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The thermal decomposition of dimethyl acetal by the flow-tube method. II. A study of the abstraction… Lips, Alair 1940

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L lf^> A?. fix. -I * I , THE THERMAL DECOMPOSITION OF DIMETHYL ACETAL BY THE ' FLOW-TUBE METHOD ..•II. A STUDY OF THE ABSTRACTION OF POTASSIUM ETHYL XANTHATE FROM SOLUTION BY PURE LEAD SULFIDE • A l a i r L i p s A T h e s i s s u b m i t t e d i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r t h e DEGREE OF MASTER OF ARTS i n the Department of C h e m i s t r y A p r i l , 1940 Vancouver, B.C. ACKNOWLEDGEMENT S i n c e r e a p p r e c i a t i o n t o Dr. W i l l i a m Ure f o r h i s gen-erous h e l p and ever ready coun-s e l throughout the course o f the i n v e s t i g a t i o n . CONTENTS Page Purpose o f the I n v e s t i g a t i o n 1 Apparatus 2 E x p e r i m e n t a l Procedure 4 M a t e r i a l s 5 D e t e r m i n a t i o n o f P r o d u c t s (a) Q u a l i t a t i v e 7 (b) Q u a n t i t a t i v e 9 I n t e r p r e t a t i o n o f T a b l e s 13 D i s c u s s i o n o f R e s u l t s 14 B i b l i o g r a p h y 16 Tables 18 THB THERMAL DECOMPOSITION OF DIMETHYL AQSTjX •1. PURPOSE 0? THE INVESTIGATION T h i s work was attempted i n o r d e r to supplement r e a c t i o n r a t e data o b t a i n e d i n t h i s l a b o r a t o r y by W. G. P i e r c e 8 and 20 G. H. Turner on the thermal decomposition o f d i m e t h y l a c e t -a l . I t was d e s i r e d to determine the n a t u r e and the r e l a t i v e amounts o f the p r o d u c t s o b t a i n e d by the p y r o l y s i s o f t h i s s ubstance. T h i s i n f o r m a t i o n would be u s e f u l i n d e c i d i n g the type o f c h e m i c a l r e a c t i o n t o which the p a r t i c u l a r breakdown belongs* I n the above i n v e s t i g a t i o n s , the p r o d u c t s were o b t a i n e d i n so s m a l l a q u a n t i t y as to make e s t i m a t i o n o f the c o n s t i t u -ents d i f f i c u l t . I t was f e l t t h a t w i t h the f l o w o r hot tube method o f d e c o m p o s i t i o n * l a r g e enough q u a n t i t i e s o f m a t e r i a l c o u l d be used t o ensure a p p r e c i a b l e amounts o f the v a r i o u s p r o d u c t s . A l s o , by a d j u s t i n g the r a t e o f f l o w and the temper a t u r e of t h e hot tub e , the p r i m a r y breakdown substances c o u l d be secured w i t h o u t c o n t a m i n a t i o n r e s u l t i n g from t h e i r progres s i v e d e c o m p o s i t i o n . R An a r t i c l e by a French worker was thought t o p r o v i d e some c l u e as t o the p o s s i b l e n a t u r e of the r e a c t i o n * T h i s worker found t h a t a t 400°, i n the presence o f c e r t a i n o x i d e s , d i m e t h y l a o e t a l was l a r g e l y d i s i n t e g r a t e d t o m e t h y l a l c o h o l and m e t h y l v i n y l e t h e r . S i n c e the a l c o h o l i s not f u r t h e r de-o 6 composed below 900 , i t s d e t e r m i n a t i o n would r e v e a l the ex-t e n t t o which the breakdown had o c o u r r e d , and the e t h e r , a o 7 gas a t room temperature (B.P. 12-14 ) , would be easy t o de-t e c t because of i t s u n s a t u r a t i o n . I t was. expected t h a t these p r o d u c t s might be formed under the i n f l u e n c e o f heat a l o n e . 2i APPARATUS, The runs were c a r r i e d out i n the apparatus shown i n F i g . 1. C g i s the d e t a c h a b l e s t a r t i n g b u l b . The s e a l e d - i n tube at the top p r e v e n t s vapors from l i q u i d i n the b u l b from r i s -i n g to d i r e c t c o n t a c t w i t h the grease of the ground g l a s s . j o i n t , and t h e s m a l l o r i f i c e slows up the escape o f vapors d u r i n g the run o r w h i l e a weighing i s b e i n g made. For the f i r s t seven r u n s , a s i m p l e s t a r t i n g b u l b was s e a l e d on f o r each experiment* The removable condenser tube C2 was a l s o i n t r o d u c e d w i t h Run #8, t o f a c i l i t a t e removal o f l i q u i d p r o d u c t s . The use o f C s and speeded up o p e r a t i o n s c o n s i d e r a b l y * The ground g l a s s j o i n t s gave no t r o u b l e , and t h e r e was no evidence t h a t the grease ( A p i e z o n M) was a t t a k e d by vapors * C i and C2 are condensers* I n the e a r l i e r d e t e r m i n a t i o n s , the l i q u i d p r o d u c t s were, caught i n b u l b s a t the bottoms of these t r a p s * and were then broken o r s e a l e d o f f . The c y l i n d r i c a l b u l b B^ i s heated by the e l e c t r i c r e s i s t -ance f u r n a c e F, whose temperature .is m a i n t a i n e d a t any d e s i r e d v a l u e by means o f a p h o t o - e l e c t r i c s e t - u p . T h i s arrangement was used by P i e r c e 1 , and i s d e s c r i b e d i n h i s t h e s i s * T i s a-p l a t i n u m e l e c t r i c r e s i s t a n c e thermometer. B-^  j _ s covered w i t h aluminum f o i l t o ensure u n i f o r m h e a t i n g * 5 Y i s .a double mercury v a l v e , by means of which p a r t of the apparatus can be segregated i f n e c e s s a r y . The c o n s t r u c t -i o n i s such t h a t mercury w i l l not be pushed i n t o the furnace or the condensers i f a i r i s a c c i d e n t a l l y a d mitted t o the ap-pa r a t u s o r i f a break o c c u r s . B-^  and Bg are gas s t o r a g e b u l b s . M i s an .open mercury c o n t a i n e r — a s a f e t y - v a l v e which p e r m i t s gas to escape i f the p r e s s u r e i n s i d e the apparatus s h o u l d exceed one atmosphere. The' h e i g h t o f the mercury dolumn here forms a convenient mea-sure of the gas p r e s s u r e . A i r may be a d m i t t e d through the d r y i n g tube D and s t o p -cock Sg. T h i s f l o w - t u b e set-up i s j o i n e d to the main vacuum l i n e 2 o f the apparatus used by C.B. S h i p t o n and d e s c r i b e d by him i n d e t a i l . The arrangement employed f o r the i o d i n e a d s o r p t i o n work on gaseous p r o d u c t s i s e s s e n t i a l l y t h a t which was s t u d i e d by 3 " S h i p t o n , The volume of the gas b u r r e t t e was checked by weigh-i n g the amount of mercury i t c o u l d c o n t a i n , and was found to agree c l o s e l y w i t h h i s v a l u e o f 35cc. T h i s f i g u r e was used i n the c a l c u l a t i o n o f the volume o f the f l o w - t u b e apparatus ( o b t a i n e d by measurement of the volume o f gas which produced a known drop i n the s a f e t y gauge Sg) A m o d i f i e d Thunberg tube was adopted as an a d s o r p t i o n p i p e t t e s i n c e the l a r g e ground g l a s s s t o p p e r p e r m i t t e d easy renewal of the reagent and ready c l e a n i n g * Other gas a n a l y s i s were performed w i t h a s t a n d a r d Hempel o u t f i t A 4 5. EXPERIMENTAL PROCEDURE I n making a run t h i s procedure was f o l l o w e d C s was c l e a n e d , and weighed by s u s p e n s i o n i n a l o o p of w i r e from the arom of the b a l a n c e . Then, f r e s h l y d i s t i l l e d d i m e t h y l a c e t a l was i n t r o d u c e d i n t o the b u l b by means of a dropper w i t h a l o n g f i n e t i p u n t i l the d e s i r e d weight had been added. The s t a r t i n g tube was r e p l a c e d on the frame w i t h -out d e l a y , t o a v o i d l o s s by v a p o r i z a t i o n , and surrounded w i t h a Dewar f l a s k c o n t a i n i n g l i q u i d a i r ( o r , i n a few i n s t a n c e s , s o l i d COg). The apparatus was now evacuated u n t i l the McLeod guage showed a p r e s s u r e of 1.8 x 10"^cm o r l e s s . I n the q u a l i t a t i v e work, at t h i s stage the Dewar was r e -moved, and any c o n t a i n e d gas a l l o w e d t o b o i l out o f the a c e t a l b e f o r e r e p l a c i n g the c o o l i n g agent. For the q u a n t i t a t i v e de-t e r m i n a t i o n s , t h i s was not done, s i n c e i t was t h e r e d e s i r e d t o determine any p o s s i b l e l o s s by v a p o r i z a t i o n . I n any case, the amount o f a i r i n the f r e s h l y d i s t i l l e d substance was neg-l i g i b l e . Meanwhile, the f urnace was brought t o the d e s i r e d temp-e r a t u r e , and kept i n t h a t s t a t e by proper adjustment of the p h o t o - e l e c t r i c o o n t r o l . Stopcock S4 was c l o s e d , and Sj_ p l a c e d i n the p o s i t i o n shown i n F i g u r e 1, Now, the l i q u i d a i r r e -m a i n i n g i n the Dewar on G g was removed, and the f l a s k immed-e a t e l y r e p l a c e d around the tube. Another c o n t a i n e r of l i q u i d a i r was put on , and thus by s l o w v a p o r i z a t i o n i n G g and by c o n d e n s a t i o n i n C^, the a c e t a l was induced t o f l o w through the f u r n a c e . Other attempts t o c o n t r o l the r a t e o f passage 5 were made by s u r r o u n d i n g C g w i t h s o l i d C0 g or i c e and s a l t a f t e r the l i q u i d a i r had been removed. The m a t e r i a l caught i n t h e bottom b u l b o f Gj_ was s e a l e d o f f , o r was t r a n s f e r r e d t o detachable Gg by means of l i q u i d a i r . B e f o r e removing any l i q u i d s from the apparatus by s e a l -i n g or o t h e r w i s e , they were a l l o w e d t o r i s e t o a known temp-e r a t u r e , and the f u r n a c e was brought t o room temperature by b l o w i n g a i r through i t . Stopcock Sg was then c l o s e d , thus s e p a r a t i n g a p o r t i o n o f gas, c o l l e c t e d at a known p r e s s u r e and temperature, f o r a n a l y s i s . The next s t e p was t o admit a i r through Sg. Cg was r e -moved from the tube by means of a dropper, and G g was weighed a g a i n . The p r o d u c t s were ready f o r v a r i o u s d e t e r m i n a t i o n s . 4. MATERIALS ( i ) D i m e t h y l a c e t a l was prepared from m e t h y l a l c o h o l and acetaldehyde a c c o r d i n g to the method o f A d k i n s and M s sen . I t was washed w i t h s a t u r a t e d c a l c i u m c h l o r i d e ( n e u t r a l ) s o l -u t i o n t o remove meth y l a l c o h o l , and f r e e d from acetaldehyde by r e p e a t e d f r a c t i o n a l d i s t i l l a t i o n from anhydrous potassium carbonate. The m a t e r i a l thus o b t a i n e d was a l l o w e d to s t a n d over m e t a l l i c sodium, and r e d i s t i l l e d to c o n s t a n t b o i l i n g p o i n t from p o t a s s i u m carbonate j u s t b e f o r e u s i n g . The p u r i t y o f the product was checked by r e f r a c t i v e i n d e x d e t e r m i n a t i o n s • a w i t h A p u l f r i c h r e f r a c t o m e t e r . D e s p i t e r e p e a t e d p u r i f i c a t i o n s , the a c e t a l , which was prepared i n c o l l a b o r a t i o n w i t h G.H. Turner of t h i s l a b -o r a t o r y , gave a v a l u e f o r the r e f r a c t i v e i n d e x (average n-Q z 1,36585 which was d i f f e r e n t from t h a t o f P i e r c e 7 and from t h a t of another worker . G.H. Turner determined the d e n s i t y o f d i m e t h y l a c e t a l as D S3 = ,8479 and D 25 = ,8456, 4 4 hut. these f i g u r e s and f o u r o t h e r s , 8 > 1 5 » 1 6 > 1 7, when reduced t o a common temperature, a l l d i s a g r e e d . I n o r d e r t o check the p r o p e r t i e s of the d i m e t h y l a c e t a l , Turner and the author attempted t o prepare the substance by another method , i n v o l v i n g the use o f a boron o x i d e c a t a l y s t ; but u n f o r t u n a t e l y no y i e l d was' o b t a i n e d . Other methods i n -v o l v i n g the use of m e t a l l i c s a l t s 9 as c a t a l y s t s were not a t -tempted, s i n c e data i n r e g a r d t o t h e i r e f f i c a c y was c o n f l i c t -i n g " ^ . Other c a t a l y t i c p r o c e d u r e s ^ ' ' i n v o l v i n g the use o f hydrogen c h l o r i d e gas, h y d r o c h l o r i c a c i d , or g l a c i a l a c e t i c a c i d t o e f f e c t the combination o f a l c o h o l and aldehyde t o form d i e t h y l a c e t a l might have been used to prepare the d i -methy l compound. An attempt t o prove the p u r i t y of the a c e t a l by m o l e c u l a r 14 weight d e t e r m i n a t i o n by the V i c t o r Meyer method proved un-s a t i s f a c t o r y , s i n c e the vapor d i s s o l v e d i n the water used t o measure i t s p r e s s u r e . I t was planned to o b v i a t e t h i s d i f f i c -u l t y by an a d a p t a t i o n of a method d e s c r i b e d by N i e d e r l , i n - • v o l v i n g the measurement of mercury d i s p l a c e d by the vapor o f the substance t o be determined. An apparatus was s p e c i a l l y made f o r t h i s purpose, but the m o l e c u l a r weight of pure methyl a l c o h o l c o u l d not be found w i t h i n Zfo o f e r r o r . I t was seen t h a t the l i m i t o f e x p e r i m e n t a l e r r o r here was g r e a t e r than i n the measurement of r e f r a c t i v e i n d e x , so the work was d i s c o n -7 ..tinned. E v e r y p o r t i o n o f p u r i f i e d d i m e t h y l a c e t a l c o n t i n u e d to show constant p r o p e r t i e s , so i t was d e c i d e d to go ahead w i t h the i n v e s t i g a t i o n , s i n c e the substance was e v i d e n t l y homogen-eous . However, i t was noted t h a t exposure t o m o i s t a i r f o r any l e n g t h of time produced a v e r y s l i g h t but d e t e c t a b l y de-c o m p o s i t i o n of the m a t e r i a l , HgC0 3. For t h i s r e a s o n , o n l y f r e s h l y p u r i f i e d product was used throughout the r e s e a r c h . ( i i ) . Pure m e t h y l a l c o h o l f o r t e s t purposes was prepared from B a k e r 5 s C P . methanol. T h i s was a l l o w e d t o s t a n d over anhydrous CaO f o r s e v e r a l days and was then d i s t i l l e d from f r e s h CaO u n t i l a c o n s t a n t b o i l i n g p o i n t was a t t a i n e d . ( i i i ) . ~ A c etaldehyde was prepared from paraldehyde by 19 d e p o l y m e r i z a t i o n w i t h d i l u t e s u l p h u r i c a c i d , and was p u r i -f i e d by r e p e a t e d f r a c t i o n a l d i s t i l l a t i o n . I t was n o t i c e d t h a t d i m e t h y l a c e t a l which had been prepared from impure a c e t -aldehyde s m e l l e d s t r o n g l y o f c r o t o n aldehyde, and t h a t t h i s substance was d i f f i c u l t t o remove c o m p l e t e l y by f r a c t i o n a t i o n , d e s p i t e i t s h i g h b o i l i n g p o i n t . Grotonaldehyde i s prepared by the a c t i o n of c o l d , c o n c e n t r a t e d s u l p h u r i c a c i d upon p a r -21 aldehyde , and t h i s would account f o r i t s s l i g h t f o r m a t i o n a l o n g w i t h a c e t a l d e h y d e . ( i v ) . Other c h e m i c a l s used were Baker's C P . s t o c k or from Eimer and Amend. 5. ANALYTICAL .(.a) QUALITATIVE ( i ) B o i l i n g p o i n t s of l i q u i d s were o b t a i n e d by • 8 22 S i w o b o l o f f * s method . ( i i ) L i q u i d s were t e s t e d f o r u n s a t u r a t i o n by sh a k i n g i n a g l a s s - s t o p p e r e d b o t t l e w i t h a carbon t e t r a c h l o r i d e s o l u t i o n o f i o d i n e . 23 ( i i i ) A l c o h o l s were d e t e c t e d by F e i g l ' s t e s t s and by m e t a l l i c sodium. F e i g l ' s #1s f o r any common a l c o h o l , depends on the e s -t e r i f i c a t i o n o f the a l c o h o l and the f o r m a t i o n by the e s t e r of a- c h a r a c t e r i s t i c a l l y - c o l o r e d i r o n s a l t . An a l l - g l a s s m i c r o -r e f l u x was c o n s t r u c t e d f o r t h i s d e t e r m i n a t i o n . F e i g l ' s #2 f o r p r i m a r y and secondary a l c o h o l s i s based upon t h e i r c o n v e r s i o n by carbon d i s u l p h i d e and sodium hy-dr o x i d e t o a l k a l i xanthogenates which y i e l d a c h a r a c t e r i s t i c c o l o r r e a c t i o n w i t h molybdates. G l a s s s t o p p e r e d tubes were used here t o do away w i t h c o r k c o n t a m i n a t i o n . Both F e i g l ' s #1 and #2 were performed w i t h pure d i m e t h y l a l c o h o l and pure a c e t a l d e h y d e , and were found t o g i v e no t e s t i n these i n s t a n c e s . M e t a l l i c sodium produces no r e a c t i o n w i t h d i m e t h y l a c e t a l but i f m e t h y l a l c o h o l i s p r e s e n t , bubbles o f hydrogen are formed, and in. a d d i t i o n a y e l l o w s o l i d compound appears. T h i s l a t t e r substance seems t o be a polymer of the a c e t a l , formed by the a c t i o n o f sodium m e t h y l a t e on t h a t compound. T h i s would be analogous t o the p o l y m e r i z a t i o n of acetaldehyde by 1 24 NaOH, and would be i n l i n e w i t h the statement by Bernthsen t h a t a c e t a l s undergo aldehyde p o l y m e r i z a t i o n . I f a c e t a l d e -hyde i s pres e n t i n the a c e t a l - a l c o h o l m i x t u r e t h a t too i s p o l y m e r i z e d . ( i v ) Aldehydes were t e s t e d f o r by the use of NaOK and T o l l e n ' s r e a g e n t " ^ , A c e t a l d e h y d e , when heated w i t h NaOH, forms a y e l l o w p o l -ymer. T o l l e n ' s ammoniaca1 s i l v e r n i t r a t e s o l u t i o n i s much more s e n s i t i v e , and p r e c i p i t a t e s out b l a c k m e t a l l i c s i l v e r when reduced by t r a c e s o f any aldehyde. Another t e s t , i n v o l v i n g the r e d u c t i o n of f u c h s i n s u l p h u r -OUB a c i d 1 5 , was a l s o s t U d l e d . These t h r e e procedures were b l a n k - t e s t e d w i t h methyl a l -c o h o l and d i m e t h y l a c e t a l , and were found t o be s a t i s f a c t o r y . (v) . Gaseous p r o d u c t s were withdrawn from the apparatus i n t o evacuated b u l b s , and were shaken w i t h p o t a s s i u m perman-ganate s o l u t i o n , bromine water, and i o d i n e i n carbon t e t r a -c h l o r i d e t o t e s t f o r u n s a t u r a t i o n . (b) QUANTITATIVE ( i ) P r e l i m i n a r y The q u a l i t a t i v e data e s t a b l i s h e d the f a c t t h a t the l i q u i d i p r o d u c t s would c o n t a i n o n l y d i m e t h y l a c e t a l and met h y l a l c o -h o l under normal c i r c u m s t a n c e s . The s e p a r a t i o n of these two s u b s t a n c e s , or the d e t e r m i n a t i o n o f one i n the presence of the o t h e r , c o n s t i t u t e d a d i f f i c u l t problem. T h e i r p h y s i o a l p r o p e r t i e s ' , are s i m i l a r ; t h e i r b o i l i n g p o i n t s are p r a c t -i c a l l y i d e n t i c a l , and t h e i r ' d e n s i t i e s and r e f r a c t i v e i n d i c e s are v e r y c l o s e . They are b o t h s o l u b l e i n a l l the common 10 s o l v e n t s . Chemical methods which would remove methyl a l c o h o l i n -v o l v e the use of m i n e r a l a c i d s or s t r o n g o x i d i z i n g agents which would h y d r o l y s e or d e s t r o y the d i m e t h y l a c e t a l . Sub-26 stnaces such as 2, 4 d i n i t r o b e n z o y l c h l o r i d e which p r e c i p -i t a t e s m e t h y l a l c o h o l , cannot be used, s i n c e i n m o i s t a i r they would h y d r o l y s e t o form s m a l l q u a n t i t i e s o f m i n e r a l a c i d s . 27 S i m i l a r l y , P r e g l * s method o f d e t e r m i n i n g methoxy groups might be used t o measure the r e s i d u a l d i m e t h y l a c e t a l i f t h a t substance were not h y d r o l y s e d by the h y d r i o d i c a c i d used i n the p r o c e s s . ( i i ) The f i r s t method o f e s t i m a t i o n d e v i s e d f o r methyl a l c o h o l was an a d a p t a t i o n o f a q u a l i t a t i v e t e s t f o r a c e t a l -25 dehyde . P r e p a r e d m i x t u r e s of a l c o h o l and a c e t a l were r e -f l u x e d w i t h d i l u t e IIC1 i n an a l l g l a s s a p p a r a t u s ; the r e s u l t -i n g a c e t a l d e h y d e was p r e c i p i t a t e d by 2*. 4 d i n i t r ophe n y l h y dr a -z i n e as the hydrazone, and t h i s p r e c i p i t a t e was p u r i f i e d and weighed. The r e s u l t s o b t a i n e d from two such d e t e r m i n a t i o n s were i n f a i r l y c l o s e agreement (1,2%), but the pr o c e s s was found to be time-consuming. The use of m e t a l l i c sodium was next i n v e s t i g a t e d . Re-f e r r i n g back t o F i g . 1, a r u n (#10) was completed i n the u s u a l ' manner, but the l i q u i d p r o d u c t s were kept i n C^. Cg was r e -moved , p a r t i a l l y f i l l e d w i t h f r e s h l y cut sodium, and r e p l a c e d . C^ was then surrounded w i t h l i q u i d a i r , and the apparatus ev-acuated. The p r o d u c t s were d i s t i l l e d over i n t o C2, and t h i s t r a p was c o o l e d w i t h i c e - w a t e r t o prevent the heat of sodium 11 r e a c t i o n from v a p o r i z i n g the l i q u i d s . When the a c t i o n was complete, a Dewar o f l i q u i d a i r was p l a c e d about the condenser and hydrogen pumped o f f and measured* T h i s procedure was found to possess c e r t a i n drawbacks. The r e a c t i o n w i t h sodium c o n t i n u e d i n d e f i n i t e l y , and i t was i m p o s s i b l e t o a s c e r t a i n when e v o l u t i o n of hydrogen had ceased. I n a d d i t i o n t o t h i s , the d i m e t h y l a c e t a l formed a y e l l o w p o l -ymer which coated the sodium and impeded the a c t i o n . Sodium m e t h y l a t e i s l i s t e d as p o s s e s s i n g two mo l e c u l e s o f me t h y l a l -c o h o l o f c r y s t a l l i z a t i o n , so a l l the OHgOH may not be t r a n s -formed. . The use o f the r e f r a c t o m e t e r i n the p u r i f i c a t i o n o f d i -methyl a c e t a l suggested another method of d e t e r m i n i n g the a l -c o h o l . The r e f r a c t i v e i n d e x of the l i q u i d p r o d u c t , s i n c e i t c o n s i s t e d of o n l y two su b s t a n c e s , s h o u l d f u r n i s h i n f o r m a t i o n about t h e i r r e s p e c t i v e p r o p o r t i o n s , even i f the r e l a t i o n s h i p between r e f r a c t i v e i n d e x and c o m p o s i t i o n i s not a l i n e a r one. A s e r i e s o f s t a n d a r d m i x t u r e s o f methy l a l c o h o l and d i -methyl a c e t a l was made up, and t h e i r r e f r a c t i v e i n d i c e s meas-ured* These m i x t u r e s were prepared from f r e s h l y d i s t i l l e d m a t e r i a l s , were weighed i n g l a s s - t o p p e d b o t t l e s , and were de-termined i m m e d i a t e l y * R e s u l t s were graphed, and from t h i s graph, percentages i n unknowns were r e a d , knowing the r e f r a c -1^.5 25 t i v e i n d e x , n^ ~*. and n D f o r m e t h y l a l c o h o l were found t o be 1.35114 and 1.32759 r e s p e c t i v e l y , c h e c k i n g c l o s e l y w i t h the l i s t e d v a l u e s of 1,33118 and 1.32761. I I 12 (iii)„ The e s t i m a t i o n of v i n y l , m e t h y l e t h e r was suggested by the work o f C h a l m e r s 5 , who observed t h a t the eth e r r e a o t s v i o l e n t l y w i t h i o d i n e , f o r ming a h i g h l y - v i s c o u s p i t c h - b l a c k polymer. The a c t i o n i s spontaneous, and a p p a r e n t l y a v e r y s m a l l q u a n t i t y of i o d i n e w i l l e f f e c t the p o l y m e r i z a t i o n . The gaseous p r o d u c t s from our r e a c t i o n were put i n con-t a c t w i t h e l e m e n t a l i o d i n e i n an a d s o r p t i o n p i p e t t e , and an i d e r i t i c a l phenomenon o c c u r r e d . Pure p r e p a r a t i o n s of d i m e t h y l a c e t a l , m e t h y l a l c o h o l , and aceta l d e h y d e were v a p o r i z e d and s u b j e c t e d to the same t e s t . They produced no s i g n s of p o l y -m e r i z a t i o n , f o r m i n g o n l y a s l i g h t brown s t a i n on the w a l l s o f the a b s o r p t i o n p i p e t t e . ' T h i s was caused' by a p a r t i a l of the i o d i n e by the c o n c e n t r a t e d v a p o r s , l e a v i n g the i o d i n e very f i n e l y d i v i d e d when the p i p e t t e was pumped out. None of these t h r e e substances s u f f e r e d any measurable l o s s i n volume, whereas the gaseous m i x t u r e c o n t a i n i n g the e t h e r was apprec-i a b l y d i m i n i s h e d . There was no f u r t h e r decrease i n volume when the m i x t u r e was p l a c e d i n c o n t a c t w i t h f r e s h r e a g e n t , p r o v i n g t h a t the removal o f m e t h y l v i n y l e t h e r had been com-p l e t e . I n p r a c t i c e , the f r e s h l y f i l l e d a d s o r p t i o n p i p e t t e was evacuated w h i l e surrounded w i t h s o l i d C 0 g . The vapor p r e s s u r e o f the i o d i n e i s so s l i g h t (.202mm at 20 0) t h a t i t sh o u l d not a f f e c t the a c c u r a c y o f the d e t e r m i n a t i o n s a p p r e c i a b l y , and t h i s e r r o r i s d i m i n i s h e d by r e a c t i o n o f the gaseous i o d i n e w i t h the mercury i n the T o p l e r pump. A f t e r the p i p e t t e had been pumped o u t , the reagent was induced by g e n t l e h e a t i n g t o cover most of the i n s i d e s u r f a c e of the tube w i t h a f i n e l a y e r of c r y s t a l s . The method of e s t i m a t i n g the e t h e r l e f t something t o be d e s i r e d , s i n c e the r e a c t i o n between the i o d i n e vapor and the mercury formed an u n d e s i r a b l e c o a t i n g on the i n s i d e of the T o p i e r pump. I n a d d i t i o n , the i o d i n e vapor adsorbed on s t o p -cock grease and n e c e s s i t a t e d i t s f r e q u e n t renewal. ( i v ) G o n d e n s i b i l i t y o f t h e gaseous r e a c t i o n p r o d u c t s was a s c e r t a i n e d by measuring the f r a c t i o n o f the m a t e r i a l t h a t would condense out i n the a d s o r p t i o n p i p e t t e when i t was surrounded w i t h s o l i d COg. 6., INTERPRETATION OF THE TABLES ( i ) The p o s i t i v e t e s t s f o r aldehyde i n runs #1 and #3 i n d i c a t e I n s u f f i c i e n t p u r i f i c a t i o n o f the s t a r t i n g m a t e r i a l . The l i q u i d p r o d u c t s were a l l o w e d to assume room temper-a t u r e b e f o r e removal from the a p p a r a t u s , thus a l l o w i n g any d i s s o l v e d m e t h y l v i n y l e t h e r t o escape. Hence these s u b s t a n -ces d i d not e x h i b i t any u n s a t u r a t e on. • ( i i ) The t a b l e s p r e s e n t o n l y the p e r c e n t of meth y l a l -c o h o l i n the l i q u i d p r o d u c t s , so t h i s f i g u r e s h ould be s l i g h t -l y lower t h a n t'he va l u e o b t a i n e d f o r the e t h e r , i f the two are formed i n e q u a l q u a n t i t i e s . T h i s i s found t o h o l d w e l l f o r the cases where the l i q u i d s a re r a i s e d t o room temperature, and e x t e n s i v e v a p o r i z a t i o n occured. The t o t a l volume of gas i s seen to be f a i r l y c o n s t a n t , and t o depend not on the amount of a c e t a l used, but upon the temperature to'which the l i q u i d p roduct was r a i s e d and the 14 amount of permanent gas p r e s e n t . C a l c u l a t i o n r e v e a l s t h a t i f the gas i s considered, as d i m e t h y l a c e t a l vapor, i t s weight ap-proximates the d i f f e r e n c e s i n weight l i s t e d i n Table 5, s i n c e i n no ease d i d e x t e n s i v e d e c o m p o s i t i o n of the s t a r t i n g mater-i a l "occur. The time of the r u n c o u l d not be determined e x a c t l y , s i n c e the a c e t a l d i d not go through the furnace a t a u n i f o r m r a t e . When a p o r t i o n o f m a t e r i a l had l e f t the s t a r t i n g b u l b , t h i s c o o l e d the r e s i d u a l l i q u i d , so t h a t v a p o r i z a t i o n remained s t a t i o n a r y f o r v a r y i n g l e n g t h s o f t i m e . Thus the f i g u r e s ob-t a i n e d are not v e r y s i g n i f i c a n t except i n s o f a r as t h e y r o u g h l y i n d i c a t e t h a t a l o n g e r exposure t o heat u s u a l l y produced g r e a t -e r d e c o m p o s i t i o n ^ 7. DISCUSSION OF RESULTS ( i ) The q u a l i t a t i v e i n f o r m a t i o n s t r o n g l y i n d i c a t e s t h a t the thermal d e c o m p o s i t i o n o f d i m e t h y l a c e t a l i s a s i m p l e s p l i t i n t o m e t h y l a l c o h o l and m e t h y l v i n y l e t h e r . T h i s may be com-p l i c a t e d by the f u r t h e r d e c o m p o s i t i o n o f the e t h e r t o y i e l d permanent gases, and by s l i g h t h y d r o l y s i s of the a c e t a l i f the m a t e r i a l i s exposed to m o i s t a i r f o r any l e n g t h of t i m e . The 64-66° b o i l i n g range o f the l i q u i d p r o d u c t , the r e s u l t s of the a l c o h o l and aldehyde t e s t s , and the u n s a t u r a t i o n o f the gas but not o f the l i q u i d do not seem t o permit any o t h e r pos-s i b i l i t y . ( i i ) On the...quantitative- s i d e , the evidence f o r equal p r o p o r t i o n s of m e t h y l a l c o h o l and m e t h y l v i n y l e t h e r i n the breakdown product i s f a i r l y c e r t a i n . However, here the ac-15 cura c y of the r e s u l t s i s l i m i t e d by c e r t a i n f a c t o r s . When the l i q u i d product i s not r a i s e d t o room temperature, some methyl v i n y l e t h e r may remain d i s s o l v e d . T h i s w i l l a f f e c t the i o d i n e a n a l y s i s , but s h o u l d not d i s t u r b the r e f r a c t i v e i n d e x d e t e r -m i n a t i o n s i n c e the e t h e r w i l l r a p i d l y escape d u r i n g the hand-l i n g i n the l a t t e r measurement. I f the pr o d u c t s are r a i s e d t o room-temperature b e f o r e w i t h d r a w a l from the appa r a t u s , much o f the m a t e r i a l w i l l v a p o r i z e , and the p r o p o r t i o n s of a l -c o h o l and a c e t a l may be d i f f e r e n t i n the gas phase from those i n the l i q u i d phase. However, the amounts of a l c o h o l and e t h e r are of the same order e xcept i n those cases where per-manent gas was formedi ( i i i ) I t i s e v i d e n t , t h a t the optimum c o n d i t i o n s f o r de-c o m p o s i t i o n were never a t t a i n e d . Only i n a few i n s t a n c e s where l a r g e q u a n t i t i e s o f the a c e t a l were used, d i d p a r t o f t h i s m a t e r i a l happen to pass through the furnace s l o w l y enough t o produce e x t e n s i v e decomposition> and the f l o w o f t h i s p o r -t i o n was so slow t h a t p r o g r e s s i v e breakdown o c c u r r e d . I t would seem t h a t the d i s i n t e g r a t i o n w i l l o c cur anywhere between 300-500°j a l t h o u g h the temperature a t which the r e a c t i o n be-g i n s was not a s c e r t a i n e d . For f u r t h e r study on t h i s s u b j e c t , a s u i t a b l e means of measuring and c o n t r o l l i n g the f l o w o f m a t e r i a l s through the f u r n a c e . s h o u l d be developed. P a c k i n g the f l o w tube w i t h g l a s s wool s h o u l d d i m i n i s h the r a t e of passage, and would r e v e a l the e f f e c t o f i n c r e a s e d s u r f a c e upon the e x t e n t of decom p o s i t i o n . 16 BIBLIOGRAPHY -I . W. G. P i e r c e , T h e s i s , 1939* 2* G. B., S h i p t o n , T h e s i s , 1939. 3. G. B. S h i p t o n , T h e s i s , 1937. 4* M. Gabanac, Compt. Rend., 190 ,: 881,-1930. 5. B e i l s t e i n , 1, 276, 1918. 6. ¥. Chalmers, Can. J o u r . Res., 7, 472, 1932. 7. Organic S y n t h e s e s , 3, 1, 1923. 8* H i n t o n and N i e w l a n d , J.A.C.S. , 52, 2892, 1930. 9. C. A., 11, 86, 1917. 10. J . A. G. S., 44, 2749, 1922. I I . Ann*, 126, 62, 1862. 12. B e r . , 30, 3053, 1897, 13. S a b a t i e r , C a t a l y s i s i n Organic C h e m i s t r y . 14. S h e r r i l l , L a b o r a t o r y E x p e r i m e n t s . 15. M u l l i k a n , I d e n t i f i c a t i o n of Pure Organic Compounds, V . I . 16. Handbook o f C h e m i s t r y and P h y s i c s , 1939-40. 17. B e i l s t e i n , 1, 921, 1893. 18. N i e d e r l a n d N i e d e r i , Organic Q u a n t i t a t i v e M i c r o - a n a l y s i s , pge. 175. 19* McLeod, Am. Cham. J o u r . , 37, 27, 1907. 20. G. H. T u r n e r , T h e s i s , 1940 21. D e L i s l e , F o w l e r , Love11 & U r e , Thermal Decomp. o f Croto n a l d e h y d e . T r a n s . R.S.C. , S e c t i o n 111, 1936. 22. Lassar-Cbhm, O r g a n i c L a b o r a t o r y Methods, pge. 365. 23. G e i g l , Spot T e s t s , pge. 250. 17 24. B e r n t h s e n , Organic C h e m i s t r y , pge. 136* 25. S h r i n e r and Fuson, I d e n t i f i c a t i o n of Organic Compounds, pge, 148. 26. Melons & R e i d , J.A.C.S. , 51, 3426, 1929. 27. P r e g l , Q u a n t i t a t i v e Organic M i c r o a n a l y s i s , pge. 181. 18 TABLE I 'QUALITATIVE DETERM! NAT I ON OF PRODUCTS 20 \$Z 360 " t v e I \$3 360° " ve ve I v if4 360° Gases f.lun T I j , i n Na F e i g l ' s F e i g l ' s NaOH T o l l e n s Av. nr> Unsat. of [ — ~ §01, ~ #1 "- - -\fl 360° no j change t v e if *5 400° " ve ve ve ve ve ve ve + ve -ve -ve -ve -ve B.P. ~ D C ~ A l k a l i n e t v e 64.2 KHH0 A l i g h t e n e d -ve 66.1 1.36360 ve 64.65 -ve 64.75 -ve 64.90 C o l o r r e -moved from I 2 i n GC1A C o l o r r e -moved from B r g water. TABLE; I I ANALYSIS OF PERMANENT GASES [tan %Water %Condensible C o m o o s i t i o n o f Non-condensibles S o l u b l e by Ice.& Water 0 g G0g H i g h e r Ho- E t h y l e n e CO HHg CH, mologues o f ...Ethylene 61.7 71.8 0 0 0 8.8 41.2 12.6 35.8 79.4 0 0 1.4 14.9 37.5 17.8 27.2 I f TABLE I I I Run Weight of Wt. of L i q u i d D i f f e r e n c e n£ p&eOE from S t a r t i n g P r o d u c t Graph M a t e r i a l 6 • 14*0? 13.637 .363 1.36624 2.9 7 9*868 9.480 .388 1.36430 8.6 8 2.847 2,569 © 2 79 1.36641 . 2.1 9 2.502 2«232 .270 2.4 10 2 .747 2.481 .266 17.6cc;H * 1.82 at N.T.P. 11 3.930 3.671 e 2*59 1.36625 2*9 12 3.264 2.978 .286 1.36598 4.0 13 2.807 2.545 • 2 6 2 1.56623 2.9 14 3.029 2.695 .334 1.36616 3.3 15 5.347 5.009 .338 1.36617 3.3 16 4.093 3.740 o 353 1.36600 3.4 17 6.269 5.958 o 311 1*56624 2.9 18 4*672 4.326 .346 1*36630 2 & 7 19 5*189 4.857 1*36642 2.1 Run Barom. P. P B S a f e t y Guage P. p ^ s g P B-P J> 75.60 5 5 • 5 5 20.05 7 75.45 53.55 20.90 8 76.00 61i60 14.40 9 75.40 61.00 14.40 10 76.10 61.65 14.45 11 76.12 62.5 13.70 12 76.10 5 9 © 9 5 16.15 13 75.85 63.20 12.65 14 76.30 59.35 16.95 15 75.8 -58.9 16.9 16 75.7 58.9 16.8 17 76.00 58.65. 17.35 18 76.05 58.20 17.85 19 76.10 58.85 17.25 TABLE I T T A T o t a l v o l . gas at N.T.P. P B - P S g s 270 - v o l . o f = V. 21.40 93.4 22.5 102.2 22 9 4:5 71.8 21.7 69.5 21 o 35 68.5 22 • 5 68.5 20.5 73.6 23.65 67,4 22.8 86.0 ESiBS' 85.8 24.55 91.7 23.5 88.8 22.0 89.0 21«8 89.1 P o l 14.Gem Run P l P 2 6 31.20 19.45 7 19.25 16.60 8 18.25 17.25 9 27*3 24.4 10 35*65 31.60 11 29.70 23.90 12 18.9 16.6 13 29.3 24,55 14 3*J e X 24:* 5 5 15 2 5 o 6 19 • 3 5 16 22.5 19.85 17 23.40 18 c 3 18 23.05 19, 6 19 27.2 22 g 9 21 TABLE ¥ p l ~ p 2 E x V x 58 r — — 22400 l n fw - % E t h e r g 1 - P 0 : Sample Wt. X 1 0 0 / 0 .683 1.76 % .503 2.01 9 235 2«20 •218 2«32 .187 1.80 .369 2.48 .457 3.98 .310 2,83 .311 3.41 o 5o*7 3 o 3 3 ,582 3.31 e 54:2 2*96 .380 . 2.80 .327 2.17 22 TABLE Y I Run Temt>, o 0~ Time . h r s . feOH E i t h e r foNon-oon-d e n s i b l e s Temp. Product LOSE Wt. of Y T R a i s e d To °C 6„ 360 18 2 « Q 1.76 93.4 15 .363 7 360 18 8,6 2. 01 25.17 X 0 2 & 2 15 ,,388 8 360 14 2.1 2.20 0 71.8 15 .279 9 360 12 2.4 2«32 0 69,5 15 .270 10 360 10 1.82 1.80 0 68.5 15 .266 11 •.' 360 15 2. 9 2.48 0 68,5 14.2 .259 12 340 15 4.0 3.98 1.97 73,6 15 .286 13 350 17 2.9 B. 83 .— - 67.4 14.5 ^262 14 410 5 3 e 3 3.41 0 86,0 . 19.5 .354 15 460 . 4 3 # 3 3 o 3o 1.12 85.8 19 .358 16 425 5 3.4 3.31 3.0 91.7 24.55 « 3 53 17 465 6 2.9 2.96 0 88.8 23 .511 18 360 10,5 2.7 2.80 0 89.0 25 .346 19 320 15 2 o 1 2.17 0 89.1 22.8 ft 332 TABLE V I I STANDARD REFRACTIVE INDICES Wt. of A c e t a l Wt. o f A l c o h o l tfMe OH 20 nD 1.36694 0 100 1.32919 2.610 .176 6.74 1,36541 2.164 .368 17.01 1.36192 1.945 .644 33.1 1.35532 1.782 1.005 56.4 1.34955 3.101 .040 1,28 1.56664 2.710 .276 9.25 1.36445 2.273 .559 19.76 1.36025 3.377 .170 4. 78 1.56576 3.229. .109 3 © 2 2 1.36606 3.006 .093 3.10 1.56620 2.912 .071 2.40 1.56637 CONTENTS Page I n t r o d u c t i o n . 1 M a t e r i a l s S Apparatus 3 E x p e r i m e n t a l Methods of Santhate D e t e r m i n a t i o n 3 T i t r a t i o n w i t h I o d i n e 4 Other T i t r a t i o n Methods 4 C o l o r i m e t r i c Methods 5 Xanthate A b s t r a c t i o n and R e l a t e d Methods 6 D i s c u s s i o n 15 B i b l i o g r a p h y 17 1 THE ABSTRACTION OF POTASSIUM ETHYL XANTHATS' FROM SOLUTION BY PURE LEAD SULPHIDE INTRODUCTION When r e s e a r c h on f l o t a t i o n was begun i n t h i s l a b o r a t -o r y , the c h i e f problem t o be a t t a c k e d was the q u e s t i o n of •what p r o p e r t y , c h e m i c a l or p h y s i c a l , o f the c o l l e c t i n g agent caused the m i n e r a l p a r t i c l e t o be f l o a t e d . I t was thought t h a t a st u d y o f c o l l e c t o r a b s t r a c t i o n , by the m i n e r a l from s o l u t i o n might y i e l d some c l u e as to the s t a t e o f a f f a i r s at the p a r t i c l e s u r f a c e and, w i t h t h a t end i n view, the work d e s c r i b e d i n t h i s r e p o r t was done. A pure prepared m i n e r a l r a t h e r than a pure n a t u r a l l y - o c c u r r i n g one was used i n the exp e r i m e n t s , i n orde r t h a t the observed r e s u l t s might not be i n f l u e n c e d by i m p u r i t i e s i n the substance. A thorough r e v i e w of f l o t a t i o n l i t e r a t u r e , i n c l u d i n g t h a t on the t h e o r i e s of c o l l e c t o r a c t i o n , has been made by 1 Bennett , and no attempt w i l l be made t o r e s t a t e any o f t h i s m a t e r i a l . MATERIALS AND PREPARATIQMS Pure P o t a s s i u m E t h y l Xantfaate and r e c r y s t a l l i z e d l e a d l i t r a t e were prepared a c c o r d i n g t o methods d e s c r i b e d by P e a r c e 2 . Lead S u l p h i d e was produced from Pb(NOg) g s o l u t i o n by the a c t i o n o f washed hydrogen s u l p h i d e . The r e s u l t i n g p r e c i p -i t a t e was t r e a t e d w i t h d i s t i l l e d water i n an e l u t r i a t o r u n t i l the wash l i q u i d gave no t e s t f o r l e a d i o n w i t h H gS, To prevent i t s o x i d a t i o n , PbS was s t o r e d under water u n t i l r e q u i r e d . S t a r c h I n d i c a t o r f o r I o d i n e - X a n t h a t e . T i t r a t i o n was f i r -s t made from s t a r c h and water o n l y , but a s o l u t i o n c o n t a i n i n g 3 m u r c u r i c i o d i d e was found t o g i v e a sharper end-point,. P r a c t i c a l l y a l l o f the chemieals used were Baker's 0. P. s t o c k . Some workers p o s t u l a t e the f o r m a t i o n of dixanthogen and x n a t h i c a c i d from x a n t h a t e i n c e r t a i n f l o t a t i o n r e a c t i o n s 1 . The p r e p a r a t i o n o f these substances was attempted, i n order t h a t some degree of f a m i l i a r i t y w i t h them might be a t t a i n e d . 4 Dixanthogen was made as o u t l i n e d i n B e i l s t e i n , and was found •to be an o i l y brown l i q u i d which d i d not c r y s t a l l i z e i n f o u r and o n e - h a l f months o f s t a n d i n g . X a n t h i c a c i d was prepared by 4 the a c t i o n o f d i l u t e HOI on KEtX- a t 0° , but the r e s u l t was u n c e r t a i n . The product was found t o e x e r c i s e a r e d u c i n g aet^-i o n upon KHnO^ s o l u t i o n * i n d i c a t i n g "that i t would be t i t r a t -a b l e . bisti/ted Water-Oeerf/o ~Bgure_L— Ground. Glass 3;: APPARATUS The equipment f o r t h i s work i n c l u d e d a pR" meter, a c o l o r i m e t e r and an e l e c t r i c a l l y d r i v e n a g i t a t o r f o r sh a k i n g b o t t l e s . A l l b u r e t t e s and p i p e t t e s used f o r a n a l y t i c a l work were c a l i b r a t e d . Gas a n a l y s e s were performed by standard me-thods. Lead s u l p h i d e was washed i n an e l u t r i a t o r ( F i g . 1) which p e r m i t t e d easy removal of the substance. An apparatus was developed f o r the continuous d e t e r -m i n a t i o n of pl-l of a s o l u t i o n under any d e s i r e d atmosphere ( F i g . 2} A new c o n t a i n e r ( F i g . 3) was d e v i s e d f o r the sh a k i n g e x p e r i m e n t s , but i t s p o s s i b i l i t i e s were not f u l l y i n v e s t i g -a t e d . By s u i t a b l e m a n i p u l a t i o n , gas can be withdrawn from t h i s apparatus w i t h o u t d i l u t i o n of the c o n t a i n e d s o l u t i o n . S o l i d s a re e a s i l y i n t r o d u c e d , and samples of s o l u t i o n may r e -a d i l y be removed by p i p e t t e . EXPERIMENTAL METHODS OF XANTHATE DETERMINATION B e f o r e b e g i n n i n g the a b s t r a c t i o n work, an attempt was made t o f i n d the method be s t s u i t e d f o r xanthate d e t e r -m i n a t i o n s . 4 ( i ) T i t r a t i o n with. I o d i n e ( S t a r c h I n d i c a t o r ) T i t r a t i o n of e q u i v a l e n t q u a n t i t i e s of EEtX s o l u t i o n at d i f e r e n t pH v a l u e s y i e l d e d the f o l l o w i n g r e p r e s e n t a t i v e f i g u r e s pH I o d i n e T i t r e (cc) ' 1.05 0.5 2.16 0.95 5.01 X s 3 4.20 2.6 5.15 3.9 6.11 4.2 7.42 4.7 8.19 8.3 9.60 15.35 11.83 19.2 r e s u l t s i n d i c a t e t h a t v a l u e s o b t a i n e d f o r i o d i n e xanthate are u s e l e s s u n l e s s o b t a i n e d at constant pH. S o l u t i o n s s h o u l d t h e r e f o r e be b u f f e r e d , i . e . , w i t h ITaHCOg, b e f o r e d e t e r m i n a t i o n s a r e made. ( i i ) Other T i t r a t i o n Methods S i n c e KEtX i s a r e d u c i n g agent and a l s o p r e c i p i t a t e s many me t a l s from s o l u t i o n , i t s d e t e r m i n a t i o n by t i t r a t i o n w i t h v a r i o u s o x i d i z i n g agents and s a l t s was attempted. KMnO^:-The a d d i t i o n of xanthate gave an i n d e f i n i t e c o l o r change from p i n k t o y e l l o w . I n the presence of diphenylamine, excess KEtX produced a whi t e p r e c i p i t a t e , w h i l e excess KMnO^ caused a^purple p r e c i p i t a t e t o appear. GuSO^-The. i n t e r a c t i o n of GuS0 4 and KEtX gave a y e l l o w p r e c i p i t a t e o f C u ( E t X ) 2 . Excess copper was d e t e c t e d by the use of NH^OH as an e x t e r n a l i n d i c a t o r . T h i s method.-was found t o be s a t i s f a c t o r y o n l y when c o n c e n t r a t e d s o l u t i o n s o f both r e a g e n t s were used. AgNQg:-Xanthate here produced a white p r e c i p i t a t e of Ag ( E . t X ) g i Excess s i l v e r was d e t e c t e d by" an e x t e r n a l i n d i c a t o r • s o l u t i o n o f HC1. T h i s method too was found t o be good o n l y f o r h i g h e r c o n c e n t r a t i o n s of the m e t e r i a l s i n q u e s t i o n . K a B i O g t - T h i s formed a b l a c k p r e c i p i t a t e , and the p o i n t at which p r e c i p i t a t i o n ' was complete was d i f f i c u l t t o d e t e c t . . O e r i c Ammonium; S u l p h a t e : - T h i s reagent had t o be used i n s t r o n g l y a c i d ( H 2 S 0 4 ) s o l u t i o n t o prevent h y d r o l y s i s of the cerium s a l t , and the e f f e c t o f t h i s a c i d on the xanthate was u n c e r t a i n . KgGrjgO^r-An e x t e r n a l i n d i c a t o r of K 4Fe(CB'} 6 was used. T i t r a t i o n s were not r e p r o d u c i b l e a t any c o n c e n t r a t i o n o f xan-t h a t e , and a p r e c i p i t a t e o f unknown c o m p o s i t i o n was formed. N i ( M 0 2 ) : - A p r e c i p i t a t e of c o b a l t xanthate obscured the p o i n t at which the green c o l o r d i s a p p e a r e d from the s o l -u t i o n . C o ( H 0 g ) 2 ; - S i m i l a r t o H i ( N O g ) £ . ( i i i ) G o l o r i m e t r i o Methods:-Experiments were performed t o determine xanthate by the amount of t u r b i d i t y or c o l o r produced by r e a c t i o n w i t h c e r t a i n r e a g e n t s , and-by comparison of, these r e s u l t s w i t h the v a l u e s 6 o b t a i n e d f o r m i x t u r e s of known c o m p o s i t i o n . Of the m e t a l l i c s a l t s , o n l y 0 uS0 4 and AgNOg showed p r -omise h e r e , and o n l y at v e r y low c o n c e n t r a t i o n s . At the con-c e n t r a t i o n s encountered i n the a b s t r a c t i o n work, the p r e c i p i t -a t e s which these substances produced tended t o f l o c c u l a t e , and t h i s r u i n e d the measurement i n t h a t range. ( N H / ) 0 M 0 Q 4 : - B e i l s t e i n s t a t e s : " M o l y b d a t e g i v e s i n min-e r a l a c i d s o l u t i o n s w i t h KEtX a r e d p r e c i p i t a t e , s o l u b l e i n o r g a n i c s o l v e n t s " . I t was found however, t h a t the r e d c o l o u r o f t h i s substance was not s t a t i o n a r y , but changed t o p u r p l e and then t o b l u e by f u r t h e r r e d u c t i o n o f the molybdate w i t h x a n t h a t e . XANTHATE ABSTRACTION AND RELATED WORK (1) Shaking Experiments w i t h Pb3 and KEtX I n t h i s work, m i x t u r e s o f s u l p h i d e and xanthate s o l u t i o n were, shaken i n s t o p p e r e d b o t t l e s , and the l o s s of xanthate de-t e r m i n e d by t i t r a t i o n w i t h s t a n d a r d i o d i n e p r e p a r a t i o n , and NaHCOg as a b u f f e r , u s i n g s t a r c h as an i n d i c a t o r . A l l t i t -r a t i o n s were made on E5cc of f i l t e r e d s o l u t i o n , and the o r i g -i n a l x a n t h a t e c o n c e n t r a t i o n was the same i n each of the f o u r b o t t l e s used i n a r u n . PbS c o n c e n t r a t i o n was always 25cc of f r e s h l y washed m a t e r i a l per l i t r e . The b o t t l e s were a l l made t o up A the same volume w i t h d i s t i l l e d water. 7 RESULTS Run #1 B o t t l e pH Before A f t e r Ip T i t e r ( c c ) B e f o r e A f t e r Time of Shaking PfcS + X 1 6.15 6.30 12 h r s . P b S ^ X 2 . 6.21 6.37 1.0 PbS-f-X 3 6.13 6.28 1.0 KEtX 4 Average 7.10 8.13 a b s t r a c t i o n 2.85 63% 2.7 pH of f r e s h l y washed PbS p u l p 5. 83. Run #2 B o t t l e pH Before A f t e r I ? T i t e r (cc) Befor e A f t e r Time of Shaking 6 h r s . PbS ~j- X 1 6.00 6.06 ' —.— 1.7 PbS+ X 2 6.13 6.21' 1.8 PbS + X 3 6.04 6.15 1.85 KEtX 4 Ave rag ;e 6.91 7.43 a b s t r a c t i o n • 3.05 38.3% 3.0 pH of f r e s h l y washed PbS-— 5.90 Run #3 B o t t l e pH B e f o r e A f t e r I T i t e r ( c c ) Time o f Before A f t e r Shaking PbS-HX 1- •6.17 6.33 3.3 18 h r s . PbS-P X 2 6.14 6.29 3.2 PbS-f- X 3 6.13 6.30. —.— 3.35 KEtX. 4 7.10 8.22 10.1 Average a b s t r a c t i o n - — 6 6 . 7 % pH o f f r e s h l y washed PbS 9.9 5.99 Run #4 B o t t l e pH pH B e f o r e A f t e r I g T i t e r ( c c ) B e f o r e A f t e r Time o f Shaking PbS -Fx PbS f X PbS +- X K E t X 1 2 3 4 6.20 6.39 6.12 6.31 ' 6.25 6.40 7.09 8.36 10.2 pH of f r e s h l y washed P b S — 2.8 2.6 2.65 9.85 5.88 24 hrs Av. Abst i s 73.3% 8 The pH of f r e s h l y prepared xanthate s o l u t i o n was found t o be always near 7. T h i s f i g u r e i n c r e a s e d g r a d u a l l y over a p e r i o d of days u n t i l a maximum of about 10 was reached, pre-sumably because of s l i g h t d e composition of KEtX t o a l c o h o l and carbon d i s u l p h i d e . A s l i g h t vacuum was n i t i c e d when the b o t t l e s were un-corked a f t e r s h a k i n g . A white t u r b i d i t y i n the l i q u i d i n d i c -a t e d t h a t l e a d e t h y l x a n t h a t e had been formed. GOMCLTTSICHS Xan t h a t e i s a b s t r a c t e d from s o l u t i o n i n amounts which i n c r e a s e w i t h the time of s h a k i n g . Lead s u l p h i d e i t s e l f does not produce enough l e a d i o n s to r e a c t w i t h any a p p r e c i a b l e amount o f KIStX, so another more s o l u b l e s a l t of l e a d must be p r e s e n t t o account f o r the p r e c i p i t a t i o n o f l e a d e t h y l x a n t h a t e . I f PbSO^ were p r e s e n t , i t would produce a r e l a t i v e l y much l a r -ger l e a d i o n c o n c e n t r a t i o n than PbS, and t h i s would e x p l a i n the disappearance o f the x a n t h a t e . A c a l c u l a t i o n r e v e a l s t h a t the amount of a i r i n a b o t t l e (lOOcc) would c o n t a i n s u f f i c i e n t ox-ygen t o o x i d i z e enough PbS t o PbSQ^ t o account f o r any xanthate l o s s . The amount of P b ( l t X ) g p r e c i p i t a t e d , and hence the xan-t h a t e a b s t r a c t i o n , would be a f f e c t e d by the pH, s i n c e pH i n -f l u e n c e s the s o l u b i l i t y o f t h a t s a l t . 9 ( i i ) As i n ( i ) , I n N i t r o g e n Atmoshpere I n t h i s group of e x p e r i m e n ts, n i t r o g e n was bubbled i n t o c e r t a i n b o t t l e s , so t h a t the e f f e c t of absence of oxygen upon the a b s t r a c t i o n might be determined. Run #1 B o t t l e Atmosphere c o n t a i n e d Iodine t i t e r a f t e r 18 hours PbS X 1 a i r 3.25 PbS X 2 n i t r o g e n 5.6 • KEtX 3 a i r ' 10,1 KEtX 4 n i t r o g e n 10.2 Run #2 PbS X 1 a i r 2.65 PbS X 2 n i t r o g e n 5.1 KEtX 3 . ' a i r . 9.8 • KEtX 4 n i t r o g e n 10.0 REMARKS I n n i t r o g e n atmosphere, xanthate a b s t r a c t i o n i s decre-ased, but some o x i d a t i o n o f PbS a p p a r e n t l y takes p l a c e , no m a t t e r how t h o r o u g h l y the s u l p h i d e i s washed and how q u i c k l y the subsequent n i t r o g e n treatment i s g i v e n . The presence of n i t r o g e n i n the KEtX b o t t l e s e v i d e n t l y d i m i n i s h e d the r a t e ' o f decomposition o f t h a t substance. 10 ( H i ) Time of Washing and Immediate Xanthate A b s t r a c t i o n Here, the m i x t u r e s were o n l y shaken momentarily, then were f i l t e r e d and t i t r a t e d . S o l u t i o n Time a f t e r washing of PbS l 0 T i t e r KEtX 1 1 minute 2 2 " 3 5 " 4 10 " CONCLUSIONS A l a r g e q u a n t i t y o f xanthate i s a b s t r a c t e d almost im-m e d i a t e l y . Two f a c t o r s are i n d i c a t e d ; e i t h e r (1) The method o f washing l e a v e s behind a c e r t a i n amount of o x i d i z e d l e a d compounds, or (2) The o x i d a t i o n of PbS i s so r a p i d , t h a t i n the time which e l a p s e s b e f o r e d e t e r m i n a t i o n s can be made, a p p r e c i a b l e changes t a k e s p l a c e . I t may be t h a t t h e r e i s f i r s t a r a p i d o x i d a t i o n , f o l l o w e d by one which proceeds a t a much slower r a t e . (IV) Time of Washing and Amount o f Lead Ion A. Lead i o n , as determined c o l o r i m e t r i c a l l y by the i n -t e n s i t y of r e d c o l o r produced w i t h d i - t h i o c a r b a z o n e , was found to i n c r e a s e s l o w l y from the time of washing of PbS. With t h i s agent, however, q u a n t i t a t i v e r e s u l t s c o u l d not be o b t a i n e d , as i t was f a r too s e n s i t i v e . B. Another c o l o r i m e t e r i c method, which i n v o l v e d the p r e c i p i t a t i o n o f l e a d i o n w i t h HgS water and the s t a b i l i z a t i o n cc 10.4 5.9 5.85 5.7 5.6 . 11 of t h e . r e s u l t i n g c o l l o i d a l form w i t h sugar and a c e t i c a c i d 1 , was found t o y i e l d r e p r o d u c i b l e r e s u l t s . Run_#l Gone, o f Pb I o n - ' - g / l i t r e 1. D i s t i l l e d water ( ,0011 2. PbS m i x t u r e , 1 rain, a f t e r washing ,0065 3. " 2 min. " " .0067 4. " 5 min. " " .0067 5. " 10 min, " " .0068 CONCLUSIONS There i s an i n i t i a l h i g h c o n c e n t r a t i o n of l e a d i o n , (perhaps caused by the presence of oxygen i n the d i s t i l l e d water) which would account f o r immediate p r e c i p i t a t i o n of a l a r g e p r o p o r t i o n of added x a n t h a t e . Lead i o n i n c r e a s e s t h e n c e f o r t h s l o w l y w i t h time. (V) R e l a t i v e P r e s s u r e Drops over PbS, Xanthate and PbS and Xa n t h a t e . These p r e s s u r e drops were determined w i t h a water man-ometer b o t t l e s which c o n t a i n e d an i n i t i a l equal volume of a i r . F r e s h l y washed PbS gave a n o t i c e a b l e p r e s s u r e l o w e r i n g almost at once* PbS and Xanthate showed decreases i n i t i a l l y ; a f t e r a l o n g time b u i l t up p r e s s u r e s . Xanthate alone y i e l d e d a s l i g h t drop at f i r s t , but soon b u i l t up a p r e s s u r e . Re-s u l t s were not e x a c t l y r e p r o d u c i b l e , so no f i g u r e s are g i v e n . CONCLUSIONS The p r e s s u r e decrease i s c o m p l i c a t e d by such t h i n g s as s o l u b i l i t y of the atmospheric gases, vapor p r e s s u r e of the 12 s o l u t i o n s , and temperature o f the s u r r o u n d i n g s . The main l o w e r i n g may he a s c r i b e d t o o x i d a t i o n of PbS. P r e s s u r e i n c r e a s e s i n xanthate m i x t u r e s t o the f o r m a t i o n of the v o l a t i l e carbon d i s u l p h i d e . (VI) T i t r a t i o n of X a n t h a t e - v s - P r e s s u r e Drop i n B o t t l e s A sample r e s u l t here w i l l i n d i c a t e the l a c k o f c o r r e l -a t i o n which was observed. B o t t l e Drop I o d i n e t i t e r Time cc h r s . 1 PbS 10cm H 20 — — 6 2 PbS X 5.5 4.5 6 3 PbS X 7.8 4.5 6 4- EEtX — 1 9.95 6 5 EEtX 2.4 10.1 6 The c h i e f source of e r r o r i n such d e t e r m i n a t i o n s on PbS and Xanthate i s the tendency of these two substances t o have an o p p o s i t e e f f e c t upon the p r e s s u r e . ( V I I ) I o d i n e Titer-vs-G-as A n a l y s i s I n t h i s experiment, the b o t t l e s were f i t t e d w i t h rubber s t o p p e r s b e a r i n g i n t a k e and o u t l e t t ubes. The system was not a convenient one, however, s i n c e d r i v i n g the gas from the s h a k i n g b o t t l e s to the gas b u r e t t e i n v o l v e d d i l u t i o n of the c o n t a i n e d m i x t u r e s . Sun #1 B o t t l e Amt. 0 g d i s a p p e a r e d i g t i t e r a f t e r (from lOOcc approx) 18 h r s . ( c o r r e c t e d cc PbS 1 2.0 f o r d i l u t i o n ) E E tX 2 0.1 10.05cc PbS & X 3 1.2 3.5 PbS & X 4 1.4 3.1 13 Run ,f2' B o t t l e Amt. Op disappeared I g t i t e r a f t e r (from lOOec approx) 15 h r s . (oorre-oted f o r d i l ' n PbS • 1 1.8 cc ~ PbS 2 - 2.5 " KEtX 3 0.0 9.8 PbS & X 4 . 1 . 6 3.0 C a l c u l a t i o n r e v e a l s t h a t not enough oxygen disappeared t o account f o r a l l the a b s t r a c t i o n , assuming the change:-PbS P b S 0 4 P b ( E t X ) 2 T h i s would a g a i n i n d i c a t e t h a t some o x i d a t i o n of PbS takes p l a c e b e f o r e i t s t r a n s f e r t o the b o t t l e s . ( Y l l l ) I o d i n e t i t e r . , G-as A n a l y s i s , and Lead Ion Before and A f t e r Shaking Run #1 ?b Ion B o t t l e Ogdisa-pneared B e f o r e A f t e r 1?_ T i t e r PbS 1 2.2 cc .0059 .0098 KEtX 2 0.2 .0009 .0006 9.8 PbS & X 3 1.9 .0011 .0017 2.9 I n PbS and Xanthate , the b u l k of the l e a d i o n i s removed at once by x a n t h a t e . I n the above experiment, the xanthate a b s t r a c t i o n and the l e a d i o n removed by KEtX are approximat-e l y c h e m i c a l l y e q u i v a l e n t . OTHER MEASUBEMSNTS ( i ) Time was a v a i l a b l e f o r o n l y one d e t e r m i n a t i o n w i t h the apparatus shown i n F i g . 2, and t h i s was made on PbS i n an a t -mosphere o f a i r . (Other Measurements) Time pH March 10 11:40 A.M. 2.62 12:30 " 2.63 « 5:30 P.M. 2.63 torch 11 8:30 A.M. 2.65 9:15 A.M. 2.65 l i a r oh 12 1:00 P.M. 2.70 5:15 P.M. 2.72 March 13 8:15 A.M. 2.80 IT ' 5:00 P.M. 2.84 March 14 8:15 A.M. 2.88 t t 5:30 P.M. 2.90 March 15 ' 8:15'A.M. 3.02 t t 5:30 P.M. 3.10 March 16 8:15 A.M. 5.27 t t 1:30 P.M. 3.33 t t 5:30 P.M. 3,34 March 17 12:00 A.M. 3.83 March 18 9:00 A.M. 4.61 March 19 3:00 P.M. 5.15 March 20 8:15 A.M. 5.24 tt 2:00 P.M. 5 e 2 9 tt 5:30 P.M. 5.31 March 21 8:15 A.M 5,36 tt 5:30 P.M 5.40 15 (Table.Cont'd) : Day . Time pH March 22 8:15 A.M. 5.42 5:30 P.M. 5.45 March 23 5:00 P.M. . 5.45 March 24 4:00 P.M. 5.56 March 25 10.00 A.M. 5.69 T h i s r i s e i n pH i s p r o b a b l y due to removal o f the a c i d f o r m i n g S= i o n by o x i d a t i o n , and to s o l u t i o n of b a s i c con-s t i t u e n t s from the g l a s s . DISCUSSION The amount o f -experimental work done i n t h i s i n v e s t i g -a t i o n does not warrant statement o f d e f i n i t e c o n c l u s i o n s . However, i t seems c e r t a i n t h a t the c o l l e c t o r i s removed from s o l u t i o n by c h e m i c a l a c t i o n . One may a l s o say t h a t the c o l -l e c t o r does not coat the s u r f a c e of m i n e r a l p a r t i c l e , thus c a u s i n g i t s f l o t a t i o n , s i n c e t h a t would r e q u i r e f a r more c o l -l e c t i n g agent than ever d i s a p p e a r s from s o l u t i o n . The a b s t r -a c t i o n s appears t o be due o n l y t o i m p u r i t i e s on the s u r f a c e , or t o i m p u r i t i e s which go i n t o s o l u t i o n from the s u r f a c e of the p a r t i c l e , and i s a p p r o x i m a t e l y p r o p o r t i o n a l t o the amount of t h a t f o r e i g n m a t e r i a l . The method o f d e t e r m i n a t i o n o f xanthate e v i d e n t l y l e a v e s be something to be d e s i r e d , w h i l e i t may/yseen t h a t the p r e p a r a t -i o n of a b s o l u t e l y pure l e a d s u l p h i d e i s not f e a s i b l e . Since t t h i s work was done the whole problem of c o l l e c t o r a c t i o n upon 16 g a l e n a has been d e a l t w i t h i n a more r i g o r o u s and d e t a i l e d 5 f a s h i o n by H. K. Herd , who uses e l e c t r o m e t r i c t i t r a t i o n f o r h i s xanthate d e t e r m i n a t i o n s . 17 BIBLIOGRAPHY 1. R. B. Bennett, T h e s i s , 1938. '2. R. F. P e a r c e , T h e s i s , 1938. 3. Handbook o f Chemistry and P h y s i o s , p963, 1938. 4. B e i l s t e i n , 3, 214, 1918. 5. H. H, Herd, T h e s i s , 1940. 

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