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UBC Theses and Dissertations

The surface reactions between flotation re-agents and minerals. The action of cyanide in the flotation… Fitch, Fred Troop 1940

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THE SURFACE REACTIONS BETlfEEN FLOTATION REAGENTS AND MINERALS THE ACTION Off CYANIDE IN THE FLOTATION OF SPHALERITE by F. T. F i t c h A Thesis submitted f o r the Degree of MASTER OF ARTS i n the Department of ' CHEMISTRY A p r i l , 1940 ACKNOWLEDGEMENT I s h o u l d ' l i k e to take t h i s opportunity to express my thanks to Dr. W i l l i a m TJre, under whose su p e r v i s i o n t h i s work was un-dertaken, f o r h i s u n f a i l i n g i n t e r e s t and ma-ny h e l p f u l suggestions. CONTENTS Page I . P r e l i m i n a r y Survey • f l o t a t i o n 1 Frothing Agents 2 C o l l e c t i n g Agents 4 A c t i v a t i o n , D e a c t i v a t i o n , Depressing Agents 5 F l o t a t i o n of S p h a l e r i t e 7 Objects of Present Work 13 I I . Experimental Work Methods of A n a l y s i s CN" Determination 14 Zinc Determination 15 Santhate Determination 16 F l o t a t i o n Tests and Results 18 A c t i v a t i o n and Dea c t i v a t i o n 24 Xanthate A b s t r a c t i o n Tests 26 Cyanide A b s t r a c t i o n Tests 27 I I I . Summary of Results 32 References 34 PRELIMINARY SURVEY FLOTATION F l o t a t i o n i s a method of ore concentration dependent up-on the tendency of a constituent or constituents of a f i n e l y ground mineral to c o l l e c t at an air-water i n t e r f a c e ^ I t con-s i s t s of introducing a quantity of gas bubbles i n t o a pulp of ore and water, and obtaining the valuable p o r t i o n i n the r e -sulta n t f r o t h . As the bubbles r i s e , they come i n contact with the mineral p a r t i c l e s , and the desired c o n s t i t u e n t s , attached to the bubbles, are c a r r i e d upward. That mineral which c o l -l e c t s at the i n t e r f a c e / i s known as the "concentrates" be-cause of i t s high content of valuable substances, while that p o r t i o n which d i d not c o l l e c t there, but s e t t l e d to the bottom i s c a l l e d the " t a i l i n g s " * and i s u s u a l l y discarded. The f r o t h i s allowed to overflow and c a r r i e s with i t the concentrates. In order to make t h i s process possible i n i t s present form, a number of f l o t a t i o n agents must be added p r i o r to and during flotation» c o n t r o l of these reagents being probably the most important f a c t o r i n the operation. Without these reagents the m i l l operator would have to depend on only a s l i g h t f r o t h to keep the mineral at the surface , and on the r e l a t i v e n a t u r a l f l o a t a b i l i t i e s of the constituents to achieve h i s separations* With only these to r e l y on, the present day .operation of many plants would not be economically possible or p r a c t i c a l . F l o t a t i o n depends upon the a b i l i t y of the; a i r to displace 2 .water from the p a r t i c l e surface. Thus the surface must be or i g i n a l l y hydrophobic or, as i n most cases, rendered so by treatment -with the c o l l e c t o r . The 'contact angle, formed by the air-^water and water s o l i d i n t e r f a c e s i s considered to be "an i n d i c a t i o n of the: tendency of a gas to d i s p l a c e water from contact-with the mineral. F l o t a t i o n has been studied by means of the contact angle by Wark ,.and Cox ( 2 ) , and numerous other i n v e s t i g a t o r s . I t s presence has been used e x t e n s i v e l y to show f l o t a t i o n p o s s i b l e without the. a c t u a l f l o t a t i o n operation,, and also to give an i n d i c a t i o n of the c o n d i t i o n of the mineral surface. FLOTATION REAGENTS F l o t a t i o n agents have many functions. C h i e f l y they have to do with the formation of a f r o t h , or with m o d i f i c a t i o n s of the f l o a t a b i l i t y of the m i n e r a l , whether by a c t i o n on the min e r a l i t s e l f or by c o n t r o l l i n g the conditions during the oper-a t i o n . An idea of the many functions of these reagents may b obtained by a glance at the names of the various groups, such as; f r o t h i n g agents, c o l l e c t i n g agents, a c t i v a t i n g , deactivat ing and depressing agents, pH r e g u l a t o r s , cleansing agents, T 1 < } . S o l i d 3 and f i n a l l y . d i s p e r s i n g agents. In addition, these reagents may have more than one function at the same time f o r a mineral, or may have d i f f e r e n t functions f o r d i f f e r e n t ores. I t i s by taking advantage of the properties of these f l o t a t i o n agents that the present day m i l l operations are c a r r i e d on. :'FROTHING i 5 W S For e f f i c i e n t , f l o t a t i o n , a f r o t h on the surface i s nec-essary to r e t a i n the mineral brought up by the bubbles. This i s obtained by the a d d i t i o n of a very small amount of f r o t h i n g agent, o r d i n a r i l y l e s s than one pound per ton of ore. Froth-i n g agents are u s u a l l y organic compounds which lower the sur-face tension of the s o l u t i o n , sometimes considerably despite very small concentrations, and thus i n accordance with Gibb's adsorption equation tend to concentrate at the air-water i n -t e r f a c e . Most of these reagents have s t r u c t u r a l formulas characterized by the presence o f two constituents of opposite properties i n the molecule, that i s each have a polar and a non-polar p o r t i o n ; and as a r e s u l t tend to arrange themselves at an i n t e r f a c e so that the pola r end i s attached to the water and the non-polar away from the water. Therefore the bubbles tend to come i n t o contact with each other without coalescing due to the p r o t e c t i v e sheath of f r o t h e r molecules at the i n t e r -face, and form a f r o t h instead of breaking when',,-they reach the surface. In the s e l e c t i o n of a f r o t h i n g agent, cost, a v a i l -a b i l i t y , and lack of c o l l e c t i n g p r o p e r t i e s , since they would l i m i t reagent c o n t r o l are sought. In a c t u a l p r a c t i c e today, probably, the most widely used f r o t h e r s are pine o i l and cres-4 y l i c a c i d . COLLECTING- AGENTS C o l l e c t i n g agent i s the term used to describe those chem-i c a l s necessary i n most cases to b r i n g the desired mineral i n -to the f r o t h i n appreciable q u a n t i t i e s . I t was f i r s t used to apply to the c o l l e c t i n g o i l s i n o i l f l o t a t i o n j and Is s t i l l retrained "although the a c t i o n of the modern c o l l e c t i n g agent-is apparently very d i f f e r e n t to the no longer used c o l l e c t i n g o i l s . C o l l e c t o r s form a non^polar water r e p e l l e n t coating on the surface of c e r t a i n mineral p a r t i c l e s j e i t h e r by adsorp-^ t i o n or by chemical r e a c t i o n with the surface. This enables the mineral to attach i t s e l f to the gas bubble r e a d i l y . Since the e f f e c t of c o l l e c t i n g agents vary with the d i f f e r e n t min-e r a l s , the constituents can be separated from each other, a process known as s e l e c t i v e f l o t a t i o n * In some cases the c o l -l e c t o r s have been shown to form d e f i n i t e compounds by meta-t h e s i s at the surface * f o r example, galena and the xanthates ( 3 j ( f ) ) while i n other cases the c o l l e c t o r i s known to be r e -moved from s o l u t i o n j although the mechanism f o r t h i s i s not c l e a r . Like f r o t h e r molecules, the c o l l e c t o r molecules are composed of two pa r t s * polar and non«polar, and are capable of r e a c t i n g or adsorbing'on the mineral. There are' a great var-i e t y of c o l l e c t o r s i n use at the present time j organic com-pounds of nitrogen and sulphur being used mostly f o r the met-a l l i c s u l p h ides. The use of xanthate with metal sulphides, p a r t i c u l a r l y i n regard to s p h a l e r i t e w i l l be discussed l a t e r . 5 ACTIVATING-,) DEACTIVATING AND DEPRESSING/AGENTS Many chemicals through t h e i r e f f e c t upon the surface of the mineral change the f l o a t a b l e properties of the ore with the usual c o l l e c t o r s . These chemicals* known as a c t i v a t i n g * d e a c t i v a t i n g , and depressing agents are widely used i n the present day s e l e c t i v e f l o t a t i o n processes to f u r t h e r modify the f l o a t a b i l i t y of the various c o n s t i t u e n t s . Perhaps the best known examples of these are the a c t i v a t i o n of s p h a l e r i t e by copper sulphate, the d e a c t i v a t i n g e f f e c t of potassium cy-anide on s p h a l e r i t e , and the depressing e f f e c t of potassium chromate on p a r t l y oxidized galena; A c t i v a t i n g agents are used to make poorly f l o a t a b l e min-e r a l s more amenable to f l o t a t i o n under the usual conditions* Their e f f e c t i s due to t h e i r a c t i o n on the surface, namely forming a compound more' i n s o l u b l e than those of the metal com-pounds already there, but which i s s t i l l able to react r e a d i l y with the c o l l e c t o r to form.a l e s s soluble surface s a l t than would be normally formed. Supporters of the chemical theory go so f a r as to say.that with a complete table of water s o l -u b i l i t i e s , one should be able to pick an a c t i v a t o r f o r a min-e r a l even before t r i a l * Thus s a l t s of mercury, copper, and l e a d , whose sulphides 1 and organic s a l t s are g e n e r a l l y more i n -s o l u b l e than those of other metals, often prove to be the best a c t i v a t o r s . Chemicals that undo the work of a c t i v a t o r s are known as d e a c t i v a t i n g agents. They are srery important i n floa-t a t i o n , being required to overcome the n a t u r a l l y occuring act-i v a t i o n among the minerals, such as the a c t i o n of copper s a l t s i n complex .copper zinc ores. Other reagents, known as depressing agents, are used to decrease the f l o a t a b i l i t y of c e r t a i n r e a d i l y f l o a t a b l e con-s t i t u e n t s of the ore. They form upon the mineral surface a coating much l e s s f l o a t a b l e than the mineral surface i t s e l f . Thus the d i f f e r e n c e between an a c t i v a t o r and a depressor would appear to be that the surface compound formed by the l a t t e r i s both poorly f l o a t a b l e and r e s i s t a n t to r e a c t i o n with the c o l l e c t o r . 7 THE FLOTATION OF . SPHALERITE S p h a l e r i t e , the most common ore of zin c * i s found assoc-i a t e d with other sulphide ores of i r e n * copper, cadmium, and . lead* I t " ' i s a l i g h t g rayish yellow colour when pure, but traces of i r o n sulphide, which i t most commonly contains change the ore to a much darker brown colour. 'It has a r e s i n -ous l u s t e r , s p e c i f i c g r a v i t y of 3.9 to 4*1, and i s b r i t t l e with a: d e f i n i t e cleavage. • Sph a l e r i t e i s one of the most d i f f i c u l t minerals to f l o a t * under conditions as obtained i n the m i l l c i r c u i t s dur-i n g the commercial process i t i s not recovered unless subject-ed to a c t i v a t i o n by added s a l t s due to presence of other ores. Pure s p h a l e r i t e Is only f l o a t e d w i t h i n a narrow pH range, and then only by some c o l l e c t o r s , e s p e c i a l l y those containing a carbon chain of f i v e or more atoms. Basic and a c i d i c s o l -utions d e f i n i t e l y prevent f l o t a t i o n . There seems to be much di f f e r e n c e of opinion i n the reports regarding the f l o t a t i o n of s p h a l e r i t e • b y the lower xanthates. Yamada and Yaganuma (4) reports 99$ recovery f o r pH's of 5.5 to 7*5 using potassium e t h y l xanthate, while above t h i s i t drops to 10$. Gaudin (5) and ( 6 ( e ) ) , reports p r a c t i c a l l y no recovery f o r s p h a l e r i t e of 100 to 600 mesh with potassium e t h y l xanthate. Wark and Gox (3(a) p.199 and 220/) who used contact angles as an i n d i c a t i o n of f l o a t a b i l i t y report that no contact angle i s obtained i n e i t h e r d i s t i l l e d water, or a potassium e t h y l xanthate s o l u t -i o n . They also s t a t e that no contact angle i s obtained f o r 8 amyl and lower xanthates without a c t i v a t i o n . Experiments con-ducted i n t h i s laboratory and to be discussed l a t e r have shown f l o t a t i o n p o s s i b l e f o r a pH range of roughly 4.to 7.5 f o r the unactivated ore* I t i s reported from s e v e r a l sources that s p h a l e r i t e does not abstract potassium e t h y l xanthate from s o l u t i o n (5) and (8) and that no l a y e r can be leached from the ore; while the a c t i v a t e d ore has been shov/n to abstract xan~ < thate from s o l u t i o n (5). C.R. Ince (6(b)) has shown sphaler-i t e to remove xanthate from solution'* although not nearly t o the same extent as galena. G-alena ((5) p66) has been shown to abstract xanthate Ion from s o l u t i o n and f u r t h e r the metal xan-thate so formed has been leached from the ore and i d e n t i f i e d as such. While galena••(&(f)) i s probably the only mineral f o r which f l o t a t i o n has d e f i n i t e l y been shown to be due to the formation of a metal xanthate' surfa'ee compound, removal of xanthate Ion would be expected to accompany f l o t a t i o n , what-ever the mechanism involved. Thus t h i s would i n d i c a t e that no f l o t a t i o n took place under the conditions f o r which the above measurements showed no removal. In l i n e with the chemical theory of f l o t a t i o n , i t has been suggested that the s o l u b i l i t y of z i n c e t h y l xanthate was ( . . . • . -responsible f o r some of the f l o a t a b l e p r o p e r t i e s of s p h a l e r i t e * Zinc e t h y l xanthate i s more solu b l e than most of the other metal xanthates, being reported as 0.355g/litre (9) and (10). Thus under conditions where other minerals might f l o a t , there would be no f l o t a t i o n because the concentration of z i n c ions. and xanthate ions would not be high enough to cause the form-9 at i o n of a-metal xanthate layer on the surface. For low pH's s u f f i c i e n t xanthate ion would be destroyed due t o the decom-p o s i t i o n of xanthate^ or removed due to the unionized xanthie a c i d to prevent f l o t a t i o n * where as f o r a l k a l i n e ranges, the concentration of zi n c ion would be kept down enough by the formation of i n s o l u b l e z i n c hydroxide or zincate ions to pre-vent the formation Of zi n c e t h y l xanthate on-the ore surface. The much greater pH range through ydiich galena and copper ores f l o a t i s . explained by the extreme i n s o l u b i l i t y of t h e i r metal xanthates« Despite the c o n f l i c t i n g reports 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 j a l l agree that the pure untreated mineral w i l l not f l o a t i n a l k a l i n e s o l u t i o n s . Thus to recover s p h a l e r i t e i n the m i l l s where a l k a l i n e c i r c u i t s are now almost u n i v e r s a l l y used, i t must be treated f i r s t w i t h some s a l t to a c t i v a t e i t , that i s t o permit i t to react with the c o l l e c t o r . The most common s a l t f o r t h i s purpose i s copper sulphate, but any cop-per s a l t has been found t o have p r a c t i c a l l y the same e f f e c t . This i s a t t r i b u t e d to the cupric ion r e a c t i n g at the surface to form a l a y e r of copper sulphide and r e l e a s i n g the zinc ion i n t o the s o l u t i o n i n chemically equivalent amounts (6(d&e))„ i . e . G\x + Z n S — * Zn+++ CuS. Most of the work seems to favour the opinion that the l a y e r so formed i s cupric sulfide» although others have stated that i t i s cuprous s u l p h i d e , or a mixture of both (9). This cupric sulphide i s capable of oxidation and subsequent r e -ac t i o n with the c o l l e c t o r , thus g i v i n g f l o t a t i o n . Experiments 10 have been conducted to see i f cuprous s a l t s mere more e f f i c i -ent a c t i v a t o r s , but have shown that f o r equivalent amount of copper, they have approximately the same e f f e c t ( 6 ( d ) ) . Other metal ions have been shown to have a s i m i l a r act-i v a t i n g e f f e c t on s p h a l e r i t e . . In general, those s a l t s forming sulphides l e s s soluble than z i n c sulphide have been found ef-f e c t i v e . (11 ) . Most of these metals also form xanthates much more i n s o l u b l e than zi n c e t h y l xanthate, thus ex p l a i n i n g why such a sulphide, l a y e r should give f l o t a t i o n * Ralston and Hunter have stated that the lead i o n shows no a c t i v a t i n g e f-fec t on s p h a l e r i t e , but others have found d e f i n i t e a c t i v a t i o n by t h i s i o n . They a l s q examined the a c t i v a t i n g e f f e c t of the metal ions f o r percentage zi n c i n the concentrates.and also percentage z i n c e x t r a c t e d , r e p o r t i n g copper to give the best . , (15), r e s u l t s * R a v i t z and Wall (12>) and others A\14) give a d d i t i o n a l information about the e f f e c t of copper sulphate on s p h a l e r i t e . In a c t u a l p r a c t i c e copper, sulphate i s added t o the pulp, p r e c i p i t a t e d as hydroxide, carbonate, or basic carbonate, which then allows s u f f i c i e n t copper i o n concentration f o r the form-a t i o n of a surface cupric sulphide l a y e r . S p h a l e r i t e i s not n a t u r a l l y f l o a t a b l e i n a l k a l i n e c i r c u i t s , and i s only obtained i n the concentrates when i t has been a c t i v a t e d by some such s a l t , e i t h e r added f o r t h i s purpose, or formed by ox i d a t i o n of one of the constituents of the ore* ' Because of t h i s n a t u r a l l y occuring a c t i v a t i o n of the s p h a l e r i t e , a means of d e a c t i v a t i o n i s necessary f o r s e l e c t i v e f l o t a t i o n . I t has been found that the a d d i t i o n of some cyanide 11 s a l t , such, as sodium or potassium cyanide w i l l reduce the f l o -t a b i l i t y to that of the unactivated ore* This i s considered due to the removal of the cupric sulphide layer with the form-a t i o n of a very s l i g h t l y d i s s o c i a t e d complex cupro*>cyanide ion GutCM")^ *"* ( 6 ( e ) ) . Cyanide i s also found to be e f f e c t i v e i n preventing the f l o t a t i o n of many other sulphide minerals such as p y r i t e , c o v e l l l t e , and other copper ores» while i t has no e f f e c t at a l l on the recovery of galena* In a d d i t i o n to t h i s d e a c t i v a t i n g e f f e c t , cyanide i s by many (9)* (10), (.15.),; (16), considered to form a h y d r o p h i l i c l a y e r of i n s o l u b l e and. complex s a l t s on the mineral surface* thus f u r t h e r impeding f l o t a t i o n ; , Del Guidice, i n a d d i t i o n , states that ore treated with ECU does not abstract potassium • e t h y l xanthate from s o l u t i o n . On the other hand, TucKer and Head (17) found cyanide to have l i t t l e e f f e c t on the f l o t a t i o n of s p h a l e r i t e * In support of t h i s j Gaudin (5, p77 and 224) (6 e) reports cyanide to be without e f f e c t upon "the unactivat-r ed ore, and to reduce the f l o a t a b i l i t y of the a c t i v a t e d ore to that of the untreated mineral* Perhaps the most extensive work on the e f f e c t -of cyanide i n f l o t a t i o n has been done by l a r k 'and Cox (2) (3a, b, c }) (18) who used contact angle meas-urements. They found f o r the various minerals a , c e r t a i n cyan-ide s a l t concentration f o r each pH which would d e f i n i t e l y pre-vent contact of a i r and m i n e r a l . Further i n v e s t i g a t i o n of t h i s data showed the cyanide i o n concentration to be constant throughout f o r each mineral. These r e s u l t s , despite being the most extensive oh the subject, f a i l to i n d i c a t e the mechanism 12 involved..*' C. R. Ince (6(b)) and Brighton, Burgener, and Gross (12) have showed small q u a n t i t i e s of cyanide ion to be removed from s o l u t i o n by contact with s p h a l e r i t e . Yet even with a l l t h i s data a v a i l a b l e , the a c t i o n of cyanide/remains somewhat clouded. I t s d e a c t i v a t i n g e f f e c t , depending upon the removal of CuS, i s recognized by a l l , while other theories such as the formation of a water avid l a y e r ; as the removal of metal xanthate l a y e r due to increased s o l u b i l i t y i n cyanide s o l u t i o n and others remain disputed. S p h a l e r i t e i s also de-pressed by seve r a l other s a l t s , such as soluble s u l p h i t e s ; t h i o s u l p h a t e s a n d sodium sulphide. Further, i t was also shown that washing the ore with a d i l u t e a c i d was such as HgSO^ (5) (19) and HOI (20) p r i o r to the f l o t a t i o n t e s t s gave much higher recovery. This was explained as a cleansing a c t i o n which removed slime coatings, and thus aided f l o t a t i o n . A s i m i l a r e f f e c t was also reported for :p|?i?£te"iion. 13 OBJECT OF PRESENT'WORK In the present day s e l e c t i v e f l o t a t i o n of s p h a l e r i t e two reagents, copper sulphate'and sodium cyanide seem to play a major part. -While the a c t i o n of the former i s understood, there s t i l l remains considerable doubt as to the function of the cyanide. I t has been suggest-ed that cyanide., i n ad d i t i o n to removing the a c t i v a t i n g f i l m of cupric sulphide on the min-e r a l surface , a l s o may form a h y d r o p h i l i c l a y e r i t s e l f , or may di s s o l v e the metal xanthate l a y e r . In the present work i t was hoped to f u r t h e r c l a r i f y t h i s , and, i f p o s s i b l e , to de-termine whether the cyanide's only e f f e c t was that of deact-i v a t i o n . For t h i s , copper free samples of s p h a l e r i t e were used, and a l s o , as i n previous i n v e s t i g a t i o n s i n t h i s lab-* oratory, potassium e t h y l xanthate and t e r p i n e o i were selected as a t y p i c a l c o l l e c t o r and f r o t h e r , .'._ . 14 EXPERIMENTAL WORK METHODS. OF ANALYSIS Cyanide, Determination The methods suggested i n the l e t e r a t u r e were of two types, namely b y : t i t r a t i o n , e i t h e r potentiometric* or using E C l a s an i n d i c a t o r , or by c o l o r i m e t r i c determination*. The potentiometric a n a l y s i s (21) was discarded when i t was found that an u n s a t i s f a c t o r y end-point was obtained at the desired concentrations. Two c o l o r i m e t r i c methods, the f i r s t depend* ing on the formation of red Fe(CNS) 3 (22) and the second de-pending upon the formation of prussian blue (23) was d i s c a r d -ed as u n s a t i s f a c t o r y before a s u i t a b l e t e s t was,found. The former gave very low r e s u l t s , while the l a t t e r was not s e n s i t -ive enough,; f a i l i n g to i n d i c a t e the presence of GN i n a s o l -u t i o n of 1 part NaCN i n 50,000 parts water* However a method reported by R. G-. Smith (24) proved to be very s e n s i t i v e and convenient* This determination depended on the c o l o r a t i o n on heating of an a l k a l i n e s o l u t i o n of sat-urated p i c r i c a c i d i n the presence of cyanide, due to the f o r -mation of a sodium s a l t of i s o p u r p u r i c a c i d . For t h i s work, a standard colorimeter machine, No 7-089 Fi s h e r Electro-photo-meter, was a v a i l a b l e . Tests were conducted on a s e r i e s of d i f f e r e n t cyanide s o l u t i o n s , and the machine readings p l o t t e d against concentration. The r e s u l t i n g values were found to f a l l on a s t r a i g h t l i n e , the slope of which var i e d s l i g h t l y i i © _ 1 i -1 s -——,—^-^™—|—: —;—'— —• :\ 7 • J . ; • - - 1 - -| j , ..... Q \ \ \ ' -a - - i\ I \ c id c o —a —aj if a-id a-*.2 °i s -OJ-S-* 4 p 15 from .day to day,"apparently depending on how external condit- ' ions a f f e c t e d the s e n s i t i v i t y of the colorimeter. The method adopted was to prepare standard s o l u t i o n s of nearly.the same .concentration as the unknown, and then compare readings> all determinations being made at the same time* The procedure;as described i n the l i t e r a t u r e was modified to increase i t s s e n s i t i v i t y , in. the f o l l o w i n g manner:-The c o l -oured sample was. prepared by heating Sec's of unknown oyanide s o l u t i o n with 3ce's of p i c r i c a c i d s o l u t i o n (3 volumes of saturated p i c r i c a c i d and 1 volume of 1,0% Na 2C0 g s o l u t i o n ) f o r f i v e minutes on a steam bath. The s o l u t i o n was. then immediat-e l y cooled i n running/Water and d i l u t e d t o 25cc's. Results of determinations over concentration ranges of 0 to 1.6 parts per 100,000 parts water, and over 1.6 parts per 100,000 to 1 part per 12,500 are shown* The d i f f e r e n c e i n slopes of the l i n e s obtained by p l o t t i n g these readings ag-a i n s t concentration i s due to the two sets ofrvalues being de-termined separately i n the color i m e t e r ! The values f o r the more concentrated s e r i e s show very l i t t l e d e v i a t i o n from a s t r a i g h t line., and i n d i c a t e that concentrations of from .02 to *09mg/cc, the range i n which we are i n t e r e s t e d , maybe deter-mined with much l e s s than 5% error by the above method, Zinc. A n a l y s i s . Zinc was determined by potentiometric t i t r a t i o n as des-cribed by I . R. Pearce (7) and G. G. Reissaus (25). The ap-paratus used was modified i n the f o l l o w i n g manner:-The stand-ard c e l l , composed of a platinum electrode wire ,'• and a few 1*0 300 o too O- Hoc <J ;S 000 . 100. volume & dded volume K^Ff'lCN)6 solubfon in c.c A . E 1 Z A C volume* added -12, 16 . i< volume K^feC?N)6• soVljiorv m ccj Reference I CiectJrode .wipe.. Pl&binum Kqi _j.oitilL„ <XbM7J£ "electrode: 16 cc's .pf.K^e(GN) * s o l u t i o n (40cc's of' K 4Fe(CN)g standard and 2cc's of concentrated HgSO^) i n a small glass tube with a platinum s e a l at. the bottom, was in s e r t e d i n t o a test tube of saturated KG1 s o l u t i o n , to which had been joined two inches of glass tubing with a ground glass j o i n t at i t s bottom. During the t i t r a t i o n of the zinc with the K^Fe(CN) ^  s o l u t i o n , t h i s ground glass j o i n t was dipped i n t o the s o l u t i o n , and the r e -s u l t i n g changes i n p o t e n t i a l measured by means of a Beckmann pH meter and a voltage extender. In t h i s way the s a l t bridges and standard c e l l were combined i n t o a s i n g l e convenient unit.' Apart from t h i s , the procedure was the same as they described. Xanthate Determination Xanthates were determined'by potentiometric t i t r a t i o n with i o d i n e , using a calomel and a platinum electrode. The •  xanthate ion was o x i d i z e d q u a n t i t a t i v e l y to dixanthogen and the presence of free iodine at the end-point detected by the p o t e n t i a l of the h a l f c e l l , P t { I g , I ~ ) . This was used i n pref-erence- to a .starch i n d i c a t o r , as some of the metal ions pre-vent an accurate end-point. A Beckmann pli meter, with c a l -omel and platinum electrodes, was used i n t h i s determination, and gave a sharp end-point with a change i n readings of about f i v e u n i t s . I t was often necessary to wait almost f i v e minutes to obtain constant readings a f t e r each a d d i t i o n when close to the end-point. However,' despite this-, the determinations were q u i c k l y and a c c u r a t e l y c a r r i e d out, and the- end-points found by p l o t t i n g A l / A G against concentration. 17 Copper and Iron Determinations Copper was determined i n the conventional manner with KI and NagSgOg, while i r o n was found by t i t r a t i n g with KMnO,. 18 FLOTATION TESTS Tests i n a small f l o t a t i o n c e l l , as described by R. 1. Bennett (1) were used to measure the f l o a t a b i l i t i e s of the •minerals. Since f l o t a t i o n i s thought to be due to the ore possessing a hydrophobic surface, these t e s t s were, considered to i n d i c a t e the condition of the surface, and to give a meas-ure of i t s degree of water r e p e l l e n c e , or f l o a t a b i l i t y . Fur-t h e r , i t was hoped to obtain an idea of the behavior of the ore under c e r t a i n conditions* which would, i n future serve as a guide to the state of the orei-:."For instance , i t was neces-sary to know whether'the ore could be considered to be In an ac t i v a t e d or deactivated s t a t e . Since these terms had been used to describe ore used I n a l k a l i n e m i l l c i r c u i t s , u s u a l l y about a p'H of 9 or higher, a c t i v a t e d s p h a l e r i t e was consider-ed to be that which f l o a t e d at t h i s pH, while unactivated. or deactivated s p h a l e r i t e was t h a t which d i d not f l o a t at t h i s pH. For t h i s work, seve r a l samples of s p h a l e r i t e were a v a i l -able. Two of these, both copper f r e e , but containing consid-erable i r o n were selected for the f o l l o w i n g work, most of which was done with Sample #2, .as there was i n s u f f i c i e n t time In most cases to d u p l i c a t e the work with Sample #3. Sample #£—57.8% Zn and. 7.6% Fe. Sample #3—60.8% Zn and 5.5% Fe. In both samples there were small q u a n t i t i e s of antimony and cadmium, with also a trace of arsenic. Of Sample #2, 19 approximately 1$ was i n s o l u b l e i n d i l u t e HG1 s o l u t i o n . Samples for these te s t s were prepared by grin d i n g f o r 1/2 to 3/4 of an hour i n a b a l l m i l l and then s i z i n g the ore by means of an e l u t r i a t o r tube. The e l u t r i a t o r tube consisted of a t a l l glass c y l i n d e r , 7.3cm i n diameter, standing i n a large evaporating dish . Water was passed i n t o t h i s at the bottom by means of a long glass tube, at a constant r a t e . The overflow was c a r r i e d down to the large evaporating dish by means of a siphon. The ground mineral, was placed i n the c y l -i n d e r , and that which was c a r r i e d over when the rate of addit-ion of the water was 170cc's per minute, or having an upward v e l o c i t y of 4cm per minute i n the c y l i n d e r , was discarded. The rate of flow was then increased to 500ec's per minute, or an upward v e l o c i t y of 12cm per minute* and the ground m a t e r i a l which overflowed with the water,-'and s e t t l e d out i n the evap-o r a t i n g d i s h , was saved for the t e s t s . Thus the ore sample®•-?j£.r;v used were composed of p a r t i c l e s having a s e t t l i n g rate bf 4 to 12cm per minute. Microscopic examination showed these p a r t i c l e s to be i r r e g u l a r and f l a k y i n shape, ranging i n size from 5 to 30 microns across. F l o t a t i o n t e s t s were conducted as f o l l o w s : -The c e l l ¥/.as f i l l e d with the s o l u t i o n to be used, and a i r supplied at a pressure of 40cm of mercury as in d i c a t e d by a manometer* The ore sample was then put i n t o the c e l l , and s o l u t i o n added u n t i l the f r o t h * which, was then, skimmed o f f with a sp a t u l a , just overflowed. The t e s t l a s t e d f i v e minutes, unless a dark f r o t h i n d i c a t e d that f l o t a t i o n was s t i l l t a king 30 place, t,hus r e q u i r i n g more time* Usually f i v e minutes was suf-f i c i e n t , and at the end white f r o t h covered the c e l l . S o l -u t i o n was added v/hen necessary t o keep the f r o t h high enough to j u s t overflow. The s o l u t i o n used contained 25cc's of t e r -.pineol s o l u t i o n (250mg/l) as a f r o t h e r * and 25cc's KEtX s o l -u t i o n (mg/ce) as a c o l l e c t o r per l i t r e . Tests showed 25cc's of KEtX s o l u t i o n to be s u f f i c i e n t , as higher concentrations gave no a d d i t i o n a l recovery* RESULTS OF FLOTATION TESTS Recovery EEtX pH •. . Comments % mg/l 7.1 0 5.. 8 83 25 6 83 100 6 10.4 25 9.5 68.6 25 8.6- Ore prewashed with CuSO^ s o l . 88 25. 6 23mg K C N / l i t r e added 77.4 25 6.4 ;115mg K C N / l i t r e added 9 25 9 23mg K C N / l i t r e added 71*5 25 5.2 Prewashed with 0*003N KCN 7.2 25 8.8 Prewashed with 0.003N KCN 72 25 5.8 Prewashed with CuS0 4 sol'n and 23mg/litre KCN .added 12.6 35 8.6 Prewashed with CuS0 4 s o l ' n and 23mg/litre KCN added The above t e s t s were conducted f o r the most part i n a pH range of from 5 to 7 or from 8 to 10, because i t was found that the untreated s p h a l e r i t e f l o a t e d i n the former range, and because the higher pH range could be used to i n d i c a t e whether the ore was a c t i v a t e d or deactivated. Good recovery of about 80% was obtained f o r a pH of 6, while a recovery of only 10% was obtained at a pH of 9.5, thus i n d i c a t i n g the ore to be unactivated* The presence of cyanide i n the s o l u t i o n , or prewashing the ore i n very d i l u t e cyanide s o l u t i o n did not a f f e c t the r e s u l t s f o r these pH's. Prewashing the ore with CuSO^ s o l u t i o n gave a good recovery f o r a pH of '8.6, while the presence of cyanide returned the f l o a t a b i l i t y of the ore to that of the unactivated mineral. In t h e s e . t e s t s , the cyanide does not seem to a f f e c t the un-ac t i v a t e d ore but only to deactivate the CuSO^ treated ores. In order to examine more f u l l y the part played by zinc sulphate formed by the ox i d a t i o n of sulphide at the mineral surface, samples were washed I n d i l u t e H^SO^, and then by means of a Buchner funnel f u r t h e r washed with a continuous stream of d i s t i l l e d water, using at l e a s t two l i t r e s , p r i o r to the f l o t a t i o n t e s t . In a d d i t i o n , a few samples were t r e a t -ed for f i v e minutes i n warm N/10 KGN s o l u t i o n * about 60°C, f i l t e r e d , and xrashed with l e s s than 50cc fs of d i s t i l l e d water before the t e s t . Nitrogen was used i n some of the f l o t a t i o n t e s t s to prevent r e d x i d a t i o n of the mineral surface* 22 Results of; F l o t a t i o n Tests on A c i d Washed Ore...Samples Recovery KEtX pH . , Comments. mg/1 o 1. 58 0 .6*5 Used a i r i n c e l l 2. 36.4 0 5.4 Used a i r i n c e l l , added • V • 23mg/litre of, KCN 3. 24.1 0 9.5 Used a i r i n c e l l , added 23mg/litre of KCN 4. 50.1 0 7.1 Used Ng i n c e l l 5. 37.8 . 0 8 Used N g i n c e l l , added 23mg/litre KCN 6. 34 0 , -6.5 . N g i n c e l l , added 23mg/l KCN The f o l l o w i n g ore samples were washed i n warm KCN:,N/10 s o l , 7. 36 0 6,5. Passed a i r through pulp i n c e l l f o r l/2hr p r i o r to t e s t , - -40.2 0 5.9 Added 25mg/litre KEtX and ran t h i s test on t a i l i n g s 8. 69.6 0- 7 Used Ng i n c e l l 9. 33.5 0 6.4 Used N ? i n c e l l , added 23mg/l . ' 'ECET In t e s t #5—Only 13$ a d d i t i o n a l recovery hy adding 25mg/l KEtX and running an a d d i t i o n a l 5 minutes* A d d i t i o n of a c o l -l e c t o r did not seem to increase recovery as. there w a s ' ' s t i l l very s l i g h t f l o t a t i o n taking p l a c e , p r i o r to t h i s a d d i t i o n , and t h i s with the mechanically c a r r i e d over ore could e a s i l y amount to .13$ These t e s t s showed that recoveries i n excess of 50$, us-in g a i r or nitrogen i n the c e l l , could be obtained with the a c i d washed ore, as compared t o recoveries of l e s s than 10$ 23 using the, untreated mineral. Thus the cleaned sulphide min-e r a l possessed a n a t u r a l f l o a t a b i l i t y once the soluble surface sulphate s a l t was removed. Test #5 showed that the c o l l e c t o r had no a d d i t i o n a l e f f e c t upon the cleaned mineral surface * and thus substantiated the claim that a soluble zinc, s a l t , ' ZnSO^j was necessary f o r the formation of a hydrophobic metal xanthate surface l a y e r . Test #7 showed that the mineral would o x i d i z e i n contact with a i r , and decrease the recovery without a c o l l e c t o r . However, the a d d i t i o n of 25mg/litre KEtX gave a fur t h e r recovery of 40%, thus I n d i c a t i n g approximately the extent of the oxidation during the h a l f hour that a i r was passed through the c e l l . The t o t a l recovery, w i t h and without c o l l e c t o r , was approximately the same as that i n Test #8, us-ing nitrogen i n the c e l l . These t e s t s show the n a t u r a l s u l -phide surface to be very d i f f e r e n t from the oxidized, surface which i s necessary for f l o t a t i o n as pr a c t i s e d * Perhaps more important however, i s the part played by cyanide i n these t e s t s . Ore pre washed i n warro.H/10 KC3ST s o l -u t i o n gave an exc e l l e n t recovery when nitrogen-was used i n the f l o t a t i o n c e l l , thus i n d i c a t i n g cyanide to have a cleansing a c t i o n on the surface. Further, i t could not have formed'a h y d r o p h i l i c l a y e r of Zn(GB")g, as predicted by many, or i f such a l a y e r was formed, i t should be hydrophobic, and thus b e n e f i c i a l to f l o t a t i o n . Secondly the presence of cyanide i n the c e l l during f l o t a t i o n d e f i n i t e l y decreased the recovery. This would i n d i c a t e that the cyanide had some a d d i t i o n a l ef-fe c t on the sulphide surface. Perhaps the formation of a com-24 ple'x zinc cyanide s a l t , occuring s l i g h t l y when i n contact with cyanide i o n , had much the same e f f e c t as a soluble surface s a l t . However these t e s t s do i n d i c a t e , that i f such a zinc cyanide surface s a l t i s formed, i t would be very e a s i l y r e -moved, and ?/ould not prevent the c o l l e c t o r from acting on the mineral. ACTIVATION-AND DEACTIVATION' ' Tests •• .. T r i a l a c t i v a t i o n and d e a c t i v a t i o n tests.were conducted t o see which i o n s , and in' what q u a n t i t i e s were removed from s o l -u t i o n . The procedure consisted of t r e a t i n g the ore with a s o l u t i o n of known volume and concentration, f i l t e r i n g on a Gooch.crucible * and determining the concentration of the var-ious ions to see which" had been removed or returned to the s o l u t i o n . The ore was f i r s t treated with GuSO^. i n t h i s manner and then with KON s o l u t i o n . Results A c t i v a t i o n Tests -Cu and l e q u a n t i t i e s are represented as the' sulphates. I . Sample of 7.687g removed 5.61 mg of CuSO^. No zinc was r e -turned .to s o l u t i o n , but i r o n was found present i n the ferrous, state* The ore was an unsized coarse sample. Time of con-t a c t was 15 minutes. I I . —Sample consisted of 15.021g of s i z e d ore* Of the 16.3g of CUSO4 present, only a barely detectable amount of 1 t o 2mg 25 was l e f t . -,. In i t s place, 5mgs of FeSO^ and no zin c were found. A f l o t a t i o n t e s t on t h i s sample at a pH of 8-9 showed good recovery. Deactivation Test Sample consisted of 8.801g of a c t i v a t e d ore from #2 act-i v a t i o n t e s t , and was treated with a: s o l u t i o n containing 14.8mg of KCN. There was 5.Q8mg of KCN l e f t , thus approxim-a t e l y 9i7mg had been removed from s o l u t i o n . In the s o l u t i o n there was found 5.97mg of CuS0 4 (the Cu found i s expressed here as CuSQ4, despite the f a c t that i t was present as a com-plex ion with CN. This was shown by the f a c t that i t was necessary to evaporate the s o l u t i o n to dryness, before any te s t for Cu could be obtained). A f l o t a t i o n t e s t on t h i s sample gave no recovery* An examination of these r e s u l t s show the amount of GuS0 4 absorbed from s o l u t i o n was greater for••"the fine sample * a f a c t already reported i n the l i t e r a t u r e . The amount of FeSO^ returned to the s o l u t i o n i n the a c t i v a t i o n process was approximately l/3' r of that required to be chemically equiv-alent to the CuS0 4 removed. No zin c was returned to the s o l -u t i o n , a f a c t which might be predicted from the s o l u b i l i t y —23 products of the respective s u l f i d e s , namely 1.2 x 10 f o r -19 z i n c sulphide and 3.7 x 10 for ferrous sulphide. , In the d e a c t i v a t i o n process, 5.97mg of GuSO^ were r e -turned to s o l u t i o n , and 9.7mg of KCN removed. The amount of KCN required to remove the Cu as Cu(CN)5 was 7.3mg, about 26 2.3mg l e s s than that a c t u a l l y used up. Further the amount of GuSO^ returned t o s o l u t i o n was only approximately 2/3 of that adsorbed i n the a c t i v a t i o n process (note:-although cyan-ide removed Is r e f e r r e d to throughout as KCN i t i s only the cyanide i o n which i s abstracted from the s o l u t i o n ) . XANTHATE'ABSTRACTION TESTS . • By these t e s t s , i t had been hoped to determine the am-ount of xanthate removed from the s o l u t i o n by the ore under d i f f e r e n t c o n d i t i o n s , and p a r t i c u l a r l y to see i f the presence of cyanide a f f e c t e d t h i s quantity. The method followed was to prepare a s o l u t i o n of 150cc's containing 25cc's of EEtX s o l u t i o n , adjust the pH, and then s t i r lOOcc's of t h i s with ,15g of ore f o r 10 minutes. The s o l u t i o n was then f i l t e r e d on a Gooch c r u c i b l e , and the f i l t r a t e t i t r a t e d with i o d i n e . Xt was found that i f the sample was l e f t in.the. s o l u t i o n , no end-point was obtained. In a d d i t i o n to t h i s , there was a l -ways present some grayish white c o l l o i d a l s p h a l e r i t e which i n t e r f e r r e d with the end-point, causing i t t o be not so d i s -t i n c t , and to be obtained only a f t e r an excessive quantity o f Ig s o l u t i o n had been added. A b i g i n i t i a l drop i n p o t e n t i a l a f t e r ' l o p of Ig s o l u t i o n had been added, was noted when a s o l -u t i o n of the c o l l o i d a l m a t e r i a l was t i t r a t e d . This i n d i c a t e d that the iodine was. being used up slowly, thus preventing an accurate determination of the xanthate present. T i t r a t i o n s of xanthate s o l u t i o n s containing small amounts of z i n c , f e r r o u s ; and f e r r i c ion to see i f two end-points i n -27 &ieating.KEtX .and metal xanthate would occur, gave only one end-point corresponding to the t o t a l xanthate. ' In each case, there was a faint^opalescence i n d i c a t i n g the formation of the i n s o l u b l e metal xanthates. A l l of these three xanthates are much more soluble than P b ( E t X ) g with F e ( E t X ) 3 being the most soluble of the three* Because of the c o l l o i d a l s p h a l e r i t e present, i t was de-cided to add the Ig s o l u t i o n at a constant r a t e , and take readings at p e r i o d i c i n t e r v a l s . From the time values, the volume of Ig s o l u t i o n added, could be found. In t h i s way, the c o l l o i d a l m a t e r i a l would not be able to hide the end-point by the slow using up of i o d i n e . This method does not a l l o w f o r e q u i l i b r i u m readings i n the region of the end-point, or for small additions to enable a more accurate determination yet the r e s u l t s were i n d i c a t i v e of the r e l a t i v e amounts of xanthate removed from s o l u t i o n . T i t r a t i o n s to determine the e r r o r from the f i r s t source showed i t to amount, to l/2ce f o r a f a i r l y f a s t a d d i t i o n to l | c c f o r a slow a d d i t i o n * ! Results of Xanthate A b s t r a c t i o n Tests with KEtX only i n S o l u t i o n (In a l l cases KEtX present was equivalent to 9cc's of Ig s o l u t i o n — a t a pH of 5-6, which.should give f l o t a t i o n - -samples of 14 to 17g required' approximately 7. 5cc' s of I g s o l -ution-( a f a i r l y sharp end-point was obtained). At a pH of 8-10, which should not give f l o t a t i o n — s a m p -l e s of 16g to 20g required approximately 12.5ec 1s of I g s o l -u t i o n . sbuipvajj Jarful w 28 For conditions under which f l o t a t i o n should take place, approximately 5cc's of I g s o l u t i o n * or 4.6mgs of KEtX, repre-sented the a d d i t i o n a l xanthate removed from s o l u t i o n . With KCN i n S o l u t i o n No s a t i s f a c t o r y end-points were obtained with cyanide i n s o l u t i o n , due to the a c t i o n of iodine on cyanide. Solutions of K l t X and KCN f a i l e d to give s a t i s f a c t o r y end-points when t i t r a t e d with Ig s o l u t i o n s . However, end-points obtained were approximately,Slcc's f o r a pH of 5-6 and 22-24cc*s'for a . pH of 8-9. Values obtained with only KEtX present T/ere l a t e r cheeked by t e s t s i n which "the c o l l o i d a l s p h a l e r i t e was removed with a Zeiss f i l t e r , -These values with two obtained with KCN pre-sent are shown i n F i g . IV. In a d d i t i o n , an attempt was made to remove the xanthate l a y e r by means of an organic solvent, and then determine i t by t i t r a t i o n - a s above. These attempts proved unsuccessful, a l -though by using acetone, and evaporating almost t o dryness by means of a water pump, the amount removed was equivalent to l i c e ' s of Ig s o l u t i o n , or 1.47mg of KStX. There were also i n d i c a t i o n s that some of the xanthate removed had been decom-posed during the evaporation. Cyanide A b s t r a c t i o n Tests Ore samples were s t i r r e d mechanically f o r 15 minutes with lOQcc's of s o l u t i o n containing a known amount, of KCN at a given pH. These s o l u t i o n s were then f i l t e r e d i n t o a Gooch , 29 c r u c i b l e , and the f i l t r a t e analyzed f o r cyanide s t i l l remain-ing. From these t e s t s i t was hoped to determine i f the am-ount removed depended upon weight of sample and pH, or i f cy-anide was removed u n t i l a c e r t a i n concentration of cyanide ion remained i n e q u i l i b r i u m with the sample at the d i f f e r e n t pE's. C o l l o i d a l ore i n the f i l t r a t e could not be avoided. At the s t a r t t h i s e f f e c t was considered n e g l i g i b l e , and the values were not corrected i n any way. Later t e s t s were cor-rected f o r t h i s i n e i t h e r one of two ways, f i r s t by running a blank on the c o l l o i d a l m a t e r i a l , and secondly by allowing the f i l t r a t e to stand at l e a s t 48hrs to allow the c o l l o i d a l m a t e r i a l to s e t t l e , and also allowing the coloured sample to stand in'order that the s t i l l remaining c o l l o i d might coagul-ate and s e t t l e . Results of Tests In a l l t e s t s lOOcc's of s o l u t i o n containing .0986mg/cc KCN was used. pH Wt. of Sample F i n a l O r i g ' l mg/g Ore Comments conc'n conc'n removed g rng/cc Big/ c c mg/g • 1. 9.3 6.1394 .0710 .0986 . .450 Shaken i n enclosed Erlenmeyer 4.5 6.7696 .0786 .0986 .296 »» 3. 10.3 14.1190 .0775 .0986 .149 ! • 4.1 8.2.707 .0490 .0986 .599 5." 8.5 8.823 .0495 .0986 .556 KEtX pres-ent i n s o l . 4.1 9.2630 .0565 .0986 .455 30 A l l the above sol u t i o n s contain an e r r o r due to the pre-sence of c o l l o i d a l s p h a l e r i t e , which blank determinations sh-owed to be equal to .01 to ,02mg/cc of KCN, and with a v a r i -a t i o n i n each error of not greater than .Olrng/cc KCN. Thus a l l f i n a l concentrations of KCN are excessive by t h i s amount. The f o l l o w i n g values were corrected f o r c o l l o i d a l m a t e r i a l . PH. Wt-, Sample F i n a l cone. Orig. Cone. mg/g Ore Removed S mg/ cc mg/cc mg/g 1> 6 11.1945 .0318 .0986 .521 9.5 10.834 ,0648 .0986 «312 10.2 15.914 .066 ,0986 .205 10. 9.4 5.3065 .0638 .0704 .652 11. 9.55 15.351 * .059 .0704 .072 #7 & #8 and-:;#9 corrected by standing. #10 & #11 corrected with blanks. A glance at the above fi g u r e s w i l l show that the amount of cyanide removed to be dependant upon the f i n a l concentration rather than upon the weight of sample present. They a l s o i n -dicate considerable l o s s of cyanide i n t o the a i r at the lower pH's. Comparison of t e s t #2, conducted i n an enclosed e r l e n -meyer, with others, i n d i c a t e d the lower values f o r a c i d pH's to be almost e n t i r e l y due to t h i s source. A d d i t i o n a l t e s t s were conducted, to determine the concen-t r a t i o n of zinc and i r o n present i n s o l u t i o n s of d i s t i l l e d water, KEtX s o l u t i o n s , and s o l u t i o n s of KEtX and KCN, which had been s t i r r e d f o r 2hrs i n contact with the ore. 31 Results S o l u t i o n Conc'n of Zn Conc'n of Fe D i s t i l l e d Water l - 2 m g / l i t r e Zn 37.2mg/litre Fe 25mg/l KEtX Sol'n l - 2 m g / l i t r e Zn 15.9mg/litre Fe Sol'n containing 25mg/l KEtX and 23mg/l KCN 9.8mg/litre Zn l.Smg/Litre Fe These r e s u l t s would i n d i c a t e that the cyanide removed from s o l u t i o n , formed a soluble z i n c cyanide complex, rather than a surface s a l t on the mineral. Thus any influence cyan-ide would have on the unactivated s p h a l e r i t e should be due to t h i s cleansing a c t i o n , rather than -due to preventing the f o r -mation of a surface xanthate l a y e r by a zinc cyanide complex s a l t on the mineral surface. 32 SUMMARY OF RESULTS The r e s u l t s presented were obtained from f l o t a t i o n t e s t s a c t i v a t i o n and d e a c t i v a t i o n t e s t s , xanthate a b s t r a c t i o n t e s t s , and cyanide a b s t r a c t i o n t e s t s . B r i e f l y they i n d i c a t e the f o l -lowing:-I . That cyanide does not a f f e c t the recovery of unact-ivated s p h a l e r i t e . I t depresses the recovery of a c t i v a t e d s p h a l e r i t e to that of the unactivated mineral by the removal of the a c t i v a t i n g cupric sulphide l a y e r . The copper thus r e -moved I s i n the form of a complex copper cyanide s a l t . (G-au-din has stated t h i s to be GuCCN)^) I I . The sulphide mineral surface, cleaned by an a c i d or KCN wash, i s f l o a t a b l e . Oxidation by a i r w i l l slowly ren-der t h i s surface u n f l o a t a b l e . The presence of cyanide i n s o l -u t i o n decreases the f l o a t a b i l i t y of t h i s surface. The oxid-i z e d surface, presumably because of the presence of soluble ZnSO^ i s necessary f o r a c t i o n with the c o l l e c t o r , leading to formation of an i n s o l u b l e metal xanthate surface l a y e r . I I I . Xanthate was abstracted from s o l u t i o n s i n greater quantity under conditions f o r which f l o t a t i o n of s p h a l e r i t e would take place* The presence of cyanide prevented accurate determination of xanthate abstracted. The surface metal xan-thate was abstracted with acetone, although not q u a n t i t a t i v e l y . 17. A b s t r a c t i o n t e s t s showed cyanide to be removed from s o l u t i o n , depending upon the pH of the s o l u t i o n and f i n a l concentration of cyanide rather than upon the weight of ore, 53 or area of mineral surface. The cyanide removed appeared to be present i n the s o l u t i o n i n the form of a soluble zinc cy-anide complex. Cyanide removal i n s o l u t i o n s of a c i d pH was mainly due to l o s s i n t o the a i r . The a c t i o n of cyanide i s mainly a cleansing a c t i o n , r e -moving the cupric s u l f i d e layer i n the case of ac t i v a t e d s p h a l e r i t e and removing some of the soluble zinc s u l f a t e from the surface i n the case of the unactivated mineral. This l a t -'ter e f f e c t i s not pronounced enough at the d i l u t e c o n c e n t r a t i -ons experienced i n f l o t a t i o n , t o influence the recovery. I t d e f i n i t e l y does not prevent f l o t a t i o n , as has often been sug-gested, by the formation of a h y d r o p h i l i c l a y e r of zinc cyan-ide i n place of a water r e p e l l e n t layer of zinc e t h y l xanthate. 34 REFERENCES 1,. "The Surface Chemistry of F l o t a t i o n — R . L. Bennett. Thesis submitted f o r M. A. So, U n i v e r s i t y of B r i t i s h Columbia', 1938. 2. " F l o t a t i o n " — I . W. Wark. 3. 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 (Trans), V o l . 112. (a) P r i n c i p l e s of F l o t a t i o n I--An Experimental! Study of.the E f f e c t of Xanthates on Contact Angles at Mineral Surfaces--!. W. Wark & A. B. Cox* pl89, (b) P r i n c i p l e s of F l o t a t i o n I I — A n Experimental Study, of the Influence of Cyanide, A l k a l i s , and Copper Sulphate on the E f f e c t of Potassium E t h y l Xanthate at M ineral Surfaces''— :-I. W. Wark & A. B. Cox, p245. (c) P r i n c i p l e s of F l o t a t i o n I I I — A n Experimental Study on the Influence of Cyanide, A l k a l i s , and Copper - S u l p h a t e on the E f f e c t of Sulphur bearing C o l l e c t o r s at M ineral S u r f a c e s — I . W. Wark & A. B. Cox, p267. (d) Reactions of Xanthates with Sulphide Minerals---—A. M. Gaudin* F, Dewey, W. E. Duncan* R. A. Johnson, & 0* F. Tangel, J r . p319. (f) A c t i o n of A l k a l i Xanthates on Galena—T. G. Taylor, & A. F . K n o l l . p382. 4. G. A. —30> 6679 9—The E f f e c t of Hydrogen Ion Concentrat-i o n on F l o t a t i o n of Sp h a l e r i t e Yamada and Vaganuma. (Unavailable reference) References cont'd. 5. " F l o t a t i o n " — A. M. Gaudin > 1932. 6. American I n s t i t u t e of Mining & M e t a l l u r g i c a l Engineers. V o l . 87. (a) . Chemical Reactions i n F l o t a t i o n A. F. Taggart, T, G. Tayor & A. F. K n o l l , p217. (b) A Study of. D e f f e r e n t i a l F l o t a t i o n - - G. R. Ince. ' - p261. .(c) Experiments with F l o t a t i o n Reagents— A. F. Taggart, T. 0. Taylor, & G.R. Ince, p285. (d) A c t i v a t i o n of S p h a l e r i t e for F l o t a t i o n — — G. C. Ralston & G , Hunter j p401. 7. Jour. Phys. Ghem. 37, 833, 45, "Surface Actions of Some Sulphur-bearing Organic Compounds on Some F i n e l y Ground Sulphide Minerals"--- A. M. Gaudin &•¥*'£>. Wildinson. 8. Jour. Phys. Chem. v o l . 36, 1.30, 1932. "Mineral F l o t -a t i o n " — - A . F. Taggart. 9. Eng. & Min. Jour. v o l . 135, p350, 1934. "The Function of Depressors and P r o t e c t i v e Agents i n Conditioning f o r F l o t a t i o n - - - - - - G. R. M. Del Guldice. 10* Jour. Phys. Ghem. 40, p799, 1936. "The P h y s i c a l Chem-i s t r y of F l o t a t i o n V I I I — - E. E. Wark and I . W. Wark. 11. Eng. & Mini- Jour. v o l . 133, p276, 1932. "Depression by Cyanide i n F l o t a t i o n C i r c u i t s " - — T. B. Brighton, G. Burgener, & J . Gross. 12. Jour. Phys. Chem. v o l . 38, 15-18* 1934. "Adsorption of Copper Sulphate-by S p h a l e r i t e and i t s R e l a t i o n to F l o t a t i o n " References cont'd 15. Transactions of the Canadian I n s t i t u t i o n of Mining and Metallurgy, v o l . 29, p251, 1926. "Synthetic Testing for F l o t a t i o n " - — G. G. McLachlan. 14. Chem. & F l o t . P r o c e s s — American Cyanide Co. Tech. Paper No. 17, 1930— Christmann. 15. C. A. 33, 9221 . "Physicochemical Role of A i r i n the F l o t a t i o n of Non-ferrous Ores, Pt I I A. M a l i n o v s k i . 16. American I n s t i t u t e of Mining & M e t a l l u r g i c a l Engineers V o l . 73. " E f f e c t of Cyanogen Compounds on F l o a t a b i l i t y of Pure S u l f i d e M i n e r a l s " — - E . L. Tucker & R. E, Head. 17. Trans, of Electrochemical S o c i e t y , No 61, p426, 1932. "The P h y s i c a l Chemistry of F l o t a t i o n " — - I , W. Wark, 18. A u s t r a l i a n I n s t i t u t e of Mining and Metallurgy (Trans) No. 102, pl02. "On Functions of Chemical Reagents i n F l o t a t i o n " by R. Nevett. 19. Mining Mag. v o l . 49, 1933 p317 "Sphalerite F l o t a t i o n " R. L. Kidd & W. A. Wall. 20. Z e i t s c h i f t f u r Anorganische Chemie, v o l . 121, p!78 1922. "Die Electrometusche Bestimmung des Cyans neben den Halogenen"- E. M u l l e r & H, Lauterback. U. S. Bureau of Standards-- Journal of Research No 7 913, 33, 1931. " A n a l y s i s of Cyanide S i l v e r - p l a t i n g S o l u t i o n s " — R . M, Wick. 21. Engineering & Mining J o u r n a l , v o l 136, p280, 1935, "Determining Cyanide and Sulphocyanate i n Small Amounts" by E. C. Boyman. Reference cont'd 22. B u l l e t i n de La Societe Chimique (5) 2, p845, 1935. "Recherche du Eerrocyanure et des Products cyanes de l e Y i n Technique et Limited S i n s i b i l i t e " 23. Journal of the American Chemical Society, v o l 51, p l l 7 1 , 1929. "A Method f o r the Quantitative Determination of Cyanide i n Small Amounts" R. G Smith. 24. Z e i t s c h r i f t f u r Analytische Chemie, v o l 69, p450, 1926. "Bestimmung des Zink durch Electrometrische T i t r a t i o n " by G. G. Reissaus. 

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