o -carbonates h i g h e r than p r o p y l t r i t h i o c a r b o n a t e ; c e r t a i n amines such as monoisoamylamine; and c e r t a i n h y d r a z i n e s such as p h e n y l h y d r a z i n e . S p h a l e r i t e r e c o v e r y i s an optimum at a c e r t a i n ph f o r each c o l l e c t o r s t u d i e d (28.19.1). T h i s has been ex-p l a i n e d (32.8.1) by assuming t h a t the maximum r e c o v e r y zones correspond t o pn bands of maximum r e a c t i o n v e l o c i t y between c o l l e c t o r and m i n e r a l . Kraeber (30.25.2) f i n d s t h a t maximum re c o v e r y i s a t -t a i n e d at pti 6 to 7; and t h a t the optimum pri decreases as 21 the i r o n content of the s p h a l e r i t e i n c r e a s e s . . - F l o t a t i o n t e s t s made by Yamada and Naganuma (36.25.7) i n d i c a t e t h a t s p h a l e r i t e i s not f l o a t e d at a pH above 7.6. C h a l c o c i t e F l o t a t i o n t e s t s made by Gaudin and Sorenson (28.19.1) show t h a t the a c t i v i t y of c o l l e c t o r s f o r c h a l c o c i t e i n c r e a s e s as the non-polar p a r t of the molecule i s made more complex, and t h a t a l i p h a t i c s u l f i d e s and d i s u l f i d e s are more a c t i v e than aromatic s u l f i d e s and d i s u l f i d e s , but t h a t the converse i s t r u e f o r the h y d r o s u l f i d e s . De W i t t , Makens and H e l z (35.1.1) c o r r e l a t e the s u r f a c e t e n s i o n of normal xanthate s o l u t i o n s , from e t h y l t o h e p t y l , to t h e i r c o l l e c t o r a c t i v i t y , as r e f e r r e d to c h a l c o c i t e and m a l a c h i t e . Gaudin mentions methyl q u i n o l i n e (32.25.5) and mono-isoamylamine (29.10.1) as c o l l e c t o r s f o r c h a l c o c i t e C h a l c o p y r l t e Gaudin (32.25.5) s t a t e s pure c h a l c o p y r l t e , I f un o x i d i g e d , i s r e a d i l y f l o a t e d , w i t h a f r o t h e r only* The r e c o v e r y of c h a l c o p y r l t e decreases from 96% to 84,4% through the pri range 10.42 to 11.76, a c c o r d i n g to iamada and a s s o c i a t e s (36.25.6) M i s c e l l a n e o u s S u l f i d e M i n e r a l s 1amada and a s s o c i a t e s (34.25.5) f i n d t h a t complete f l o t a t i o n of p y r r h o t i t e i s p o s s i b l e w i t h camphor blue o i l and c o a l t a r In the pn range 4.6 to 5; but t h a t f l o a t a b i l i t y i s n e g l i g i b l e at a pn g r e a t e r than 5. 22 Recent tests made by'the same authors show that the recov-ery of-arsenopyrite" is decreased from 88$ at a pH below 5 to zero afeov«.pH f (36.".'25vl) j - that ©nargite gives low recover-ies above pH 6 (36.25.Si'-; and that - the optimum recovery, of stibnite is 'attained-.'in the- pH range 4 to 6,5• (37-*25.,3.)V The recovery of • marmati-te is- decreased from. 4V'&¥''60% to 2% as thepH is In-creased -from,'5.7 to 12 (37,25.2..). : Oxidized Minerals '"•""--The oxidized minerals which are considered,'in partic-ular, are' azurite and malachite (basic- copper carbonates), eerus site- (lead.carbonate) and angles ite (lead sulfate). In general,'oxidized.minerals are less readily floated than the sulfides, Malachite and azurite - (32 ,25.5') .l-are .collected by'''higher fatty acids, and soaps, which separate the.minerals from ' quartz, but not from ealcite. -There is' an-optimum pH (28'.-19.1A-T-.P>9,) fdr the f l o t a -tion of cerussite, of 9.0 with potassium amyl xanthate, and 7.8 with thlocresol. Gaudin (32.25.5) states that cerussite and angles i t e are floated" by soaps '•; and may be separated from a siliceous .gangue by fatty, a c i d s G e r u s s l t e ' ; i s : col-lected by thionaphthol and * by amyl xanthate., but'not'by methyl xanthate. • Plumbojarosite, (32.25.5) can hot be sulfidlzed, -is not -collected by ethyl or amyl xanthates, but is collected by :n-o-ctyi and n-lauryl xanthates i f these reagents are-used: in large amounts. 23 Non-rnetalll-p minerals •} -Graphite,and sulfur are readily floated. An instance is-reported (24.19.1) Of the flotation of sulfur with amyl alcohol as the only reagent. . Gaudin (32.25.5) does, not .pelleve that xanthates exert any collecting action on sulfur or graphite. The recovery of sulfur Is affected by the pH (30.6.1). A pH of 7.5- to 8.0 has been suggested as an opti-mum range. • • '. In contrast 'to the' view that graphite has Inherent f l o -t a b i l i t y is that of Wark and.: Cox <(35-«8.1)' who find that a high concentration, of frother (which has graphite"collecting power) Is required to float 'graphite.; They, note' that' certain frothers-are ineffective as collectors, and conclude: that graphite requires &.-collector, such as a- xanthate, for - f l o - " tat Ion-.' Confirmatory :work (57.8.1). in which i t Is found that-amyl and'ethyl xanthates increase the f l o a t a b i l i t y of charcoal, leads Wark and Cox to conclude: that the flotation -of .graphite, obtained In their previous work, was" not'due to metallic Impurities in the graphite. -• Although Sulfur ;usually floats without a collector, Wark and Cox(35.8.1) show that the presence of a collector enhances Its flotation. - ' . : Beri and associates (23.23.1) (24.12-.1)(:24.12.2) (24.12.5;) have studied the flotation- of various minerals, particularly • a r t i f i c i a l l y prepared s i l i c a , by the use of dyes, which, by . adsorption on specific minerals, make them hydrophobic and cause.the mineral to f l o a t . 24 The ' e f f e c t of s o l u b l e metal, salts.'on quartz f l o t a t i o n has" been i n v e s t i g a t e d by Kraeber and Boppel (34.9.1), who advance the theory that a complex i s formed between the s a l t c a t i o n and the oxygen of the m i n e r a l s u r f a c e , and t h a t the character of the complex and i t s f l o t a t i o n effect:"'depend on the pH of the s a l t s o l u t i o n . • The f l o t a t i o n o f - n o n - m e t a l l i e s , p a r t i c u l a r l y w i t h r e -gard t o .past and present p r a c t i c e , i s e x t e n s i v e l y reviewed by Ralston (37.5.1). A b i b l i o g r a p h y c o n t a i n i n g 126 r e f e r -ences t o t h i s phase of f l o t a t i o n i s appended. S p e c i f i c E f f e c t s of C o l l e c t o r s on M i n e r a l s • Gaudin (34.3.5A) r e c a p i t u l a t e s the known e f f e c t s of xanthates" • I n increasing, the f l o a t a b i l i t y of m i n e r a l s , as f o l l o w s : : They are without e f f e c t on s i l i c a t e s , s i l i c a and' gangues g e n e r a l l y ; i n small amount they increase the f l o a t -a b i l i t y of copper, l e a d , s i l v e r , i r o n , and mercury s u l f i d e s , and of elemental copper, s i l v e r and g o l d . They increase the f l o a t a b i l i t y of z i n c s u l f i d e s only when the mineral i s f i r s t a c t i v a t e d , as by copper s u l f a t e . I n large' amounts they increase the f l o a t a b i l i t y of o x i d i z e d l e a d and copper m i n e r a l s ; and of o x i d i z e d z i n c minerals onl y when the xan-thate contains a long-chain hydrocarbon group.- I r o n oxides and carbonates are not f l o a t e d by xanthates. S u l f i d e s of not t y p i c a l l y m e t a l l i c elements ( s t i b n i t e , r e a l g a r , molyb-denite) are not made to f l o a t markedly b e t t e r by xanthate treatment. 25 Gaudin (32.25.5) notes the s e l e c t i v e ' a c t i o n of c e r t a i n c o l l e c t o r s f o r s p e c i f i c m i n e r a l s , and gives the f o l l o w i n g l i s t : Soaps c o l l e c t the minerals of a l l d l - and t r l - v a l e n t m e t a l s , and -minerals of c e r t a i n monovalent metals such as s i l v e r . . The lower xanthates c o l l e c t copper, l e a d , I r o n , s i l v e r and mercury s u l f i d e s t o the e x c l u s i o n of the s u l f i d e s of z i n c , c a l cium, barium -and aluminium-. Xanthates c o l l e c t l e a d .minerals In .preference t o copper or mercury m i n e r a l s . S u b s t i t u t e d dithiophosphates s e l e c t copper minerals•-. - A l i -p h a t i c mercaptans s e l e c t copper, s i l v e r and mercury m i n e r a l s . - I n f l u e n c e of Temperature on F l o a t a b i l i t y . -•'•'. Huber-Panu. (31.9 .1) s t a t e s t h a t each ore and method has an- optimum f l o t a t i o n temperature between 23°' and 40° .G. As the stemperature i s Increased the time of f l o t a t i o n i s ' d e -creased,, and the t o t a l recovery Is increased up to a c e r t a i n p o i n t . I t i s supposed t h a t the decrease i n recovery above t h i s - p o i n t i s due t o i n c r e a s e d o x i d a t i o n of the m i n e r a l , and inc r e a s e d s o l u b i l i t y of the compounds formed at the mineral s u r f a c e . 26 .-EXPERIMENTAL EVIDENCE FOR THE REACTION OF COLLECTORS WITH MINERALS ' ~<2- . i in i • i ' ' -} 11 i in , Changes in a Collector Solution:in Ggntact with a Mineral Considerable study-has been-made of the changes i n a collector s.olution'-'-when i t is brought Into contact with a • minerali^. Experimental methods .usually- consist in agitating the.: solution, with a known -weight of sized mineral,/ for a given time, and determining, by analytical methods 'or"sur-face tension measurements;, ahy'-ohanges resulting''in the col-lector-solution:. If a change in concentration of collector results, the collector is .said'-^b'be abstracted- by the min--'• erai-*!'- '' Abstraction.,.'. in 'general..•. ; :The f i r s t work dealing with-abstraction of flotation' reagents by minerals was probably that of Fahrenwald (21.25.1) who found, by measuring the surf ace tension-of an oil--water -emulsion- or solution before and gf.t#r .bringing" i t into con-tact with minerals, that a l l minerals investigated abstracted o i l from the emulsion- or sblutidnj that sulfides'' abstracted more than.gangue minerals| and that, in general, the f l o a t -a b i l i t y of a treated mineral was proportional to'the amount of o i l abstracted* -He rioted that electrolytes -affect the amount -.-of .-oil abstracted. Taggart and Gaudin (22.3*1.) made a-similar study with confirmatory results*' 27 Other workers (33.8.3)(32,8 ,1 ) have noted a c l o s e con-n e c t i o n between the a b s t r a c t i o n of a s o l u b l e c o l l e c t o r by a m i n e r a l and the* s o l u b i l i t y of the s a l t of the c o l l e c t o r and the metal contained i n the'mineral«• When the metal s a l t i s r e l a t i v e l y s o l u b l e , c o n c e n t r a t e d c o l l e c t o r s o l u t i o n s " a n d long treatment are n e c e s s a r y to e f f e c t a b s t r a c t i o n , : Rimskaya (37,.16.I) has s t u d i e d the w e t t i n g isotherms of p y r i t e i n sodium o l e a t e j m a l a c h i t e i n h e p t y l i c a c i d ; g a l e n a • i n b u t y l xanthate s o l u t i o n s , and I n t e r p r e t s them as showing two p a r t s , the f i r s t c o rresponding to g r a d u a l s a t -u r a t i o n o f a u n i m o l e c u l a r c o l l e c t o r l a y e r ; the second to a s a t u r a t e d f i l m , which shows the l e a s t w e t t i n g . A b s t r a c t i o n by g a lena Taggart, T a y l o r and K n o l l (30.3.1) prove t h a t t h e r e i s a m e t a t h e t i c a l e q u i v a l e n c e between the-amounts of xanthate i o n a b s t r a c t e d from s o l u t i o n by g a l e n a , and the o x i d a t i o n p r o d u c t s 1 of galena appearing i n s o l u t i o n . They were unable t o de t e c t s u l f i d e ions In s o l u t i o n , and suggest the mechan-ism of a b s t r a c t i o n i s p u r e l y chemical: Lead s u l f i d e i s o x i -d i z e d to l e a d s u l f a t e , which r e a c t s w i t h xanthate i o n t o form i n s o l u b l e l e a d xanthate, - The f a c t that the xanthate- a b s t r a c -r t i o n i s decreased by g r i n d i n g and t r e a t i n g galena i n the absence of a i r , and i n c r e a s e s w i t h the time of exposure of galena to moist a i r , i s taken t o confirm t h i s mechanism. Ta g g a r t , T a y l o r and Ince (30.3.3) and T a y l o r and K n o l l (34.3.7) continued t h i s work and found t h a t the potassium concentrat i o n was unchanged, and that no l e a d i o n could be 28 detected i n .the s o l u t i o n a f t e r a b s t r a c t i o n had taken p l a c e . The: n e c e s s i t y f o r o x i d a t i o n of galena t o precede r e a c t i o n w i t h the c o l l e c t o r i s confirmed by Ralston et a l (30.3.4) who found that galena ores , ground In the absence of oxygen, gave poor f l o t a t i o n r e s u l t s ; and by W i l k i n s o n (35.9.1) who sta t e s t h a t p a r t i a l - . o x i d a t i o n of galena i s e s s e n t i a l , I f xanthate i s t o be adsorbed. B e r i , Schmitt and Schulz (33.12.1) note t h a t o x i d a t i o n - o f galena increases i t s c o l l e c t o r r e -quirements. I n contrast to the above views i s that of R a v i t z and P o r t e r (34.3.1) who f l o a t e d galena i n the absence of a i r , and consider o x i d a t i o n products on the surface i n h i b i t f l o -t a t i o n , and are not e s s e n t i a l f o r the f l o t a t i o n of galena w i t h e t h y l xanthate. Gaudin and W i l k i n s o n (33.8.5) s t a t e t h a t galena ab-s t r a c t s dlxanthogen from an aqueous suspension. I t has been shown. t:B8«9.2) that the a b s t r a c t i o n of c a p r i e a c i d from aqueous s o l u t i o n by galena f o l l o w s the; law: •;.v= . -; .oc = ' f i ^ n - CX = weight a b s t r a c t e d c — e q u i l i b r i u m c o n c e n t r a t i o n i n s o l u t i o n ; /5 = 67 ' . ± = .-a.5. ' ......... n and was f u r t h e r noted that; dry galena shows leas adsorptive power than wet galena. - Tnce (.30.3.2) notes t h a t galena a b s t r a c t s - more t h i o -c a r b a n l l i d than s p h a l e r i t e does. 29 •• I t has been shown that galena abstracts palmitate Ion only from a solut i o n of sodium palmitate, presumably to form insoluble lead .palmitate (-29:,25^1),(29-.15.1) and abstracts . oleate Ion from sodium oleate solution (34.3.6). Taggart (32.8.1) reviews the experimental work to date and notes that a-naphthylamine, potassium ethyl xanthate, mono- and d l -phenylatMlourea, ..and p - t h i o c r e s o l ' are -abstracted by-galena* Himskaya (37.16.1) has studied the wetting isotherms of galena i n butyl xanthate. Abstraction by p y r i t e I t i s stated (34.3.6) that p y r i t e abstracts only ethyl xanthate ion from a so l u t i o n of potassium ethyl xanthate. Gaudin and Wilkinson (33.8.5) advance evidence to show that the xanthate, on abstraction,'-is changed to dixanthogen. Taggart (32.8.1) reviews the experimental work-on "abstraction and states that p y r i t e abstracts a-naphthylamine, potassium ethyl xanthate, mono- and diphenyl thiourea and p-thlocres.ol. Wark and Cox (38.3.1) were unable to determine the xanthate abstracted by cyanide-treated p y r i t e , because reducing ions were l i b e r a t e d by the a l k a l i present. By an in d i r e c t method however, they show that the depressant reduced, and. probably prevented xanthate abstraction. Abstraction by sphalerite The non-abstraction of ethyl xanthate by pure sphaler-i t e has been noted by Taggart, Taylor and Kn o l l (30.3.1) and confirmed by others (30.3.7)(33.8.5), and i s considered due to the high s o l u b i l i t y of zinc ethyl xanthate (30.3.1) 30 A b s t r a c t i o n of e t h y l xanthate i o n by copper^activated s p h a l e r i t e has been measiired by Gaudin (30.3.7), who f i n d s i t to be g r e a t e r than the a b s t r a c t i o n by cyanide-treated copperized s p h a l e r i t e . Taggart st a t e s (32.8.1.) that during a b s t r a c t i o n of c o l l e c t o r by-copperized s p h a l e r i t e , , s u l f a t e ions appear In s o l u t i o n . v' ::A; ;:very^lowvabstraction of c o l l e c t o r 'by- cyioaide ^ t r e a t e d s p h a l e r i t e was noted by Inoe (30.3,«2), who a l s o found ! that pure s p h a l e r i t e a b s t r a c t s l e s s t h i o c a r b a n i l i d than galena does. According t o B e r i , Schmitt and Schulz '(33.12.1)who determined the amount of c o l l e c t o r r e q u i r e d t o make a mineral hydrophobic, as shown by:the I n v e r s i o n of a benzehe-in-water t o a water-in-benzene emulsion, the o x i d a t i o n of s p h a l e r i t e decreases i t s c o l l e c t o r requirement, by v i r t u e of the high s o l u b i l i t y of z i n c s u l f a t e . Gaudin, Haynes and Haas (28.19.1 - T.P. 4) showed that c e r t a i n amines which f l o a t s p h a l e r i t e , do not form I n s o l u b l e z i n c s a l t s or s u l f i d e s . . A b s t r a c t i o n by c h a l c o c i t e Glial co c i t e a b s t r a c t s e t h y l xanthate Ion from a "solu t i o n of potassium e t h y l xanthate (34.3.6) A b s t r a c t i o n by c h a l c o p y r l t e The a b s t r a c t i o n by c h a l c o p y r l t e of v a r i o u s c o l l e c t o r s , i n c l u d i n g potassium e t h y l xanthate, has been noted by Taggart (32.8.1). Gaudin and Schumann (36.8.3) found that c h a l c o p y r l t e a b s t r a c t s e t h y l xanthate i o n only, very r a p i d l y , 31 from potassium e t h y l xanthate s o l u t i o n , In q u a n t i t y t o form cuprous e t h y l xanthate; and t h a t h y d r o x y l , carbonate, s u l f a t e , and r e d u c i n g - i o n s of the form S m 0 £ " are thrown i n t o s o l u t i o n , i n t o t a l amount m e t a t h e t i c a l l y e q u i v a l e n t to the amount of xanthate i o n a b s t r a c t e d . A b s t r a c t i o n by s u l f u r and g r a p h i t e In c o n t r a d i c t i o n t o Gaudin (32,25.5), Wark and Cox (SbeBtil) show t h a t a wide v a r i e t y of minerals., I n c l u d i n g s u l f u r , g r a p h i t e , c e r u s s i t e and g o l d , a b s t r a c t xanthate from s o l u t i o n . The a b s t r a c t i o n of e t h y l and amyl xanthate from s o l u t i o n does not • change the pH of the solution..- In f u r t h e r work (37.8,1) they f i n d that c h a r c o a l a b s t r a c t s both anions and c a t i o n s of potassium amyl and e t h y l xanthates from s o l u t i o n ; t h a t more xanthate i o n than potassium i o n i s a b s t r a c t e d ; and t h a t the d i f f e r e n c e i s accounted f o r as an i n c r e a s e i n . the a l k a l i n i t y • of the s o l u t i o n . The : abstraction.; of potassium i o n p r o b a b l y takes p l a c e by exchange a d s o r p t i o n w i t h hydrogen ions of the c h a r c o a l , and the i n c r e a s e i n a l -k a l i n i t y by exchange a d s o r p t i o n of xanthate w i t h h y d r o x y l i o n s . A b s t r a c t i o n by. m i s c e l l a n e o u s . m i n e r a l s O x i d i z e d m i n e r a l s (malachite) a b s t r a c t xanthate ions from s o l u t i o n (32.25.5), and a d s o r p t i o n isotherms of e t h y l and b u t y l xanthates on m a l a c h i t e are g i v e n by Shneerson (36.16.4) The e q u i v a l e n c e of the reaction?'between c e r u s s i t e and 1. PbC0 3 2EtX~ =~ P b ( E t X ) 2 + • GOg" ' 32 xanthate has, been shown by Gaudin (34.3.5A) by ti t r a t i n g the carbonate formed. Wark and Cox (36.3.1) state that anglesite and cerussite abstract sodium sulfide i n preference'to xanthate. Apatite-removes palmitate ion from solution, as deter-mined by surface tension measurements, presumably to form an insoluble calcium palmitate (29 .25.1)(29.15.1). Gas-slter-. ite (29,25.1), which does not normally abstract palmitate Ion, w i l l abstract It from sodium palmitate solution-after ..the mineral has been treated with calcium hydroxide. .. .Volk ova. et a l . ('5'5'.*12..1)- show that, In the flotation of talc by isovaleric acid, an exchange reaction occurs .-and magnesium passes • Into.-solution. Gaudin (32.25,5) states that certain s i l i c a t e s , actIvated-by metal ions, abstract soap collectors from solution. Volkova and Zaporozhetz (35.12,2) find that, in the flotation of certain.finely-powdered•non-metallic, iaiherals. with isOamyl;alcohol, adsorption of alco-hol-, as evidenced by surface tension measurements, does not occur. Peetz (28.9.2) finds that quartz does not abstract capric acid from solution. • - Changes i n a.Mineral in Contact . With'a 'Collector Solution .Physical nature of A-coa;t^ag Visible" :coatings • formed-by collectors on various min-erals have been- noted. It Is stated that visible coatingg are formed on malachite by treatment' with xanthates ("34,3,..§*A) on azurite by amyl xanthate (28.19.1j, and on lead carbonate 33 by xanthates,, .mercaptans and thiophenols (32.25.5), , Fahrenwald (24*3.1) estimated the thic k n e s s of the o i l f i l m formed oh'%ul f i d e s i n o i l f l o t a t i o n was 1 0 t o . 1 0 0 molecules:, but was g r e a t e r i f h i g h concentrations of o i l were used. The a b s t r a c t i o n of va r i o u s c o l l e c t o r s b y p y r i t e , malachite and galena ( 3 7 . 1 6 . 1 ) and c o p p e r i z e d - s p h a l e r i t e •' f 3 7 . 1 6 . 4 ) c o r r e l a t e d t o the" amount of w e t t i n g , I n d i c a t e s that maximum f l o a t a b i l i t y i s a t t a i n e d when a-mon©molecular f i l m Is'formed on the mineral s u r f a c e . . £r^kXfsii(0f'.;c^t±n-ga on galena-; ' When s l i g h t l y , o x i d i s e d galena, -which'-has been..treated w i t h a xanthate, Is leached w i t h a solvent .for l e a d xan-thate , l e a d xanthate : Is obtained i n the leac h ' l i q u i d -(33.25.3 through 32.25.5). On longer treatment w i t h xanthate, s u l f u r a n d - u n i d e n t i f i e d ' o i l s are also'leached from the sur-face (33.8.5). Gaudin (54,5=.5A) b e l i e v e s t h a t , ..on long treatment, the lead xanthate which forms f i r s t , decomposes t o s u l f u r and o i l s (probably dixanthogen), -since-the'amount of l e a d xanthate recovered decreases w i t h the time of t r e a t -ment while the amount of s u l f u r and o i l s i n c r e a s e s . Lead xanthate i s a l s o leached from the surface of galena t r e a t e d w i t h dixanthogen (32.25.5) A n a l y s i s of coatings on p y r i t e Gaudin et a l (34.3.5A) s t a t e that xanthates react w i t h a p y r i t e - s u r f a c e t o form- f e r r i c xanthate, which decomposes r a p i d l y t o s u l f u r a n d a n o i l . For the l a t t e r reason, i t i s not u s u a l l y p o s s i b l e t o e x t r a c t f e r r i c xanthate from the 34 m i n e r a l s u r f a c e . . . . . . . . . . . 'Analysis of . coatings j on c h a l c o c i t e ... Cuprous xanthate i s e x t r a c t e d from the surface of c h a l -c o c i t e which has been t r e a t e d w i t h an a l k a l i xanthate (34.3.5A). Saudi-n and Schumann' - (-36.8.3) leached x a n t h a t e - t r e a t e d , c h a l -c o c i t e w i t h water, and w i t h p y r i d i n e , Leaching w i t h water had no e f f e c t on the f l o a t a b i l i t y of the t r e a t e d m i n e r a l . The p y r i d i n e e x t r a c t contained cuprous xanthate, and probably s m a l l amounts of other substances.- They conclude" t h a t the f i l m i n g of c h a l c o c i t e by xanthates Is accompanied by r e a c t i o n -of p a r t of the xanthate t o form cuprous xanthate and other substances removable by"organic s o l v e n t s . The c o a t i n g formed by dixanthogen on c h a l c o c i t e gives ho t e s t s f o r s u l f u r , dixanthogen,- or o i l , but shows' the presence of various other p r o d u c t s , presumably o x i d a t i o n products of cuprous xanthate (34.3.5A) A n a l y s i s o.f! Coatings on miscellaneous minerals Base metal xanthates have been i d e n t i f i e d by Gaudin (34.3.5A) i n the v i s i b l e coatings formed by xanthates on malachite and c e r u s s i t e . C o v e l l i t e r e a c t s w i t h dixanthogen and a l k a l i xanthates t o form cuprous xanthate and. s u l f u r . I n the r e a c t i o n w i t h xanthates, dixanthogen i s formed as an intermediate product, (34.3.5A) , and may be e x t r a c t e d from the c o a t i n g . Wark and CSX (35.8,1)" were unable t o recover amy! xanthate from hot water or a l c o h o l washings of t r e a t e d g r a p h i t e i but obtained an i n d i c a t i o n of xanthate ;by'an 35 i o d i n e t i t r a t i o n of a suspension of t r e a t e d g r a p h i t e , •" Taggart, d e l G i u d i c e and Z l e h l (34,3,6) c o n s i d e r the f o r m a t i o n of discahthogen on m i n e r a l s t r e a t e d with- xanthate as noted toy Gaudin (33,8,5)(34.3.5A) i s not a s i g n i f i c a n t f a c t o r In t h e i r f l o t a t i o n ^ s i n c e Wark and Gox (34,3.2) have shown-that the c h a r a c t e r i s t i c c o n t a c t angles f o r dixanthogen and xanthate are d i f f e r e n t , and that x a n t h a t e - t r e a t e d galena g i v e s the t y p i c a l xanthate contact angle 36 CONTACT ANGLES AS A MEASURE OF FLOATABILITY The Contact.Angle When a gas bubble is brought into contact with a s o l i d surface .in a li q u i d , the bubble may become attached to the solid, 5 or may f a i l to make contact. If attacbSttent occurs, a definite angle is subtended between the plane .tangent to the. bubble -and .'the plane of the solid surface at-any point along the. line of three phase contact, -This angle, measured 50L\O across the water phase, is called the contact angle. Keinder's relates the contact angle to the ihter f a c i a l tensions: 7 The "bubble machine", an apparatus for measuring con-tact angles, was introduced by Taggart, Taylor and Ince-(30.5.3) and has been described in detail by del-GiudiCe (36*6.1)* A similar apparatus to that . ;of Taggart is used i T g s -a T a i + T l gcos a Tg S = gas-solid Interfacial tension T'si'-'a= solid-liquid M ' !! T l g s liquid-gas " " —: contact angle 37 by Wark and.Cox (36.6.2), who describe their machine, and give notes on the technique of operation. Significance of the.. Contact Angle As a Measure of Floatability Taggart and Beach (16,3.1) used Relnder's equation as a qualitative guide in expressing the relation between con-tact angles and flotation results. Shepard (32.10.1) shows that the work to pull a bubble away from a solid surface is Txg(l - cos0), and that, as a close approximation, collectivity is directly proportional to the contact angle. Wark (32.22.1) gives the quantity T]|_g(l - cos9)••••as the free energy change (-AF) associated with bubble adhesion. Wark and Cox (32.22.1)(33.8.1), before using contact angle .measurements as the major tool in their Investigations of flotation, made a thorough study of the significance of the contact angle, from a mathematical, thermodynamic, and practical point, of view. They show that the contact angle is directly proportional' to the force of .air''-solid adhesion, and is the best measure of the adhesion of a bubble of air and a single solid particle. del Giudice (34.6.3) reviews certain work on contact angles. Valentiner (36.9.1) does not consider the contact angle is a measure of floatability, because the conditions under which it can be measured do not correspond to those in flo-38 tation.' > Effect of v a r i o u s factors on the contact angle • ..4. . The following results, have been obtained by Wark and •Goat, - from an extensive study of contact angles (33.8.3) (34.3.2) ('35.8a')r(37.8.1) (38,3.1), •'. Glean surfa-ces of a l l the minerals examined, Including galena, sphalerite,^.."pyrite and pyrrhotite,' do not develop "contact with am air bubble, in pure water. • •On, treating the mineral with -a xanthate solution, i f it'then makes contact with the a i r bubblethe magnitude ' of the contact angle is Independent of the mineral^| but depends only upon the non-polar group In the collector mol-ecule?' ' This i s further evidence for the outward-orientation of this non-polar group, at the mineral surface. Certain sulfides.make contact with air-In the presence ;of any xanthate. ' Other sulfides and xanthates require a c t i -vation before contact develops. 'Whether any contact w i l l develop'between an air bubble 1. Metallic copper, various sulfides, graphite, sulfur, and activated charcoal a l l show the same contact angle,in a given xanthate solution. 2, F o r example; Diethyl dithiophosphate P^O^L*J and S-C^s] give the same contact angle because they have the same 'non-polar group. 39 and a - s u l f i d e i n a given xanthate s o l u t i o n , depends i n general upon the s o l u b i l i t y of the xanthate of the metal contained i n the mineral". S u l f i d e s whose metal c o n s t i t u e n t s form r e l a t i v e l y s o l u b l e xanthates, and gangue m i n e r a l s , do not show a i r - m i n e r a l contact i n a xanthate s o l u t i o n . ' • • ; • I n an homologous s e r i e s of xanthates, the magnitude of" the c h a r a c t e r i s t i c contact angle increases w i t h the molec-u l a r weight of the xanthate. For each m i n e r a l , In.a given xanthate s o l u t i o n , there is' a c r i t i c a l pH above which contact Is Impossible j'and below' which the f u l l . a n g l e , c h a r a c t e r i s t i c of-the'xanthate, i s obtained. For a concentration of 25 mgm. per l i t r e of potassium e t h y l xanthate, the c r i t i c a l pH values f o r galena and p y r i t e are about 10.-2 and 10.5 r e s p e c t i v e l y , at room temperature.. As the c o n c e n t r a t i o n of a p a r t i c u l a r xanthate i s i ncreased; or i f a more complex xanthate Is used at the same c o n c e n t r a t i o n , the c r i t i c a l pH becomes h i g h e r . 1:. I t was found, w i t h the" f o l l o w i n g c o l l e c t o r s ; (1) sodium d i e t h y l dithi©phosphate (2) potassium e t h y l xanthate (3) sodium d i e t h y l d i t h i o c a r b o n a t e (4) Potassium isoamyl xanthate ( 5 ) potassium dl-n-amyl dithiocarbamate arranged In order of decreasing s o l u b i l i t y of t h e i r heavy metal s a l t s , t h a t c h a l c o p y r i t e responds t o a l l f i v e j galena and p y r i t e respond t o a l l except the f i r s t ; s p h a l e r i t e responds to the f i f t h only.. 40 :Anglesit©responds to potassium ethyl xanthate best -between' pH 9 and 11; cerussite at a pH less than 9. In the presence of sodium carbonate, a higher xanthate concentration Is necessary to produce contact with these minerals. As the temperature is decreased from 35°C to 10°C, the c r i t i c a l pH for galena, pyrite and chalcopyrite, in the pres-ence of ethyl xanthate only, becomes lower. The- following values are givenV , C r i t i c a l pH 35"® C To 0 C ' Galena 10.8 9.7 Pyrite -10,7 ..' . 10,0 ' . - .Chalcopyrite '12.7 10 99 ; • 'Hysteresis' of Cent act Angle Sulman noted (20.25.1) that, contact angles show hy-steresis, and considered that flotation depends on this-factor, Wark and. Cox (34.3.2) however, believe that .hy-steresis of the contact angle i s due to f r i c t i o n . They , were-able to eliminate i t in their experiments, and: conclude that i t does not help flotation. - •'" - ] '•"''. ;T'$me to Develop Contact - Freundlieh, i a i s l i h and: Lindau (33.25.1) (33.25.2) have studied the rate of wetting of minerals. They note that zinc- sulfide; and copper sulfide are wetted-'.slowly; lead sul-fide and iron sulf id© rapi d l y ; and that oleic acid favors wetting.' " Sven Nilsson (34.12,1) correlates f l o a t a b i l i t y to i n -41 .duct ion'"time (the time required.,' i n contact angle measure-ments, for an air bubble to make contact with a mineral), and shows that ..collectors decrease this time, while depres-sors Increase i t , Wark and Cox (36.8,1) comment on this work, and show that the induction time depends on ..the concen-tration of collector solution. Methods for measuring wetting hysteresis in:powdered minerals and ores are described by Klyachko (37.12*1)>; -who observes a possible, correlation between f l o a t a b i l i t y and differential wetting hysteresis of a given powder, before and after adsorption of a wetting agent. - Miscellaneous Contact Angle Investigations Contact angle studies made by Wark and Cox (35.8.2) with amines and sulfide minerals show that the maximum con-tact angle is Independent of the amine| that copper minerals and activated sphalerite respond most readily; pyrite least readily to an amine; and that hexylamine allows -sphalerite -to be floated away from galena. They state that contact angle measurements closely parallel flotation tests. Mokrushin and Demenev (35.18.3) have measured contact angles on metal sulfide films formed on a solution of the metal salt (35.12.4). They conclude that wetting of the films i s a temporary phenomenon., not explainable entirely by molecular orientation, but due also to ion adsorption from solution. They state that sulfide films adsorb anions pre-ferentially. 42 Demeney ,(36.25.3) f i n d s t h a t xanthates do not change the w e t t a b i l i t y of s u l f u r f i l m s formed by hydrogen s u l f i d e on f e r r i c c h l o r i d e , which i s taken to i n d i c a t e t h a t there i s l i t t l e or no a d s o r p t i o n . He was unable t o o b t a i n the con-st a n c y of contact angle claimed by Wark.and Cox. 43 ELECTRICAL EFFECTS IN FLOTATION  Charge .'oh: .•Minerals, A i r Bubbles-, and O i l P a r t i c l e ' s ... I t h a s been shown .(1-4,25.1.) (22*25,.l) (24,.2'5.3) t h a t a i r bubbles and o i l d r o p l e t s i n pure water c a r r y an e l e c t r i c charge, that the number of f r e e charges i s very small ( 2 7 ^ 2 4 . 2 ) , and that the o r i g i n of the charge i s probably I o n i c r a t h e r t h a n - e l e c t r o s t a t i c . " Ince (30,.3.2.) shows t h a t , i n , - s i m i l a r aqueous s o l u t i o n s , c e r t a i n ,minerals are p o s i t i v e l y charged; others n e g a t i v e l y . S v e n - l i l s S o h ( 3 2 . 2 5 . 6 ) s t a t e s that a i r - m i n e r a l adhesion i s good a t ' h i g h values of the p o t e n t i a l measured by e l e c t r o -c a p i l l a r y t e s t s ; poor at low v a l u e s . The value of the pot-e n t i a l at which the a i r - a d h e r i n g tendency of the m i n e r a l changes v a r i e s w i t h the m i n e r a l . P o t e n t i a l of M i n e r a l E l e c t r o d e s - -The p o t e n t i a l s of galena, copperized s p h a l e r i t e , and glass e l e c t r o d e s , against a calomel e l e c t r o d e , have been measured by Kamienski and Benis ( 3 7 . 1 6 . 5 ) . • E f f e c t of Reagents on M i n e r a l Charge Kamienski ( 3 2 . 2 5 . 1 ) ( 3 2 . 2 5 . 2 ) found that the p o t e n t i a l of negative p l a t l n u m , galena and graphite electrodes i n potassium c h l o r i d e s o l u t i o n becomes more negative; but th a t the p o t e n t i a l of z i n c i s unchanged, on adding t e r p i n e o l and 44 potassium e t h y l xanthate to the e l e c t r o l y t e . T h i s work was c a r r i e d out to t e s t the theory that w e t t i n g of the electrode w i l l reduce its- p o s i t i v e charge. He suggests that o i l - s u l -f i d e adhesion i s due,, t o - s t a t i c phase-boundary p o t e n t i a l s . B u l l (29.24.1) determined the p o t e n t i a l developed by -galena; and by q u a r t z , c a r r y i n g I n i t i a l " p o s i t i v e ! and negative charges r e s p e c t i v e l y , on f a l l i n g through s o l u t i o n s of metal s a l t s . - It. :.is suggested that c e r t a i n ions r a i s e the' charge on galena and prevent i t s c o l l e c t i o n . : Both lime, and o l e i c a c i d reverse the charge on quartz, and potassium e t h y l xanthate changes the s i g n on p y r i t e , according t o Tikhonov (35.25,1). The e l e c t r o - k i n e t i c p o t e n t i a l of p r e c i p i t a t e d p a r t i c l e s of metal ferrocyanides and s u l f i d e s Increases during pep-t i z a t i o n 136.25.5). 45 THERMODYNAMICS OF FLOTATION Heat of Wetting -.'•-'The heat of wetting of--silica was measured-'by Parks (02.25.1) andEdser (22.24.1). Fahrenwald (31.311) noted that the heat of wetting i s ah approximate measure of the adhesion of a mineral to water; and Wark (32.22,1) showed, from a "thermodynamic treatmentthat i t i s only a- rough i n -dication of the adhesive: force, and that the contact - angle • "" is a better measure: of• this' force. Recently (37V25..1) the heats-of wetting by water,'ethyl alcohol, and carbon ' tetra---ehloride, of powdered, barium sulfate and potassium halides have been measured. ' Surfabe Energy . Fahrenwald (31.3,1;) has estimated the surface, energy'' of quartz." Displacement Pressure and' Adhesion Tension Bartell and associates (27-.ll.l)'(27.,25;il) (33.8.6) have developed a'/method for measuring the pressure of displacement of one 11quid,by another at the surface : of a powdered solid, by which the liquid-solid adhesion tension may be evaluated. -The adhesion tension of crude oils (28.11.1), various "".organic liquids and water (32.8,3) on s i l i c a have been determined by this method. 46 A r e l a t i o n between the i n t e r f a c i a l angle and adhesion t e n s i o n i s given by B a r t e l l and B a r t e l l (34.1.1), which a l l o w s , from one determination of the adhesion t e n s i o n or contact angle of a l i q u i d on a s o l i d , the c a l c u l a t i o n of the adhesion t e n s i o n of the s o l i d on water or on a n y ' l i q u i d whose i n t e r f a c i a l t e n s i o n against water i s known. B a r t e l l and Greager (32.8.3) found t h a t the adhesion t e n s i o n of various l i q u i d s on s i l i c a , carbon b l a c k , and c a l -cium- f l u o r i d e , i s a l i n e a r f u n c t i o n of the absorbtion of the l i q u i d by the s o l i d , i n those cases where l i q u i d drops make zero contact angle on the s o l i d ; and t h a t o i l absorbtion Is low i f the adhesion t e n s i o n i s h i g h , or i f the contact angle Is l a r g e . I t i s s t a t e d (32.11.2) that aqueous s o l u t i o n s which are most e f f e c t i v e i n d i s p l a c i n g crude o i l and benzene ' from s i l i c a are adsorbed on, or react chemically w i t h the s i l i c a . I f the v a r i o u s l i q u i d s s t u d i e d (33.8.6) are arranged i n the order o f . i n c r e a s i n g adhesion t e n s i o n against s i l i c a , i t i s found t h a t t h i s s e r i e s i s the reverse of the s e r i e s f o r carbon; and t h a t , f o r any given l i q u i d , the sum of the ad-h e s i o n t e n s i o n on s i l i c a and the adhesion t e n s i o n on carbon i s approximately constant. The adhesion t e n s i o n of l i q u i d s (34,8.2) against strong-l y h y d r o p h i l i c s o l i d s i s Independent of the s o l i d used. From -this i t i s concluded that the s o l i d s are covered'by ah ad-sorbed water f i l m . Adhesion t e n s i o n s t u d i e s of s t i b n i t e (34.8.3) and 47 galena (35.8.3) indicate that the former changes slowly from a hydrophilic to an hydrophobic solid as i t ' is. • subjected to successive limited oxidations, and that-the latter Is either an organophilie or hydrophilic solid, depending on whether i t i s f i r s t wetted by an organic l i q u i d , or by water.1 The rate of displacement of water by pine oil'from min-eral surfaces has been measured by Barsky and Falconer ,(31.22.1), following the method of Bartell (27.11.1 j (27,25.1).. They found that reagents which produce flotation''cause the o i l to'-displace the water, whereas depressants have the re-verse effect. Wark (32.22.1) discussed this work and c r i t i -cized the conclusions, David and Curtis (32.11.1) have also studied wetting of minerals by water and organic compounds. Contact Angle as a Thermodynamic Quantity Wark (32.22.1) gives the following rela t i o n s h i p s : y;• - A F - T i g ^ 1 c o s - 0 ) " . A P = A H - T A S A S = (§±MJ\ -V dT /p. Tjg _ -liquid-gas interfacial tension B = Contact angle/ A H = heat of wetting 48 MISCELLANEOUS STUDIES OF WETTING Agnes Pockels ( . 3 3 . 1 2 . 2 ) - noted that the readiness with which a solid is wet by water decreases after drying. Metals and metalloids, crushed under water and then brought to the surface, exhibit certain water-repellent Characteristics, according to Dey-aux. ( 3 3 . 2 5 . 5 ) Luyken and Bierbrauer ( 2 9 . 2 5 . 1 ) measured the"wetting of minerals by the contact angle formed at a drop of sol-ution on the mineral surface. * ' Bartell, in connection with his work on adhesion ten-sion- of liquids against solids, has determined the. contact angle formed by liquid drops on solid surfaces ( 2 9 * 1 1 * 1 ) (32.8'*3)(34.1.1)(35.8.3), and has studied the wetting char-acteristics of t a l c , waxes and resins- ( 3 6 . 1 . 1 ) by this technique, tie found that water and organic liquids form contact angles on t a l c , waxes and resins, and concluded that the surface tension of these solids is low. He states that solids which are soft-and have a low surface tension are wetted less -readily by liquids than hard solids of higher surface, tension. 49 THEORIES OF COLLECTOR ACTION Introductory Several theories of c o l l e c t o r action have been pro-posed. Most workers now agree that the c o l l e c t o r or c o l -l e c t o r ion i s removed from solu t i o n by the mineral, with consequent a l t e r a t i o n of the mineral surface to make i t more hydrophobic. The mechanism of the a l t e r a t i o n i s not agreed upon* It 'is" thought to toe." eit h e r metathesis between negative ions of c o l l e c t o r and p o s i t i v e ions from the mineral:!' or ad-sorption of an unspecified nature. Chemical Theory 1 What has become known as the chemical theory of f l o t a -t i o n was introduced by Taggart, Taylor and K n o l l (50.3.1), and amplified i n l a t e r papers by Taggart and his associates (32.8.1)(34.3.6). In the f i r s t paper the generalization i s made that soluble c o l l e c t o r s react with minerals by meta-thesis between mineral cations and c o l l e c t o r anions; and that the formation of a water-repellent f i l m on.the mineralmakes i t - f l o a t a b l e , while the formation of,& water-avid f i l m makes i t non-floatable. I t i s further stipulated that the reaction of a xanthate with galena requires previous oxidation of the galena to form lead s u l f a t e . This mechanism was v e r i f i e d by the stoichiometric balance between the xanthate ion abstrac-ted by the galena and the ions, derived from galena, which 50 appear 1B s o l u t i o n ! by the non-change i n potassium ion. con-c e n t r a t i o n i n s o l u t i o n ; by t h e n o n - d e t e c t i o n of s u l f i d e ion-i n s o l u t i o n ; by the r e c o v e r y of l e a d xanthate from the sur-f a c e of t r e a t e d galena; and by the poor f l o a t a b i l i t y of f r e s h g a l e n a . Opponents of the chemical t h e o r y , however, have noted, t h a t the f l o a t a b i l i t y of a n g l e s i t e ( n a t u r a l l e a d s u l f a t e ) I s - l e s s than the f l o a t a b i l i t y of .galena; t h a t c e r t a i n "miner-a l s such as g o l d (34.5.1)(33.8.3), s u l f u r and g r a p h i t e (35.8,1) (37.8.1)," which do'not i o n i z e i n the u s u a l sense, are c o l l e c t e d by xanthates; and t h a t xanthates are more s o l -u b l e than the corresponding s u l f i d e s , r e n d e r i n g improbable the suggested r e a c t i o n in. which a s u l f i d e Is r e p l a c e d by a xanthate.' Taggart (34.3.6) does not b e l i e v e t h a t g o l d f l o -t a t i o n d i s p r o v e s the chemical t h e o r y , as he was unable t o f l o a t -pure g o l d u n t i l i t had been t r e a t e d by a d i s s o l v i n g agent; presumably t o p r o v i d e g o l d ions r e q u i r e d by the chemical t h e o r y . He e x p l a i n s the a c t i v a t i n g e f f e c t of sod-ium hydroxide on e a s s i t e r i t e , and of s u l f i d e s on o x i d e s , as b e i n g due to s i m i l a r e f f e c t s . Cox and Wark (33.8.2) c o n t r a s t e d the chemical theory to a d s o r p t i o n t h e o r i e s , and p o i n t e d out t h a t -a-true chemical theory i m p l i e s a d s o r p t i o n can.only.occur when t h e - s o l u t i o n i s s a t u r a t e d w i t h r e s p e c t t o the adsorbed compound. Gaudin (32.25.5)(54.5.5A) takes an int e r m e d i a t e s t a n d . He-believes .that chemical r e a c t i o n i s r e s p o n s i b l e f o r t h e c o l l e c t i o n of some m i n e r a l s , (e.g. a z u r i t e by amyl xanthate, 51 which forms, a v i s i b l e c o a t ) ; t h a t metathesis i s the mechan-ism, at l e a s t i n part,;'for c o l l e c t i o n of gal e n a , c h a l c o c i t e and c o v e i l i t e b y xanthates; but that the o r i g i n a l r e a c t i o n i s f o l l o w e d by decomposition or o x i d a t i o n of the c o a t i n g , so that, the coat d u r i n g f l o t a t i o n may or may not be' base metal x a n t h a t e . He s t a t e s t h a t - c o l l e c t i o n of s p h a l e r i t e ' by phenyl h y d r a z i n e , and mono-isoamyl' amine j and of chalcocite...by. mono-isoamylamine and methyl q u l n o l i n e i s not e x p l a i n a b l e on the b a s i s of -insolublet compound f o r m a t i o n s A mechanism f o r the f l o t a t i o n of p y r i t e , i n accordance w i t h the chemical t h e o r y , i s s t a t e d by Taggart et a l ( 3 4 . 5 . 6 ) : P y r i t e i s o x i d i z e d '-to f e r r i c s u l f a t e ; which, by metathesis . w i t h xanthate i o n , forms f e r r i c x a nthate. . . A d s o r p t i o n Theory. '" Pahrenwald* s e a r l y work d e a l i n g w i t h o i l f l o t a t i o n :(24^3.1)- l e d him t o b e l i e v e t h a t the h e t e r o p o l a r o i l s used' as reagents were adsorbed, p o s s i b l y as o r i e n t e d f i l m s , on the m i n e r a l s u r f a c e , and t h a t a d s o r p t i o n took p l a c e when the m i n e r a l p a r t i c l e s and o i l d r o p l e t s c a r r i e d u n l i k e charges. As e a r l y as 1921, Kyskewitsch (21.25.2) s t a t e d , "the d i f f e r -ence of a d s o r p t i o n oh gangue m i n e r a l s and m e t a l l i c minerals i s due t o d i f f e r e n c e of s t r u c t u r e . The space l a t t i c e of gangue m i n e r a l s i s made up of molecules; t h a t o f " m e t a l l i c m i n e r a l s of atoms. The m e t a l l i c minerals t h e r e f o r e have a r e s i d u a l v a l ence or unbalanced s t a t i c f o r c e at the s u r f a c e which i s r e s p o n s i b l e f o r a d s o r p t i o n " . 52 B e r l and a s s o c i a t e s (25.25.1)(24.12.1) were able t o f l o a t quartz by the use of dyes, and conclude that adsorption of the dye at the m i n e r a l surface forms a hydrophobic coating which renders the m i n e r a l f l o a t a b l e . They s t a t e that there i s no r e l a t i o n between the s i g n of the charge on a mineral and i t s f l o a t a b i l i t y . Gaudin (28.3.1) p o s t u l a t e d that xanthates adsorbed at mineral surfaces t o form non-Daltonlan compounds. Schaum and a s s o c i a t e s (32.12.3) s t a t e d that c o l l e c t i n g a c t i o n i s due to i c n l c a d s o r p t i o n . B a r t e l l , M i l l e r and Alray (33.1.1) discussed the a p p l i c a t i o n of the Gibb's adsorption theorem t o s o l i d - l i q u i d i n t e r f a c e s . Adsorption of the c o l l e c t o r at a m i n e r a l surface i s thought by Cox and Wark (35.8.2)(54.5.2) to r e s u l t i n a c l o s e l y packed f i l m , w i t h the a l k y l groups o r i e n t e d outward. Gaudin (54.3.5A) discussed the adsorption theory, and noted that there i s doubt as t o whether the adsorbed e n t i t y i s x a n t h i c a c i d or a l k a l i xanthate molecules; xanthate i o n ; base metal xanthate molecule; or xanthate o x i d a t i o n products. Adsorption t h e o r i e s , i n g e n e r a l , have been c r i t i c i z e d by Taggart and associates (34.3.6) as not e x p l a i n i n g the unchan-ged potassium i o n c o n c e n t r a t i o n , or the recovery of l e a d xanthate from t r e a t e d m i n e r a l s . T h e i r conception of adsorp-t i o n i s based on the Gibb's equation. De Boer and Custers (34.25.4) have attempted to c a l c u -l a t e the energy of adsorption by c o n s i d e r i n g i t t o be the sum of the van der Waal's and e l e c t r o s t a t i c f o r c e s . They 53 show t h a t molecules w i t h a h i g h - d l p o l e 1 moment are l a r g e l y adsorbed e l e c t r o s t a t i c a l l y , w h i le van der Waal's f o r c e s a c t , w i t h the non-p<3lar p o r t i o n of the adsorbed mo l e c u l e . Wark and Cox (35.8.1), on the b a s i s of t h i s work, c o n s i d e r t h a t the unbalanced f o r c e s , p a r t i c u l a r l y e l e c t r o s t a t i c f o r c e s , at s o l i d s u r f a c e s , act e i t h e r on d i p o l e s or d i s s o c i a t e d ions of the c o l l e c t o r ; ' s i n c e c o l l e c t o r s have e i t h e r a h i g h d l p o l e moment, or a h i g h degree of d i s s o c i a t i o n . S p e c i f i c a l l y , on g r a p h i t e , xanthate i o n i s adsorbed w i t h a surrounding l a y e r of potassium i o n s , and every second carbon atom of the g r a -p h i t e s u r f a c e , c a r r y i n g an unshared e l e c t r o n , should be able t o adsorb a xanthate i o n , They c o n s i d e r that the f o r c e b i n d -i n g e t h y l xanthate i o n t o l e a d s u l f i d e - i s s t r o n g e r than t h a t -b i n d i n g i t t o l e a d e t h y l xanthate, and th a t the c o n c e n t r a t i o n of xanthate ions i n . e q u i l i b r i u m w i t h s u c h d i f f e r e n t ; s u r f a c e s must a l s o be d i f f e r e n t . ' 0 s t w a l d i s'. The Cry Wolfgang Ostwald (32.12.1) i n t r o d u c e d the concept of " l i n e a r " , f l o t a t i o n , which i n v o l v e s a three-phase ( a i r - w a t e r -m i n e r a l ) l i n e a r contact;. as' c o n t r a s t e d ' to o i l ' ' f l o t a t i o n , , which i n v o l v e s o n l y a two-phase ( o i l - m i n e r a l ) c o n t a c t . Be s t a t e s that f i l m f l o t a t i o n uses d i p h i l i c c o l l e c t o r s such as o l e i c a c i d , w h i l e " l i n e a r " f l o t a t i o n uses- t r i p h i l l c c o l l e c -t o r s . A t r i p h i l l c c o l l e c t o r contains a c a p i l l a r y a c t i v e group, and groups w i t h a f f i n i t y f o r metal and f o r water r e s -p e c t i v e l y . He s t a t e d t h a t e t h y l dixanthogen i s not a c o l l e c -54 t o r , because, of the absence of a h y d r o p h i l i c group, wh i l e c a r b a n i l i d and t h i o u r e a l a c k c a p i l l a r y a c t i v e groups. Evidence i n support of Ostwald's Theory i s adduced by Ki n g (33,12.3) from observations w i t h n i c k e l dimethyl and diphenyl glyoximes and galena, Gstwald's Theory i s c o n t r a d i c t e d by photographic e v i -dence (32.12,2) which shows tha t the m i n e r a l t . as such, does not extend i n t o the a i r phase. The compounds s t a t e d by Ost-wald t o be n o n - c o l l e c t o r s , are' c o l l e c t o r s i n a l c o h o l i c s o l -u t i o n . Wark and Gox (33,8.4) have.also- c r i t i c i z e d Gstwald's Theory. E l e c t r i c a l Theories E a r l y explanations of f l o t a t i o n (15.25«2)(16.25*1) : (17.25,1) considered t h a t a i r - m i n e r a l adherence was due t o "di f f e r e n t e l e c t r i c a l ' c h a r g e s on these phase's. Gaudin (32,25,5) b e l i e v e s , however, th a t the e a r l y i n v e s t i g a t o r s confused the e l e c t r o s t a t i c charge on minerals w i t h the charge due t o the Helmholz double l a y e r , which e x i s t s around a i r - b u b b l e s , and notes t h a t the existence of e l e c t r o s t a t i c -.charges on p a r t i c l e s i n . an ore ;pulp presupposes the pulp i s a d i e l e c t r i c , which i s not the case. Pahrenwald (24.3.1) b e l i e v e d t h a t s e l e c t i v e o i l i n g of a mineral was the r e s u l t of fa v o r a b l e e l e c t r i c a l charges on -the O i l and on c e r t a i n m i n e r a l - p a r t i c l e s , and tha t f l o t a t i o n could be c o n t r o l l e d by r e g u l a t i n g the charge. He c o r r e l a t e d f l o c c u l a t i o n and p e p t i z a t i o n , , a s i n d i c a t i o n s of the r e l a t i v e 55 charge c a r r i e d by the p a r t i c l e s , to f l o t a t i o n and depression r e s p e c t i v e l y . Ridsdale E l l i s (US Pat. 1,425,185) agrees w i t h Fahrenwald*, and considers the,.function of chemical r e -agents i s t o c o n t r o l the si g n of the charge on p a r t i c l e s . Previous c o r r e l a t i o n between f l o c c u l a t i o n -and f l o t a t i o n : had been noted by Sulman (20.25.1), Edser (22.24.1) and Bartsch (24.25.1). R a l s t o n and Barker (31.22.3) commented on the e f f e c t o f . c o l l e c t o r s ©n f l o c c u l a t i o n i n p r a c t i c a l f l o t a t i o n . Fahrenwald (31.22.4) advanced the f a c t s t h a t s p h a l e r i t e i s weakly p e p t i z e d i n water,, s t r o n g l y i n d i l u t e sodium cyanide; quartz i s p e p t i z e d i n water; copper sulphate f l o c c u l a t e s a s p h a l e r i t e suspension i n sodium cyanide as f u r t h e r evidence f o r the connection between f l o c c u l a t i o n and f l o t a t i o n , and between p e p t i z a t i o n and w e t t i n g . . T a g g a r t , Taylor and Knoll.(30.3.1) o b s e r v e d ' t h a t ' p a r t i c -l e s i n Brownian movement do not f l o a t ; and noted that Brown-i a n mavement can be c o n t r o l l e d by the presence of reagents. These workers could not e x p l a i n c e r t a i n ©f t h e i r results by the k i n e t i c theory. T a g g a r t , i n a l a t e r review (32.8.1) however, o f f e r s an e x p l a n a t i o n f o r the p r e v i o u s l y observed e f f e c t s of reagents on the Brownian movement, which is not i n disagreement w i t h k i n e t i c t heory. Wark (32.22.1) b e l i e v e s t h a t d i s p e r s i o n , as such, i s no bar t o f l o t a t i o n ; but that the surface conditions which l e a d t o d i s p e r s i o n a l s o hinder f l o t a t i o n . Gaudin (32.25.5) takes the opposing view t o Fahrenwald, Taggart, et a l , and considers d i s p e r s i o n i s necessary f o r f l o t a t i o n . He c i t e s 56 the..practical, use of d i s p e r s i n g agents (such as sodium s i l i -cate) which produce cleaner concentrates and y i e l d higher r e c o v e r i e s . In. more recent work (54.3.6) Taggart concludes that f l o c c u l a t i o n i s Independent of f l o t a t i o n , but that par-t i c l e s i n Brownianmovement- w i l l not f l o a t because they are already wetted. Tikhonov (35.25.1) noted that xanthate changes the sign of the charge on a m i n e r a l , but does not consider t h a t e l e c -t r o s t a t i c charges can account f o r a l l f l o t a t i o n phenomena. Hecent work.by Shneerson (36.16.4) shows that xanthates i n -crease the r a t e of f l o c c u l a t i o n of malachite suspensions j and t h a t f l o c c u l a t i o n i s due to a d s o r p t i o n , and f i x a t i o n of p o l a r groups on the m i n e r a l . Mi seellaneous The o r i e s Volkova (35.12.5) has explained the f l o t a t i o n of asbes-tos and b a r i t e by assuming o r i e n t e d coagulation of powder p a r t i c l e s a t - a phase - boundary,. Hel'd (35.16.1) d i s t i n g u i s h e d three types of molecular a t t r a c t i o n i n f l o t a t i o n : (a) molecular adsorption (b) i o n i c a d s o r p t i o n , and (c) chemical r e a c t i o n . He s t a t e s that the type i s determined by the p r o p e r t i e s of the c o l l e c t o r , and the elements of the m i n e r a l c r y s t a l l a t t i c e . Shvedov (36.16.2) advanced a modified chemical theory f o r the r e a c t i o n of c o l l e c t o r s w i t h the products of semi-o x i d a t i o n of minerals-. 57 > DEPRESSIOT A depressor i s a chemical, used e i t h e r b e f o r e , or i n conjunction w i t h a c o l l e c t o r , t o decrease the recovery of a s p e c i f i c m i n e r a l . 'Acids - and - a l k a l i s may be c l a s s e d as depressors. T h e i r a c t i o n , however, has been considered under the heading of the e f f e c t of pH ©n c o l l e c t o r a c t i o n . Sodium cyanide i s used e x t e n s i v e l y t o depress sphaler-i t e . S oluble chromates are used t o lower the recovery of galena; and'lime i s sometimes employed t o depress p y r i t e . EVIDENCE OF DEPRESSION OBTAINED FROM FLOTATION TESTS AND PRACTICE Galena "The depressing e f f e c t of va r i o u s - cations (28.19.1-TP. 1) (29.8.1; on galena, which decreases through the s e r i e s ; Cr? Thf A l ? Cu? Fe? Hg? Eg] Ag} Pbf Cd? Co? corresponds roughly t o the i n s o l u b i l i t y of the s u l f i d e s formed by the c a t i o n s . Gaudin (32.25,5) terms t h i s c l a s s of depressant " t o x i c agents", because there i s no evidence of chemical r e a c t i o n between reagent and m i n e r a l . Oxi d i z e d galena (32.25.5) i s depressed by chromates, phosphates, t u n g s t a t e s , arsenates and a r s e n i t e s . Compounds of l e a d w i t h these anions a re, i n g e n e r a l , l e s s s o l u b l e than e i t h e r the o x i d i z e d coating on galena, or the l e a d s a l t of 58 th© c o l l e c t i o n u s e d 9 :' • Buchanan and Ghristmanm ( 2 7 . 2 . 1 ) from f l o t a t i o n t e s t s on pure galena*specimens, u s i n g as c o l l e c t o r s (1) p i n e o i l and potassium e t h y l xanthate (2) p h o s p h o c r e s y l i c reagent-, and (S) t h i o c a r b a n i l i d - o - t o l u l d i n e mixture; found that lime depressed galena'With a l l t h r e e c o l l e c t o r s , w h i l e sodium carbonate and cyanide were depressants only when u s i n g the t h i r d c o l l e c t o r ; Trusov ( 3 5 , 1 6 . 2 ) found t h a t galena i s t e m p o r a r i l y de-pr e s s e d by sodium hyposulfit©, but not b y . s u l f i t e or-thi©- ' s u l f a t e . P y r i t e The depressant a c t i o n on p y r i t e of lime ( 3 0 . 3 . 4 ) and of sodium cyanide ( 3 0 . 2 5 , 2 ) have been s t u d i e d . Buchanan and Christmann ( 2 7 . 2 . 1 ) found t h a t lime s t r o n g l y depresses p y r i t e at c o n c e n t r a t i o n s above 0 .75 gnu per l i t r e (pH 7 .0 or h i g h e r ) ; sodium carbonate up t o 4 gm. p e r - l i t r e has l i t t l e e f f e c t w i t h the f i r s t two c o l l e c t o r s ; but a t c o n c e n t r a t i o n s above 1 gm. per l i t r e has a marked d e p r e s s i n g a c t i o n when used w i t h the t h i r d c o l l e c t o r ; sodium cyanide i s a s t r o n g depressant at c o n c e n t r a t i o n s g r e a t e r than 1 gm. per l i t r e f o r the f i r s t , and g r e a t e r than 0 .25 gm. per l i t r e f o r the other c o l l e c t o r s . B r i g h t o n , Burgener and Gross ( 3 2 . 6 . 2 ) found that the de p r e s s i o n of p y r i t e i s p r o p o r t i o n a l t o the sodium cyanide c o n c e n t r a t i o n f o r a gi v e n s i z e of p a r t i c l e . Smaller p a r t i c l e s r e q u i r e a g r e a t e r c on cent r a t I on of cyanide t o e f f e c t the 59 same amount, of d e p r e s s i o n . Pure S p h a l e r i t e - d e p r e s s i o n by cyanide Gaudin (50.3.7) found t h a t sodium cyanide has no de-pressant a c t i o n on u n a c t i v a t e d s p h a l e r i t e when reagents are used which c o l l e c t u n a c t i v a t e d s p h a l e r i t e (e.g. amyl xan-t h a t e , t h i o c r e s o l , amyl mereaptan), Wark and Cox (34,3.4) do hot agree w i t h Gaudin. A c c o r f i l n g to Yamada (36.25,7) the e f f e c t of cyanide on the f l o a t a b i l i t y . of s p h a l e r i t e i s ve r y s l i g h t . . . ' A c t i v a t e d .Sphalerite - d e p r e s s i o n by cyanide P l o t at ion of s p h a l e r i t e , ' p o s s i b l y u n i n t e n t i o n a l l y a c t i -vated,: was 'studied by.Buchanan and Ghristmann (27.2.1), who found t h a t sodium cya n i d e , at c o n c e n t r a t i o n s g r e a t e r than 0.25 gms. p e r l i t r e , Is a s t r o n g depressant. ..If s p h a l e r i t e i s . i n t e n t i o n a l l y ' a c t i v a t e d by copper s u l f a t e , more cyanide is r e q u i r e d t o cause d e p r e s s i o n . , Gaudin (30.3.7) showed t h a t cyanide completely depresses c o p p e r - a c t i v a t e d s p h a l e r i t e , by d i s s o l v i n g the copper s u l f i d e c o a t i n g and removing the copper i o n from s o l u t i o n as u n d l s -s o c l a t e d •Gu(GN)5".ion. .• The d e p r e s s i o n by cyanide of s p h a l e r i t e i s l e s s than t h a t of p y r i t e , a c c o r d i n g t o B r i g h t o n , Burgener; and Gross (32,6.2). pH as 'a f a c t o r in d e p r e s s i o n was r e c o g n i z e d by Gaudin (29.10.1). Kraeber (30.25.2) has s t u d i e d the i n f l u -ence of cyanide on the f l o a t a b i l i t y of z i n c m i n e r a l s . necent work i n c l u d e s t h a t of Mi t r o f o n o v and Arashkevich (36.16.1), and Mantsev (37.16.2). The l a t t e r found t h a t 60 c o p p e r - a c t i v a t e d s p h a l e r i t e i s completely depressed, as evidenced from w e t t i n g diagrams, by 0,005$ sodium cyanide, when using' pofasslum iso-amyl xanthate as c o l l e c t o r . S p h a l e r i t e •» d e p r e s s i o n by reagents other than cyanide P a l l a n c h (28.3.2) showed t h a t s o l u b l e s u l f i t e s depress s p h a l e r i t e * but not g a l e n a . Trusov '(35.16.2) found, t h a t s p h a l e r i t e i s s l i g h t l y depressed by sodium h y p o s u l f i t e , but s t r o n g l y depressed by i t s decomposition products: s u l f i t e s and t h l o s u l f a t e s . . - ' H e l l s t r a n d (US Pat 1,469,042 - 1923) has patented the use of sodium : s u l f i d e as a'depressor for-'sphalerite"-.. \Slad-kov (36,16,3), as a r e s u l t of l a b o r a t o r y and p l a n t t e s t s on a l e a d - z i n c - c o p p e r - i r o n - g o l d o r e , con s i d e r s sodium s u l f i d e i s a b e t t e r s p h a l e r i t e depressant than cyanide* ' Buchanan and Christmann (27,2,1) found, t h a t lime de-presses s p h a l e r i t e s t r o n g l y w i t h the f i r s t , s l i g h t l y w i t h the second c o l l e c t o r they s t u d i e d ; and t h a t sodium carbonate depresses i n the r e v e r s e o r d e r . The depressant a c t i o n of sodium carbonate and z i n c s u l f a t e has been i n v e s t i g a t e d by M i t r o f o n o v (36.16.1). Mantsev (37.16.2), from a study of w e t t i n g diagrams, s t a t e s t h a t f e r r o c y a n i d e does not depress a c t i v a t e d z i n c s u l f i d e , and t h a t f e r r i c y a n i d e i s l e s s e f f e c t i v e than cyan-ide as a depressant. The a c t i o n of f e r r i c y a n i d e i s i n c r e a s e d below pH 5, and decreased above pH 9. S p h a l e r i t e i s depressed by potassium dichrornate (500 g. per t o n of ore) at a pH above 5.45; by t a n n i n (500 g. per 61 ton of ore) .at a pH afeove 5.25; and by potassium permangan-ate: (100 g. per t o n of o r e ) ; but i s not m a t e r i a l l y a f f e c t e d by z i n c s u l f a t e * or sodium c h l o r i d e (56.25.7) C h a l c o c i t e Tucker, Gates and Head (26.5.1) observed t h a t c h a l c o c i t e i s depressed by cyanide i n a l k a l i n e s o l u t i o n . A c c o r d i n g t o Gaudin (52.25.5), c h a l c o c i t e i s depressed by t h i o s u l f a t e , s u l f i t e , s u l f i d e , and f e r r o - and f e r r i c y a n i d e . C h a l c o p y r l t e C h a l c o p y r l t e i s depressed by o x i d i z i n g agents, cyanide, s u l f i d e , and lime (52.25.5), but not by h y p o s u l f i t e , s u l f i t e , or t h i o s u l f a t e (55.16.2). B r i g h t o n , Burgener and Gross (52.6.2) however, s t a t e t h a t sodium cyanide, up t o 1 l b . per to n of o r e , has no d e p r e s s i n g e f f e c t , . Recent work of/Yamada and a s s o c i a t e s (56.25,6) i n d i c a t e s t h a t 893 g. potassium cyanide per t o n of ore, at pH 7.8, causes a sudden decrease i n the f l o a t a b i l i t y of c h a l c o p y r l t e . :' Mis oel'ianeous m i h e r a l s . The work of Yamada and a s s o c i a t e s on a r s e n o p y r i t e (36.25.1), e n a r g i t e (56.25.2) , marmatlte (57,25.2) and s t i b -n i t e (37.25.3), i n d i c a t e s t h a t a r s e n o p y r i t e i s depressed by copper s u l f a t e below pH 5, and by sodium s u l f i t e , potassium cyanide, z i n c s u l f a t e and t a n n i n above about pH 5;. that . e n a r g i t e i s p o s s i b l y depressed by cyanide i n a l k a l i n e s o l -u t i o n ; t h a t marmatite i s depressed by z i n c s u l f a t e above pH 5.4, and i s a l s o depressed by t a n n i n ; t h a t s t i b n i t e i s de-pressed by copper s u l f a t e i n the pH range 3.5 to 7.0, and 62 toy t a n n i n in;th© rang© 6.2 t o 7.2. .- Gaudin s t a t e s t h a t c e r u s s i t e i s depressed by a l k a l i chromates (32.2§ .5). Belash (56.16.5) f i n d s t h a t sodium s u l f i d e depresses molybdenum I n • p a r t i a l l y . o x i d i z e d s u l f i d e ores of' molybdenum.• S u l f i d i z e d ' m a l a c h i t e (37.16.2), as evidenced by w e t t i n g diagrams, i s completely depressed by cyanide, b u t ' u n a f f e c t e d by f err®--- and f e r r i c y a n i d e s 63 :EXPERIMENTAL EVIDENCE FOR THE REACTION OF DEPRESSORS WITH MINERALS Changes In;a S o l u t i o n o f Depressor i n Coat a c t w i t h a ..Mineral ' , ( A b s t r a c t i o n of Depressor) g a l e n a . ; 'Galena does not •' a b s t r a c t c y a n i d e i o n from s o l u t i o n (32.6.2) P y r i t e " P y r i t e a b s t r a c t s cyanide In p r o p o r t i o n t o the- s o l u b l e I r o n p r e s e n t , and t o the exposed m i n e r a l s u r f a c e (32.6*2) C h a l c o p y r i t e " C h a l c o p y r i t e a b s t r a c t s more cyanide than s p h a l e r i t e , but l e s s than p y r i t e (32.-6.2.) S p h a l e r i t e The a b s t r a c t i o n of cyanide from, s o l u t i o n by s p h a l e r i t e i s g r e a t e r - t h a n t h a t by g a l e n a (30.3.2), but l e s s than t h a t by'., p y r i t e (32.6.2), s i n c e s p h a l e r i t e i s d i s s o l v e d by sodium cyanide (30.3.8). When s p h a l e r i t e a b s t r a c t s cyanide from s o l -u t i o n , the c o n c e n t r a t i o n o f s u l f a t e Ion i n s o l u t i o n Increases . (30.3.1). The a b s t r a c t i o n by oopperlzed s p h a l e r i t e Is g r e a t e r than by u n a c t i v a t e d m i n e r a l (30.3.7). Mokrushin and V i l l e s o v a (55.18.2) found t h a t copper s u l f i d e f i l m s , formed on the s u r f a c e of a copper s u l f a t e - s o l -u t i o n , adsorb c h l o r i d e i o n from sodium c h l o r i d e s o l u t i o n , and z i n c ions from z i n c s u l f a t e s o l u t i o n . They b e l i e v e t h a t the l a t t e r ions are h e l d as i f a z i n c atom had r e p l a c e d a copper 64 atom in the.>crystal l a t t i c e ; while chloride ions are held as i f "by true adsorption. Changes i n a Mineral In Contact with a Depressor Solution Tucker and associates •(25,3,1} (26.3.1) claim that cyanide produces a visi b l e change on the mineral surfaces they inves-tigated. -Previous experiments (20.25.2), and later attempts to duplicate Tucker ss findings (30.3.3)(30.3,7)(28.9.1 ) do not confirm-"the .presence of visible coatings. Tucker and associates also claim to, have analyzed the coating formed on sulfide minerals • by lime and cyanide, Gaudin (32.25.5) states that chromates produce a visible coating on oxidized, but not on fresh galena. 65 CONTACT ANGLE STUDIES OF DEPRESSION . The result's' of contact angle measurements, o u t l i n e d below,, are those- of Wark and Cox (34.5.2) (34.3.3) (34'.'3,4f '. ' (3 6 . 3 . 1 ) ( 3 6 9 8 9 l H 3 7 a 8 . 1 ) ( 3 8 . 3 . 1 ) , except where otherwise noted, - ' D'spyessloh by Cyanide; . . Galena Cyanide, i n t h e u s u a l c o n c e n t r a t i o n s , does not a f f e c t a i r - g a l e n a contact w i t h amy of the c o l l e c t o r s s t u d i e d . P y r i t e - pu r e ' m i n e r a l • Cyanide lowers the c r i t i c a l pH f o r p y r i t e . As the pH i s Increased, the c r i t i c a l cyanide c o n c e n t r a t i o n f o r p y r i t e and c h a l c o p y r l t e i s decreased. The-cyanide c o n c e n t r a t i o n - to prevent contact w i t h p y r i t e .and'chalcopyrite, when u s i n g the f o l l o w i n g c o l l e c t o r s ' t ' 1. sodium d i e t h y l d i t h i o p h o s p h a t e 2. potassium e t h y l xanthate 3. sodium d i e t h y l dithloear'bamate • 4. potassium isoamyl. xanthate 5. potassium dl-n-amyl dithlocarbamate (arranged In o r d e r of d e c r e a s i n g s o l u b i l i t y of t h e i r heavy metal,' s a l t s ) , ihOr.ease's In th© order 1 t o 5. ' The c o n c e n t r a t i o n of cyanide t o depress p y r i t e and c h a l -c o p y r l t e decreases s l i g h t l y as the temperature i s r a i s e d from 10 G0. t o 35°C. 66 I f t r i m e t h y l c e t y l ammonium bromide i s used as c o l l e c t o r , p y r i t e i s not depressed by cyanide, but i s depressed by cop-per s u l f a t e used w i t h cyanide; presumably by the e f f e c t of the c u p r l c y a n i d e i o n . P y r i t e - I n the presence of copper s u l f a t e - ' v I f copper s u l f a t e i s a l s o p r e s e n t , contact i s s i m i l a r l y prevented by cyanide w i t h a l l f i v e c o l l e c t o r s noted. With e t h y l xanthate, at- a g i v e n pH, the cyanide concen-t r a t i o n t© prevent contact w i t h p y r i t e i s l e s s when copper s u l f a t e i s p r e s e n t ; but w i t h c h a l c o p y r i t e , Is g r e a t e r . The c o n c e n t r a t i o n of sodium cyanide t o prevent a i r - p y r i t e c o ntact -in the presence, of copper s u l f a t e , and e t h y l xanthate, i n c r e a s e s r a p i d l y w i t h temperature t o a maximum at about 3 5 ° - 4G°C. I t i s suggested, t h e r e f o r e , t h a t the best separ-a t i o n of s p h a l e r i t e or c h a l c o p y r i t e from p y r i t e i s e f f e c t e d at- a l o w temperature and low-xanthate c o n c e n t r a t i o n . Sphaler1te . - pure Pure s p h a l e r i t e responds t o potassium di-n-amyl d i t h i o -carbamate and makes contact w i t h an a i r - b u b b l e . I f cyanide i s added t h i s response i s prevented. Mokrushin and Demenev ( 3 5 . 1 8 . 1 ) have found that p o t a s -sium cyanide decreases the contact angle t o zero at a z i n c s u l f i d e f i l m on the s u r f a c e of a l i q u i d . S p h a l e r i t e - a c t i v a t e d by copper s u l f a t e Cyanide makes c o p p e r - a c t i v a t e d s p h a l e r i t e non-responsive, and prevents a c t i v a t i o n of pure s p h a l e r i t e by copper compounds un l e s s the copper i o n c o n c e n t r a t i o n i s i n excess of the r a t i o 6 7 lCu:3CN. • • • j ; „' An increase' In the pH improves the action of cyanide. Temperature h a s * l i t t l e effect on the concentration of cyanide required to depress copper-activated sphalerite. When amyl xanthate is used as collector, in the presence Of copper sulfate, and at a given pH, a greater concentration of cyanide Is•required to prevent contact, than when ethyl xanthate is used as the collector. The effect Is greater If the pH Is high. Taggart and associates (34.3.6) noted that a sphalerit e particle, showing no contact• in a xanthate-cyanide-copper sulfate solution containing cyanide in excess of 3GN:lGu rati©, does not respond to. xanthate after i t is removed from the solution and washed* -3 "If copper sulfate is present, the cyanide and/or'alkali necessary to prevent contact with sphalerite is proportional to' the copper sulfate present. ; In the presence .of a collector, less cyanide' is required to prevent activation of fresh sphalerite, than to"deactivate sphalerite that has-been previously activated. ' The amounts approach each other as collectors are- used i n the order 5, 4, 3, 2, 1.) i n . the series given. With diethyl dithiophosphate, the amounts are. equal. This suggests that mc-re cyanide i s required to remove the copper xanthate, than to -remove the copper-hearing activation'film from .sphalerite. I f trimethylcetyl:ammonium bromide is used as'a collector sphalerite i s not depressed by cyanide, but i s depressed by a 68 mixture, of: copper s u l f a t e .and sodium cyanide j presumably by : the 'cupricyanide i o n , 0halc6pyr.ite (she a l s o P y r i t e ) I f copper s u l f a t e i s p r e s e n t , the amount of cyanide and a l k a l i , used e i t h e r ; alone or t o g e t h e r , which i s necessary to prevent contact on c h a l c o p y r i t e , i s p r o p o r t i o n a l t o the cop-p e r s u l f a t e p r e s e n t , 'Temperature has l i t t l e effect., oh. the c o n c e n t r a t i o n o f cyanide r e q u i r e d t o depress c h a l c o p y r i t e i n the presence of .copper s u l f a t e . . Mokrushin and Demenev (35.18,1) found t h a t potassium cyanide decreases, the c o n t a c t - a n g l e to zero a t a copper s u l -f i d e f i l m on the s u r f a c e of a l i q u i d . M i s c e l l a n e o u s .-minerals -C o v e l l i t e i s l e s s s e n s i t i v e t o cyanide than i s a c t i v a t e d s p h a l e r i t e . '• Marmatite, C h r i s t o p h i t e and s p h a l e r i t e , in the presence of copper sulfate', are e q u a l l y s e n s i t i v e t o cyanide and/or alkali. P y r r h o t i t e is not a c t i v a t e d by copper s u l f a t e " i n the same manner. . G r a p h i t e and charcoal are u n a f f e c t e d by sodium cyanide, w i t h e t h y l xanthate as c o l l e c t o r . T i n s t o n e i s depressed by a mixture of copper s u l f a t e and Sodium, cyanide, u s i n g t r i m e t h y l c e t y l ammonium bromide as c o l -l e c t o r . A r s e n o p y r i t e , l i k e g a lena, Is u n a f f e c t e d by cyanide i n the absence o f copper s u l f a t e . I n the presence of copper s u l -f a t e , the e f f e c t of cyanide i s s i m i l a r t o i t s e f f e c t on p y r i t e . 69 '.•.The c o n t a c t angle a t f i l m s of bismuth s u l f i d e formed on • t h e " s u r f a c e of a l i q u i d i s decreased by potassium cyanide, and" more s t r o n g l y decreased by s i l v e r n i t r a t e , a c c o r d i n g t o Mokrushin and Demenev (35.18.1) .•.Depression by Sodium. S u l f i d e . Sodium s u l f i d e depresses s u l f i d e s . The c o n c e n t r a t i o n of sodium s u l f i d e t o prevent contact i s a f u n c t i o n o f pH. HS" i o n i s the e f f e c t i v e depressant. There i s a c r i t i c a l HS" c o n c e n t r a t i o n f o r each m i n e r a l , j u s t s u f f i c i e n t ' t o prevent response t o a g i v e n potassium e t h y l xanthate c o n c e n t r a t i o n . •The xanthate c o n c e n t r a t i o n does not g r e a t l y a f f e c t ' t h e c r l t -ieai\HS""' c o n c e n t r a t i o n . Gopper s u l f a t e .influences the e f f e c t of sodium s u l f i d e ' oh •.•chalcopyrlte and galena, p r o b a b l y by removing the s u l f i d e Ion" as " c o p p e r s u l f i d e . *•'""''. i f t r l m e t h y l c e t y l 'ammonium bromide i s used as a c o l l e c t o r sodium s u l f i d e does not depress s p h a l e r i t e or p y r i t e . -D epression by other Reagents. Gopper s u l f a t e depresses pure p y r i t e , under c e r t a i n c o n d i t i o n s , w i t h sodium d i e t h y l a n d potassium dl-n-diamyl. d i t h i o c a r b a m a t e s . ' S i l v e r n i t r a t e reduces s l i g h t l y , the contact angle on f i l m s of copper s u l f i d e and z i n c s u l f i d e on t h e s u r f a c e ' o f a l i q u i d , a c c o r d i n g t o Mokrushin and Demenev (35.18.1) 70 5 Depression in -general The.• amount*of cyanide, at a given pH, to prevent contact with pure-minerals j, Increases through the series pyrite, chal-copyrite, bornit©, covellite, and ..chalcocite. . I f "copper sulfate is also present, the order is pyrite, sphalerite, chalcopyrite. The resistance of a given mineral ,t© depression by cyanide becomes greater, as collectors are used'which: form more insoluble salts of the metal i n the mineral. The; influence of cyanide ©n copper and-iron minerals appears to depend only upon the cyanide ion concentration. , There is a c r i t i c a l cyanide ion concentration for each min-eral, just' sufficient to prevent contact. The pH of the solution, i f below the c r i t i c a l value (see-Collectors.-Effect of. pM, on Contact Angle) Is Important only so far as It' controls the cyanide-ion concentration* If the pH-.'is . above the c r i t i c a l - value, contact i s Impossible, whether cyanide Is present or n o t . 71 THEORIES OF DEPRESSOR ACTION Dep r e s s i o n by Cyanide A c c o r d i n g t o Ince (30.3,2), cyanide forms an i n s o l u b l e metal Cyanide on z i n c and I r o n s u l f i d e s w i t h the-water-avid cyanogen groups outer-oriented,, He s t a t e s t h a t no simple cyanide o f . l e a d i s known, but t h i s ' - i s not confirmed by hand-books, •;..':•.:...-.. A t h e o r y of d e p r e s s i o n has been advanced by B e r l and Schmitt (30 912,3). Cnristmann (30.2,1) and ^ Buchanan" .(31.22,3A) b e l i e v e t h a t complex cyanide ions are adsorbed by s p h a l e r i t e , but may be r e p l a c e d by copper. They a l s o suggest (27.2,1) t h a t p y r i t e Is de p r e s s e d by complex I r o n cyanides formed by the r e a c t i o n o f cyanide and s o l u b l e iron,, Fahrenwald (31,22,4) b e l i e v e s t h a t d e p r e s s i o n i n v o l v e s p e p t i z a t i o n ; and t h a t cyanide forms' a z i n c cyanide f i l m on s p h a l e r i t e which does-•.not r e a c t w i t h the c o l l e c t o r . The de-s i r a b i l i t y of making e l e c t r o - o s m o t i c measurements on s p h a l -e r i t e i n the presence of sodium cyanide, t o determine I f i t becomes more p o l a r , Is suggested by Buchanan (31.22.4) Taggart. (32,8,1) contends t h a t depressors r e a c t w i t h m i n e r a l s u r f a c e s t o form adherent s a l t s which are l e s s s o l u b l e than the s a l t s of ;the c o l l e c t o r w i t h the metal i n the m i n e r a l . • Gaudin (32,25.5) s t a t e s t h a t the e f f e c t of cyanide on p y r i t e may c o n s i s t of c o a t i n g the m i n e r a l s u r f a c e , or i n the s o l u t i o n of an a c t i v a t i n g copper f i l m . B r i g h t o n , 72 Burgener and, Gross (32.6.2) conclude t h a t cyanide prevents m e t a l l i c xanthate f o r m a t i o n on the s u r f a c e s of p y r i t e and s p h a l e r i t e , e i t h e r by forming a p r e c i p i t a t e , a weak s a l t , or complex ion;• or by d i s s o l v i n g an e x i s t i n g f i l m of xanthate. Gaudin (30.3.7) s t a t e s that d e p r e s s i o n of c o p p e r - a c t i v a t e d s p h a l e r i t e i s due to s o l u t i o n of the copper-bearing c o a t i n g t o form u n d i s s o c i a t e d Cu(GN'};3~ i o n s . - . • , Taggart .and a s s o c i a t e s (34.3.6) advanced the theory t h a t cyanide e i t h e r d i s s o l v e s the copper s u l f i d e f i l m on ac-t i v a t e d s p h a l e r i t e or r e a c t s w i t h and removes the' copper ton " made a v a i l a b l e by o x i d a t i o n . Because the c o n c e n t r a t i o n of cyanide t o cause d e p r e s s i o n var i e s ' w i t h the c o l l e c t o r used, they s t a t e t h a t removal of a : c o p p e r s u l f i d e f i l m - c a n not be the e n t i r e mechanism. They i n c l i n e t o the view t h a t cyanide d i s s o l v e s a''-film of cuprous , xanthate from a c t i v a t e d s p h a l e r -i t e b u t - a l s o forms an i n s o l u b l e z i n c cyanide coat on pur© s p h a l e r i t e . They a l s o suggest t h a t d e p r e s s i o n of p y r i t e by cyanide Involves coating, the m i n e r a l s u r f ace w i t h a'complex c o p p e r - i r o n cyanide, s i n c e d e p r e s s i o n , i n .contact'angle meas-urements, appears t o be r e l a t e d t o c u p r i c y a n i d e i o n concen-t r a t i o n . Wark and Cox (34.3.2) adduced evidence to prove t h a t cyanide removes the copper compound formed on a c t i v a t e d s p h a l e r i t e , p r o b a b l y as a complex cuprocyanlde; and that p r e v e n t i o n of contact i n cyanide s o l u t i o n i s due t o p r e v e n t i o n of a d s o r p t i o n by the m i n e r a l of a f i l m of c o l l e c t o r , not due to f o r m a t i o n of a cyanide f i l m at the m i n e r a l s u r f a c e . T h e i r 73 recent work .(38.3.1) I n d i c a t e s t h a t the combination of cop-per; s u l f a t e and cyanide i s a more e f f e c t i v e p y r i t e depressor than e i t h e r compound used a l o n e , presumably by the a c t i o n of a complex copper cyanide Ion.. The combination i s p a r t i c u l a r l y e f f e c t i v e at low temperatures (10° C.) '•Depression-by Reagents other; than'Cyanide Chromates Gaudin (32.25.5) b e l i e v e s a l k a l i .chromates' depress c e r -r u s s i t e and galena by c o a t i n g them, w i t h l e a d chrornate, which i s l e s s s o l u b l e than the e x i s t i n g coat on the m i n e r a l (e.g. l e a d c a r b o n a t e ) . I n t h i s way they cause the m i n e r a l t o r e s i s t the a c t i o n of c o l l e c t o r s . Taggart-and a s s o c i a t e s (34.3 .6) suggest a s i m i l a r mechanism f o r the d e p r e s s i o n of galena by chromates, tout p o s t u l a t e t h a t the chrornate may a l s o oxidize.-an e x i s t i n g c o l l e c t o r f i l m . Lime R a l s t o n (30,3.4) showed t h a t p y r i t e r e a c t s w i t h 11m© to form s o l u b l e s u l f i d e s and t h i o s u l f a t e s , which are then o x i -d i z e d to s u l f a t e s . He c o n s i d e r s that the o x i d a t i o n products cause d e p r e s s i o n . Gaudin (32.25.5) suggested t h a t lime.may d i s s o l v e p y r i t e to some extent; at the same time c o a t i n g the m i n e r a l w i t h e f f e c t i v e d e p r e s s a n t s . S u l f i t e s ' . P a l l ah eh (28*3.2) b e l i e v e s t h a t s u l f i t e s depress s p h a l -e r i t e i n the presence of galena by forming a z i n c s u l f i t e c o a t i n g on the z i n c but not on the l e a d m i n e r a l . . 74. Mis c e l l a n e o u s Reagents ; The a c t i o n of reagents such as aluminium and chromium s a l t s i n i n h i b i t i n g f l o t a t i o n i s a s c r i b e d , by Gaudin (32„25.5) t o h y d r o l y s i s of the reagent, w i t h the f o r m a t i o n of c o l l o i d a l hydroxides which adhere i n d i s c r i m i n a t e l y t o the m i n e r a l s u r f a c e s . . . '. 75 ACTIVATION An a c t i v a t o r Is a reagent, used w i t h a g i v e n m i n e r a l and c o l l e c t o r t o cause the m i n e r a l , otherwise u n f l o a t e d , t o be f l o a t e d by the c o l l e c t o r . The most common -example of t h i s c l a s s of reagent Is copper s u l f a t e , used as an a c t i v a t o r f o r s p h a l e r i t e . E t h y l xanthate does not c o l l e c t s p h a l e r i t e u n t i l the m i n e r a l has been t r e a t e d w i t h an a c t i v a t o r such as copper s u l f a t e . In the s e p a r a t i o n of galena from s p h a l e r i t e , g a l e n a i s f i r s t f l o a t e d away from,cyanide-depressed s p h a l e r i t e . Copper s u l -f a t e i s then added t o a c t i v a t e the s p h a l e r i t e and'allow I t to be f l o a t e d . '' EVIDENCE OF ACTIVATION OBTAINED FROM FLOTATION TESTS AND PRACTICE P y r i t e Although Gaudin (32.25.5) s t a t e d t h a t pure p y r i t e i s a c t i v a t e d by s o l u b l e copper,- contact angle measurements by Wark and Cox (38 . 3 . 1 ) I n d i c a t e t h a t , under no circumstances, i s pure p y r i t e a c t i v a t e d by copper s u l f a t e . Recovery of p y r i t e , which has been depressed by l i m e , sodium carbonate, or sodium cyanide, i s enhanced by copper s u l f a t e w i t h e t h y l x a n t h a t e , but not wit h TT mixture or phos-p h o c r e s y l i c reagent as c o l l e c t o r s (27.2.1). Depressed p y r i t e i s a p p a r e n t l y a c t i v a t e d by s o l u b l e s u l f i d e s , or by an a c i d 76 c i r c u i t (32.25.5) S p h a l e r i t e T h e , a c t i v a t i o n of s p h a l e r i t e by c o p p e r ' s u l f a t e has been s t u d i e d by Buchanan and Christmann (27.2.1) and by Gaudin and a s s o c i a t e s 128.19.1—TP 1 & TP 7 ) . The l a t t e r found t h a t s p h a l e r i t e i s a c t i v a t e d by s a l t s of metals whose s u l f i d e s are l e s s , s o l u b l e i n water than z i n c s u l f i d e ''(e':.g.- s i l v e r , copper, mercury, cadmium, and l e a d ) ; t h a t copper s u l f a t e widens the pH zones of h i g h e s t recovery; and, w i t h c e r t a i n c o l l e c t o r s , a l s o i n c r e a s e s the r e c o v e r y . R a l s t o n and Hunter ( 3 0 . 3 . 6 ) noted t h a t cuprous and c u p r i c s a l t s are e q u a l l y e f f e c t i v e a c t i v a t o r s . They c o r r e l a t e the a c t i v a t i n g e f f e c t of a g i v e n metal i o n to the p o s i t i o n of the metal i n the e l e c t r o m o t i v e s e r i e s . Prom copper t o s i l v e r , a c t i v a t i o n d e creases. Lead, cadmium and z i n c are d e p r e s s o r s . They a l s o noted t h a t copper o l e a t e s , r e s i n a t e s and x a n t hates, when added as such t o a f l o t a t i o n p u l p , are n o n - e f f e c t i v e as a c t i v a t o r - c o l l e c t o r s . M i t r o f o n o v and,Arashkevich ( 3 6 . 1 6 . 1 ) have s t u d i e d the e f f e c t of copper s u l f a t e on the f l o a t a b i l i t y of s p h a l e r i t e . • In the presence of copper s u l f a t e ( 5 0 0 g. CuSO^.SHgO per ton of ore) s p h a l e r i t e i s completely recovered i n the pH range 1.3 t o 11.65 a c c o r d i n g to Yamada (36.25.7) M i s c e l l a n e o u s s u l f i d e m i n e r a l s O x i d i z e d s u l f i d e ores of molybdenum (36.16.5) are a c t i -vated by treatment w i t h copper s u l f a t e f o l l o w e d by sodium s u l -f i d e . i t i s presumed t h a t a copper s u l f i d e c o a t i n g i s formed. 77 Marmatite i s a c t i v a t e d by copper- s u l f a t e i n the pH range 2 to 11; by z i n c s u l f a t e i f the pH i s below 5. Above pH 5.4 z i n c s u l f a t e aots as a depressor (37.25.2) S t i b n i t e Is a c t i v a t e d by Pb0(Ac)g i n the pH range 6.5 to 6.8 (37.25.3) O x i d i z e d m i n e r a l s M a l a c h i t e i s a c t i v a t e d by l e a d s a l t s (28.19.1 - TP 9 ) , c e r u s s i t e by s o l u b l e s u l f i d e s (32.25.5), presumably by coat-i n g the" m i n e r a l w i t h l e a d s u l f i d e . ifron-metallic m i n e r a l s Gal.cit.e, a c t i v a t e d by copper and l e a d i o n s , w i l l respond t o soap c o l l e c t o r s (34.6.3). 78 .' EXPERIMENTAL EVIDENCE FOR THE REACTION OF ACTIVATORS WITH MINERALS' '* ".il "-j I 'lli - ' I ' II' Changes'' I n "a. :So"Iut'loh of'. .AVblvat or i n Contact' w i t h a M i n e r a l .(AbstractIon of A c t i v a t o r ) Various- i n v e s t i g a t o r s (25.6 .1) (2.4.3.1) (26.5.1) have shown t h a t c o p p e r s u l f a t e . i s ' a b s t r a c t e d - from s o l u t i o n by sphalerite„ At the same: time a c o a t i n g of copper s u l f i d e . Is formed on t h e ' m i n e r a l and the- c o n c e n t r a t i o n of z i n c . i o n i n s o l u t i o n i n c r e a s e s . The a b s t r a c t i o n of copper s u l f a t e by pure m i n e r a l s (30*3,5).increases i n the order; p y r i t e , c h a l -c o p y r i t e , " s c h i s t , and s p h a l e r i t e . Ihce (30.3.2) found t h a t more copper s u l f a t e 1 ' i s " . a b s t r a c t -ed by c y a n i d e - t r e a t e d s p h a l e r i t e , than by the p u r e / m i n e r a l . -.'• The a b s t r a c t i o n of metal ions from s o l u t i o n by s i l i c a t e s has been noted toy Gaudin (32,25,5). Such metal-coated s i l i -cates are a c t i v a t e d towards a soap c o l l e c t o r i f the metal coat forms an i n s o l u b l e soap w i t h the c o l l e c t o r . Changes i n a M i n e r a l i n Contact w i t h a n . A c t i v a t o r . S o l u t i o n . Rogers (11.25.1) and Tucker and Head (25.3.1) have observed v i s i b l e coatings on copper ,.sulfate-treated. s p h a l e r -i t e , but Ince (30.3.2), Mitrofenoff- ?(28.9.1) and R a l s t o n , et a l (30.3.5) were unable t o d u p l i c a t e t h e i r r e s u l t s . Gaudin (30.3.7) found that s p h a l e r i t e r e a c t s r a p i d l y , at f i r s t , w i t h c u p r i c n i t r a t e i n a c i d s o l u t i o n t o form a t h i n 79 c o a t i n g of c u p r i c s u l f i d e , but t h a t the r a t e decreases w i t h the" time of r e a c t i o n . He noted (32.25.5) that the c o a t i n g formed on s p h a l e r i t e by the a c t i o n of copper s u l f a t e i s v i s i b l e i f h i g h temperatures are employed. A v i s i b l e c o a t i n g (32,25,5) i s formed by sodium s u l f i d e on c e r u s s i t e . Although Wentworth (10,6.1) was unable t o "detect any s u r f a c e a l t e r a t i o n he found t h a t the c o n d u c t i v i t y of s p h a l e r i t e i n c r e a s e d ' a f t e r treatment w i t h copper s u l f a t e . I t - i s . g e n e r a l l y considered (25.19.2)'f26,3.1) (28.19.1--TP 7)(30.3.5)(30.3.6) t h a t the c o a t i n g formed by copper s u l f a t e on s p h a l e r i t e i s c u p r i c s u l f i d e , sometimes r e f e r r e d t o as e o v e i l i t e . Gaudin (30.3.7) s t a t e d t h a t the coating"' has been shown to c o n t a i n copper, and t o be n o n - r e a c t i v e toward s i l v e r n i t r a t e . I t Is presumed t o be c o v e l l i t e oh the b a s i s of the demonstrated r e a c t i o n ; ZnS -t- Cu**-* GuS + Zn** Taggart (32,8,1) takes an opposing.view, a p p a r e n t l y without p r e s e n t i n g experimental evidence f o r the c o n t e n t i o n , t h a t the c o a t i n g c o n s i s t s of cuprous s u l f i d e w l l o h i s subsequently o x i d i z e d . Because n a t u r a l c o v e l l i t e i s d i f f i c u l t t o f l o a t , Beck (34.25.1J suggests that the f i l m formed i s a mixture of c u p r i c and cuprous s u l f i d e s and s u l f u r , r a t h e r than c o v e l l i t e , and that f r e e s u l f u r i s the a c t i v a t o r . Kamenetzi (54.25.2) found t h a t 0.01 N s i l v e r n i t r a t e r e a c t s v/lth such m i n e r a l s u r f a c e s as c h a l c o p y r l t e , p y r i t e , galena, c o v e l l i t e , o r p i -ment, and s p h a l e r i t e , to p r e c i p i t a t e Ag gS and throw s u l f i d e i n t o s o l u t i o n . 80 Ravitz xand wall (34.8.1), assuming t h a t copper s u l f a t e forms cupric s u l f i d e on s p h a l e r i t e , found the concentration of copper s u l f a t e to give the best f l o t a t i o n recovery i s that required to form a monomolecular f i l m on the surface of the sphalerite. They noted that the abstraction from the s o l -utions used i n p r a c t i c e i s i n excess of t h i s amount. On the b a s i s of Zwicky fs theory of mosaic c r y s t a l structure (29.25.3) (30 g25^3 ;)f33,13»l), they e x p l a i n the f a c t ' t h a t smaller" p a r -t i c l e ' s r e q u i r e l e s s copper s u l f a t e than i s r e q u i r e d to form a ; moh©molecular f i l m , i n order to e f f e c t the'same f l o t a t i o n recovery as attained w i t h large p a r t i c l e s . 81 CONTACT ANGLE STUDIES OF ACTIVATION The r e s u l t s o f contact angle measurements, o u t l i n e d below, are those of Wark and Cox (34.3*3)(34.3.4)(36.3.1) (36.8.2)(37.8.1)(38.3.1). Copper s u l f a t e a c t i v a t e s S p h a l e r i t e and a c t i v a t e s galena;above i t s c r i t i c a l pH. I t i s without e f f e c t on the response of pur© p y r i t e , g r a p h i t e , o r c h a r c o a l , t o potassium e t h y l xanthate,' .Copper s u l f a t e i s a more e f f e c t i v e a c t i v a t o r f o r s p h a l e r i t e i n n e u t r a l c y a n i d e - f r e e s o l u t i o n than i n an ' a l k a l i n e - s o l u t i o n . c o n t a i n i n g cyanide. Copper s u l f a t e , i n combination w i t h cyanide, depresses, r a t h e r than a c t i v a t e s p y r i t e . S a l t s of such metals as p l a t i n u m , g o l d , bismuth, mer-cury, s i l v e r , copper, cadmium, l e a d , cerium, antimony • and a r s e n i c , a c t i v a t e s p h a l e r i t e , so t h a t i t w i l l respond"to potassium e t h y l x anthate. T h a l l i u m and c o b a l t s a l t s have a s l i g h t a c t i v a t i n g tendency, w h i l e s a l t s of t i t a n i u m and t i n show none. In g e n e r a l , those metals which are e f f e c t i v e a c t i v a t o r s form s u l f i d e s less-, s o l u b l e than z i n c s u l f i d e , while the n o n - e f f e c t i v e metals form s u l f i d e s which are more s o l u b l e . However, t h a l l i u m s u l f i d e Is r e p o r t e d more s o l u b l e , and stannous s u l f i d e as l e s s s o l u b l e than z i n c s u l f i d e . These metals are a p p a r e n t l y exceptions t o the g e n e r a l i z a t i o n . S p h a l e r i t e , depressed by sodium s u l f i d e , may be a c t i -vated by copper s u l f i d e , i f the copper s u l f a t e i s i n s t o i c h i o -m e t r i c excess of the sodium s u l f i d e . C o n t r o l l e d concentrations 82 of sodium s u l f i d e a c t i v a t e a n g l e s i t e and c e r u s s i t e , presum-a b l y by c o a t i n g the m i n e r a l s w i t h a l e a d s u l f i d e f i l m , so t h a t they w i l l r e s p o n d to a lower c o n c e n t r a t i o n of xanthate. Excess sodium s u l f i d e , however, prevents response, i n c e r t a i n cases sodium phosphate may be s u b s t i t u t e d f o r sodium s u l f i d e as an a c t i v a t o r f o r these m i n e r a l s . 83 THEORIES OF ACTIVATOR ACTION A l l t h e o r i e s f o r the a c t i v a t i o n o f • s p h a l e r i t e by copper s u l f a t e are B a s i c a l l y the same. They p o s t u l a t e the f o r m a t i o n , on the s p h a l e r i t e s u r f a c e , o f a c o p p e r - c o n t a i n i n g coat'which w i l l r e a c t w i t h the c o l l e c t o r , whereas the u n a l t e r e d s p h a l e r -i t e s u r f a c e does not r e a c t . The v a r i o u s t h e o r i e s ; d i f f e r as to the composition of the c o a t i n g , and the mechanism by which i t i s formed. V a r i o u s t h e o r i e s have suggested, on the b a s i s of" the-r e a c t i o n : , ZnS -*•' : Ou** ^  OuS •*• Zn** that, the c o a t i n g i s e u p r i e s u l f i d e . As p o i n t e d out by R a l -ston., K i n g and T a r t a r o n (30.3.5) however, the m i n e r a l 'covel-i i t e , which i s c u p r i c s u l f i d e , Is d i f f i c u l t t o f l o a t . M i t r o f a n o f f (28,9.1)" suggested the formation,."in an. a l k a l i n e copper s u l f a t e s o l u t i o n c o n t a i n i n g cyanide, o f a c o a t i n g of h y d r a t e , cyanide or carbonate, f o l l o w e d toy the f o r m a t i o n o f the corresponding copper compounds, which r e a c t w i t h xanthate to form i n s o l u b l e copper xanthate. Ince (30.3.2) advanced the t h e o r y t h a t an I n s o l u b l e eup-r i e cyanide i s formed at the s u r f a c e Of c y a n i d e - t r e a t e d s p h a l e r i t e . 'Cyanide i o n i s thus removed, and f r e e s the z i n c • of the m i n e r a l t o r e a c t w i t h the c o l l e c t o r , Taggart (32.8.1) contended t h a t the cuprous s u l f i d e c o a t i n g f i r s t formed i s o x i d i z e d and then r e a c t s w i t h xanthate 84 t o form cuprous xanthate. The a b s t r a c t i o n of xanthate i o n , a n d * l i b e r a t i o n of s u l f a t e i o n i s evidence f o r such a r e a c t i o n . The a c t i v a t i o n o f c y a n i d e - t r e a t e d s p h a l e r i t e i s thought to be e f f e c t e d by the decomposition of z i n c cyanide, accompanied by the f o r m a t i o n of s o l u b l e cuprocyanide i o n s . Taggart and a s s o c i a t e s (54.5:.6) discuss* a c t i v a t i o n i n terms of the' chemi-c a l t h e o r y . • R a l s t o n , K i n g and• ..Tartaron • (30.5,5) noted that the f i l m formed by copper s u l f a t e on s p h a l e r i t e i s p r o b a b l y d i f f e r e n t In n a t u r e from t h a t on p y r i t e , because d i s p l a c e d z i n c i s s o l u b l e , while: i r o n i s I n s o l u b l e i n a l k a l i n e s o l u t i o n s . They co n s i d e r t h a t t h i s d i f f e r e n c e may account f o r the f a c t : t h a t copper s u l f a t e a c t i v a t e s s p h a l e r i t e t o a g r e a t e r extent than p y r i t e . 85 REFERENCES FOR BIBLIOGRAPHY I n the accompanying l i s t the r e f e r e n c e s have been num-- bered, according t o the f o l l o w i n g conventions; The f i r s t num-be r i n d i c a t e s the'year of p u b l i c a t i o n ; the second the j o u r n a l i n which the: a r t i c l e Is p u b l i s h e d ; and the t h i r d i s the se-quence number of the r e f e r e n c e to a ' p a r t i c u l a r j o u r n a l and year.* The two numbers on the r i g h t hand s i d e of a r e f e r e n c e . r e f e r t o the volume and page of Chemical A b s t r a c t s , respec-t i v e l y . The key numbers u s e d ' f o r V a r i o u s j o u r n a l s are as 'follows %--1, : J o u r n a l of the American Chemical S o c i e t y . 2. American' Cyanamid Company" P u b l i c a t i o n s 3 , P u b l i c a t i o n s of the American I n s t i t u t e of Mining and M e t a l l u r g i c a l Engineers 4. Canadian M i n i n g J o u r n a l ' 5 . P u b l i c a t i o n s of the Canadian I n s t i t u t e of Mining and M e t a l l u r g y 6, • E n g i n e e r i n g and M i n i n g J o u r n a l ; .7. Economic Geology 8• / J o u r n a l of P h y s i c a l Chemistry •9. M e t a l l und E r z - . 1 0 , Mining -and M e t a l l u r g y .;;••' 1 1 . I n d u s t r i a l and E n g i n e e r i n g Chemistry ::'.:,12'. K o l l b i d Z e i t s c h r i f t 13. P u b l i c a t i o n s of the U n i t e d S t a t e s Bureau of Mines 14. P u b l i c a t i o n s of Utah E n g i n e e r i n g Experiment S t a t i o n 86 15. Z e i t s c h r i f t f u r t e c h n i s c h e P h y s l k 16. V a r i o u s Russian P u b l i c a t i o n s : 17. Congress i n t e r n , mines metal g e o l . a p p l . 18. J o u r n a l of P h y s i c a l Chemistry (U.S,S.R.) 19. P u b l i c a t i o n s of the U n i v e r s i t y of Utah 20* M i t t . b e r g . Huttenmann, e t c . 21. Science 22. T r a n s a c t i o n s of the E l e c t r o - C h e m i c a l S o c i e t y 23. Z e i t s c h r i f t f u r angewandte Chemie 24. C o l l o i d Symposium 25. M i s c e l l a n e o u s P u b l i c a t i o n s • 1835.25.1 Z e i s e Ann. p h y s i k . Chem. Pogg. 35, 487; 1835 02.25.1 ON THE HEAT EVOLVED OR ABSORBED WHEN A LIQUID IS BROUGHT IN CONTACT WITH A FINELY DIVIDED SOLID Parks, G.J. P h i l , Mag. 4, 240j 1902 03. 8.1 THE COMPOSITION OF THE SURFACE LAYERS OF AQUEOUS AMYL ALCOHOL Benson, Miss J . Phys. chem. 7, 532; 1903 08.25.1 XANTHOGENIC ACID Ragg, M. Chem. Z t g . 32, 630; 1908 2:2547 08.25.2 XANTHOGENIC ACID Ragg, M. Chem. Z t g . 32, 654 and 677; 1908 2:2813 10. 6.1 ELECTKOSTATIC SEPARATION OF MINERALS IN ORES Wentworth Eng. Mining J . 90, 15; 1910 10.25.1 XANTHOGENIC ACID AND DIXANTHOGEN Ragg, M. Chem. Z t g . 34, 82; 1910 4:2104 87 11,25.1 13,25.1 14.25.1 Rogers Columbia Sen. Mines q t r l y . 32, 298; 1911 XANTHOKJENIC ACID AND THE KINETICS OP ITS DECOMPOSITION von Halban, H. and A. K i r s c h Z. p h y s i k . Ghem. 82, 326; 1913 15.25.1 15.25.2 16. 3.1 THE ELECTRIFICATION OF LIQUID-GAS SURFACES McTaggart, H.A. - P h i l . Mag, 27, 297; 1914 P h i l . Mag. 28, 367; 1914 WHY DO MINERALS FLOAT • R a l s t o n , 0 .C. Mi n i n g S c i . Press 111, 623; 1915 THE ELECTRICAL THEORY OF FLOTATION Bains Mining Sci'. P r e s s 111, 824; 1915 111, 883; 1915 AN EXPLANATION OF THE FLOTATION PROCESS Taggart, A.F., and F.E. Beach Tr a n s . A.I .M.E, 55, 547; 1916 7:2004 8 % 1898 8:3744 16.25.1 THE ELECTROSTATICS OF FLOTATION Mi n i n g S c i . Press 112, 375; 1916 16.25.2 THE CONSTITUTION OF LIQUIDS WITH SPECIAL REFERENCE TO SURFACE TENSION PHENOMENA Langmuir, I . • Ghem., Met. Eng. 15, 4 6 8 ; 1916 10; 3008 17.25.1 ELECTROSTATICS AND FLOTATION B l a c k " F l o t a t i o n " p. 200; Mining S c i . Press 1917 -18.25.1 XANTHIC ACIDS AND THE KINETICS OF THEIR DECOMPOSITION von Halban, H. and W. Hecht Z. Elektrochem. 24, 65; 1918 J . Chem. Soc. 114, 11-222; 13; 277 20.25.1 A CONTRIBUTION TO THE STUDY OF FLOTATION Sulman, H.L. • T r a n s . I n s t . Mining and Met... (London) 29,44; 1920 20.25.2 MICROSCOPIC EXAMINATION OF THE ORE MINERALS (Book) Davy, and Farnham - McGraw H i l l , 1920 88 21.25.1 SURFACE ENERGY AND ADSORPTION IN FLOTATION Fahrenwald, A.W. ; M i n i n g S c i . Press 125, 227; 1921 • 21.25.2 THE FLOTATION PROCESS OF ORE DRESSING Ryskewits ch Chem. Z t g . 45, 478; 1921 22. 3.1 SURFACE TENSION AND ADSORPTION PHENOMENA IN FLOTATION Taggart, A.F., and A.M. Gaudin T r a n s . A.I.M.E. p r e p r i n t 1185M; Sept. 1922 Tra n s . A.I.M.E. 68, 479; 1923 22.24.1 THE CONCENTRATION OF MINERALS BY FLOTATION Edser , E. 17: 715 4th Report B r i t . Assn. Ad. S c i . p.265; 1922 22.25.1 THE ELECTRIFICATION OF LIQUID GAS SURFACES McTaggart, H.A. P h i l , Mag. 44,. 386; 1922 22.25.2 MOLECULAR STRUCTURE AND THE PHYSICAL PROPERTIES OF LIQUIDS Edser , E. Report B r i t . Assn. Ad. S c i . p.40; 1922 17:659 25.25.1 THE FLOTATION PROCESS B e r l , E. and H. V i e r h e l l e r Z. angew.Ghem, 36, 161; 1923 17:3855 24. 3.1 SURFACE REACTIONS IN FLOTATION Fahrenwald, A.W. .. T r a n s . A.I,M.E. No.,1283M; Jan 1924 18:1104 24.12.1 THE FLOTATION PROCESS I . THE BEHAVIOR OF SILICIC ACID IN THE FLOTATION PROCESS B e r l , E . and W. Pfannmuller " K o l l o i d Z. 34, 328; 1924 . . ' . ' 18:2863 24.12.2 THE FLOTATION PROCESS I I . THE BEHAVIOR OF OXIDES, CARBONATES AND SULFATES IN THE FLOTATION PROCESS B e r l , E. and W. Pfannmuller K o l l o i d Z. 35, 54; 1924 18:5161 24.12.5 THE FLOTATION PROCESS I I I . THE BEHAVIOR OF ALUMINIUM OXIDES IN THE FLOTATION PROCESS B e r l , E. and W. Pfannmuller K o l l o i d Z. 55, 106; 1924 19: 561 24.19.1 FLOTATION OF A UTAH SULFUR ORE Sherman, H.C. Utah Eng. Exp. Stn B u l l . 17; 1924 89 24.25.1 24.25.2 24,25.3 25, 3.1 25. 6.1 25 ® X0 • 2 23.« 3 ® X 26. 5.1 26.12.1 2*7 © 2 © X 27. 3.1 27. 6.1 FOAM, Ba r t s e n , 0. Kol l o i d c h e m . B e i h e f t e 20, 1; 1924 19:1076 THE THEORY OF FOAM FLOTATION Bart&ch, 0. Kolloid c h e m . B e i h e f t e 20, 50; 1924 19:1077 THE ELECTRIFICATION OF LIQUID GAS SURFACES Mctaggart, H.A. Trans. Roy. Soc. Can. 18, III-129; 1924 EFFECT OF CYANOGEN COMPOUNDS ON THE FLOATABILITY OF PURE SULFIDE MINERALS Tucker, E.L., and R.E. Head Trans. A.I.M.E. No. 1487B; Aug 1925 19:3450 DEVELOPMENT AND OPERATION OF A 50-GRAM FLOTATION MACHINE Gates', J . F . , and L...K., Jacobsen Eng. M i n i n g J . P f e s s 119, 771; 1925 '. 19:2319 Gates , J .F., and L.K. Jacobsen Utah Eng. Exp. S t n . B u l l , 16;.1925 THJS EFFECT OF CYANOGEN COMPOUNDS ON THE FLOATABILITY OF PURE SULFIDE MINERALS Tucker, E.L.. > J . F . Gates and K.E . Head Mi n i n g Met. 7, 126| 1926 20:1376 SYNTHETIC TESTING FOn FLOTATION McLachlan, C.G. . B u l l , Can. I n s t . M i n i n g and Met. 19, 987; 1926 Trans. " " " " " 29, 251; 1926 FOAMING POWER AND SURFACE TENSION B a r t s c h , 0.. :Koll©id Z.: 38, :177i. 1926 : 20;311© THE EFFECT OF CERTAIN CHEMICALS ON THE ELOATABILITY OF GALENA, SPHALERITE AND PYRITE Buchanan, G.H. and L . J . Christmann American Cyanamld Co. T.P. 9; May 1927 FLOTATION MECHANISM. A DISCUSSION OF THE FUNCTIONS OF FLOTATION REAGENTS Gaudin, A.M. . A.I .M.E. - T.P. 4; 1927 21:3176 THE "WHY" OF FLOTATION Gaudin, A.M. -Eng. Mining J . 124, 1045; 1927 22: 934 90 27.11.1 DETERMINATION OP THE WETTABILITY OP A SOLID BY A 'LIQUID B a r t e l l , P.E. and H.J. Osterhof Ind. Eng. Chem. 19, 1277; 1927 22s 523 27.24.2 DETERMINATION OF THE NUMBER OP FREE ELECTRIC CHARGES ON AIR BUBBLES AND OIL DROPLETS DISPERSED IN WATER CONTAINING A SMALL AMOUNT OF CETYL SULFONIC ACID McBainy J.W.-and R.C. W i l l i a m s C o l l o i d Symposium Ann. 7, 104j Wiley, 1927 27.25.1 WORK OF ADHESION BETWEEN SOLID AND LIQUID PHASES B a r t e l l , F.E. and H.J. Osterhof Z. p h y s i k . Chem. 130, 715; 1927 22s 531 28. 3.1 FLOTATION MECHANISM. A DISCUSSION OF THE FUNCTIONS OF FLOTATION REAGENTS Gaudin, A.M. • " F l o t a t i o n P r a c t i c e " p 50, A.I.M.E. 1928 28. 3.2 THE ROLE OF SULFITES IN THE DIFFERENTIAL FLOTATION PLANTS OP THE TX.S. SMELTING AND MINING CO . Pa.llan.ch, R. A.. "• . ••"notation P r a c t i c e " p 78, A.I .M.E. 1928 28. 6.1 EARLY EFFORTS IN FLOTATION OF DRY MINERALS Wood, M.E. Eng. Mining' J. 126, 571; 1928 . 28. 9, Mitrofanoff, S . I . and A.S. Mitrofanoff - M e t a l l u . E r z 25, 644; 1928 28. 9.2 THE INFLUENCE OP ADSORPTION ON FLOTATION PROCESSES Pee t z , E. M e t a l l u. E r z 25, 494; 1928 23:2913 28.11.1 DEGREE OF WETTING OF SILICA BY CRUDE PETROLEUM OILS B a r t e l l , F.E. and 'F.L.-.: M i l l e r Ind. Eng. Chem 20,' 738; 1928 ./ -22:35-20; 28.19.1 FLOTATION FUNDAMENTALS: FLOATABILITY OF PURE MINERALS AND THEIR MIXTURES (iaudln, A.M., et a l 25:1188 Univ. Utah T e c h n i c a l Papers, i n c l u d i n g : P t . 1 T.P. 1 Gaudin, A.M., H . G l o v e r , M.S. Hansen and C .W. Orr 1 9 2 8 P t . 2 T.P. 3 Gaudin, A.M. and P.M. S or ens en, 1928 P t . 3 T.P. 5 Gaudin, A.M. and J.S. M a r t i n , 1929 P t . 4 T.P. 7 Gaudin, A.M., C.B. Haynes and E.G. Haas, 1930 P t . 5 T.P. 9 Gaudin, A.M. and A.E. Anderson, 1930 91 28.19.2 THE PREPARATION OF XANTHATES AND OTHER ORGANIC " THIOCARBONATES r o s t e r , L.S. Utah Eng. Exp. S t n . T .P. 2; 1928 29. 8.1 A STUDY OF THE EFFECT OF CERTAIN CATIONS ON THE FLOTATION OF GALENA T a y l o r , N.W. and H.B. B u l l J . Phys. Ghem 35, 041f 1929 '29. 9.1 INVESTIGATIONS ON THE RELATION BETWEEN ADSORPTION, WETTING AND FLOTATION .:.'». Luyken, W., and E-. B i e r b r a u e r • 'Metall u-. Erz 26,-197; 1929 ' 25:4911 29.10.1 THE INFLUENCE OF HYDROGEN-ION CONCENTRATION ON RECOV-ERY IN 'SIMPLE FLOTATION SYSTEMS Gaudin,A.M. ".' Mining Met. 9, ,191 1929 '" —-29.11.1 RELATION OF ADHESION TENSION TO "LIQUID ABSORPTION" B a r t e l l , F.E. and 0.H. Greager - Ind. Eng. Ghem 21, 1248; 1929 • 24: 7 6 6 29.15.1 WETTING AND ADSORPTION IN RELATION TO FLOTATION •Bierbrauer, E. v • . - ; Z* t e c h . Phys Ik 1©,139.; 1929 , 23:2913 29.24.1 ELECTROSTATICS OF FLOTATION B u l l , H.B. / . •• C o l l o i d Symposium 7, 115 j ' 1929 ' '24:4248 29.25.1 INVESTIGATIONS ON THE THEORY OF FLOTATION Luyken, W. and E. B i e r b r a u e r - M i t t . K a i s e r Wilhelm I n s t . , Eisenf'orsehung 1 1 , ' 57; 1929 . 25:2912 29.25.2 SOME SURFACE-CHEMICAL STUDIES CONTRIBUTING TO THE THEORY OF FLOTATION Takakuwa, T. 25:5370 Pro c . world Eng. Congr. Tokyo 1929. 35, 395; 1951 29.25.3 MOSAIC CRYSTALS Zwicky, P r o c . Nat. A c S c i . 15, 816; 1929 24:1005 29.25.4 THE TREND OF FLOTATION Weinig,.A.J. and I.A. Palmer 24•5006 Colorado School Mines q t r l y . v24 #4, 146 pp;l929 29.25.5 -rHE ADSORPTION OF OIL ON MINERAL SURFACES WITH SPECIAL REFERENCE TO FLOTATION Okada, J . 25:5570 P r o c . World Eng. Congr. Tokyo 1929 55, 367; 1931 92 30. 2.1 CHEMISTRY AND THE FLOTATION PROCESS Christmann, L . J . American Cyanamid Go. T.P. 17; Nov 1930 30. 3.1 CHEMIGAL REACTIONS IN FLOTATION Taggart, A . F . , T.C. T a y l o r and A.F. K n o l l 24:2404 A.I.M.E.—T.P. 312; 1930 Trans. A.I.M.JS., - M i l l i n g Methods (1930) 217 30. 3.2 A STUDY OF DIFFERENTIAL FLOTATION I n c e , C.R. • • A.I-.M.JS.--T .P. 195; 1929 Trans. A.I.M.E. . , M i l l i n g Methods (1930) 261 30. 3.3 EXPERIMENTS WITH FLOTATION REAGENTS Taggart, A.F., T.C. T a y l o r and O.R. Ince A.I.M.E.—T.P. 204; 1929 Trans. A.I.M.E., M i l l i n g Methods (1930) 285 30. 3.4 REDUCING AND OXIDIZING AGENTS AND LIME CONSUMPTION IN FLOTATION PULP R a l s t o n , O.C., L . K l e i n , C.R. K i n g , T.F. M i t c h e l l . 0.E. Young, F.H. M i l l e r and L.M. Barker A.I.M.E.--T.P. 224; 1929 a r a n s . A.I.M.E., M i l l i n g Methods (1930) 369 30. 3.5 COPPER SULFATE A S A FLO x A xION ACTIVATOR FOR SPHALERITE R a l s t o n , 0 .C., C.R, K i n g and F.X. T a r t a r o n A.I.M.E.—T.P. 247; 1929 24: 42 Tra n s . A.I.M.E., M i l l i n g Methods (1930) 389 30. 3.6 ACTIVATION OF SPHALERITE FOR FLOTATION R a l s t o n , O.C. and W.C. Hunter A.I.M.E.--T.P. 248; 1929 24: 42 Trans. A.I.M.E., M i l l i n g Methods (1930) 401 30. 3.7 THE EFFECT OF XANTHATES, COPPER SULFATE AND CYANIDES ON THE FLOTATION OF SPHALERITE Gaudin"-, A.M. Trans. A.I.M.E., M i l l i n g Methods (1930) 417 30. 3.8 THE EFFECT OF COPPER AND ZINC IN CYAN1DATION Leave r , E.S. and J.A. Woolf Trans. A.I.M.E., M i l l i n g Methods (1930) 536 30. 6.1 THE pH VALUE IN FLOTATION AND MAXIMUM PROFIT Hazen, H.L. Eng. M i n i n g J . 129, 458; 1930 24:3864 30.12.1 FLOTATION AND THE ELECTRICAL CHARGE ON PRECIPITATES Talmud, D. and N.M. Lutetian K o l l o i d Z. 50, 163; 1930 24:2355 93 30.12.2 FUNDAMENTALS OF FLOTATION WITH XANTHATES NO. 1 K © H e r m a n n , K and E, Bender K o l l o i d Z. 52, 240; 1930 24:5682 30.12.3 WETTING PHENOMENA ON SPHALERITE AND GALENA B e r i , E. and B. Schmitt K o l l o i d Z. 52, 333; 1930 24:5682 30.25.1 FLOTATION REAGENTS Holman, B.W. B u l l . I n s t . M i n i n g and Met. 314; 1930 25: 268 30.25.2 INVESTIGATIONS ON THE INFLUENCE OF THE IRON CONTENT OF ZINC BLENDES ON THEIR FLOATABILITY K r a e b e r , L . M i t t . K a i s e r Wilhelm I n s t . 12, 343; 1930 25:2082 30.25.3 EXPERIMENTAL EVIDENCE OF THE MOSAIC STRUCTURE OF BISMUTH SINGLE CRYSTALS Goetz, A. P r o c . Nat. Acad. S c i . 16, 99; 1930 24:2928 31. 1.1 COMPOSITION OF COPPER XANTHATE Matuszak, M . P . J . Am. Chem. Soc. 53, 4451; 1931 26: 433 :31. 3.1 Fahrenwald, A.W. A.I.M.E.--T.P. 416; 1931 31. 9.1 INFLUENCE OF TEMPERATURE UPON FLOTATION Huber-Panu, I . •Metall' u. E r z 28, -545; 1931 • 26:1221 31. 9.2 XANTHATES AS COLLECTORS S l e d l e r , P. M o t a l l u. E r z 28, 425; 1931 25:5882 31.16.2 PHYSICAL CHEMISTRY OF FLOTATION 3. INFLUENCE OF FLOTATION REAGENTS ON SELECTIVE WETTING AS CHAR-ACTERISTIC OF COLLECTING POWER L i o e t z, M.E. and M.M. Rimskaya T z v e t n u i e M e t a l 1931, 990 * 26:1882 31.22.1 DIFFERENTIAL WETTING EFFECTS IN FLOTATION Barsky, G. and S.A.Falconer 25:4824 Tra n s . Electrochem. Soc. p r e p r i n t 60; 1931 31.22.2 ON THE PHYSICAL CHEMISTRY OF FLOTATION F r e u n d l i c h , H. 25:4824 T r s n s . Electrochem. Soc. p r e p r i n t 60; 1951 94 31.22.3 FLOCGUL ATION AND FROTH QUALITY IN FLOTATION Ralston,'0.G. and L.M. Barker 25:4824 Trans. Electrochem. Soc. p r e p r i n t 60; 1931 31.22.3A Buchanan, G.H. T r a n s . Electrochem. Soc. p r e p r i n t 60, 93; 1931 31.22.4 SOLUBILITY, PEPTIZATION, WETTING AND FLOTATION Fahrenwald, A.W. 25:4824 Trans. Electrochem. Soc. p r e p r i n t 60, 311; 1931 31.25.1 ADSORPTION INTENSITY AND ITS IMPORTANCE IN TECHNICAL PROCESSES Traube, I . •Z. angew.. Chem. 44; 1931 , . 25:2616 32. 1.1 SURFACE RELATIONS OF POTASSIUM ETHYL XANTHATE AND PINE OIL NO. 1 De W i t t , C.C. and E.E. Roper J . Am. Chem. Soc. 54 y 444;- 1932 . '26:1840 32. 6.2 DEPRESSION BY CYANIDE IN FLOTATION CIRCUITS B r i g h t on, T.B.., G. Burgener and J » Gross "Eng.- Mining J . 133, 276; 1932 26:3758 32. 6.5 PERFECTION AND USE OF THE 50-GRAM FLOTATION CELL Hansen, M.S. Eng. Mining. J . 133, 28}.' .1932' 32. 8,1 MINERAL FLOTATION ffaggart, A.F. J . Phys. Chem. 36, 130; 1932 26:1221 32. 8.3 ADHESION TENSION B a r t e l l , r , E . and. C .E. Whitney ; j . Phys-.. Chem. 36, 3115; 1952 • 27rl255 32.10.1 BUBBLE ATTACHMENT IN FLOTATION Shepard, 0.C. Mining; Met. 13, 282; 1932 32.11.1 PREFERENTIAL WETTING OF SOLIDS BY LIQUIDS David, N.S. and H.A. C u r t i s i n d . Eng. Chem 24, 1137; 1932 26:5816' 32.11.2 DISPLACEMENT OF CRUDE OIL AND BENZENE FROM SILICA BY AQUEOUS SOLUTIONS B a r t e l l , F.E. and F.L. M i l l e r Ind. Eng. Chem. 24, 335; 1932 26:3366 95 32.12.1 THEORY OP FLOTATION Ostwald, Wo. K o l l o i d Z. 58, 179; 1932 26:2946 32.12.2 THEORY OF FLOTATION S i e d l e r , P., A. M o e l l e r and T. Reddehase K o l l o i d Z, 60, 318; 1932 26:5884 32.12.3 HYDROLYSIS AND DISSOCIATION OF XANTHATES Schaum, K., P. S i e d l e r and E. Wagner > K o l l o i d Z. 58, 341; 1932 26:3430 32.22.1 THE PHYSICAL CHEMISTRY OF FLOTATION Wark, I.W. 26:1550 Tra n s . Electrochem. Soc. p r e p r i n t 61, 427; 1932 32.25.1 ELECTROSTATIC EXPLANATION OF FLOTATION Kamienski, B. • Nature, 129', 59; 1932 -'. 26:1550" 32.25.2 ELECTROSTATIC POTENTIALS AT PHASIC BOUNDARY ELECTROLYTE-UNATTACKABLE ELECTRODE AND THE PHYSICAL CHEMISTRY OP FLOTATION Kamienski, B. . Z. physIk. Chem. A158, 441; 1932 26:2660 32.25.3 MECHANISM OF THE FLOTATION PROCESS Talmud, D.L. PhysIk Z. Sowjetunion 1, 603; 1932 26:5519 32.25.4 THE EFFECT OF ACTIVATED CHARCOALS ON THE FLOTATION OF ORES B r a u n s t e i n , i t . '. : K o h l e u.;Erz 29, 189; 1932 27:2117 32.25.5 FLOTATION (Book) Gaudin ? A.M. McGraw H i l l ; 1932 32.25.6 ELECTRO CAPILLARY TESTS IN CONNECTION WITH THE PROBLEM OF FLOTATION Sven-Ni l s s o n , I . Iva 3, 50; 1932 27:2116 33. 1.1 APPLICATION OF THE GIBB'S ADSORPTION THEOREM TO SOLID-LIQUID INTERFACES B a r t e l l , F.E., F.L. M i l l e r and E.G. Almy J . Am. Chem. Soc. 55, 466; 1933 27:1798 33. 5.1 SOLUBLE METAL XANTHATES AND THEIR EFFECT ON DIFFER-ENTIAL FLOTATION Warren, S.P. 27:2915 B u l l . Can. I n s t . Mining Met. 251, 186; 1933 96 55. 8.1 PHYSICAL CHEMISTRY OF FLOTATION 1. SIGNIFICANCE OF THE CONTACT ANGLE Wark, I *W. . ' . J * Phys. Chem. 37, 623; 1933 27:4194 33. 8.2 rHYSICAL CHEMISTRY OF FLOTATION 2. NATURE OF ADSORP-TION OF SOLUBLE COLLECTORS Cox, A.B. and I.W. Wark J • Phys. Chem. 37, 797;.1933 27:1596 33. 8.3 PHYSICAL CHEMISTRY OF FLOTATION 3. THE RELATION BETWEEN CONTACT ANGLE AND CONSTITUTION OF COLLECTOR Wark, E.E. and I.W. Wark • J , : Phys. Chem. 37, B©5; 1933 27:4194 33. 8.4 PHYSICAL CHEMISTRY OF FLOTATION 4. CRITICISM OF OSTWALD'S THEORY Wark, ±.W. and A.B. Cox J . Phys i Chem. 37, 815; 1935 '27:4195 55. 8.5 SURFACE REACTIONS OF SOME SULFUR BEARING ORGANIC COMPOUNDS WITH SULFIDES Gaudin, A.M. and W.D. W i l k i n s o n J . Phys. Chem. 57, 853; 1933 28: 79 33. 8.6 ADHESION TENSION. PRESSURE OF DISPLACEMENT METHOD B a r t e l l , P.E. and H.J. Osterhof J V Phys. Chem. 37, '545; 1933 ' 27:3868 35.12.1 WETTING EXPERIMENTS ON HYDROPHILIC AND HYDROPHOBIC POWDERS IN SYSTEMS OF TWO IMMISCIBLE LIQUIDS. 2. ADSORPTION AND WETTING OF GALENA AND SPHAL-ERITE B e r l , E., B. Schmitt and H. Schuiz K o l l o i d Z. 63,'327} 1953 ' 27:4149 55.12.2 THE DEPENDENCE OF WETTING OF SOLIDS ON THE TIME OF CONTACT P o c k e l s , Agnes '•; • K o l l o i d Z. 62, 1} 1933 : 27:1798 55.12.5 MICROSCOPY OF FLOTATION PHENOMENA IN REFLECTED LIGHT K i n g , N. -K o l l o i d Z. 62, 345; 1933 ' 27:2117 35.12.4 IHE MECHANISM OF THE FLOTATION PROCESS Talmud D. K o l l o i d Z. 62, '375;. 1933 27:2116 33•13 • X Dean, R.S., J . Gross et a l U.S. Bur. Mines 544B; 1935 97 33.25.1 KATE OP WETTING AND FLOTATION Freundlich, ri., 0. Ens 1 i n and G-. Lindau K o l l o i d B e i h e f t e 37, 281.1 .1933 27:3376 33.25.2 INFLUENCE OF FOREIGN SUBSTANCES ON THE UPTAKE OF LIQUIDS BY NON-SWELLING POWDERS F r e u n d l i c h , H., 0 ..Ens 1 In and G. LIndau . • . K o l l o i d B e i h e f t e 37, 242; 1933 27:3376 33.25.3 THE REACTION OF CERTAIN SULFUR-BEARING COLLECTORS WITH CERUSSITE AND GALENA Johnson, R.A. ... Thesis, Montana School of Mines;; 1933 -;; 33.25.5 THE WATER-AVIDITY OF INSOLUBLE SUBSTANCES, AND THE REMARKABLE FORCES OF ATTRACTION EXISTING AT THE INTERFACE OF NON-MISCIBLE LIQUIDS • Demaux,,H. , Gompt. rend. 197, 105; • 1933 27:4983-33.25.6 THE CHEMICAL BASIS OF FLOTATION Wark,:iI.W. 28:1307 Proc. A u s t r a l a s i a n ; I n s t . Mining Met. 90, 83|1953 34. 1.1 QUANTITATIVE CORRELATION OF INTERFACIAL FREE SURFACE ENERGIES B a r t e l l , F.E., and L.S. B a r t e l l . J . Ala. Ghem. Soc. 56, 2205; 1934 29: 973 34. 3.1 uXYGEN-FREE FLOTATION. 1. FLOTATION OF GALENA IN THE ABSENCE OF OXYGEN Ravitz, S.F. and R.R, P o r t e r A.I.M.E.—T.P. 513; 1933 28:1308 34. 3.2 PRINCIPLES OF FLOTATION. 1. AN EXPERIMENTAL STUDY OF THE EFFECT OF XANTHATES ON CONTACT ANGLES AT MINERAL SURFACES Wark, I..W. and A.B. Cox A.I .M-.E.--T .P . 461; 1932 Trans. A.I.M.E. 112, 189; 1934 26:1881 34. 3.3 PRINCIPLES OF FLOTATION, 2. AN EXPERIMENTAL STUDY OF THE INFLUENCE OF CYANIDE, ALKALIS AND COPPER SULFATE ON THE EFFECT OF POTASSIUM ETHYL XANTHATE AT MINERAL SURFACES Wark, I.W. and A.B. Cox A.I.M.E.—T.P. 495; 1933 Trans. A.I.M.E. 112,"245; 1934 27:1596 98 34. 3.4 PRINCIPLES OP FLOTATION, 3. AN EXPERIMENTAL STUDY OP ' THE INFLUENCE OP CYANIDE, ALKALIS AND COPPER SULFATE ON THE EFFECT OF SULFUR-BEARING COLLEC-TORS AT MINERAL SURFACES Wark, I.W. and A.B. Cox A.I.M.E.—T.P. 574; 1934 Tran s . A.I.M.E. .112, 267; 1934 34. 3.5A REACTIONS OF XANTHATES WITH SULFIDE MINERALS Gaudin, A.M., F. Dewey, W.E. Duncan, K.A. Johnson and O.F. Tangel J r . T r a n s , A.I.M.E. 112, 319; 1934 34. 3.6 THE CASE FOR THE CHEMICAL THEORY OF FLOTATION Taggart, A.F., G.R.M. d e l G i u d i c e and 0 .A. Z i e h l T r a n s . A.I.M.E,.112, 348; 1934 .29:7886 34. 3.7 THE ACTION OF ALKALI XANTHATES ON GALENA T a y l o r , T.C. and A.F. K n o l l A.I.M.E.--Contribution #26; 1933 • . Trans. A.I.M.E. 112, 382; 1934 34. 3.9 RELATIVE FLOATABILITY OF SILICATE MINERALS Patek, J.M. . A.I.M.E.—T.P. § 6 4 ; 1934 T r a n s . A.I.M.E. 112, 486;:1934 28:6664 34. 6.2 SOAP FLOTATION—ACTION OF DEPRESSING GELS Patek, J.M. Eng. Mining J . 135, 125; 1934 ' 28:2649 34. 6.3 FUNDAMENTALS OF FLOTATION IN THE LIGHT OF MODERN RESEARCH . d e l Giudice-, G.R.M. •' Eng. Mi n i n g J . 135,- 152; 1934 : 28:3341 135, 213; 1934 28:3695 135, 257; 1934 .135, 350; 1934 28:5789 34. 6.4 COLLOIDAL DEPRESSORS IN SOAP FLOTATION Patek, J.M. Eng. Mining J . 135,.558; 1934 29:1037 34. 8.1 ADSORPTION OF COPPER SULFATE BY SPHALERITE AND ITS RELATION TO FLOTATION RavItV, S.F. and W.A. Wall j . Phys. Chem. 38, 13; 1934 28:2591 34. 8.2 ADHESION TENSION OF LIQUIDS AGAINST STRONGLY HYDRO-PHILIC SOLIDS. A SERIES OF LIQUIDS AGAINST BARITE B a r t e l l , F *E. and H.Y. Jennings J . Phys. Chem. 38, 495; 1934 28:4288 99 3 4 . 8.3. ALTERATION OF THE SURFACE PROPERTIES OF STIBNITE AS ' REVEALED BY ADHESION-TENSION STUDIES B a r t e l l , tr.E. and C J . Walton J . Phys. Chem. 38, 503; 1934 28:3960 34. 9.1 EFFECT OF METALLIC SALTS UPON FLOTATION OF OXIDIC MINERALS . Kraeber, L . and A. Boppel : M e t a l l u, E r z 3 1 , 412; 1934 ' 2 9 : ' 85 34.12.1 EFFECT OF CONTACT TIME BETWEEN MINERAL AND AIR-BUBBLE ON FLOTATION - S v e n - N l l s s o n , I . , ~ ' Kolloid.'Z. 69, 230; 1934 '29:1367 34.12.2 CONTRIBUTION TO THE THEORY OF FLOTATION S i e d l e r , P. • K o l l o i d Z. 6 8 , 8.9;, 1934' . • : . 28:6403 34.12.3 THE THEORY OF FLOTATION I I I . Ostwald, Wo., . . '..•;.-.-' K o l l o i d Z. 68, 103| 1934 : 28:6403 34.16.1 MECHANISM OF FLOTATION WITH WATER-INSOLUBLE REAGENTS 1. FUNCTION OF THE NON-POLAR PHASE IN THE PROCESS OF ADSORPTION OF A REAGENT ON THE SUSPENSION PARTICLES Vo l k o v a , Z«.V. and N.N. Serb-Sertoina . • M i n e r a l S u l r ? e 9 , #10,19; 1934 29:1899 34.16.2 APPLICATION OF THE SATURATION METHOD FOR THE INVESTI-GATION OF THE MINERAL DISPERSOIDS. A STUDY OF THE COMPARATIVE WETTING OF CORUNDUM POWDERS Volkova, Z.V. -A c t a Physiooohim. U.R.S.Si 1, 247; 1934 29:7744 34.25.1 ACTIVATION OF SPHALERITE Beck, A.B. Chem. and Ind. 1934, 104 . -29:2122 34.25.2 ACTION OF DILUTE SILVER NITRATE ON MINERAL SULFIDES Kamenetzi, S.A. . - Z. anorg. allgem. Chem.'219, 335; 1934 29: 24 34.25.4 THE NATURE OF ADSORPTION FORCES de Boer, J.H. and J.F.H. Ousters Z. physIk. Chem. 25B, 225; 1934 28:4646 3 4 . 2 5 . 5 EFFECT OF pH AND VARIOUS CHEMICALS ON THE FLOTATION OF PYRRHOTITE Yamada, ( i . and M. Muraoka Suiyokwai-Shi .8 , 435; 1934 28:4687 100 35. 1.1 SURFACE RELATIONS OF THE XANTHATES De W i t t , u . C , R.F. Makens and A.W. Helz J . Am. Chem. Soc. 57, 796; 1935 29:4298 35. 3.1 NEW FLOTATION REAGENTS Dean, R.S. and A.B, Hersberger A.I.M.E.—T.P. 605; 1935 29:2121 35. 6.1 FATTY ACID AND SOAP FLOTATION APPLIED TO OXIDIZED COPPER ORE Rey, M. Eng. Mining J . 136, 221; 1935 35. 8.1 PHYSICAL CHEMISTRY OF FLOTATION 5. FLOTATION OF GRAPHITE AND SULFUR BY XANTHATE COLLECTORS, AND ITS BEARING ON THE THEORY OF ADSORPTION Wark, I.W. and A.B. Cox J . Phys. Chem. 39, 551; 1935 29:6974 35. 8.2 PHYSICAL CHEMISTRY OF FLOTATION 6. ADSORPTION OF AMINES BY SULFIDE MINERALS Wark,, I.W. and E.E. Wark J . Phys. Chem. 39, 1021; 1935 30: 59 35. 8.3 THE WETTING CHARACTERISTICS OF GALENA B a r t e l l , F.E. and G.B. Hatch J . Phys. Chem. 39, 11; 1935 29:2420 35. 9.1 ACTION OF XANTHATES ON GALENA Wilkinson,'W.D. ' M e t a l l i i . E r z 32, 157} 1935 29:5789 35.12.1 MECHANISM OF FLOTATION. ADSORPTION ON TALC AND ITS FLOTATION. Vol k o v a , Z.V., N.N. Serb-Serbina and A.V. Zaporozhetz K o l l o i d Z-. 7 1 / 230; 1935 29:7703 35.12.2 MECHANISM.OF FLOTATION. ROLE OF HIGHLY DISPERSED POWDER Volkova, Z.V. and S.V. Zaporozhetz K o l l o i d Z. 72, 82; 1935 29:7703 35.12.3 MECHANISM OF FLOTATION. 4. ORIENTED COAGULATION IN NON-POLAR AND AQUEOUS MEDIA Volkova, Z.V. -K o l l o i d Z. 72, 229; 1935 29:7703 35.12.4 EXPERIMENTAL INVESTIGATION OF LAMINAR SYSTEMS. 1. UNIMOLECULAR AND MULTIMOLECULAR SULFIDE AND HY-DROXIDE FILMS AT INTERFACES Mokrushin, S.G. K o l l o i d Z. 70, 48; 1935 29:2420 101 35.16.1 ADSORPTION OF ORGANIC SUBSTANCES ON THE SURFACE OF CRYSTALS AND THE EFFECT OF ELECTROLYTES ON THE EXTENT OF ADSORPTION H e l ' d , N.A. • Mekhanobr ( i n English;), 161; 1935 30:2451 35.16.2 DEPRESSING ACTION OF HYPOSULFITES Trusov, P.D. Mekhanobr, R u s s i a 1, 164; 1935 30:3375 35.17.1 CONTRIBUTION TO THE THEORY OF FLOTATION Rey, M. Congr, I n t e r n m i n e s metal geol, a p p l , 7e session,-. • . . . P a r i s 1955, Mines 1, 270 . 50:7075 55.18.1 LAMINAR SYSTEMS 8. EFFECT OF ELECTROLYTES ON THE WETTABILITY OF FILMS OF METALLIC SULFIDES Mokrushin, S.G. and N. Demenev J . P h y s . Chem.(U.S.S.R.) 6, 1269; 1955 50:7415 55.18.2 LAMINAR SYSTEMS 5. ADSORPTION OF ELECTROLYTES BY COPPER .SULFIDE FILMS '' Mokrushin, S.G. and G.F* V l l l e s o v a " J. Phys. Chem. (U.S.S.R.) 6, 640; 1955 29:7748 35.18.3 LAMINAR SYSTEMS 7. WETTING PHENOMENA ON SURFACE FILMS OF METALLIC SULFIDES Mokrushin, S.G. and isl. Demenev J, Phys.-Ghem. (U.S.S.R.) 6, 1066; 1935 31: 18 35.25,1 ACTION OF FLOTATION REAGENTS ON THE CHARGE IN MINERAL SUSPENSIONS . Tlkhonov:,. M.K. . . . S917886 B u l l . acad. S c i . U.R.S.S. 1935; 253 ( i n E n g l i s h ) 35.25.5 THE THEORY OF FLOTATION Ostwald, Wo. Z. p h y s i k . Ghem.,AI73, 595; 1955 29:7705 55.25.4 THE THEORY OF FLOTATION Wark, I .W. .Z. p h y s i k . Ghem. A175, 265; 1935 29:7703 36. 1.1 WETTING CHARACTERISTICS OF SOLIDS OF LOW, SURFACE TENSION, SUCH AS TALC, WAXES AND RESINS. B a r t e l l , F.E. and -Zuidema - J. Am. Ghem. Soc. 58, 1449; 1936 30:6620 56. 3.1 PRINCIPLES OF FLOTATION 4. AN EXPERIMENTAL STUDY OF THE INFLUENCE OF SODIUM SULFIDE, ALKALIS AND COP-PER SULFATE ON THE EFFECT OF XANTHATES AT MINERAL SURFACES Wark, I.W. and A.B. Cox A.I.M.E.— T.P. 659; 1936 30: 997 102 36. 3.2 PRINCIPLES OF FLOTATION 5. CONCEPTION OF ADSORPTION APPLIED TO FLOTATION REAGENTS Wark, I.W. and A.B. Cox A.I.M.E.—T.P. 732, B59; 1936 36. 6.1 THE BUBBLE MACHINE FOR FLOTATION TESTING d e l G i u d i c e , G.R.M. Eng..Mining JV 137,291}•1936 36. 6.2 THE BUBBLE MACHINE FOR FLOTATION TESTING Cox, A.B* Eng.. Mining J . 137, 641; 1936 36. 8.1 PHYSICAL CHEMISTRY OF FLOTATION 7. TRIMETHYLCETYL AMMONIUM BROMIDE AS A FLOTATION REAGENT Wark, I.W. J . Phys. Chem..40, 661; 1936 ' 36. 8.2 PHYSICAL CHEMISTRY OF FLOTATION 8. THE PROCESS OF ACTIVATION Wart, E .E. and. I.W. Wark . J . Phys. Chem. 40, 799; 1936 .30:8106 36. 8.3 ACTION OF POTASSIUM ETHYL XANTHATE ON CHALCOCITE • Gaudin, A.M. and Schumann ' J> Phys, Chem.-40,-257; 1936 : 30:4443 36. 9.1 MARGINAL ANGLE AND FLOTATION ABILITY .' " Valentlner.,. S . • ' M e t a l l uvErz 33,. 221; 1936 30:4443 36.16.1 FLOTATION AND SUSPENSION STABILITY OF ZINC BLENDE M l t r o f a n o v , S-X and Ara s h k e v i c h Gorho-Obogatitel Zhur. 4, 9; 1936 31: 636 36.16.2 THE FLOTATION OF SULFIDE AND OXIDIZED MINERALS Shvedov, D.A. Gorno-Otoogatltel Zhur. 6, 24; 1936 31:2133 36.16.3 THE USE OF SODIUM SULFIDE AT ZYRYANOVSK ORE-DRESSING PLANT Sladkov, ' . • ' • [ Tsvetnye Metal 1, 66; 1936 .31*5303 36.16.4 A QUANTITATIVE STUDY OF FLOCCULATION AS A METHOD FOR CHARACTERIZING THE REACTION OF THE MINERAL WITH THE REAGENT IN THE FLOTATION PROCESS Shneerson, V.B. .TsTetnye M e t a l . 10, 33} 1936 31:2133 36.16.5 DEPRESSING AND ACTIVATING ACTION OF SODIUM SULFIDE DURING FLOTATION B e l a s h , • . ' . ' • ^ ..n Redkle Metal 5, #6, 27; 1936 31:6159 103 36.25.1 THE EFFECT OF pH AND THE ADDITION OF VARIOUS CHEMICALS ON THE FLOTATION OF ARSENOPYRITE Yamada, G. and Jyo Suiyokwai-Shi 9, 83; 1936 31:1329 36.25.2 THE EFFECT OF pH AND THE ADDITION OF VARIOUS CHEMICALS ON THE FLOTATION OF ENARGITE Yamada, G. and Koizumi Suiyokwai-Shi 9, 89; 1936 31:1329 36.25.3 THE EFFECT OF XANTHATES ON THE WETTABILITY OF SULFUR Demenev, N. C o l l o i d J . (U.S.S.R.) 2, 665; 1936 31:2064 36.25.5 THE RELATION BETWEEN PEPTIZATION OF A PRECIPITATE AND ITS ELECTROKINETIC POTENTIAL Ghaudbury, and Sen-Gupta J . I n d i a n Chem. Soc. 13, 670; 1936 31:376!) 36.25.6 THE EFFECT OF pH AND THE ADDITION OF VARIOUS CHEMICALS ON THE FLOTATION OF CHALCOPYRITE Yamada, G. and Waksaugi and Naganuma Suiyokwai-Shi 8, 943; 1936 30:3755 36.25.7 THE EFFECT OF pH AND THE ADDITION OF VARIOUS CHEMICALS ON THE FLOTATION OF SPHALERITE Yamada, G. and Naganuma Suiyokwai-Shi 9, 47; 1936 30:6679 37. 4.1 REVIEW OF RECENT FLOTATION PATENTS B a s s e t t , I . Can. Mining J . 58, 185; 1937 : 58, 255; 1937 58; 304; 1937 58, 356; 1937 37. 5.1 FROTH FLOTATION AND AGGLOMERATE TABLING OF NONMETALLIC MINERALS R a l s t o n , 0.C, B u l l . Can. I n s t . Mining Met. 307, 691; 1937 Tra n s . " " " " 40, 691; 1937 37. 6.1 THE PROBLEM OF MEASURING SETTLING RATES OF MINERAL SUSPENSIONS WITH DATA ON THE FLOTATION OF QUARTZ Fahrenwald, A.W. and J . Newton Eng. Mining J . 138, 23; 1937 37. 8.1 PHYSICAL CHEMISTRY OF FLOTATION 9. ADSORPTION OF XANTHATES BY ACTIVATED CARBON AND GRAPHITE AND ITS RELATION TO THE THEORY OF FLOTATION Wark, l.W. and A.B. Cox J . Phys. Chem. 41, 673; 1937 1 0 4 37.12.1 DISPERSE HYSTERETIC DIFFERENTIAL WETTING. THE KINETICS OF WASHING OFF THE ADSORPTION LAYERS AS A METHOD OF STUDYING CHEMICAL REACTIONS IN THE SURFACE FILM Klyachko, Kolloid Z. 78, 171; 1937 31:4560 37.13.1 USE OF WETTING AGENTS IN FLOTATION Dean, R.S., J.B. Clemmer and S.R.B. Cooke U.S. Bur. Mines R.I. 3333; 1937 37.13.2 ORE DRESSING TESTS AND THEIR SIGNIFICANCE D i e t r i c h , </v .F ., A.L. Engel and M. Guggenheim U.S. Bur. Mines R.I. 3328; 1937 37.16.1 ADSORPTION OF FLOTATION REAGENTS ON MINERAL SURFACES Rimskaya, G o m o - O b o g a t i t e l Zhur. 2, 27; 1937 37.16.2 ISOTHERMS OF WETTING AS APPLIED TO FLOTATION ' ;Mantsev ;•' " Gomo-Obogatitel,Zhur. 2,-32; 1937 .31:5303 37.16.3 STUDY OF GOLD FLOTATION BY THE "ZERO" METHOD •.-•Mitrofanov, $,t. Gorno-Obogatitel Zhur. 3 / 2 2 ; 1937 37.16.4 ISOTHERMS OF WETTING OF ZINC SULFIDE AND LEAD SULFIDE GENERAL HYSTERESIS OF WETTING Mantsev, , .Gorno-Obogatitel Zhur. 3, .28; 1937 31:5728 37.16.5 ELECTRIC POTENTIALS AT THE INTERFACE OF PHASES IN THE FLOTATION PROCESS Kamienski, and Benis Roezniki Chem. 17, 89; 1937 31:4560 37.16.6 INFLUENCE OF OXIDATION ON THE FLOTATION OF SULFIDE MINERALS Shvedov, D.A. and Shorsher ..Gorno-Obogatitel Zhur. 9-10, 24; 1937 32:1218 37.16.7 FLOTATION OF GOLD BY THE ZERO METHOD Mitrofanov, S.I. :Gorno-Obogatitel Zhur. 9-10, 31; 1937 -37.16.8 WETTING OF MINERAL SURFACES AND THE PHENOMENON OF FLOTATION OF MINERAL SURFACES Gorno-Obogatitel Zhur. 9-10, 39; 1937 32:1217 105 37.25.1 ADSORPTION FORGES AND THEIR ELECTRICAL NATURE I I I . NATURE OF THE FORCES OF WETTING I l l i i n , Leontiew and Bragin P h i l . Mag. 23, 294; 1937 31:3774 37.25.2 THE EFFECT OF pH AND THE ADDITION OF VARIOUS CHEMI-CALS ON THE FLOTATION OF SULFIDE MINERALS 9. MARMATITE Yamada, G. and Naganuma Suiyo k w a i - S h i , 9, 197; 1937 37.25.3 THE FLOTATION OF STIBNITE Yamada,- G. and Yokoyama Suiyokwal-ShI 9, .245; 1937 38. 3.1 PRINCIPLES OF FLOTATION 6. INFLUENCE OF TEMPERATURE ON THE EFFECT OF COPPER SULFATE, ALKALIS AND SODIUM CYANIDE ON THE ADSORPTION OF XANTHATES AT MINERAL SURFACES Wark, l.W. and A.B. Cox A.I.M.E.—T.P. 876; Jan. 1938 38. 3.2 OIL-AIR SEPARATIONS OF NON-SULFIDE AND NON-METALLIC MINERALS Taggart, A.F. A.I.M.E.—T.P. 838; 1938 38. 4.1 A REVIEW OF RECiiNT FLOTATION PATENTS Bassett, I . Can. M i n i n g J . ( i n press) THE SURFACE CHEMISTRY OF FLOTATION PART 2. EXPERIMENTAL The S o l u b i l i t y o f Lead. E t h y l Xanthate and' The F l o t a t i o n o f Lead S u l f i d e . ACKNOWLEDGMENT The author a p p r e c i a t e s the guidance of Dr. Wm, Ure, under whose g e n e r a l d i r e c t i o n t h i s r e s e a r c h was c a r r i e d out; and the help of Rex F. Pearce, B.A.Sc., who a s s i s t e d i n p r e p a r i n g m a t e r i a l s used i n the work. THE SURFACjg CHEMISTRY OP FLOTATION PART 2. EXPERIMENTAL The S o l u b i l i t y o f Lead E t h y l Xanthate and The F l o t a t i o n o f Lead S u l f i d e CONTENTS Page INTRODUCTION TO EXPEKlMENTAL WORK 1 PREPARATION OF MATERIALS, ETC. 2 SOLUBILITY OF LEAD ETHYL XANTHATE 3 G r a v i m e t r i c Procedure , 5 Colorimetrio Procedure 4 SOLUBILITY OF CUPROUS ETHYL XANTHATE 12 METHODS FOR MEASURING FLOATABILITY 14 FLOTATION WITHOUT REAGENTS 16 FLOTATION WITH TERPINEOL ALONE (Inherent F l o a t a b i l i t y ) 27 FLOTATION OF XAN THATE-TREATED GALENA WITH TERPINEOL 30 A FURTHER EFFECT OF pH 35 SUMMARY 37 ILLUSTRATIONS F i g . Pacing Page 1 . Lead i o n C o n c e n t r a t i o n i n S o l u t i o n s of Var i o u s pH C o n t a i n i n g s o l i d Lead E t h y l Xanthate ' 12 2. F l o t a t i o n C e l l 1 6 3. E l u t r l a t o r 2 2 i i . F i g . . • F a c i n g Pag© 4. -* F l o t a t i o n without Reagents 27 5. Recovery of X a n t h a t e - t r e a t e d Galena v s . pH 34 6. Change of pH w i t h Time. F l o t a t i o n o f Xanth a t e - t r e a t e d Galena. A l k a l i n e Rang© 34 7. Change of pH w i t h Time. F l o t a t i o n of X a n t h a t e - t r e a t e d Galena. A c i d Range ' 3 4 THE SURFACE CHEMISTRY OF FLOTATION PART I I INTRODUCTION TO EXPERIMENTAL WORK Prev i o u s i n v e s t i g a t o r s have demonstrated, t h a t f l o t a t i o n •.•pt a s o l i d Is accomplished 1 .by. m a i n t a i n i n g or producing a hydrophobic coating,on I t s s u r f a c e , and. t h a t n o n - f l o t a t i o n -r e s u l t s when, the c o a t i n g i s h y d r o p h i l l c . The mechanism by which the s u r f ace of a s o l i d m i n e r a l becomes more hydrophobic a f t e r c o n t a c t w i t h a s o l u t i o n of a c o l l e c t o r has n o t been sat - I s f a c t o r i l y e x p l a i n e d . I t i s thought t o b e : e i t h e r chemical, metathesis between e n t i t i e s " d e r i v e d from the m i n e r a l and the s o l u b l e c o l l e c t o r } ; .or a d s o r p t i o n of the, c o l l e c t o r , , i n whole or part., on the m i n e r a l s u r f a c e . - I t has been-shown- t h a t xan-t h a t e : e e l l e c t o r s are a b s t r a c t e d from s o l u t i o n b y'minerals' i f the b a s i c c o n s t i t u e n t of the m i n e r a l forms a xanthate of low / s o l u b i l i t y , and are not a b s t r a c t e d I f the xanthate has an a p p r e c i a b l e s o l u b i l i t y . I t - h a s a l s o been shown t h a t adhesion -between an a i r - b u b b l e and a x a n t h a t e - t r e a t e d m i n e r a l s u r f a c e ! i s p o s s i b l e o n l y below a c r i t i c a l pH value.} more or l e s s .' s p e c i f i c f o r a p a r t i c u l a r xanthate and m i n e r a l . I t i s the purpose of the present i n v e s t i g a t i o n t o d e t e r -mine the e f f e c t of pH on the s o l u b i l i t y of c e r t a i n base metal xanthates, and on the f l o a t a b i l i t y of the corresponding xan-t h a t e - t r e a t e d m i n e r a l s , and t o determine whether any c o r r e l a -t i o n e x i s t s between t h i s s o l u b i l i t y and the f l o a t a b i l i t y of the mineral.• F o r the I n v e s t i g a t i o n , g a lena and potassium e t h y l xan-t h a t e were s e l e c t e d as a t y p i c a l m i n e r a l and c o l l e c t o r , r e s -p e c t i v e l y . PREPARATION OF MATERIALS, ETC. The p r e p a r a t i o n and p u r i f i c a t i o n of the reagents used are d e s c r i b e d by K. F. P e a r c e l M i n e r a l specimens used i n f l o t a t i o n tests are d e s c r i b e d below: Galena #1 Massive specimen of S u l l i v a n galena obtained from Geology Dept., U n i v e r s i t y of B.C. Galena #2 Large specimen, v i s i b l y a l t e r e d on the s u r f a c e •and composed of 1/4" and l a r g e r cubes} o b t a i n -ed from Geology Dept., U n i v e r s i t y of B.C. Galena #3 F i n e c r y s t a l l i n e Galena #4 Medium c r y s t a l s , c o n t a i n i n g s p h a l e r i t e and q u a r t z . Galena #5 S i l v e r - L e a d ore from S t . Eugene Extension Mine. Massive, b r i t t l e , h i g h l y - l u s t r o u s spec! men w i t h n o . v i s i b l e i m p u r i t i e s . Obtained from B.C. Chamber of Mines, Vancouver. A l l uh determinations were made w i t h a Beckman g l a s s -e l e c t r o d e ph meter. 1. The Surface Chemistry of F l o t a t i o n . The S o l u b i l i t y or Z i n c E t h y l Xanthate, n.F.Pearce, B.A.Sc. T h e s i s , U n i v e r s i t y of B r i t i s h Columbia, 1938 3 SOLUBILITY OF LEAD ETHYL XANTHATE .. ' Gravimetric Procedure Procedure E q u i v a l e n t q u a n t i t i e s of l e a d n i t r a t e (0.2948 gms.) and potassium e t h y l xanthate (0.2852) gms.) t o form 0.4 gms. of l e a d e t h y l xanthat© were d i s s o l v e d i n separate 500 cc. por-t i o n s of water. "The s o l u t i o n s were mixed, and the mixture allowed, t o stand o v e r n i g h t , while the p r e c i p i t a t e became com-p l e t e l y f l o c c u l a t e d . T h i s suspension of l e a d e t h y l xanthate v/as f i l t e r e d through asbestos on a weighed Gooch c r u c i b l e , and the p r e c i p i t a t e washed w i t h 100 cc. water and 25 cc. e t h e r . The c r u c i b l e and contents were d r i e d overnight at 80° G. then weighed to ob-t a i n the. combined weight of p r e c i p i t a t e and asbestos. T h e contents of the c r u c i b l e was now t r a n s f e r r e d t o 1000 c c . of d i s t i l l e d water and p l a c e d on a shaking machine o v e r n i g h t . T h i s suspension was then f i l t e r e d through asbestos on a . weighed (jooch c r u c i b l e , the p r e c i p i t a t e d r i e d , and i t s l o s s i n weight determined. A second p r e p a r a t i o n of l e a d e t h y l xanthate was t r e a t e d i n the same way, but was e x t r a c t e d i n the c r u c i b l e with 1000 cc. of water i n s t e a d of b e i n g t r a n s f e r r e d from the c r u c i b l e and a g i t a t e d w i t h water. R e s u l t s T h e pH of the l e a d xanthate suspension was 5.5 - 5.6. The l o s s i n weight i n the f i r s t procedure was 198 mgms; and i n the second was 120 mgms. Conclusio n s experimental d i f f i c u l t i e s make t h i s procedure u s e l e s s as a method f o r determining the s o l u b i l i t y of l e a d e t h y l xanthate •rhe hydrophobic nature of the p r e c i p i t a t e causes i t t o form a heavy scum on the s u r f a c e of a l l suspensions, and t o climb the w a l l s of any v e s s e l i n which the p r e p a r a t i o n i s p l a c e d , tend-i n g t o cause l o s s of the m a t e r i a l and l e a d i n g t o h i g h r e s u l t s . Furthermore, the s o l u b i l i t y of the asbestos used i n the pro-cedure Is p r o b a b l y of the same order as t h a t of the le a d e t h y l xanthate. G f i l ^ r i m e t r i e Procedure P r e p a r a t i o n o f l e a d e t h y l xanthate P r e l i m i n a r y t e s t s showed t h a t a c o l o r i m e t r i c - p r o c e d u r e was s u i t a b l e f o r determining l e a d i n a s a t u r a t e d s o l u t i o n of l e a d e t h y l x anthate. The f o l l o w i n g method was adopted f o r e s t i m a t i n g the c o n c e n t r a t i o n of l e a d ions In e q u i l i b r i u m w i t h s o l i d l e a d e t h y l xanthate In aqueous s o l u t i o n at var i o u s pn v a l u e s . Two s o l u t i o n s were prepared t o c o n t a i n 0.1474 gms. l e a d n i t r a t e and 0.1454 gms. potassium e t h y l xanthate r e s p e c t i v e l y In 500 c c . of s o l u t i o n . T h i s allowed 2% excess xanthate over the amount r e q u i r e d t o r e a c t w i t h the l e a d n i t r a t e and form 0.2 gms. of l e a d e t h y l xanthate. The l e a d n i t r a t e s o l u t i o n was poured i n t o the xanthate s o l u t i o n , contained i n a l i t r e f l a s k , w h ile shaking the l a t t e r . The f i n e suspension of l e a d xanthate, which formed immediately, was then allowed t o stand, f o r two or three hours u n t i l i t be-came f l o c c u l a t e d and s e t t l e d out, l e a v i n g a c l e a r s o l u t i o n above the p r e c i p i t a t e . In t h i s c o n d i t i o n , the p r e c i p i t a t e showed no w a t e r - r e p e l l i n g tendency, and remained s e t t l e d at the bottom of the f i a s k . I f the f l a s k was a g i t a t e d , however, the p r e c i p i t a t e tended to concentrate as a dry scum at the f r e e l i q u i d s u r f a c e , and t o climb the w a l l s of the f l a s k . The c l e a r l i q u i d ' a b o v e the p r e c i p i t a t e was decanted, o f f , the p r e c i p i t a t e washed on to a paper f i l t e r , and washed on the f i l t e r w i t h 1000 c c . of d i s t i l l e d water. At no time during the washing p r o c e s s , was the p r e c i p i t a t e allowed t o become completely d r y . 'Treatment' 'of. l e a d e t h y l .xanthate A f t e r washing, the p r e c i p i t a t e was t r a n s f e r r e d t o a 1 l i t r e r ubber-stoppered b o t t l e , about 900 cc. of d i s t i l l e d water added; then v a r i o u s amounts of e i t h e r N/lO KOH or N-^ 10 HC1 t o a d j u s t the pH; and the t o t a l volume was made up to 1 l i t r e . A f t e r a couple of minutes a g i t a t i o n , the i n i t i a l pH o f the p r e p a r a t i o n was measured, and the b o t t l e and con-t e n t s p l a c e d on a r o t a r y shaking machine f o r a time i n t e r v a l v a r y i n g from 16 hours up t o s e v e r a l days. At I n t e r v a l s the b o t t l e was removed from the shaking machine and the pH of the contents measured. Determination of P b ^ c o n c e n t r a t i o n When i t was d e s i r e d to measure the Pb c o n c e n t r a t i o n i n the p r e p a r a t i o n , the b o t t l e was removed from the shaker, and the f i n a l pH reading was made. The contents of the b o t t l e was f i l t e r e d through asbestos on a Gooch c r u c i b l e , and the f i l t r a t p l a c e d i n a 1 " l i t r e Pyrex beaker. A f t e r the a d d i t i o n of 2 cc. 6N HC1, the f i l t r a t e was s l o w l y evaporated, without b o i l i n g , to a volume of 5 - 10 c c . Ammonia was added to the solution,-, u n t i l i t was s l i g h t l y a l k a l i n e t o l i t m u s . The re d e o l o r of the l i t m u s was t h e n brought back by adding g l a c i a l " a c e t i c a c i d and t h e solution'was made up w i t h d i s t i l l e d water t o a meas-ur e d volume of 100, c c . T h i s s o l u t i o n was used as the unknown i n the subsequent ©olorlmetric comparisons. '. ~~ G o l o r i m e t r l c comparisons f o r lead' • /- • / - . v . ' .Standard solut;Ions were prepared by d i s s o l v i n g 2.2881 •gms,.';.pb('GgH3G2)g.3HgG..'(;i©ad acetate) i n water and d i l u t i n g t o 500 cc* T h i s s o l u t i o n (A) contained 250© mgms. Pb^per l i t r e - . " ' 10 ec. o f s o l u t i o n (A)'were d i l u t e d , to SO© c c . t o pre -pare a s o l u t i o n (B) c o n t a i n i n g 5© mgms > Pb pe r l i t r e . 100 ce." of • s o l u t i o n (B) were d i l u t e d t o 500 cc. t o p r e -pare a s o l u t i o n (C) c o n t a i n i n g 1© mgms. Pb per l i t r e . 10 cc . of s o l u t i o n (B) were d i l u t e d t o 500 cc . t o p r e -pare a s o l u t i o n (D) c o n t a i n i n g 1.0 mgms. f b per l i t r e . , Ti/heh making a comparison w i t h the colorimeter,,. 10 c c . of unknown s o l u t i o n was p l a c e d i n one c o l o r i m e t e r cup, and 10 c c . of a s u i t a b l e standard s o l u t i o n i n the other; 4 drops of a s a t u r a t e d sodium s u l f i d e s o l u t i o n were added t o each cup, and the s o l u t i o n s s t i r r e d c a r e f u l l y . The cups were now p l a c e d on the c o l o r i m e t e r and s e v e r a l readings were taken, a f t e r which, the cups were re v e r s e d , and a-second set of readings o b t a i n e d . F r e s h p o r t i o n s of standard and unknown were now p l a c e d i n the cups, so t h a t the cup f o r m e r l y c o n t a i n i n g the standard s o l u t i o n c o ntained the unknown, and a new s e r i e s of readings was made. These p r e c a u t i o n s were found t o be e s s e n t i a l i n order to e l i m i n a t e i n s t r u m e n t a l e r r o r s . From the above readings an average value was obtained f o r the r a t i o of the depth of standard s o l u t i o n to the depth of unknown s o l u t i o n s T h i s r a t i o was m u l t i p l i e d by the l e a d i o n c o n c e n t r a t i o n i n the standar d s o l u t i o n t o o b t a i n the l e a d i o n c o n c e n t r a t i o n i n the unknown. The l a t t e r v a l u e , m u l t i p l i e d by 10, was taken t o be the l e a d Ion c o n c e n t r a t i o n i n the o r i g i n a l s a t u r a t e d l e a d xanthate s o l u t i o n . The method i s i l l u s t r a t e d by the f o l l o w i n g example: Unknown S o l u t i o n No. 11 Unknown i n Cup #1 Depth - mm. Depth «= •mm.. Standard on l e f t 41.0 Unknown on r i g h t 36.0 " " " 40.8 " " * 36.0 » » » 40.8 fS " " 36.0 " •« " 41.1 • " ' " " 36.0 • •«' • «' . r i g h t 40.8 " l e f t 36.0 « " » 40.3 " " " 36.0 » " " " 40.1 «• tl tt g 6 s 0 » '» " 40.6 " n " 56.0 Mean 40.7 Mean 36.0 R a t i o : standard ^ -40.7 ^ 1.131 : unknown' 36.0 8 \ Unknown in>Cup #2 Depth - mm. Depth - mm. •'Standard on. l e f t 47.6 Unknown on r i g h t 43.0 43.0 11 " " 48.3 " " * " . * " 47.7 " ti II " tr it 48.4 " II II " " r i g h t 47^8 " " l e f t 43.0 43.0 w - - - —«. 43.0 " " 47.8 » « » 43.0 43.0 it it « 47.7 ii it ti it ti ii 47.3 " " " 43.0 Mean 47.8 Mean 43.0 Ratio: atahdard £ 47.8 ~ 1.111 ',: ; unknown 45.0 " Mean Ratio s& 1.12 Standard s o l u t i o n s 10.0 mgm, Pb per l i t r e Unknown ..'solution « (1.12) (10.0) ,ll;-2 'mgm. Pb per 1, • O r i g i n a l ' s d l u t i o n g* (11.21 (100) vlel£ "mm. Pb pef.'il* Comparisons made between a p a r t i c u l a r unknown s o l u t i o n and d i f f e r e n t standard s o l u t i o n s gave comparable r e s u l t s . I t was concluded .that a c o r r e c t i o n f o r n o n - l i n e a r a b s o r b t i o n , as r e q u i r e d by Beer's Law, was o u t s i d e the l i m i t s of experimental e r r o r . In most comparisons, th© depth of one s o l u t i o n d i d not exceed twice the depth of the o t h e r . A blank d e t e r m i n a t i o n on the d i s t i l l e d water used i n the analyses showed a c o n c e n t r a t i o n of 0.12 mgms. Pb per l i t r e , i t i s f e l t t h a t t h i s v a l u e i s probably t oo h i g h , as i t was determined d u r i n g the e a r l y p a r t of the work, before the c o l o r -imeter technique had become s t a n d a r d i z e d . Subsequent values were not c o r r e c t e d f o r the Pb c o n c e n t r a t i o n of the water, because of the d o u b t f u l accuracy of the l a t t e r , and bacaus© I t was more d e s i r a b l e t o determine the t r e n d of Pb concentra-9 t i o n w i t h pH, than t o ev a l u a t e - the absolute values of the Pb co n c e n t r a t i o n . R e s u l t s and Conclusions The r e s u l t s of t h i s work are giv e n in t a b l e 1 and p l o t t e d i n P i g . 1. From these r e s u l t s i t is concluded t h a t : (1) . The c o n c e n t r a t i o n of l e a d ions in a s o l u t i o n which is i n . e q u i l i b r i u m w i t h s o l i d l e a d e t h y l xanthate depends on the pH of the s o l u t i o n . (2) The l e a d Ion c o n c e n t r a t i o n has a minimum value of 0.15 mgm. Pb per l i t r e at a ph of 8.0-8.2. This corresponds to a s o l u b i l i t y of l e a d e t h y l xanthate at this.pM of 0.33 mgms. per l i t r e . At pH va l u e s above or below 8.0 - 8.2, the l e a d i o n c o n c e n t r a t i o n i s g r e a t e r . (3) The s o l u b i l i t y of l e a d e t h y l xanthate i n pure water, at a pH of 6.4 i s 1.8 mgms. per l i t r e . (4) Lead e t h y l xanthate, i n the presence of water and h y d r o c h l o r i c a c i d , or potassium hydroxide, i s slow l y decomposed. This decomposition i s accompanied by a decrease in pH i n a l -k a l i n e s o l u t i o n s , and'an i n c r e a s e i n a c i d .^solutions. The decomposition i n the presence of potassium hydroxide i s a l s o accompanied by a darkening of the l e a d e t h y l xanthate. This darkening i s more r a p i d i n the more -concentrated a l k a l i n e s o l u t i o n s Note Samples of l e a d e t h y l xanthate f o r determinations 19 - 22 i n c l u s i v e were prepared from e q u i v a l e n t q u a n t i t i e s of reagents, a l l o w i n g no excess xanthate. The l e a d concentrations obtained 10 f o r these samples, as t a b u l a t e d i n Table 1, are l e s s than f o r comparable samples prepared w i t h an excess of potassium e t h y l xanthate. This i s mentioned, inasmuch as i t may.have a bearing on the s o l u b i l i t y f i g u r e s obtained from the samples as p r e -pared w i t h excess xanthate. I t i s p o s s i b l e t h a t excess xan-thate i o n may a l t e r the l e a d xanthate s u r f a c e i n such a way t h a t i t w i l l have a d i f f e r e n t s o l u b i l i t y , TO j u s t i f y t h i s assumption, f u r t h e r work i s n e c e s s a r y . lO CO N H ffl 00 (to tfi CM O co to co oo (to t in o o © © o 8 CM o in CO CM ! © S <© 8 3 o 8 CM CM to O o d d CD m © o «H m co Ol CO O CO in <T> in » * « • r> • « CO CO co CO in £>» CO in in 3 * HJO) ^ ^ ^ d * OtOEO««j*E*>©iHOt©<Oin< i-« CM CM tO CO a CO to cn .H o • © e© • at in * co o> rH 10 rH «H M> (0 en IS £ » cH « © ® 9 e 9 cn co CO en CO to iH © OO^ CQ2 ' o f E» '£» (O '<0 i H . t0 O ID tO t© in rH a> in E « - © ^ ' ( H i H i < s t o e » c n c n o j e \ s E> - c o i H co co to (0 CM CM a » ' d ' c o o > o " » c o s » m £ » e o S ' " i n m w « © "d« g>- ©2*fH A ^ TcnrQQ CM \P ^ lO ffl t i ' ^ fH IO 6 0 "Sf • ® CO o o © < H C Q P ~ l ? 3 © 6 ' 3 a - » C l » t f 5 ' r f « o » C O ^ • i s w o e o ^ r - i c n i o ^ i i s a ) e '© » © « * © « o o . • © © © © O © IBS H W g w © 0 © 0 © 0 0 0 © © 0 © 0 © $g l i ^ ^ s ? ^ ! ^ ! ^ ! ^ Missis? fe; _ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 * 3 " o o o o o o o o o o o o o o O O ^ O O O M i D O O t M < D 0 D < 0 ft in O © r t W H H H H O O O O o O O O O O © , H i H . H r t ^ r ^ r H H i H . H < N J C M e M 11A NOTES RE TABLE 1. No» 6 Y e l l o w i s h i n i t i a l l y : turned b l a c k a f t e r 24 h r s . No. 8 B l a c k a f t e r 24 h r s . ao* 1Q Dark a f t e r 24 h r s . j b l a c k e n i n g w i t h longer time 1 1 V e r y s l i g h t l y dark a f t e r 48 h r s . P i n a l f i l t r a t e and -;'^ >.// / ' / ' p r e c i p i t a t e b o t h . f a i r l y dark.. j*o. 12 Darkened a f t e r 48 h r s . «o. 13 V e r y s l i g h t l y dark a f t e r 72 h r s . F i l t r a t e and p r e c i p i t a t e both s l i g h t l y dark. mo. 14 Dark a f t e r 48 h r s . 12 SOLUBILITY OF CUPKOUS ETHYL XANTHATE E q u i v a l e n t q u a n t i t i e s of copper s u l f a t e (GuS0 4.5H g0) (13.4 gms.| and potassium e t h y l xanthate ( 1 7 . 3 gms.) to r e a c t a c c o r d i n g t o t h e ' e q u a t i o n : 2. GnSQ4 + 4 KEtX * . 2GuEtX + ( E t X ) g 2 K g S 0 4 and form 10 ••gms. cuprous e t h y l xanthate, were d i s s o l v e d i n water, and the s o l u t i o n s mixed. The p r e c i p i t a t e was f i l t e r e d and washed w i t h water and w i t h 9b% e t h y l a l c o h o l , and s t i r r e d overnight, i n water* -The - p r e c i p i t a t e was again f i l t e r e d , .extracted w i t h a l c o h o l and -ether, -and d r i e d at a low • temperature. ©.1 gm. p o r t i o n s o f dry cuprous e t h y l xanthate, prepared as above, were a g i t a t e d overnight w i t h about 1 l i t r e of water, then f i l t e r e d ; and the p r e c i p i t a t e t r a n s f e r r e d t o 1 l i t r e b o t t l e s w i t h 1000 c c . of d i s t i l l e d water, t o g i v e a s o l u t i o n h a v i n g a pH of 7.1 - 7.4. These p r e p a r a t i o n s -were a g i t a t e d f o r 21§ hours. At the end of t h i s time the pH was 5.0 - 5.1. They were then f i l t e r e d through f i l t e r paper and asbestos; but continued t o pass through the f i l t e r as a cloudy l i q u i d , p r o b a b l y an emulsion of dixanthogen. 2 c c . 6: N h y d r o c h l o r i c a c i d was added t o the f i l t r a t e , which was then evaporated almost to dryness, made j u s t a l -k a l i n e w i t h ammonia, and then b o i l e d t o expel excess ammonia. 2 c c . -ammonium n i t r a t e s o l u t i o n (100 gm. per l i t r e ) were ad-ded, and the s o l u t i o n was made up t o a volume of 60 cc. 13 A c o l o r i m e t r i e comparison was attempted between a 10 cc p o r t i o n of the above, s o l u t i o n , and a 10 ce. p o r t i o n o f a standard copper s u l f a t e s o l u t i o n , c o n t a i n i n g 4 gm. ammonium n i t r a t e per l i t r e , a f t e r adding 2 drops of potassium f e r r o -cyanide s o l u t i o n (40 gms. p e r l i t r e ) t o each. I t was found, however, t h a t i n s u f f i c i e n t c o l o r was developed t o make t h i s procedure f e a s i b l e . Further, work ©n t h e s o l u b i l i t y of cuprous e t h y l xanthat• was not attempted. 14 METHODS FOR MEASURING FLOATABILITY I f the premise i s accepted t h a t a s o l i d i s f l o a t a b l e ; when i t s s u r f a c e i s hydrophobic; and t h a t i t may possess t h i s pro-p e r t y t e a g r e a t e r or l e s s extent; the question arises:• ' How can t h i s degree of w a t e r - r e p e l l e n c e or f l o a t a b i l i t y be meas-ured? I t has been determined p r e v i o u s l y i n v a r i o u s ways . The f l o a t a b i l i t y has been measured as the percentage of f i n e l y -ground s o l i d r e c o v e r e d i n a f l o t a t i o n f r o t h , under p a r t i c u l a r c o n d i t i o n s approximating those e x i s t i n g i n I n d u s t r i a l f l o t a t i o n c e l l s . The extent t o which a s u r f a c e i s hydrophobic has been measured by the magnitude of- the contact angle between an a i r - b u b b l e and the submerged s o l i d s u r f a c e ; or between a water drop and the s o l i d s u r f a c e i n a i r . T© a l e s s e r extent, the displacement p r e s s u r e of water by a i r , and the heat of wetting of the s u r f a c e have been used as measures of f l o a t a b i l i t y . The contact angle i s p r o b a b l y the most fundamental meas-ure of the s t a t e of a - s o l i d surface., and i s a d e r i v a b l e fun- • c t i o n o f the s o l i d i n t e r f a c i a l t e n s i o n . However, the con-cent s a t i o n o f a f i n e l y - ground s o l i d at a l i q u i d - g a s i n t e r -f a c e i s a more d i r e c t measure of f l o a t a b i l i t y . In the c u r r e n t work i t was d e c i d e d to use the l a t t e r method. I t became ne c e s s a r y , t h e r e f o r e , t o develop an apparatus to make small .'.scale f l o t a t i o n t e s t s , which would permit c l o s e c o n t r o l of as many as p o s s i b l e of the v a r i a b l e s inherent i n the p r o c e s s . I t was at f i r s t thought that some i n f o r m a t i o n might be o b t a i n e d by a l l o w i n g s i n g l e a i r bubbles of known s i z e t o r i s e 15 through a pulp of m i n e r a l i n water, and determining the con-c e n t r a t i o n of m i n e r a l i n the upper p a r t of the p u l p , as a f u n c t i o n of the t o t a l i n t e r f a c i a l area represented by the bub-b l e s . No s a t i s f a c t o r y method could be d e v i s e d , however, to remove the concentrated s o l i d b efore the a i r bubbles c o l l a p s e d and .allowed the s o l i d t o s e t t l e back i n t o the p u l p . In order t o h o l d the w a t e r - r e p e l l e n t m i n e r a l above the p u l p , i t i s ne-c e s s a r y t o m a i n t a i n a f r o t h zone i n which the i n d i v i d u a l a i r bubbles are r i s i n g w i t h a v e l o c i t y g r e a t e r than the e f f e c t i v e downward v e l o c i t y of the m i n e r a l p a r t i c l e s . With t h i s i n mind, a pneumatic g l a s s f l o t a t i o n c e l l v(Fig*' 2) was developed, which I s b e l i e v e d t o have c e r t a i n advantages f o r t h e present work /Over e x i s t i n g types of l a b o r a t o r y c e l l s . The a l l - g l a s s con-s t r u c t i o n f a c i l i t a t e s - c l e a n i n g , and,minimizes contamination o f , t h e p u l p by the m a t e r i a l of the c e l l . I n p r a c t i c e i t i s found n e c e s s a r y to c l e a n the s i n t e r e d p l a t e a f t e r each run by f o r c i n g aqua r e g l a through i t , t o remove small s u l f i d e p a r t i c l e s which tend t o c l o g the p o r e s . A i r supply i s e a s i l y r e g u l a t e d . . - j s l l m i n a t i o n of mechanical a g i t a t i o n , other than -by,the stream of a i r bubbles allows; c l o s e r r e p r o d u c i b i l i t y of t h l a v a r i a b l e ' t h a n Is p o s s i b l e when an Impeller Is used. 16 FLOTATION WITHOUT REAGENTS Procedure w i t h p r e c i p i t a t e d rbS, galena, and s i l i c a . The c e l l was used f i r s t to study the f l o t a t i o n of syn-t h e t i c l e a d s u l f i d e i n d i s t i l l e d water, u s i n g no f r o t h e r or other r e a g e n t s . The c e l l was s e t up and p r o v i s i o n made t o introduce a constant stream of water (about 5 cc. per minute) at the top, to cause an overflow. Approximately 5 gram p o r t i o n s o f l e a d s u l f i d e were prepared by s a t u r a t i n g 500 c c . of a water s o l u t i o n Of 7 grams of l e a d n i t r a t e w i t h hydrogen s u l f i d e gas, and wash-i n g the p r e c i p i t a t e e i g h t times b y decanting o f f succe s s i v e 500 c c . p o r t i o n s of d i s t i l l e d water. A 5 gram p o r t i o n of lead, s u l f i d e was t r a n s f e r r e d to the c e l l , and the pulp volume made up t o about SO© c c . S u f f i c i e n t a i r p r e s s u r e was maintained t o prevent the l i q u i d running through the s i n t e r e d p l a t e , but i n s u f f i c i e n t t o cause any overflow. The pH of the pulp was taken, and the a i r p r e s s u r e Increased u n t i l overflow was j u s t about t o occur. The f e e d water was turned on, and the over-flow c o l l e c t e d f o r 10 minutes, a f t e r which the feed water was shut o f f , the a i r tu r n e d down, the volume of pulp and conce n-t r a t e n o t e d , and a pH measurement made on the p u l p . The "con-c e n t r a t e " overflow, and the " t a i l i n g s " pulp remaining i n the c e l l were f i l t e r e d through Gooch f i l t e r s , and the weights of s o l i d i n each were measured. From these weights, the t o t a l weight of l e a d s u l f i d e used, the percentage of t h i s weight recovered i n the overflow, and the percentage recovered per 17 u n i t volume of the overflow were c a l c u l a t e d . The r e s u l t s of t h i s s e r i e s of runs are g i v e n i n Table 2. I n the ahove t e s t s a c e r t a i n amount of pulp overflowed w i t h the I n c i p i e n t f r o t h . The pulp m e c h a n i c a l l y c a r r i e d a d e f i n i t e weight of s o l i d i n t o the overflow. I f the s o l i d used i s hydrophobic, the observed r e c o v e r y should be g r e a t e r than _ the mechanical r e c o v e r y ; and i f h y d r o p h i l i c , the observed r e -covery should be l e s s . I n order to c a l c u l a t e the mechanical r e c o v e r y , i t i s assumed t h a t , at any i n s t a n t , the .-concentration of s o l i d i n the o v e r f l o w i n g pulp i s the same as i n the body of the p u l p . I t i s a l s o assumed t h a t the I n i t i a l volume of pulp does not change. T h i s implies.'that the f e e d water causes an overflow'of a volume of pulp equal t o t h a t of the water added. • L e t A co. be the constant volume p f pulp -In the c e l l , and G gms. be the o r i g i n a l weight of s o l i d s In the p u l p . A f t e r n c c . of f e e d water has been added, an equal volume of concen-t r a t e , -containing x gms'. of s o l i d s has overflowed. A f t e r x gms. of . s o l i d - has overflowed, \ the instantaneous concentration. ' of s o l i d In the pulp w i l l be G - x gms. per cc. I f a v o l -A ume dn cc. now o v e r f l o w s , i t w i l l c o n t a i n dx gms., and the c o n c e n t r a t i o n of s o l i d i n the overflow w i l l , be dx gms. per c c . ..' :dn, I t has been assumed t h a t these c o n c e n t r a t i o n s are equal. T h e r e f o r e : • dx. ^ . G - x . dn - ~ ~ i r ~ f * dx : I f dh. 18 "' In A G.. h F>om t h i s e q u a t i o n , the weight of s o l i d (x gms.) overflowing " m e c h a n i c a l l y " has been '-calculated f o r the v a r i o u s t e s t s , and the r e s u l t s t a b u l a t e d i n Table 2 and subsequent t a b l e s . From the work w i t h p r e c i p i t a t e d l e a d s u l f i d e c e r t a i n con-c l u s i o n s may be d r a m , I f a l l v a r i a b l e s (pulp volume, a i r p r e s s u r e , weight of s o l i d s , and volume of feed water added)------are kept constant In a s e r i e s of runsj the volume of overflow i s n e c e s s a r i l y constant, and the weight of s o l i d s recovered i n the o v e r f l o w i s a r e p r o d u c i b l e f i g u r e . I f the a i r p r e s s u r e , i n i t i a l p u l p volume, and volume of feed water added are kept -constant i n a - s e r i e s of runs, tout g r e a t e r weights of s o l i d are used i n the c e l l , the pulp volume tends to Increase during a run, and the f i n a l volume of overflow i s l e s s . - At the same time the r e c o v e r y I n c r e a s e s , but the r e c o v e r y p e r u n i t volume of overflow tends t o remain f a i r l y c onstant. The l a t t e r f i g u r e , because i t tends to take care of . s l i g h t unavoidable v a r i a t i o n s i n . o v e r f l o w volume,, has been used as the f i n a l f i g u r e i n each ru n . The a i r p r e s s u r e which must be a p p l i e d to j u s t cause the c e l l t o overflow depends on the volume of pulp i n the c e l l . A s m a l l p u l p volume r e q u i r e s a h i g h a i r p r e s s u r e , and v i c e v e r s a . At the same time, the t o t a l r e covery, and the recovery per u n i t volume of overflow are Increased by the use of a smal-l e r pulp volume and a g r e a t e r a i r p r e s s u r e . In a l l cases, the 19 1 3 3 M Ml CQ S i SI >4 °. . o . o o -(35 o o CD S - O J O CO CM tO CxJ CO cn en 3 o CM cn i n s o e LO r-1 CM cn t© CVJ 8 O I N * « e*-CM co cn CM i n CM cn CM O - -® to to tO to CM i n © to : .to to CO to 8 3 to to tv o O • .H s CM CM m CM O OS CM to CM to CM tO 3 CM o i H •CO CM CVJ to to to E- tO 3 r-5 <H CM i H to tO r H e « to to 9 e tO i n to •in e to © to to o cn CM e to o © «o i n CM to o » to to 3 3 § 5 ID O cn o to CM 3 3 3 m to i n CM O CM to CO CO cn CM to cn PQ to o o 8 g O O O O c~ co co CM tO CM CM CM OV CO i n cn to cn co CO 2 i n o co CO • £ - • to to to 8 5 85 co to cn cn CM cn to to to cn CM CM CM CM ® © O O o O cn to to co cn rH to rH »H to e- rH cn « e « •tO to tO to i n to co © * e to to t0 tO o O o o © o © • m i n i n i n 41 <# i n m m i n o to to to i n to § o CM i n cn © tO CM to 8 8 to to CO to o i n c«- CM i n m m ft 0 » o o o oo CO I H tO to cn o CO » © e i n i n to m to 20 a c t u a l recovery Is l e s s than the c a l c u l a t e d r e c o v e r y per c c . of o v e r f l o w . T h i s i n d i c a t e s t h a t , under the c o n d i t i o n s of the experiment, p r e c i p i t a t e d l e a d s u l f i d e shows no tendency t o concentrate at the a i r - l i q u i d i n t e r f a c e ; t h a t i s , i t does not d i s p l a y any in h e r e n t f l o a t a b i l i t y . T h i s c o n c l u s i o n assumes, of course, that in the process of o v e r f l o w i n g , there i s no tendency at the overflow l i p f o r the s o l i d t o he h e l d back to a g r e a t e r extent than the l i q u i d . In -ah endeavor t o make t h i s l a t t e r assumption unnecessary, p a r a l l e l t e s t s were made w i t h l e a d s u l f i d e , galena, and an h y d r o p h i l i c m a t e r i a l such as s i l i c a . P r e l i m i n a r y t e s t s on v a r i o u s s i l i c a samples, given In Table 3 showed t h a t i t was necessary t o make comparisons between s i m i l a r l y s i z e d m a t e r i a l s . A water e l u t r i a t o r ( F i g . 3) was b u i l t , , and c a l i b r a t e d by the r i s i n g v e l o c i t y of water pro-duced at v a r i o u s stopcock s e t t i n g s . T h i s apparatus gave v e l -o c i t i e s up t o 26 cm. per minute, corresponding t o the s e t t l i n g r a t e of a quartz p a r t i c l e o f approximately 0.07 mm. diameter, or 200 mesh. Galena, f o r use i n subsequent t e s t s , was prepared j u s t b e fore u s i n g by g r i n d i n g 8 t o 10 grms. of l / 4 " mineral under d i s t i l l e d water i n a c a r e f u l l y cleaned p o r c e l a i n or agate mortar, and i n t e r m i t t e n t l y washing f i n e m a t e r i a l i n t o the e l -u t r i a t o r u n t i l the e n t i r e p o r t i o n had been t r a n s f e r r e d . Par-t i c l e s w i t h a s e t t l i n g r a t e of 3.5 to 9 cm. per minute were then separated by the e l u t r i a t o r , and t r a n s f e r r e d at once to the f l o t a t i o n c e l l . P o r t i o n s of an assay grade of powdered <s5 21 TO o B te-ra ra o o s s r-5 , © 1 EO r-8 (-8 CO « • e o o O to * •9 CQ W "<* CO. to IS o r-< ' e o o o © <# e» Cfil « » CO in PI •-5 -si o I-I t-f ra TO B P4 t*5 to tD t0 t© O TO LO o o M o TO .a O o 93 O ra & . O o r-8 ©I r-8 CO t0 i©' / • ' ' ^ I D O lO CO Os CT> w CM CM o O o o O o to era to ID ts o cn f-j CM ® » o o O o <H CO CM cn cn -* -* ^JI m r-4 22 s i l i c a were p l a c e d i n the e l u t r i a t o r , and the f r a c t i o n w i t h a s e t t l i n g v e l o c i t y i n the range 3.5 - 9 cm. per minute was removed. T h i s p o r t i o n was d i g e s t e d i n h y d r o c h l o r i c a c i d , wash-ed f r e e of f e r r i c c h l o r i d e , d r i e d , and b o t t l e d u n t i l r e q u i r e d , Wo attempt was made t o s i z e the p r e c i p i t a t e d l e a d s u l f i d e , as i t c o n s i s t e d of f l o e s which would break up when the suspension was a g i t a t e d . The r e s u l t s of t e s t s made on the s i z e d galena and s i l i c a , u s i n g th© same procedure as f o l l o w e d f o r l e a d s u l f i d e , are given i n Table 4 and Table 5. A comparison of r e s u l t s i s shown by the graph P i g , 4, I n which only comparable-results have been p l o t t e d . .. Tables 6.to 8 are the r e s u l t s of miscellaneous runs on l e a d s u l f i d e and s i l i c a w i t h the a d d i t i o n of v a r i o u s reagents -to the f l o t a t i o n p u l p . The runs made w i t h l e a d s u l f i d e i n a pulp c o n t a i n i n g 25 mgm. potassium e t h y l xanthate per l i t r e , over the pH; range 3 t o 1 0 , show t h a t xanthate s l i g h t l y i n c r e a s e s the a c t u a l r e c o v e r y per c c . I n s u f f i c i e n t wark was' done i n t h i s s e r i e s t o determine the-- e f f e c t of pH on recovery. Con c l u s i o n s • . I t may be concluded from these r e s u l t s t h a t , w i t h i n the l i m i t s of experimental e r r o r , the galena and s i l i c a p a r t i c l e s I n v e s t i g a t e d have the same f l o a t a b i l i t y ; hence, that t h i s specimen of galena has no inherent f l o a t a b i l i t y . I t i s a l s o evident from P i g . 4 that the behavior of p r e c i p i t a t e d l e a d s u l f i d e Is not m a t e r i a l l y d i f f e r e n t from that of galena or s i l i c a . © B B S 1 m o o E H o o •8 3 CVJ 0> . .3 4 » CD O o a © o cn . to o o cn e-© © r H r H © r r l ' era era era co era co • • e e o » © O O O O © in cn in in to © to © o ft ft © • to m m in to <—8 r H >* r-4 o r H OJ O © rH to CVJ OJ to to in a O <# g CO o to o CO 3 OJ cn oj to © to o to OJ co OJ cn o • ft cn to cn cn CO to » •» » to to to r-l E» © » • E - to to O o o -» • in in O © o « OJ © «# to in m in cn cn cn Ol ca OJ OJ •ft in cn ft o o s LO o» OJ o o to 8 OJ OJ © to «* ft CD « 3 co ft tn co 9 m in cvj « to o * to CO © cn •in o» in m o © cn 02 o cn OJ in cn OJ in 2 in cn OJ cn cn to o to to CVJ CO 03 r-S O cn to CVJ CVJ cn r H ' CO • « © o cn O cvj c- m e~ c- co e • • rH OJ CO CV3 OJ in OJ co cn in in to OJ 23 3 s s to to to d o d E - O « ft in to 3 3 cn & OJ 1 to o i s to rH E~ to O r H o • tO tO cn r-t ft e ID tO © © . o e « m in in to in . O © m 9 E~ • n © o in CO rH in m • in in in in cn oi o o to cn E~ OI o cn oj OI cn 03 24 CM co cr» o o d-i o o rH rH to to to to to CO 9 9 © , » • » o o o o o o o CO to o E - o » •'» -e © '•9 9 to to JS to in' rH rH rH . rH rH to Cw cn CM <x» E - to to O rH CM CM CM CM CM • 9 9 © o O © O O O E>- to t© o o Oi CO * e © 9; 9 CQ LO *#" to CM cn rH rH •H tO to co cn cn '9 » * © 9 t© to tO to to to IN CO cn to © » e » 9 to to to' tO <o to o o © o O o « o • 9 9 8 in in in m m in <# o o o © o in e « • • e to in CO tn m in in in o m in in cn en cn cn cn CM CM CM CM CM © o o O o o o o o o CO CO CO. CO to rH 10 E'- to o cn en o cn tO in to co in 9 9 « 9 9 o o O o o m cn co CO «o co E~ to E'- E-o cn cn en m <* '9 9 a • CO m o rH co o rH CM CM CM to o o to © o CO to CM to in » in to o I 3 a. M -p ra -p ® 0) 25 o W o w o r-1 o M to o o o o o o o to Oi TJ< o *# o r-8 o o o to to to to o e e • o o o o •in to o oo « LO . o r-S r-8 r-8 m co CO £*-CO CT> O in to CO CO • e e o o o o CO cvj to o * © e in co CO r-8 CVJ r H r-8 fH L V CVJ t© • e to CO CO o r-8 r-8 » • a to o - rt in in in m o M to o OS cn co CO CO ® in o cn in r-8 S (55 u o CM r-8 cn in to r H CO CVJ to in to in o in m o LO to to to co CO to o oo CVJ o o to CO cn to to to o o in 10 10 i H r H to >sS» ft! to CO to to to o o o o LO o o o o o to to , to to CO to o ©J cn £•» r-8 to in CO CO cn cn in in e, * » « o o o o o r H to fi- cn to Oi c- cn CO co o o cn en co * • « in in a r H Cvj CO •<* I o (-3 CO s M P4 M O 8 O la? O O CO P i o rH O a If s © o tra o i> era oo oo t -•tf to CO to o to to LO tra era tra tra 0 © s o O o o i n co i n co era * rH tO tO to i n rH • to o CO CVJ o o .-era' co tra i n to r H m rH "5? rH in to CVJ in ' a CVJ co rH o i n o ,* e-• 0 to m era oo CO, i n , o tOi ail CVJ m 3 § o i n m co to i n CVS CM CM o © O i n tO CM CM w o cn CM CO CM CVJ . rH © ,. ® © o o O CM era i n 00 era tra • • i n to to 00 tra tra era co PP 'rH\ •3 O O B o s-i M CO i-H OJ O O s? o (3=1 26 o to tra co era co o o i n co o o o o CM i n CM cn o o CM o i n CM co © cn tra cn 0 cn era 27 FLOTATION WITH TERPINEOL ALONE • ~ (Inherent F l o a t a b i l i t y ) ~ The runs w i t h l e a d s u l f i d e and s i l i c a , i n which e t h y l a l c o h o l was used as a f r o t h i n g agent (Tables 7 and 8) show tha t the f r o t h e r m a t e r i a l l y decreases the recovery per cc. by dec r e a s i n g the "mechanical r e c o v e r y " . While e t h y l a l c o h o l doe not g i v e a s a t i s f a c t o r y f l o t a t i o n f r o t h , the runs o u t l i n e d i n Tables 7 and 8 suggested the advantage of u s i n g a f r o t h i n g agent t o decrease t o a minimum the mechanical recovery of an h y d r o p h i l i e s o l i d , w h i l e a l l o w i n g maximum recovery, w i t h small overflow o f l i q u i d , of a s o l i d which i s hydrophobic. The f o l -lowing t e s t s were made u s i n g t e r p l n e o l as a f r o t h e r . Procedure w i t h p r e c i p i t a t e d l e a d s u l f i d e Approximately 5 gms. of p r e c i p i t a t e d l e a d s u l f i d e i n 150 of p u l p , c o n t a i n i n g 5.3 mgms. t e r p i n e o l per l i t r e was pl a c e d i n the f l o t a t i o n c e l l , and a i r pressure a p p l i e d s u f f i c i e n t to form a copious f r o t h . No t r a c e of l e a d s u l f i d e appeared i n the f r o t h . Procedure w i t h Galena #2 (Run No. 45) A l l apparatus was c a r e f u l l y cleaned w i t h chromic a c i d and d i s t i l l e d water. A sample of Galena #2 was ground under d i s t i l l e d water, s i z e d , and a 1.82 gm. p o r t i o n , having a s e t t l i n g r a t e of 9 - 25 cm. per minute t r a n s f e r r e d to the f l o t a t i o n c e l l . The pulp volume was made up to 150 c c . and 3.5 cc. t e r p i n e o l s o l -u t i o n ( I c e . = 0.25 mgrn.) added t o make the conc e n t r a t i o n of 28 t e r p i n e o l 5.8 mgm. per l i t r e . In t h i s s o l u t i o n , c o n t a i n i n g no acids or a l k a l i s ; and In the presence* of h y d r o c h l o r i c a c i d or sodium hydroxide, over the pH range 3 t o l l O t h e r e was no t r a c e of galena i n the f r o t h , Procedure w i t h Galena #5 (Run No. 58) A l l apparatus was c a r e f u l l y cleaned w i t h chromic a c i d and d i s t i l l e d water. A sample of Galena #5 was ground under d i s t i l l e d water, s i z e d , and the p o r t i o n having a s e t t l i n g r a t e of 9 - 25 cm. per minute t r a n s f e r r e d t o the f l o t a t i o n c e l l . The pulp v o l -ume was made up t o 250 c c . and 4 c c . t e r p i n e o l s o l u t i o n (1 c c . = 0.25 mgm.) added to make the c o n c e n t r a t i o n of t e r -p i n e o l 4 mgms . per l i t r e . Time was measured from the time of adding t e r p i n e o l . Three f i v e - m i n u t e concentrates were taken o f f , as shown below, w i t h the a d d i t i o n of 4 cc. of t e r p i n e o l s o l u t i o n b e f o r e concentrates #2 and #3 were removed. Run-Wo. 58 '• Product .• Weight (gms.) pH Pulp % Recovery Concentrate #1 (1-6 min.) 1.042 4.04 36.8 ..' #2 (13-18 min.) ' .0.202 4.04-4.13 7.06 " #3 (30-35 min.) 0.092 4.13 3.24 T a i l s 1.505 52.9 Heads 2.839 100g0 Conclusi o n s P r e c i p i t a t e d l e a d s u l f i d e i s not f l o a t e d by t e r p i n e o l a l o n e . Two samples of g a l e n a , both apparently pure specimens, 29 d i f f e r m a t e r i a l l y i n t h e i r f l o a t a b i l i t y w i t h t e r p i n e o l alone. Of the two samples s t u d i e d under s i m i l a r c o n d i t i o n s , the f i r s t has no in h e r e n t f l o a t a b i l i t y , while the second has an a p p r e c i -able f l o a t a b i l i t y . The galena specimen showing no n a t u r a l f l o a t a b i l i t y , i n view of e a r l i e r o b s e r v a t i o n s , y i e l d s l e a d ions t o a g r e a t e r extent than the other specimen, when p l a c e d i n water. Because of these c o n f l i c t i n g r e s u l t s , no c o n c l u s i o n can be drawn at t h i s time, as t o the inherent f l o a t a b i l i t y of galena.. I t i s probable t h a t the s t a t e of o x i d a t i o n of the galena s u r f a c e determines I t s f l o a t i n g c h a r a c t e r i s t i c s w i t h t e r p i n e o l alone. As a t e n t a t i v e h y p b t h e a i s . i t i s suggested t h a t the s u r f a c e of a pure l e a d s u l f i d e c r y s t a l (which might be o b t a i n e d by g r i n d i n g galena under oxygen-free water f o r contact angle measurements) may be n o n - f l o a t a b l e ; but t h a t a d s o r p t i o n of atmospheric oxygen may make such a surface floatable... I f the a d s o r p t i o n continues t o such a point that; the s u r f a c e becomes e s s e n t i a l l y one of l e a d s u l f a t e , o r - l e a d oxide, the c h a r a c t e r of the m i n e r a l s u r f a c e i s again hydro-p h i l i c . • •  • T h i s h y p o t h e s i s might be t e s t e d by p r e p a r i n g and f l o a t i n g galena i n the presence of some i n e r t gas, although elaborate p r e c a u t i o n s would be necessary to i n s u r e the p u r i t y of the l e a d s u l f i d e s u r f a c e , the t o t a l e x c l u s i o n of oxygen, and the e l i m i n a t i o n of any p o s s i b l e contaminants. 30 ' FLOTATION OF XANTHATE-TREATED GALENA WITH TERPINEOL Procedure • Galena was ground and s i z e d as be f o r e , and the p o r t i o n h a v ing a s e t t l i n g r a t e of 9 - 25 cm. per min. (35 - 50 microns measured p a r t i c l e s i z e ) was t r a n s f e r r e d at once to a beaker "and c a r e f u l l y s t i r r e d f o r 4 min. w i t h 250 cc. of potassium e t h y l xanthate solution (25 mgm..per l i t r e ) . The solution was poured o f f , and the m i n e r a l again t r e a t e d f o r 4 min. with 250 c c . of f r e s h xanthate s o l u t i o n of the same c o n c e n t r a t i o n . T h i s s o l u t i o n was poured o f f and the galena s t i r r e d f o r 4 min. with 250 cc. of d i s t i l l e d water, after which the wash water was decanted o f f , the galena transferred to the f l o t a t i o n c e l l , h y d r o c h l o r i c a c i d or potassium hydroxide added to c o n t r o l the pja, and the volume of pulp brought up t o 250 cc. while main-t a i n i n g a low p r e s s u r e of a i r . The pulp was a i r - a g i t a t e d i n the c e l l f o r 5 - 1 0 minutes, w h i l e i n i t i a l ph readings were made at frequent i n t e r v a l s . 4 c c . of t e r p i n e o l s o l u t i o n (250 mgm. per l i t r e ) was added to make the terpineol concentration i n the pulp 4 mgm. per l i t r e . The a i r p r e s s u r e was brought up to 45 cm. of mercury, and the o v e r f l o w i n g f r o t h c o l l e c t e d f o r 5 min. A f i n e stream of water (about 5 cc, per min.) was used to wash down the i n s i d e g l a s s w a l l s of the c e l l d u r i n g the run, and to a s s i s t the f r o t h to overflow. A f t e r the 5 min. p e r i o d , the a i r p r e s s u r e was lowered t o stop the overflow; a s e r i e s of pH measurements was made on the pulp remaining i n the c e l l ; and 31 the volume of pulp i n the c e l l was noted. The concentrate and t a i l i n g s pulps were f i l t e r e d through Gooch c r u c i b l e s ; the c r u c i b l e s were.dried overnight at approximately 80° 0., and weighed. The r e c o v e r y was c a l c u l a t e d as the percentage weight of t o t a l m a t e r i a l recovered i n the f r o t h overflow. The pH at the beginning and end of each run was obtained by p l o t t i n g pH versus time, and i n t e r p o l a t i n g . -R e s u l t s The r e s u l t s of t h i s s e r i e s of t e s t s are g i v e n i n Table 9 and F i g , 5. Runs numbered 45 - 56 were made on #2 Galena; runs #57 - #60 on No. 5 Galena. Remarks The xanthate s o l u t i o n , a f t e r i t was used f o r t r e a t i n g HO. 2 Galena, became qu i t e cloudy; but remained p r a c t i c a l l y c l e a r w i t h NO. 5 Galena. I t would appear that the former sample may have contained an a p p r e c i a b l e amount of s o l u b l e l e a d compounds whi ch r e a c t e d w i t h the xanthate s o l u t i o n t o form a suspension of l e a d e t h y l xanthate. Subsequent t e s t s (Runs 45 and 58) a l s o showed t h a t the two samples behaved d i f f e r e n t l y i n f l o t a t i o n . In a l l runs made, the pH i n a l k a l i n e s o l u t i o n s tended t o drop; and i n a c i d s o l u t i o n s , t o r i s e during the course of the r u n . T h i s change of pH w i t h time i s shown, by F i g . 6 and F i g . 7. In o n l y two cases (Runs 53 and 55) d i d the pH tend t o reach a constant value of 7.4 - 7.5. T h e r a t e of change of pH w i t h time appears t o be greatest, when the i n i t i a l con-c e n t r a t i o n of a l k a l i i p s m a l l . I t i s s i g n i f i c a n t that t h i s r-H O !2i 1 C5 CO Pq O |35 O t-H H o r-T o rH ,-H ^ W o o CM O o • 0> -P O rrj tr} rj W p p Q M Q M M s O 1 I 1 W w1 rH r-H !25 g o ! O (3! is? M w ov cn cn cr> o o o o o O • e cn i — * cn rH • © o o O > ^-^ o o o » © o o 12! © o 125 « 9 o o o O o o . © O 9 o o o a o O o CM CM o o o o © o o o 1-J rH cn to r H CO o 01 o M o 8 !25 0) E» 0 •H •** PM-rH (4 O cn CD M O 43 • O O (S rH • 4» (2? O K O © » o .o co 1 r n g o M co &1 LO c3 I I CO b o LO CM a* r H . O CM CO © » © © ® » « © © » O r H E- 50 cn co o cn cn 0> LO to 03 co CO cn co o o rH CD cn HP O <8 d •p « W o CD O LO e cn LO CM CO tO LO cn O to H rH to CM cn O cn cn O o to co CO o to co LO co O LO LO tO E~ o to O to rH o CM CO » « © « © « • ft © © 0 LO to rH o o O o to . cn CM rH' r H rH rH r H ® CM CO o O CO o CM & cn 00 o © • o CM CM tO o E» O cn CO to li- CO rH cn oo CO o to en t> to *r4 to cn o cn CM rH co LO LO 0 • © ® • * © « © •e • CO rH rH LO to CO CM rH to rH 00 ID CO CO t~ CO o CO to CO CO rH r-l ca CM CO <o E- CO CM E» LO t> to CM cn o o CO LO to rH to LO CM • • » • « © © « « ft *> *! CM «# CO LO CO CM CM to to to CO cn o rH 'OS- CO ^ « LO E~ cn -st' LO LO LO LO LO LO LO LO s M 1 S3! cn O E>- co CM CM to OS to LO cn a « © » CM E» CM O rH cn CO ft o r H LO . © © © . o o LO o in in © O © in LO in in in to to LO t0 r-H to LO LO LO CM CM CM CM CM OJ OJ OJ Oi OI CM CM CM CM © o © O o o o O o © o o o o in in LO LO lO LO LO LO LO r-H LO LO in LO OJ CM CM CM CM OJ CM OJ OI CM OJ OI OI CM <o to • • - 33 NOTES RE TABLE 9. Run #48 Measuring time from the a d d i t i o n of t e r p i n e o l , there was no t r a c e of galena i n the f r o t h at 7 min. (pH 10.91); but a s m a l l amount was v i s i b l e at 8 min. (pH 10.82). At 11 min. 2 c c . N/10 HC1 was added t o reduce the pH to 10.0, and a concentrate was taken o f f duri n g the i n t e r v a l between 14 and 19 min. The f i n a l pH observed at 14 min. was 9.23. Hun #49 As the pH continued t o drop a f t e r the run was com-p l e t e d , more galena appeared i n the f r o t h . In t h i s run, the concentrate l i q u i d was y e l l o w i s h i n .color,, but c l e a r . Run #54 An a p p r e c i a b l e q u a n t i t y of l e a d s u l f i d e was recovered from the t a i l i n g s f i l t r a t e by s a t u r a t i n g i t with hydrogen s u l f i d e gas a f t e r the run was completed. A m i c r o s c o p i c examination of the u n f l o a t e d galena i n the t a i l i n g s showed i t to " c o n t a i n a co n s i d e r a b l e amount (30 t o 50%) of a white , s i l i c e o u s - a p p e a r i n g m i n e r a l . Run #57 The pulp i n the c e l l was f r e e of galena at 5 min. The l o n g e r time and e x t r a t e r p i n e o l was used t o cause the galena a l r e a d y i n the f r o t h at 5 min. t o overflow. A n e g l i g i b l e amount of l e a d was detected i n the t a i l i n g s f i l t r a t e by s a t u r a t i n g i t with hydrogen s u l f i d e . Run #59 The t a i l i n g s f i l t r a t e was very dark i n c o l o r . D Ul bj VJ J - 2 < < w o: a. 34 change of ph i s v e r y s i m i l a r to t h a t observed w i t h the l e a d 'xanthate suspensions used i n determining the s o l u b i l i t y of l e a d xanthate. The e q u i l i b r i u m pH of 7.4 - 7.5 may correspond w i t h the pH a s s o c i a t e d w i t h minimum l e a d xanthate s o l u b i l i t y . i t i s a l s o noteworthy that the two p o i n t s on the graph ( P i g . 5) f o r runs 59 and 60, made w i t h Galena #5, f a l l on the curve obtained f o r (ialena #2. Conclusions The graph ( F i g . 5) shows that complete, or almost com-p l e t e r e c o v e r y of galena i s attained, i n the pH range 2.5 to 9,5 (approximate). Between pH 10.0 and 10.8 the recovery i s a l i n e a r f u n c t i o n of the pH, and becomes zero when the pH i s 10.8' or h i g h e r . These f i n d i n g s s u b s t a n t i a l l y agree w i t h those of Wark and Cox (34.3.2) obtained by contact angle measurements. These workers r e p o r t e d the c r i t i c a l pH of gal e n a i n a 25 mgm. per l i t r e potassium e t h y l xanthate s o l -u t i o n as 10 .1 - 10.3. 35 A FURTHER EFFECT OF pH Procedure A sample of Galena #2 was ground and s i z e d as b e f o r e , t r e a t e d w i t h potassium e t h y l xanthate i n the us u a l way, and t r a n s f e r r e d t o the f l o t a t i o n c e l l w i t h 10 cc. 0.09 N. KOH i n a p u l p volume of 245 c c . Time was measured from the time of t r a n s f e r t o the c e l l , a t 8 min. 4 cc. t e r p i n e o l s o l u t i o n was added t o make the t e r p i n e o l c o n c e n t r a t i o n i n the pulp 4 mgms. per l i t r e ; and the a i r pressure was kept j u s t below that n e c e s s a r y t o produce overflow. No c o l l e c t i o n of galena took p l a c e as the I n i t i a l pri of 11.45 dropped t o 11.2 over a p e r i o d of 12 min.; but galena s t a r t e d to show i n the f r o t h about pH 11.15. At 16-19 min. 10 ce. 0.09 KOH was added t o b r i n g the pH from 11.1 up to 11.5; but the i n c r e a s e i n pH d i d not appear t o decrease the amount of ga l e n a i n the f r o t h . f u r t h e r a d d i t i o n s of 0,09 N KOH were made as f o l l o w s : Time (min.) cc. KOH added pH before a d d i t i o n pH a f t e r 43| 5 10.98 11.28 56| 10 10.96 11.45 69i 10 11.17. 11.56 Throughout t h i s time, no decrease i n the amount of g a l -ena i n the f r o t h was observed. At 75 min, 1 c c . t e r p i n e o l s o l u t i o n (250 mgm. per l i t r e ) was added; the a i r p r e s s u r e i n c r e a s e d to 45 cm. of mercury, and a concentrate removed f o r 5 min. 36 R e s u l t s The r e s u l t s of t h i s run are as f o l l o w s : Head weights* 2*521 gms. Concentrate weight: 2.357 gms. Pulp Volume: Before run 275 cc. A f t e r run 275 cc. pulp pH: tt t! 11.46 tt tt 11.42 % Recovery. 93.4$ Conclusi o n s • I t would appear t h a t once galena Is brought up i n t o the f r o t h , i t i s not depressed, or d i f f i c u l t l y depressed by a pH above the c r i t i c a l v a l u e . The time f a c t o r may, however, p l a y some p a r t . T h i s could be checked by c o n t r o l l i n g the a d d i t i o n of a l k a l i i n such a way tha t the -pH i s always maintained above the p o i n t at which c o l l e c t i o n s t a r t s , and making the run over an extended time. 37 SUMMARY The work undertaken In the present r e s e a r c h i s explor-a t o r y i n n a t u r e . The aim has been t o cover a f a i r l y wide f i e l d , r a t h e r than t o I n v e s t i g a t e f u l l y some p a r t i c u l a r phase of t h a t f i e l d , i n - t h e hope that the gene r a l f i n d i n g s w i l l p o i n t the way to a more e x a c t i n g i n v e s t i g a t i o n of the prob-lems-presented. ' Conclusions advanced at t h i s time should be regarded, t h e r e f o r e , as suggestions f o r f u r t h e r work r a t h e r than as f i n a l , c a r e f u l l y checked statements. 1 . The c o n c e n t r a t i o n of l e a d Ions In e q u i l i b r i u m with a s a t u r a t e d s o l u t i o n of l e a d e t h y l xanthate depends on the pn of the s o l u t i o n , and i s a minimum at 0.15 mgms. per l i t r e i n the pn range 8 . 0 - 8 . 2 . 2. A pneumatic g l a s s f l o t a t i o n c e l l has been developed and found s u i t a b l e f o r making measurements of f l o a t a b i l i t y w i t h samples of m i n e r a l s weighing only a few grams. 3. A method f o r measuring the f l o a t a b i l i t y of s o l i d par-t i c l e s i n the absence of reagents other than water has been I n v e s t i g a t e d • s u f f i c i e n t l y to i n d i c a t e t h a t i t . has some m e r i t , but r e q u i r e s more c a r e f u l c o n t r o l of v a r i a b l e s i f i t i s r e -q u i r e d t o y i e l d q u a n t i t a t i v e r e s u l t s . 4. some n a t u r a l galenas may show Inherent f l o a t a b i l i t y ; others do n o t . 5. A s y n t h e t i c p r e c i p i t a t e d l e a d s u l f i d e can not be f l o a t e d w i t h t e r p i n e o l alone. 6. xhe recovery of galena t r e a t e d w i t h e t h y l xanthate 38 and f l o a t e d i n the presence of t e r p i n e o l i s s u b s t a n t i a l l y complete i n s o l u t i o n s of pH l e s s than 9.5. The recovery Is zero i f the pit of the s o l u t i o n i s 10.8 or h i g h e r . 7. A r e a c t i o n of measurable r a t e takes place when l e a d xanthate, or x a n t h a t e - t r e a t e d galena i s p l a c e d i n an aqueous a c i d or a l k a l i n e s o l u t i o n . The course of the r e a c t i o n may be f o l l o w e d by the change'in ;fH w i t h time. • 8... X a n t h a t e - t r e a t e d galena, once i t i s brought i n t o the f r o t h , i s d i f f i c u l t or impossible to depress by an i n -crease i n the pH ©f the pulp above the c r i t i c a l pH f o r the m i n e r a l . : 9.. ."Some c o r r e l a t i o n may e x i s t between the pH correspond-i n g t o minimum s o l u b i l i t y of l e a d e t h y l xanthate, and th© e q u i l i b r i u m pM a t t a i n e d when x a n t h a t e - t r e a t e d galena I s ' p l a c e d In an a l k a l i n e s o l u t i o n of pH g r e a t e r than the e q u i l i b r i u m v a l u e . • . 

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