UBC Theses and Dissertations

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UBC Theses and Dissertations

Vapor-liquid equilibrium study of benzene-propanol and benzene-pentanol Howey, George Robert Alexander 1951

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11 Tift I VAPOR-LIQUID EQUILIBRIUM STUDY , OF BENZENE-PROPANOL AND BENZENE-PENTANOL by GEORGE ROBERT ALEXANDER HOWEI A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n t h e Department o f C h e m i s t r y We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e s t a n d a r d r e q u i r e d f r a m - c a n d i d a t e s f o r t h e degree o f MASTER OF ftPR^IE^ SCIENCE Members o f the Department o f C h e m i s t r y THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1951 i ABSTRACT A s t u d y has been made o f t h e v a p o r - l i q u i d e q u i l i b r i a f o r t h e benzene-propanol and benzen e - p e n t a n o l systems a t atmos-p h e r i c p r e s s u r e u s i n g a F o w l e r - G i l l e s p i e s t i l l . R e f r a c t i v e i n d e x c u r v e s f o r t h e complete systems were a l s o o b t a i n e d a t 25°C. Thermodynamic c o n s i s t e n c y o f t h e r e s u l t s was checked w i t h t h e Van L a a r i n t e g r a t i o n o f the Gibbs-Duhem e q u a t i o n . T h i s t h e o r e t i c a l c o r r e l a t i o n o f t h e e x p e r i m e n t a l v a l u e s showed an average d e v i a t i o n o f a p p r o x i m a t e l y 1 0% between the e x p e r i -m e n t a l and t h e o r e t i c a l v a l u e s . A v a p o r - l i q u i d e q u i l i b r i u m p l o t o f t h e b e n z e n e - a l c o h o l s e r i e s f r o m methanol t o p e n t a n o l was made and t h e g e n e r a l shape of t h e c u r v e s was d i s c u s s e d w i t h r e g a r d t o the d i s a p p e a r a n c e o f t h e a z e o t r o p e . i i ACKNOWLEDGMENT The a u t h o r w i s h e s t o e x p r e s s h i s a p p r e c i a t i o n of t h e h e l p f u l i n s t r u c t i o n g i v e n by Dr. L.W. S h e m i l t under whose s u p e r v i s i o n t h i s r e s e a r c h was c a r r i e d o u t . He acknowledges t o o t h e c o n s t r u c t i v e s u g g e s t i o n s o f Mr. C. Larkam and t h e a d v i c e o f Mr. A. Werner on t h e p u r i f i c a t i o n o f t h e a l c o h o l s . S p e c i a l t h a n k s a r e a l s o due t o Mr. M. Waldichuk f o r i n t r o d u c i n g t h e a u t h o r t o t h e t h e o r y and t e c h n i q u e s i n v o l v e d . TABLE OF CONTENTS TITLE t PAGE ABSTRACT . i ACKNOWLEDGMENT i i TABLES i i i ILLUSTRATIONS i v I . INTRODUCTION 1 I I . THEORETICAL DISCUSSION 4 I I I . APPARATUS 9 A. F o w l e r - G i l l e s p i e S t i l l B. R e f r a c t o m e t e r C. Thermometers IV. MATERIALS 12 A. Benzene B. P r o p a n o l C. P e n t a n o l V. EXPERIMENTAL PROCEDURES 20 A. D e t e r m i n a t i o n o f R e f r a c t i v e I n d e x - C o m p o s i t i o n Curve f o r Benzene-Propanol B. V a p o r - L i q u i d E q u i l i b r i u m D e t e r m i n a t i o n on F o w l e r - G i l l e s p i e S t i l l C. D e t e r m i n a t i o n o f R e f r a c t i v e I n d e x - C o m p o s i t i o n Curve f o r Benzene-Pentanol V I . RESULTS 23 A. Benzene-Propanol B. Benzene-Pentanol V I I . DISCUSSION OF RESULTS 36 A. Benzene-Propanol B. Benzene-Pentanol V I I I . DISCUSSION ON BENZENE-n-ALCOHOL SERIES 38 IX . REFERENCES 40 i i i TABLES: PAGE 1. P h y s i c a l d a t a f o r benzene f r o m t h e l i t e r a t u r e . 15 2. P h y s i c a l d a t a f o r p r o p a n o l f rom the l i t e r a t u r e . 17 3. P h y s i c a l d a t a f o r p e n t a n o l f r o m t h e l i t e r a t u r e . 19 4. R e f r a c t i v e i n d e x - c o m p o s i t i o n d a t a f o r benzene-p r o p a n o l a t 25 °G. 23 5. E x p e r i m e n t a l v a p o r - l i q u i d e q u i l i b r i u m d a t a f o r ben z e n e - p r o p a n o l a t a t m o s p h e r i c p r e s s u r e . 2 4 6. Vapor p r e s s u r e d a t a f o r benzene. , 26 7. Vapor p r e s s u r e d a t a f o r p r o p a n o l . 27 8. A c t i v i t y c o e f f i c i e n t s o f benzene and p r o p a n o l f r o m e x p e r i m e n t a l d a t a . 28 9. E x p e r i m e n t a l and t h e o r e t i c a l a c t i v i t y c o e f f i c i e n t s o f benzene and p r o p a n o l . 30 10. R e f r a c t i v e i n d e x - c o m p o s i t i o n d a t a f o r benzene-p e n t a n o l a t 2 5 °C. 31 11. E x p e r i m e n t a l v a p o r - l i q u i d e q u i l i b r i u m d a t a f o r ben z e n e - p e n t a n o l a t 25°C. 3 2 12. Vapor p r e s s u r e d a t a f o r p e n t a n o l . 33 13. A c t i v i t y c o e f f i c i e n t s o f benzene and p e n t a n o l f r o m e x p e r i m e n t a l d a t a . 34 14. E x p e r i m e n t a l and t h e o r e t i c a l a c t i v i t y c o e f f i c i e n t s o f benzene and p e n t a n o l . 35 ILLUSTRATIONS To f o l l o w Page 1. F o w l e r - G i l l e s p i e a p p a r a t u s . 9 2. Benzene d i s t i l l a t i o n s t i l l . 13 3. A l c o h o l d i s t i l l a t i o n s t i l l . 16 A. B o i l i n g p o i n t a p p a r a t u s . 14 5 . B a r o s t a t f o r c o n t r o l l i n g p r e s s u r e . 2 2 6. R e f r a c t i v e i n d e x - c o m p o s i t i o n c u r v e f o r benzene-p r o p a n o l . 23 7. V a p o r - l i q u i d c o m p o s i t i o n c u r v e f o r b e n z e n e - p r o p a n o l . 2 5 T e m p e r a t u r e - c o m p o s i t i o n curve f o r b e n z e n e - p r o p a n o l . 25 9. Vapor p r e s s u r e curve f o r benzene. 26 10. Vapor p r e s s u r e c u r v e f o r p r o p a n o l . 2 7 11. P l o t o f l o g o f a c t i v i t y c o e f f i c i e n t s a g a i n s t mole f r a c t i o n o f benzene i n l i q u i d f o r benzene and p r o p a n o l . 29 12. R e f r a c t i v e i n d e x - c o m p o s i t i o n curve f o r benzene-pent a n o l . 30 13. V a p o r - l i q u i d c o m p o s i t i o n curve f o r benzene-pent a n o l . 31 14. T e m p e r a t u r e - c o m p o s i t i o n curve f o r benzene-pent a n o l . 32 15• Vapor p r e s s u r e d a t a f o r p e n t a n o l . 33 16. P l o t o f l o g of a c t i v i t y c o e f f i c i e n t s a g a i n s t mole f r a c t i o n o f benzene i n l i q u i d f o r benzene and p e n t a n o l . 34 17. V a p o r - l i q u i d c o m p o s i t i o n c u r v e s f o r benzene-methanol t o b e n z e n e - p e n t a n o l . 37 1 INTRODUCTION The s e p a r a t i o n o f a m i x t u r e o f v o l a t i l e l i q u i d s by-means o f f r a c t i o n a l d i s t i l l a t i o n i s p o s s i b l e when t h e c o m p o s i t i o n o f t h e vapor coming f r o m t h e l i q u i d m i x t u r e i s d i f f e r e n t f r o m t h a t o f t h e l i q u i d . The r e l a t i o n between t h e vapor- and l i q u i d composi-t i o n s must be known i n o r d e r t o d e s i g n a f r a c t i o n a t i n g column, o r even t o d e t e r m i n e t h e number o f t h e o r e t i c a l p l a t e s needed f o r t h e g i v e n s e p a r a t i o n o f a b i n a r y m i x t u r e . S i n c e few systems f o r m i d e a l s o l u t i o n s so t h a t e q u i l i b r i u m d a t a can be c a l c u l a t e d f r o m R a o u l t ' s Law, i t i s n e c e s s a r y t o have some means o f d e t e r -m i n i n g d a t a f o r a b i n a r y m i x t u r e o v e r t h e whole range o f c o m p o s i t i o n . The method o f o b t a i n i n g v a p o r - l i q u i d e q u i l i b r i u m com-p o s i t i o n s can be c o n s i d e r e d under two main h e a d i n g s : 1) t h e e x p e r i m e n t a l d e t e r m i n a t i o n o f e q u i l i b r i u m c o m p o s i t i o n s by t h e use o f a v a p o r - l i q u i d e q u i l i b r i u m s t i l l and 2) t h e t h e o r e t i c a l r e l a t i o n s h i p s . A number Of methods have been d e v e l o p e d t o det e r m i n e e x p e r i m e n t a l l y v a p o r - l i q u i d e q u i l i b r i u m d a t a . The f i r s t o f t h e s e i s t h e s i m p l e d i s t i l l a t i o n o f a v e r y s m a l l sample o f t h e vapor f r o m a f l a s k c o n t a i n i n g a l a r g e q u a n t i t y o f a l i q u i d . T h i s method can be i n a c c u r a t e s i n c e some r e f l u x a l m o s t a l w a y s t a k e s p l a c e , and i n a d d i t i o n , a l a r g e sample i s r e q u i r e d . A second method i s t o p a s s v a p o r o f c o n s t a n t c o m p o s i t i o n t h r o u g h a l i q u i d u n t i l e q u i l i b r i u m i s r e a c h e d . A t h i r d method c o n s i s t s o f c o l -l e c t i n g and a n a l y z i n g s e v e r a l s u c c e s s i v e f r a c t i o n s f r o m a b a t c h d i s t i l l a t i o n and t h e n e x t r a p o l a t i n g back t o a p o i n t where z e r o d i s t i l l a t e would be o b t a i n e d . A f o u r t h method and by f a r t h e 2 most s a t i s f a c t o r y , i s t h a t d e v e l o p e d by Othmer ( l ) a n d c o n s i s t s o f v a p o r i z i n g a l i q u i d , c o n d e n s i n g t h e v a p o r s , and t h e n r e c i r c u -l a t i n g t h e condensate t h r o u g h t h e c y c l e u n t i l e q u i l i b r i u m i s r e a c h e d . To make such a s t i l l o p e r a t e e f f i c i e n t l y w i t h o u t e r r o r t h e l i q u i d must be v a p o r i z e d and condensed w i t h o u t a l l o w i n g any r e f l u x between t h e time of the f i r s t v a p o r i z a t i o n and f i n a l c o n d e n s a t i o n . R e f l u x would t e n d t o g i v e a vapor r i c h e r i n t h e more v o l a t i l e component t h a n i s a c t u a l l y t h e case i n t r u e e q u i l i b r i u m . I n a d d i t i o n en-t r a i n m e n t o f l i q u i d i n t h e vapor must be a v o i d e d s i n c e t h e c a r r y i n g o v e r o f u n v a p o r i z e d m a t e r i a l w i l l g i v e an e q u i l i b r i u m v a l u e c o n -t a i n i n g l e s s ^ t h e a c t u a l amount o f l o w e r b o i l i n g component i n t h e v a p o r . T h i r d l y , no p a r t o f t h e a p p a r a t u s s h o u l d be s u p e r h e a t e d s u f f i c i e n t l y t o cause t o t a l i n s t e a d of e q u i l i b r i u m v a p o r i z a t i o n , w h i c h would a l s o g i v e a v a l u e o f vapor c o m p o s i t i o n t o o low i n t h e more v o l a t i l e component. F o u r t h l y , t h e c o m p o s i t i o n o f the m a t e r i a l i n t h e s t i l l s h o u l d remain c o n s t a n t . V a r i o u s i n v e s t i g a t o r s have t a k e n c a r e o f t h e above r e q u i r e m e n t s i n d i f f e r e n t ways. One v a p o r - l i q u i d e q u i l i b r i u m s t i l l t h a t meets t h e r e q u i r e m e n t s was d e s i g n e d by G i l l e s p i e (2) and l a t e r m o d i f i e d by F o w l e r ( 3 ) . T h i s s t i l l was used i n t h i s r e s e a r c h on t h e benzene-propanol and b e n z e n e - p e n t a n o l systems and w i l l be d e s c r i b e d l a t e r . The t h e o r e t i c a l methodsused t o o b t a i n v a p o r - l i q u i d c o m p o s i t i o n s w i t h o u t r e c o u r s e t o experiment a r e d i s c u s s e d l a t e r . Of t h e two b i n a r y systems, b e n z e n e - p r o p a n o l and benzene-p e n t a n o l , s t u d i e d i n t h i s r e s e a r c h o n l y t h e benzene-propanol system has been examined p r e v i o u s l y . I n 191S L e c a t (4) r e p o r t e d t h a t t h i s system formed an a z e o t r o p e a t 0.791 mole f r a c t i o n o f benzene w i t h a b o i l i n g p o i n t o f 77.1°C. a t 760 mm. o f p r e s s u r e . Lee (5) i n 1931 r e p o r t e d t h e p a r t i a l p r e s s u r e i s o t h e r m s o f t h e system a t 40°C. A l t h o u g h no p r a c t i c a l use c o u l d be a s c e r t a i n e d f o r d a t a on e i t h e r system, a s t u d y of t h e s e i s o f i n t e r e s t f o r considers;-, t i o n o f v a p o r - l i q u i d e q u i l i b r i u m d a t a f o r t h e b e n z e n e - a l c o h o l systems f r o m C]_ t o C*j. T h i s a l l o w s an attempt t o be made t o e x p l a i n t h e d i s a p p e a r a n c e o f t h e a z e o t r o p e w i t h the systems b e n z e n e - b u t a n o l and b e n z e n e - p e n t a n o l . The o b j e c t o f t h i s r e s e a r c h , t h e r e f o r e , i s t o o b t a i n t h e v a p o r - l i q u i d e q u i l i b r i u m c o m p o s i t i o n c u r v e s f o r the b i n a r y m i x t u r e s o f benz e n e - p r o p a n o l and ben z e n e - p e n t a n o l a t c o n s t a n t p r e s s u r e , and t o check t h e thermodynamic c o n s i s t e n c y o f t h e r e -s u l t s by an a p p l i c a t i o n o f a t l e a s t one o f the i n t e g r a t e d forms o f t h e Gibbs-Duhem e q u a t i o n . The v a p o r - l i q u i d e q u i l i b r i u m d a t a f o r t h e f i v e b e n z e n e - n - a l c o h o l systems methanol t o p e n t a n o l w i l l be p l o t t e d and d i s c u s s e d . 4 THEORETICAL DISCUSSION The most c o n v e n i e n t and s i m p l e r e l a t i o n between l i q u i d and v a p o r c o m p o s i t i o n s i s t h a t e x p r e s s e d by R a o u l t ' s Law: phase i n e q u i l i b r i u m w i t h i t s s o l u t i o n a t a m o lar c o n c e n t r a t i o n x-j_ and P° i s t h e vapor p r e s s u r e o f t h e pure component at the same t e m p e r a t u r e . A system o b e y i n g R a o u l t ' s Law i s c o n s i d e r e d i d e a l , but u n f o r t u n a t e l y few do. D e v i a t i o n s from i d e a l i t y may be due e i t h e r t o t h e l i q u i d phase, the v a p o r phase o r b o t h . These d e v i a t i o n s can be both p h y s i c a l and c h e m i c a l i n n a t u r e . The most i m p o r t a n t o f t h e s e a r e t h a t t h e m o l e c u l e s have d e f i -n i t e volume, and t h a t t h e y e x e r t a t t r a c t i v e o r r e p u l s i v e f o r c e s upon each o t h e r . A c t u a l c h e m i c a l e f f e c t s may a l s o be i n v o l v e d e s p e c i a l l y when t h e components a r e c h e m i c a l d i s s i m i l a r , e.g. b e l o n g i n g t o d i f f e r e n t homologous s e r i e s . I t has been shown e x p e r i m e n t a l l y t h a t s u b s t a n c e s h a v i n g s i m i l a r c h e m i c a l s t r u c -t u r e d e v i a t e o n l y s l i g h t l y f r o m R a o u l t ' s Law. v e n i e n t method o f e x p r e s s i n g t h e d e v i a t i o n of a g i v e n system f r o m R a o u l t ' s Law and a l s o o f i n d i c a t i n g the thermodynamic con-s i s t e n c y o f v a p o r - l i q u i d e q u i l i b r i u m d a t a i s t o p l o t t h e l o g a r i t h m o f t h e a c t i v i t y c o e f f i c i e n t s a g a i n s t t h e l i q u i d c o m p o s i t i o n s . F o r a g i v e n component the a c t i v i t y c o e f f i c i e n t i s d e f i n e d by t h e e q u a t i o n : C a r l s o n and C o l b u r n (6) have p o i n t e d out t h a t a con-P y i p i x i (2) 5 where P i s - t h e p r e s s u r e o f t h e system i n m i l l i m e t e r s o f mercury, P^ i s t h e p r e s s u r e o f the pure component i n m i l l i m e t e r s of mer-cury: a t the s o l u t i o n t e m p e r a t u r e , x^ and y^ a r e the mole f r a c -t i o n s o f component 1 i n t h e l i q u i d and vapor phases, r e s p e c t i v e l y * A number o f a t t e m p t s have been made t o d e s c r i b e t h e b e h a v i o u r o f systems which d e v i a t e f r o m i d e a l i t y i n terms o f g e n e r a l e q u a t i o n s based on thermodynamic r e l a t i o n s and depending upon a g e n e r a l e q u a t i o n o f s t a t e . A c c o r d i n g t o C l a r k (7) t h e f o l l o w i n g method can be used t o g i v e t h e s e g e n e r a l e q u a t i o n s . The e x a c t thermodynamic r e l a t i o n d e s c r i b i n g a phase i n e q u i l i b r i u m w i t h i n i t s e l f was e x p r e s s e d by G i b b s : - Sdt + Vdp - m q > o = 0 i i n w h i c h n^ I s t h e number o f m o l e c u l e s o f t h e i t h component i n t h e phase and /JJ ^  i s t h e c h e m i c a l p o t e n t i a l o f t h a t component. F o r e q u i l i b r i u m between t h e phases t h e ^ ^ f o r each component s h a l l be e q u a l a t t h e same t e m p e r a t u r e and p r e s s u r e . • :• F o r a vapor phase w h i c h i s a p e r f e c t gas a t a f i x e d t e m p e r a t u r e , o > ^ = R T d l n p ! The e q u a t i o n f o r 1 mole o f a l i q u i d phase o f com-pone n t s a t c o n s t a n t t e m p e r a t u r e may be w r i t t e n : V l i q . d P = x l d ^ l + P 2 d ^ 2 I f t h i s phase i s i n e q u i l i b r i u m w i t h a vapor phase, d/^^ and d/6^2 a r e t h e same and by s u b s t i t u t i o n we o b t a i n : V l i q . d p = R T ( x l d l n P i + x 2 d l n p 2 ) Fo r RT we can w r i t e P V v a p ^ i n which " V ^ i s t h e m o l a r volume of t h e v a p o r phase. By re-arrangement: 6 J^. E - X l d i n P l + x 2 d I n p 2 vap. ^ At o r d i n a r y p r e s s u r e s , ^ l i q . } t h e r a t i o o f the molar volumes o f Vvap. t h e two phases i s v e r y s m a l l and t h e l e f t - h a n d s i d e o f t h i s e q u a t i o n may be equated t o z e r o w i t h o u t s e r i o u s e r r o r . We t h e n o b t a i n as t h e c o n d i t i o n o f e q u i l i b r i u m a t c o n s t a n t t e m p e r a t u r e : x-j_ d l n p i + x 2 d l n p 2 = 0 T h i s i s a d e r i v a t i v e of t h e Gibbs e q u a t i o n a t t r i b u t e d t o Duhem and M a r g u l e s (#). A l t e r n a t e l y the r e l a t i o n between l i q u i d and vapor c o m p o s i t i o n s may be e x p r e s s e d i n terms o f a c t i v i t y c o e f -f i c i e n t s , V , u s i n g t h e d e f i n i t i o n p - P * x i n w h i c h X appears as t h e c o r r e c t i o n f a c t o r i n t h e statement o f R a o u l t ' s Law. By d i f f e r e n t i a t i o n and s u b s t i t u t i o n f o r d l n p t h e Gibbs-Duhem e q u a t i o n i s r e a d i l y o b t a i n e d i n t h e f o r m V d x1 ' T.P. V d x 2 ' T.P. ( 3 ) E q u a t i o n 3 i s o f v a l u e i n s t u d y i n g e x p e r i m e n t a l d a t a on vap o r -l i q u i d e q u i l i b r i u m by r e l a t i n g t h e c u r v e s o f a p l o t o f t h e ac-t i v i t y c o e f f i c i e n t a g a i n s t t h e l i q u i d c o m p o s i t i o n s o f t h e b i n a r y m i x t u r e . Inasmuch as the magnitude o f t h e s l o p e s a r e d i f f i c u l t t o d e t e r m i n e p r e c i s e l y , however, s t u d i e s have been made t o o b t a i n c o n v e n i e n t m a t h e m a t i c a l s o l u t i o n s o f t h i s d i f f e r e n t i a l e q u a t i o n . The most u s e f u l o f t h e i n t e g r a t e d forms o f E q u a t i o n 3 a r e t h e e q u a t i o n s o f M a r g u l e s [8) and Van L a a r ( 9 ) . M a r g u l e s E q u a t i o n s M a r g u l e s i n t e g r a t e d t h e Gibbs-Duhem e q u a t i o n i n terms 7 o f a p a i r o f e x p o n e n t i a l s e r i e s w i t h u n l i m i t e d numbers o f terms and t h e n d e r i v e d t h e c o n s t a n t s f o r one o f t h e e q u a t i o n s f r o m t h o s e o f t h e o t h e r by a p p l y i n g E q u a t i o n 3. As e x p r e s s e d by C a r l s o n and C o l b u r n (6) t h e two-term e q u a t i o n s o f M a r g u l e s a r e : l o g Y ' - L = ( 2 B - A) x 2 + 2(A - B ) x | l o g f 2 = < 2 A " B ) x l + 2 ( B " A> x i One f i n d s a t x x = 0, l o g ^ = A and l o g Y 2 = 0> a t X;L = 1, l o g Y i = 0 and l o g ) { 2 ~ B. I t i s o f i n t e r e s t t o note t h a t f o r t h e s e e q u a t i o n s , a t X]_ = 0.5, l o g ^ -> = T 9 X 1 ( 1 1 O S ^ 2 = T r e g a r d -l e s s o f t h e v a l u e s o f A and B . Van L a a r E q u a t i o n s Van L a a r d e r i v e d s o l u t i o n s t o E q u a t i o n 3 f r o m a thermo dynamic s t u d y and t h e s e are g i v e n below i n t h e f o r m e x p r e s s e d by C a r l s o n and C o l b u r n l o g Y 2 = . Z ( 1 + B X 2 \ 2 • V A x x / I n t h i s f o r m , c o n s t a n t s A and B have t h e p r o p e r t y o f b e i n g e q u a l t o t h e t e r m i n a l v a l u e s o f t h e l o g Y o f the p l o t o f E q u a t i o n 2 f o r V 1 and Y 2 . Thus, a t x x = 0, l o g Yj_ = A, and a t x1 = 1 when x 2 = 0, l o g Y 2 = B» I t i s o f i n t e r e s t , a l s o , t o see t h a t a t x i = 0, l o g Y 2 = 0 or.i2 = 1, and a t x1 = 1, l o g V]_ = 0 o r = 1. 8 I n a l l a t t e m p t s t o f i n d s u i t a b l e s o l u t i o n s t o t h e d i f - . f e r e n t i a l f o r m o f t h e Gibbs-Duhem e q u a t i o n t h e o b j e c t has been t o d e r i v e s e p a r a t e e q u a t i o n s f o r t h e a c t i v i t y c o e f f i c i e n t s o f t h e two components, which can be used, i n c o n j u n c t i o n w i t h t h e i r vapor p r e s s u r e s , i n t h e pure s t a t e , t o determine t h e r e l a t i o n s between t h e two phases. I n u s i n g t h e s e e q u a t i o n s a t c o n s t a n t p r e s s u r e , and c o n s e q u e n t l y w i t h v a r y i n g t e m p e r a t u r e , i t must be assumed t h a t t h e a c t i v i t y c o e f f i c i e n t v a r i e s t o a n e g l i g i b l e e x t e n t w i t h tem-p e r a t u r e o v e r t h e range e x t e n d i n g between the b o i l i n g p o i n t s o f t h e two components. T h i s a s s u m p t i o n i s i n c r e a s i n g l y d i f f i c u l t t o j u s t i f y as t h e b o i l i n g p o i n t s become f u r t h e r and f u r t h e r a p a r t . 9 APPARATUS A. The L i q u i d R e c i r c u l a t i o n A p p a r a t u s The a p p a r a t u s used t o determine t h e v a p o r - l i q u i d e q u i l i b r i u m c o m p o s i t i o n s on t h e benzene-propanol and benzene-p e n t a n o l systems was t h e same a s t h a t used by Waldichuk ( 1 0 ) . I t was d e s i g n e d t o be s i m i l a r t o t h a t proposed by E o w l e r (3) w i t h t h e f o l l o w i n g a d d i t i o n a l improvements: (1) A c a p i l l a r y s t o p c o c k was i n t r o d u c e d i n t o t h e l i q u i d t r a p f o r r e m o v a l o f t h e l i q u i d sample. T h i s e l i m i n a t e d t h e l a r g e r q u a n t i t i e s o f l i q u i d w h i c h s t a g n a t e i n an o r d i n a r y s t o p c o c k . (2) The drop c o u n t e r o f t h e G i l l e s p i e s t i l l (2) was r e t a i n e d i n t h e s m a l l b u l b above the c a p i l l a r y l e a d i n g t o t h e b o i l e r . T h i s a i d s i n a d j u s t i n g f o r a p r o p e r r a t e o f h e a t i n g t o t h e b o i l e r . (3) The vapor condensate t r a p was made s m a l l e r i n o r d e r t o a c h i e v e e q u i l i b r i u m more q u i c k l y , (4) A t y p e o f c o n t a i n e r where d r y i c e and ace t o n e m i x t u r e can be used f o r t h e c o o l i n g m a t e r i a l was i n t r o d u c e d above t h e vap o r condensate t r a p . The s t i l l as shown i n F i g , 1 was made o f P y r e x g l a s s . Tungsten l e a d s were s e a l e d i n t o t h e s t a n d a r d t a p e r s t o p p e r o f t h e f i l l i n g t u b e f o r e l e c t r i c a l i n p u t t o t h e i n t e r n a l h e a t e r . T h i s h e a t e r c o n s i s t e d o f about 10 i n c h e s o f 2&-guage p l a t i n u m w i r e , wound i n t o a s m a l l c o i l at t h e end and br a z e d t o the t u n g s t e n l e a d s w i t h c o n s t a n t i n as f l u x . A c u r r e n t of 5 amp. c o n t r o l l e d by a v a r i a c was s u i t a b l e f o r p r o p e r pumping i n the C o t t r e l l t u b e . The b o i l e r , C o t t r e l l t u b e , disengagement chamber, and thermometer w e l l were i n s u l a t e d w i t h a s b e s t o s c o r d and a s b e s t o s cement. The e x t e r n a l h e a t e r f o r the b o i l e r was wound on t h e a s b e s t o s l a g g i n g F I L L I N G Tu6E 1 r V A C C U R A T E , T H E R M O M E T E R O P E N C O N D E N S E R CoTT R ELL, TUBE F I G . i F O W L E R - G I L L E S P I E S T I L L 10 f r o m t h e s t o p c o c k a t t h e bottom o f t h e b o i l e r t o the base o f t h e f i l l i n g t u b e . I t c o n s i s t e d o f 28 t u r n s of No. 22 nichrome r e -s i s t a n c e w i r e . A p o t e n t i a l o f 38 t o 50 v o l t s was f o u n d n e c e s s a r y t o g i v e t h e p r o p e r heat f o r b o i l i n g . The e x t e r n a l h e a t e r was c o v e r e d w i t h a l a y e r o f a s b e s t o s cement and paper f o r e l e c t r i c a l i n s u l a t i o n . The whole a p p a r a t u s was mounted on a p l a t f o r m 24" by 16" w i t h u p r i g h t s t e & l support rods l o c a t e d 14" a p a r t . The v a p o r - l i q u i d e q u i l i b r i u m s t i l l u sed does an e f f e c t i v e j o b o f p r e v e n t i n g c o n d e n s a t i o n o f t h e v a p o r s i n t h e s t i l l w h i l e at t h e same time c a u s i n g c i r c u l a t i o n o f b o t h v a p o r s and l i q u i d , and k e e p i n g e r i t r a i n m e n t a t a minimum. A l t h o u g h t h e a p p a r a t u s i s based on t h e vapor r e c i r c u l a t i o n p r i n c i p l e , i t d i f f e r s e s s e n t i a l l y f r o m o t h e r s o f t h i s t y p e i n t h a t t h e b o i l i n g l i q u i d I s a l s o c i r -c u l a t e d r a p i d l y . The l i q u i d i s b o i l e d i n t h e b o i l e r A, but d i f f e r i n g f r o m o t h e r v a p o r - l i q u i d e q u i l i b r i u m a p p a r a t u s , t h e vapor and l i q u i d a r e not p e r m i t t e d t o s e p a r a t e i n t h i s chamber. They a r e m a i n t a i n e d i n i n t i m a t e c o n t a c t as t h e y p a s s up t h e modi-f i e d C o t t r e l l pump B t o the thermometer C, and hence t o t h e d i s -engagement chamber D. I n D t h e l i q u i d c o n t i n u e s t o c i r c u l a t e down t h r o u g h L, w h i l e the vapor p a s s e s t o t h e condenser F, and t h e n t o t h e condensate t r a p G. The o v e r f l o w from G r e t u r n s t o t h e b o i l e r t h r o u g h t h e s m a l l d r i p c o u n t e r H and c a p i l l a r y J . At K t h e o v e r f l o w combines w i t h the l i q u i d f l o w f r o m L and b o t h r e t u r n t o t h e b o i l e r . The r a t e of condensate r e t u r n s h o u l d be such t h a t t h e l e v e l o f l i q u i d f l u c t u a t e s g e n t l y j u s t above t h e c a p i l l a r y i n t h e d r i p c o u n t e r . B. R e f r a c t o m e t e r The a n a l y s i s o f t h e vapor and l i q u i d c o m p o s i t i o n s i s c a r r i e d out w i t h a r e f r a c t o m e t e r of t h e Spencer-Abbe t y p e . I t i s equipped w i t h A m i c i compensating p r i s m s so t h a t a w h i t e l i g h t s o u r c e can be used i n s t e a d o f monochromatic l i g h t . The s c a l e of t h e i n s t r u m e n t i s c a l i b r a t e d d i r e c t l y i n r e f r a c t i v e i n d e x as measured w i t h t h e D l i n e o f t h e sodium spectrum. Readings may be r e a d d i r e c t l y t o t h e t h i r d d e c i m a l p l a c e and t h e f o u r t h may be e s t i m a t e d w i t h an a c c u r a c y o f * 0 . 0 0 0 2 . The t e m p e r a t u r e of t h e p r i s m s was kep t a t 25°C. 1 0.2„with a w a t e r b a t h c o n t r o l l e d t o 25°C. t 0 . 1 . The t e m p e r a t u r e o f t h e p r i s m s c o u l d be r e a d t o 1°C. and e s t i m a t e d t o - 0 .2°C. on a thermometer s u p p l i e d w i t h t h e i n s t r u m e n t . No c l o s e r check on the t e m p e r a t u r e was n e c e s s a r y s i n c e a change o f 0 .2°C. o n l y a l t e r e d t h e r e f r a c t i v e i n d e x o f benzene, p r o p a n o l and p e n t a n o l by a p p r o x i m a t e l y 0.0001 u n i t s . C. Thermometers The two thermometers used i n t h i s r e s e a r c h had ranges f r o m 50° - 100° C. and f r o m 0° - 200° C. and were the o r d i n a r y m e r c u r y - i n - g l a s s t y p e . Both were c a l i b r a t e d by Waldichuk (10) a g a i n s t a p l a t i n u m r e s i s t a n c e thermometer No. 169314 w i t h N a t i o n a l Bureau o f S t a n d a r d s C e r t i f i c a t e d a t e d August 17, 1937, f o r use i n h i s r e s e a r c h . The s h o r t - r a n g e one was c a l i b r a t e d a t 5° i n t e r -v a l s f r o m 50° - 100° C. and t h e l o n g - r a n g e one at 10° i n t e r v a l s f r o m 100° - 200° C. The s h o r t - r a n g e thermometer c o u l d be re a d a c c u r a t e l y t o t h e n e a r e s t 0 .05°C. The l o n g - r a n g e thermometer c o u l d be r e a d a c c u r a t e l y t o t h e n e a r e s t 0.1°C. 12 MATERIALS' A. Benzene The benzene used was a c o m m e r c i a l l y pure grade a s sup-p l i e d by Merck and Company, I n c . I t conformed t o A.C.S. s t a n d a r d s and a l o t a n a l y s i s f o r t h e benzene's maximum i m p u r i t i e s was. g i v e n as f o l l o w s : N o n - v o l a t i l e 0.001% A c i d o r a l k a l i - - - - - - - - - - - p a s s e s t e s t S u b s t a n c e s darkened by H^jSO^ - - - p a s s e s t e s t S u l p h u r compounds (as S) - - - - - 0.005% Thiophene 0.000% Water - - - - - - - - - - - - - - p a s s e s t e s t T h i s benzene was s u b j e c t e d t o f u r t h e r p u r i f i c a t i o n as f o l l o w s : I n about 1500-ml. l o t s the benzene was a g i t a t e d w i t h C P . c o n c e n t r a t e d s u l f u r i c a c i d i n a 2 - l i t e r s e p a r a t i n g f u n n e l . The a c i d was a l l o w e d t o s e t t l e o u t , and i t was d r a i n e d o f f . The benzene was washed t w i c e w i t h 500-ml. p o r t i o n s o f d i s t i l l e d w a t e r , t h e n w i t h two 500-ml. p o r t i o n s o f 1 N sodium h y d r o x i d e . The benzene was washed f u r t h e r w i t h d i s t i l l e d w a t e r . About 150 m l . o f p u r i f i e d mercury was a g i t a t e d w i t h t h e benzene. A g r e y i s h - b l a c k scum was l e f t on t h e s u r f a c e o f the mercury. The mercury was removed and t h e benzene was f i n a l l y washed w i t h s e v e r a l p o r t i o n s o f d i s t i l l e d w a t e r . The benzene was poured f r o m the s e p a r a t i n g f u n n e l i n t o a 3 ^ * l i t e r c o n t a i n e r t o w h i c h was added f r e s h l y c u t sodium r i b b o n . The c o n t a i n e r was s t o p p e r e d l i g h t l y and t h e benzene was a l l o w e d t o s t a n d f o r a week. Any hydrogen formed f r o m t h e r e a c t i o n of t h e sodium w i t h t h e w a t e r would be 13 e v o l v e d d u r i n g t h a t t i m e . The s t i l l u sed f o r t h e benzene d i s t i l l a t i o n i s shown i n F i g . 2 . The column i s a s i l v e r e d , vacuum-jacketed one, packed w i t h a m i x t u r e o f g l a s s - b e a d s and h e l i c e s . I t has 14 t h e o r e t i c a l p l a t e s . I t i s 122 cm. l o n g and has an i n t e r n a l d i a m e t e r o f 25 cm. A 1 - l i t e r f l a s k i s used f o r t h e b o i l e r and h e a t i s s u p p l i e d through a G l a s - C o l h e a t i n g mantle c o n t r o l l e d by a v a r i a c . A r e f l u x ad-j u s t m e n t c o u l d be made i n t h e head o f t h e s t i l l t o g i v e t h e r e -f l u x r a t i o d e s i r e d . A f t e r s t a n d i n g f o r a week th e benzene was r e f l u x e d o v e r Na r i b b o n f o r t e n toa-es i n t h e benzene s t i l l . The r e f l u x r a t i o n was t h e n s e t f o r 15 : 1 and d i s t i l l a t i o n c a r r i e d out i n w h i c h t h e f i r s t 150 m l . d i s t i l l e d were d i s c a r d e d . About 650 m l . o f benzene were c o l l e c t e d i n t h e m i d d l e f r a c t i o n . T h i s benzene d i s t i l l a t i o n was r e p e a t e d t w i c e and o n l y t h e m i d d l e f r a c t i o n s d i s t i l l i n g a t c o n s t a n t t e m p e r a t u r e were c o l l e c t e d each t i m e . The d i s t i l l e d benzene was p l a c e d i n a 250-ml. e r l e n -meyer f l a s k , about 150 m l . a t a t i m e , and was f r o z e n i n a d r y i c e - a c e t o n e m i x t u r e . The l a s t few m i s . t o f r e e z e were d i s c a r d e d and t h e f i r s t 25 m l . t o m e l t were d i s c a r d e d a l s o . The p u r i f i e d benzene was t h e n s t o r e d i n a ground g l a s s s t o p p e r e d f l a s k o v e r a c t i v a t e d a l u m i n a . Over 2 l i t e r s o f p u r i f i e d benzene were c o l l e c t e d . Three s e p a r a t e checks on t h e p u r i t y o f t h i s benzene were made - r e f r a c t i v e i n d e x , b o i l i n g p o i n t , and d e n s i t y , a) R e f r a c t i v e Index The r e f r a c t i v e i n d e x of t h e p u r i f i e d benzene was checked a t 20°C. and 25°C. and t h e v a l u e s o f t h e r e f r a c t i v e i n d e x found were 1.5012 and 1 .4979, r e s p e c t i v e l y , i n good agreement w i t h t h e r e p o r t e d v a l u e s l i s t e d i n T a b l e I . FIG. Z BENZENE S T I L L . b) B o i l i n g P o i n t The d e t e r m i n a t i o n of t h e b o i l i n g p o i n t o f benzene was c a r r i e d out i n a C o t t r e l l - C h o p i n b o i l i n g - p o i n t d e t e r m i n a t i o n a p p a r a t u s shown i n F i g . 4. I t i s a s t a n d a r d form o f e b u l l i o m e t e r . The b o i l i n g p o i n t was found t o be 80.1°C. T h i s r e s u l t checks f a v o u r a b l y w i t h the b o i l i n g p o i n t s r e p o r t e d i n T a b l e I . c) D e n s i t y D e n s i t y measurements were c a r r i e d out i n a vacuum-j a c k e t e d 2 5-ml. pycnometer b o t t l e w h i c h was c a l i b r a t e d w i t h double d i s t i l l e d w a t e r a t 2 5°C. The b o t t l e was c a r e f u l l y weighed and benzene was added. The pycnometer was t h e n p l a c e d i n a c o n s t a n t t e m p e r a t u r e b a t h , t h e t e m p e r a t u r e b e i n g c o n t r o l l e d a t 2 5 . 0 0 ° C . i 0 . 0 2 . A f t e r two h o u r s t h e b o t t l e was removed from the b a t h , t h e e x c e s s benzene was c l e a n e d o f f w i t h l e n s t i s s u e and t h e b o t t l e and benzene were weighed c a r e f u l l y as b e f o r e . The d e n s i t y of t h e benzene a t 25°C. was found t o be 0 . 8 7 3 5 . Comparative v a l u e s a r e g i v e n i n T a b l e I . The b a l a n c e used f o r the w e i g h i n g s was a Ghainomatic b a l a n c e w i t h a s e n s i t i v i t y o f 3 s c a l e d i v i s i o n s p e r m i l l i g r a m and t h e w e i g h t s used were c a l i b r a t e d by t h e method o f s u b s t i t u t i o n C o r r e c t i o n f o r a i r buoyancy was made a f t e r each w e i g h i n g . F I G 4 C O T T R E L L - C H O P I N B O I L I N G - P O I N T A P P A R A T U S TABLE I PHYSICAL DATA FOR BENZENE FROM THE LITERATURE Author R.I. B.P. Density Waldichuk (10) n§ 5 = 1.4979 d 2£ = 0.87368 Wojciechowski (11) n 25 = I . 4 9 8 I 80.1°C. d|5 = 0.87366 I.C.T. (12) n^° = 1.5014 80.12°C. d 2 0 = 0.87^8 Allen, Lingo and Felsing (13) n 2 0 = 1.4980 d|5 = 0.8732 Glanville and Sage (28) n 29 = 1.5014 Handbook of Chemistry and Physics (14) n 2 0 = 1.5014 80.1°C. df° = 0.8794 D 4 Gibbons et a l . (15) n^ 5 » 1.4979 16 B. P r o p a n o l The p r o p a n o l used was a c o m m e r c i a l l y pure grade as sup-p l i e d by t h e F i s h e r S c i e n t i f i c Company w i t h a l o t a n a l y s i s f o r maximum i m p u r i t i e s as f o l l o w s : A c i d i t y (CH3COOH) 0.002% B o i l i n g range 96° - 97.5°C. N o n - v o l a t i l e m a t t e r 0.000% S u b s t s . p p t . by H2O - - - - None The p r o p a n o l was f u r t h e r p u r i f i e d by t r e a t i n g 2 l i t e r s o f i t w i t h about 5 m l . o f B ^ . The bromine was added t o remove any a l l y l a l c o h o l (B.P. 97°C.) w h i c h might be p r e s e n t . A f t e r s t a n d i n g o v e r n i g h t t h e a l c o h o l was f r a c t i o n a t e d i n t h e a l c o h o l d i s t i l l i n g column ( i l l u s t r a t e d i n F i g . 3). T h i s column i s s i m i l a r t o t h e one used f o r t h e benzene d i s t i l l a t i o n e x c ept t h a t i t s l e n g t h i s o n l y 100 cm. and i t s d i a m e t e r i s 3 cm. I t i s s i l v e r e d , vacuum j a c k e t e d and packed w i t h v e r y s m a l l h e l i c e s g i v i n g an e s t i m a t e d 20 t h e o r e t i c a l p l a t e s . The s t i l l p o t was a 2 - l i t e r f l a s k h e a t e d w i t h a G l a s - C o l m a n t l e , t h e heat i n p u t t o i t b e i n g c o n t r o l l e d by a v a r i a c . Any d e s i r e d r e f l u x r a t i o c o u l d be o b t a i n e d by t h e adjustment of a s t o p - c o c k i n t h e head o f t h e column. At a r e f l u x r a t i o o f 15:1 t h e f r a c t i o n d i s t i l l i n g o v e r -head between 96.8°to 97.4°C. was c o l l e c t e d . T h i s f r a c t i o n was d r i e d o v er Ca f o r s e v e r a l days, t h e n r e d i s t i l l e d . The p o r t i o n coming over between 97° - 97.3°C. was c o l l e c t e d and was f i n a l l y d r i e d o v e r f r e s h l y i g n i t e d CaO f o r a week, t h e n f r a c t i o n a t e d . The m i d d l e c u t d i s t i l l i n g a t 97.2°C. a t 760 mm. p r e s s u r e was c o l l e c t e d . The p u r i f i e d p r o p y l a l c o h o l was s t o r e d o v e r a c t i v a t e d 3 A L C O H O L S T I L L . alumina in a glass-stoppered flask. About 1000 ml. of alcohol was purified in this fashion. Three separate checks on the purity of the propanol were made - refractive index, boiling point, and density. a) Refractive Index The refractive index of the alcohol was checked at 20°C. and 25°C. and gave values of 1.3838 and 1.3#5#,respectively. Comparative values are given in Table II. b) Boiling; Point The boiling point determination was carried out in the apparatus shown i n Fig. 4. The value obtained was 9 7 . 2 ° C , agreeing well with the literature values. c) Density The density of the propanol was found in the same way as that used for benzene. The value of 0.8023 obtained checks well with the one reported in Table II. TABLE II PHYSICAL DATA FOR PROPANOL FROM THE LITERATURE Author R.I. B.P. Density Trev and Watkins ( 1 6 ) Wojciechowski (17) Brunei (18) Denzler (19) Webb and Lindsley (20) ng5 - 1 . 3 6 3 4 9 6 . 9 6 7 5 4 ° C . d | | - 0.80236 9 7 . 2 1 ° C . n*5 - 1.3835 97o25°C nj*0 - 1.3860 nJO » 1 . 3 8 5 5 9 7 o 2 5 ° C . 18 C. P e n t a n o l The p e n t a n o l used was a t e c h n i c a l grade o f a l c o h o l s u p p l i e d by t h e F i s h e r S c i e n t i f i c Company. A s e a r c h o f the l i t e r a t u r e r e v e a l e d t h a t t h e i s o m e r s o f n - p e n t a n o l have b o i l i n g p o i n t s t h a t d i f f e r f r o m t h a t o f t h e pure p e n t a n o l by at l e a s t 5°. The c l o s e s t i s o m e r o f n-hexanol t h a t c o u l d be found had a b.p. t h a t d i f f e r e d by 2°. I t was d e c i d e d t h e r e f o r e t o p u r i f y the p e n t a n o l by f r a c t i o n a t i o n w i t h o u t any f u r t h e r t r e a t m e n t . About 3500 ml. of t h e t e c h n i c a l p e n t a n o l had been o b t a i n e d and t h i s was charged t o t h e s t i l l pot i n two 1750-ml, b a t c h e s . A f t e r two s u c c e s s i v e f r a c t i o n a t i o n s on each b a t c h a t a 15*1 r e f l u x r a t i o about 2000 ml. o f p e n t a n o l had been c o l l e c t e d w i t h a b.p. range o f 137.5° t o 138°C. T h i s was c a r e f u l l y d i s t i l l e d once more and d r i e d o v e r CaO f o r a week. Two more f r a c t i o n a t i o n s were t h e n c a r r i e d out a t a r e f l u x r a t i o o f 20:1 t o remove a l l t r a c e s o f i m p u r i t i e s . T h i s gave a volume o f about 750 m l . o f p e n t a n o l t h a t came o v e r a t 137.9°C. Only two c h e c k s on t h e p u r i t y were c a r r i e d out -r e f r a c t i v e i n d e x and b o i l i n g p o i n t . The v a l u e s o f r e f r a c t i v e i n d e x , d e n s i t y , and b.p. v a r i e d o v e r c o n s i d e r a b l e range as r e p o r t e d i n t h e l i t e r a t u r e . Of t h e s e t h e b o i l i n g p o i n t o f f e r e d t h e b e s t agreement and t h i s seemed the most r e l i a b l e check on t h e p u r i t y . a) R e f r a c t i v e Index The r e f r a c t i v e i n d e x was o b t a i n e d a t 20°C. and 25°C. and t h e v a l u e s a r e 1.4113 and 1.4095, r e s p e c t i v e l y . Comparative v a l u e s a r e g i v e n i n T a b l e I I I . b) B o i l i n g P o i n t The b o i l i n g p o i n t d e t e r m i n a t i o n was c a r r i e d out i n t h e same a p p a r a t u s used i n t h e d e t e r m i n a t i o n o f b.p. o f benzene and p r o p a n o l . A v a l u e o f 137.9°C. was o b t a i n e d . L i t e r a t u r e v a l u e s a r e r e p o r t e d i n T a b l e I I I . TABLE I I I PHYSICAL DATA FOR PENTANOL FROM THE LITERATURE Au t h o r R . I . B.P. B u t l e r e t a l . (21) Timmermans (22) Simons (23) W o j c i e c h o w s k i (17) ng u = 1.4111 137.75°C. n 2 0 = 1.4119 138.00°C. 138.2°C. 20 EXPERIMENTAL PROCEDURES A. D e t e r m i n a t i o n o f t h e R e f r a c t i v e - I n d e x C o m p o s i t i o n Curve a t 25°C. Benzene-Propanol I n c o n s t r u c t i n g the r e f r a c t i v e - i n d e x c o m p o s i t i o n curve f o r b enzene-propanol c a l c u l a t e d amounts o f benzene were p i p e t t e d i n t o c a r e f u l l y c l e a n e d and weighed w e i g h i n g b o t t l e s . To each b o t t l e i n t u r n , a f t e r t h e benzene and b o t t l e were weighed, was added d e f i n i t e amounts o f p r o p a n o l so as t o make up c o m p o s i t i o n s r a n g i n g f r o m a p p r o x i m a t e l y 0.1 - 1.0 mole f r a c t i o n o f benzene. The b o t t l e was a g a i n weighed and t h e r e f r a c t i v e i n d e x was t a k e n o f the m i x t u r e on t h e Abbe r e f r a c t o m e t e r w i t h t h e temperature o f t h e r e f r a c t o m e t e r p r i s m s c o n t r o l l e d a t 25°C. t 0.2. Readings were t a k e n a t 1-minute i n t e r v a l s o v er a 4-minute p e r i o d a f t e r t h e m i x t u r e on t h e p r i s m s was a l l o w e d t o come up t o t e m p e r a t u r e . No change was n o t i c e d i n t h e r e f r a c t i v e i n d e x r e a d i n g s , showing t h a t t h e l i q u i d between th e p r i s m s was n o t v o l a t i l i z i n g . The l i q u i d was p l a c e d on t h e p r i s m s by f o r c i n g a few d r o p s o f i t between t h e clamped p r i s m s w i t h an eye d r o p p e r . Care was e x e r c i s e d t o see t h a t the p e r i o d o f t i m e t h e w e i g h i n g b o t t l e was u n c o v e r e d was k e p t t o a minimum so as t o r e d u c e t h e l o s s o f the v o l a t i l e components. The t r a n s f e r o f the l i q u i d t o o k a p p r o x i m a t e l y 10 s e e s . , and w e i g h i n g s made i n o r d e r t o c a l c u l a t e t h e l o s s o f benzene d u r i n g t h i s p e r i o d showed a s m a l l l o s s o f about 0.5 m i l l i g r a m s . B. V a p o r - L i q u i d D e t e r m i n a t i o n on the F o w l e r - G i l l e s p i e S t i l l I n i t i a l l y t h e b o i l e r o f t h e s t i l l was changed w i t h a p p r o x i m a t e l y 180 m l . o f pure benzene by way o f t h e i n t e r n a l h e a t e r o p e n i n g . The i n t e r n a l h e a t e r was s e t i n p l a c e , the l e a d s . . . 21 a t t a c h e d and A.C. v o l t a g e a p p l i e d t o b o t h t h e e x t e r n a l and i n -t e r n a l h e a t e r s - about 35 and 7 v o l t s , r e s p e c t i v e l y . When pumping i n t h e C o t t r e l tube had commenced t h e i n t e r n a l h e a t e r was a d j u s t e d t o g i v e smooth o p e r a t i o n . I t was d i f f i c u l t t o p l a c e the c o r r e c t q u a n t i t y o f l i q u i d i n t h e b o i l e r a t t h e s t a r t so a d j u s t m e n t s were made a f t e r t h e condensate t r a p was f i l l e d . On b o i l i n g t h e l i q u i d l e v e l s h o u l d g e n t l y f l u c t u a t e i n t h e s m a l l b u l b above t h e c a p i l -l a r y t u b e and i n t h e s m a l l b u l b a t the top o f the l i q u i d t r a p . A f t e r t h e t e m p e r a t u r e o f b o i l i n g o f the benzene was r e c o r d e d , t h e power t o t h e s t i l l was shut o f f , some benzene was removed f r o m i t , and an a p p r o x i m a t e l y e q u a l volume o f p r o p a n o l added t o i t . The power was r e a p p l i e d . A t t a i n m e n t o f e q u i l i b r i u m u s u a l l y t o o k about two h o u r s . When t h e t e m p e r a t u r e f l u c t u a t i o n was no g r e a t e r t h a n t 0.05°C. t h e b o i l i n g t e m p e r a t u r e was r e c o r d e d and samples o f t h e l i q u i d and vapor condensate were removed as q u i c k l y as p o s s i b l e . Each o u t l e t f r o m t h e t r a p s was f l u s h e d out b e f o r e t h e sample was t a k e n . Samples were c o l l e c t e d i n s m a l l g l a s s v i a l s and were t i g h t l y c o r k e d t h e r e a f t e r w i t h c o r k s t o p p e r s . R e f r a c t i v e i n d e x r e a d i n g s were t a k e n soon a f t e r i n a s i m i l a r f a s h i o n t o t h a t used f o r t h e r e f r a c t i v e i n d e x - c o m p o s i t i o n c u r v e . Atmospheric p r e s s u r e r e a d i n g s were t a k e n a t almost the same t i m e a s t h e o t h e r r e a d i n g s on a F o r t i n - t y p e of barometer, l o c a t e d about 15 f e e t above the l e v e l o f t h e v a p o r - l i q u i d s t i l l . I n subsequent r u n s b e n z e n e - r i c h m i x t u r e s were removed fr o m the condensate t r a p and pure p r o p a n o l was added t o t h e r e -q u i r e d h e i g h t i n t h e b o i l e r t o a f f e c t changes i n c o m p o s i t i o n . F o r t h e d e t e r m i n a t i o n of t h e v a p o r - l i q u i d c o m p o s i t i o n s 22 o f t h e be n z e n e - p e n t a n o l systems.the same p r o c e d u r e as above was f o l l o w e d except t h a t more heat was a p p l i e d t h r o u g h t h e ex-t e r n a l h e a t e r t o b o i l e r t o g i v e e q u i l i b r i u m c o n d i t i o n s . . I n s t e a d o f c a r r y i n g out t h e r u n s a t a t m o s p h e r i c c o n d i t i o n s , p r e s s u r e was a p p l i e d t h r o u g h a b a r o s t a t (see F i g . §) t o keep i t a t 760 ± 2 mm. o f p r e s s u r e . C. D e t e r m i n a t i o n o f R e f r a c t i v e I n d e x - C o m p o s i t i o n Curve a t 25°C. Benz e n e - P e n t a n o l T h i s r e f r a c t i v e i n d e x - c o m p o s i t i o n c u r v e d e t e r m i n a t i o n was c a r r i e d out i n a s i m i l a r manner t o t h a t used f o r the benzene-p r o p a n o l system, t h e o n l y d i f f e r e n c e b e i n g t h a t t h e p e n t a n o l was added f i r s t t o t h e w e i g h i n g b o t t l e s i n c e i t was l e s s v o l a t i l e t h a n t h e benzene. Fie. 5 M e R c u R Y B A R O S T A X RESULTS A. Benzene-Propanol The refractive index values found using varying mole fractions of the benzene-propanol system are shown in Table IV. An estimation of the error due to vola t i l i z a t i o n of the volatile components during the weighings showed i t to be approximately 0.03%. No significant error was detected during the refractive index determinations. A large plot of the refractive index versus the composition was made and i t was used to determine the compositions during the vapor-liquid equilibrium runs. Fig. 6 shows a reduced plot of the large one. TABLE IV REFRACTIVE INDEX-COMPOSITION DATA FOR BENZENE-PROPANOL AT 25°C.  MOLE FRACTION OF BENZENE REFRACTIVE INDEX 0.000 1.3838 0.094 1.3959 0.183 1.4070 0.270 1.4173 0.375 1.4298 0.488 1.4428 0.580 1.4528 0.654 1.4610 0.754 1.4714 0.802 1.4769 0.904 1.4876 1.000 1.4979 LSOOOr I.1&00 X ui O Kboo! Z UJ > P {j uioo| < u. Ui 14200 mooo 138001 M O L E F R A C T I O N O F B E N Z E N E FIG- 6 R E F R A C T I V E I N D E X , OF B E N Z E N E - P R O P A N O L M I X T U R E S A T 2 5 " C In Table V are tabulated the results of the vapor-liquid equilibrium determinations on the Fowler-Gillespie s t i l l . The termperature was read on a 50° - 100°C. thermometer read to the nearest 0.05°G. The pressure was read on a Fortin-type barometer and a l l runs were made when the atmospheric pressure was constant between 740 - 742 mm. of Hg. TABLE V EXPERIMENTAL VAPOR-LIQUID EQUILIBRIUM DATA FOR BENZENE-PROPANOL • AT ATMOSPHERIC PRESSURE . Run Duration Temp. Atm. Press. Liquid Phase Vapor Phase . of Run °C. mm. Hg R.I.atJ.. Mol. Fr. R.I.at Mol. Fr. (Hrs.) 25° C C 6 H 6 25°C. G 6 H 6 1 79.30 741 1.4979 1.000 1.4979 1.000 2 2 77.70 741 1.4937 0.960 1.4888 0.915 3 2 77.0 741 1.4908 0.935 1.4852 0.883 4 2 76 .4 742 1.4860 0.888 1.4814 0.847 5 2 1/2 76.3 742 1.4840 0.870 1.4798 0..832 6 2 1/2 76.2 742 1.4795 0.831 1.4775 0.810 7 2 1/2 76.2 740 1.4716 0.755 1.4741 0.777 8 2 76.3 740 1.4646 0.687 1.4714 0.755 9 2 1/2 76.60 741 1.4577 0.623 1.4695 0.735 10 2 76.8 741 1.4543 0.596 I .4686 0.727 11 2 78.40 741 1.4360 0.427 1.4613 0.660 12 2 1/2 79.10 741 1.4307 0.380 1.4595 0.635 13 2 1/2 80.2 740 1.4228 0.316 1.4549 0.600 14 2 . 83.00 740 1.4114 0.219 1.4460 0.518 15 2 84.90 740 1.4060 0.175 1.4390 0.455 16 2 1/2 90.10 740 1.3940 0.080 1.4179 0.274 17 96.40 740 1.3838 0 . 1.3838 0 A large scale plot of the equilibrium values was made, and also a plot of the temperature against the liquid and vapor composition of the more volatile component. The reduced graphs are shown in Fig. 7 and Fig. 8, respectively. The graphs indicate an azeotrope at x-j_ = 0.795 with a normal boiling point of 76.2°C. at 740 mm. pressure. Similar values reported by Lecat (4) give the azeotrope at x = 0.791 and a b.p. of 77.12°C. at 760 mm. pressure. The boiling-point curve for the liquid i s almost horizontal in the vicinity of the minimum, and a change in composition from 68% to 83% benzene i s accompanied by a temperature change of only 0.11°C. To check the thermodynamic consistency of the system the values of the activity coefficients obtained experimentally were compared with those calculated theoretically. The activity coefficients were computed from the equation P°x where V = activity coefficient; P = the total pressure of the system, in this case 740 - 742 mm. of mercury; P° = the vapor pressure of the pure component at the solution temperature in mm. of mercury; and x = mole fraction of the component in the liq u i d phase. The calculated values are shown i n Table VIII. Pressures of the pure components, benzene and propanol, at the particular boiling temperatures were taken from vapor pres-sure curves. For benzene, the vapor pressure data for the range of temperature used for both the benzene-propanol; and benzene-pentanol systems were obtained from various sources. Over the lower temperature range the vapor pressure values are computed by t h e e q u a t i o n i D / \ 0.05223 a ^ . l o g P (mm.) = - J +• b where T i s t h e a b s o l u t e t e m p e r a t u r e , and a and b a r e c o n s t a n t s h a v i n g t h e f o l l o w i n g v a l u e s : 0° t o 42°C. a = 34,172 42° t o 100°C. a = 32,295 b = 7.9622 b = 7.6546 F o r the r e g i o n o f t e m p e r a t u r e f r o m 100° t o 140°C. t h e e x p e r i m e n t a l v a l u e s of Smith and M e n z i e s (24) and Gornowski e t a l . (25) were used. T a b l e V I shows the vapor p r e s s u r e v a l u e s o v e r t h e t e m p e r a t u r e range concerned and F i g . 9 a p l o t o f t h e s e v a l u e s . TABLE V I Temp. VAPOR PRESSURE DATA FOR BENZENE P r e s s u r e mm. Hg Source o f Data 60 390 C a l c u l a t e d 70 548 n 80 754 tt 90 1022 ' tt 100 1360 tt 110 1751 S m i t h and M e n z i e s (24) 120 2240 n tt tt 130 2825 Gornowski e t a l . (25) 140 3518 tt tt tt The vapor p r e s s u r e d a t a f o r p r o p a n o l were t a k e n f r o m C h e m i c a l E n g i n e e r s ' Handbook (26) and a r e shown i n T a b l e V I I and a p l o t o f i t i n F i g . 10. VAPOR PRESSURE -n m z N m z m < > O Ji TJ 7) m u> u> C X) TABLE V I I VAPOR PRESSURE DATA FOR PROPANOL Temp. °C. P r e s s u r e mm. Hg 66.6 200 75.4 300 82.0 400 87.3 500 91.6 600 95.8 700 97.2 760 80o TEMPERATURE - *C TABLE V I I I ACTIVITY COEFFICIENTS OF BENZENE AND PROPANOL FROM EXPERIMENTAL DATA T°C. P mm. Hg P]_ mm. Hg ?2 ma* Hg x l n V i y 2 79.3 741 1.000 1.000 1.0 77.7 741 700 337 0.960 0.915 1.010 4.66 76.97 741 685 324 0.935 0.883 1.022 4.10 76.42 741 673 304 0.888 0.847 1.05 3.33 76.31 742 670 300 0.870 0.832 1.056 3.19 76.21 742 668 298 0.831 0.810 1.08 2.80 76.24 741 669 299 0.755 0.777 1.129 2.25 76.31 741 670 300 0.687 0.755 1.216 1.93 76.6 741 675 305 0.623 0.735 1.295 1.705 76.78 741 683 322 0.596 0.727 1.325 1.55 78.4 740 720 347 0.427 0.660 1.585 1.28 79.1 740 731 355 0.380 0.635 1.69 1.228 80.21 740 761 372 0.316 0.600 1.847 1.165 83.0 741 830 418 0.219 0.518 2.11 1.085 84.9 740 882 455 0.175 0.455 2.18 1.078 90.1 740 1025 563 0.08 0.274 2.479 1.055 96.44 741 0 740 0 0 2.768 1.000 The t h e o r e t i c a l v a l u e s o f t h e a c t i v i t y c o e f f i c i e n t s a r e c a l c u l a t e d f r o m t h e Van L a a r s o l u t i o n s o f the Gibbs-Duhem e q u a t i o n w h i c h a re g i v e n below i n t h e form p r e s e n t e d by C a r l s o n and C o l b u r n (6): { 1 + ^ 1 ] Bx. B l o g V 2 =  (l + ^z) Ax-^ where A and B a r e the v a l u e s o f l o g V j_ and l o g Y 2 for x^ = 0 and X2 = 0 , r e s p e c t i v e l y ; t h e v a l u e s g i v i n g t h e b e s t f i t o f t h e p l o t of t h e e x p e r i m e n t a l a c t i v i t y c o e f f i c i e n t s e x t r a p o l a t e d t o z e r o a r e A = 0.443 and B = 0 . 7 5 2 . F i g u r e 11 shows t h e agreement between t h e observ e d d a t a and t h e c a l c u l a t e d v a l u e s and i n T a b l e IX. t h e e x p e r i m e n t a l and t h e o r e t i c a l v a l u e s a r e g i v e n . OB 30 TABLE IX EXPERIMENTAL AND THEORETICAL ACTIVITY COEFFICIENTS, OF BENZENE AND PROPANOL x i Jf]_ E x p t . V]_ C a l c . Y 2 E x p t . V2 C a l c . 0 0 2.768 1.000 1.000 .080 2.479 2.630 1.055 1.005 .175 2.180 2.472 1.078 1.021 .219 2.110 2.394 1.085 1.051 .316 1.847 1.873 1.165 1.074 .380 1.690 1.732 1.128 1.131 .427 1.585 1.551 1.280 1.181 .596 1.325 1 . 3 2 3 1.550 1.454 . 6 2 3 1.295 1.298 1.705 1 . 5 2 0 .687 1.216 1.212 1.930 1.736 .755 1.129 1.138 2.250 2.110 .831 1.080 1.070 2.800 2.620 .870 1.056 1.042 3.190 3.010 .888 1.050 1.032 3.330 3 . 2 3 0 .935 1.022 1.012 4.100 4.100 .960 1.010 1.005 4.660 4 . 5 2 0 1.000 1.000 1.000 5.640 B. Benzene-Pentanol The r e f r a c t i v e i n d e x v a l u e s found u s i n g v a r y i n g mole f r a c t i o n s o f t h e ben z e n e - p e n t a n o l system a r e shown i n T a b l e X and a g r a p h i c a l r e p r e s e n t a t i o n o f t h e s e i n F i g . 12. An e s t i m a t i o n o f 1.5000, O 01 0.2 0 3 0.H- OS Ofa 07 Q.8 0.9 10 M O L E F R A C T I O N O F B E N Z E N E F I S . I Z R E F R A C T I V E - I N D E x O F B E N Z E N E - P E N T A N O L M I X T U R E S A T ZS'C 31 the error due to volatilization of the volatile components during the weighings showed i t to be approximately 0.03%. No significant error was detected during the refractive index determinations. A large plot of the refractive index versus the composition was made and i t was used to determine the compositions during the vapor-liquid equilibrium runs. TABLE X REFRACTIVE INDEX-COMPOSITION DATA FOR BENZENE-PENTANOL AT 25°C. Mole Fraction of Benzene Refractive Index 0.000 1.4095 0.048 1.4128 0.149' 1.4200 0.195 1.4232 0.292 1.4304 0.395 1.4383 0.492 1.4465 0.595 1.4550 0.692 1.4642 0.788 1.4739 0.896 1.4848 1.000 1.4979 In Table XI are tabulated the results of the vapor-liquid equilibrium determinations on the Fowler-Gillespie s t i l l . The temperatures over the range, 80° - 138°C, were read on two separate thermometers to the nearest 0.1°. The pressure was kept constant at 760 mm. i 2 mm. by a mercury barostat. X, Moue F R A C T I O N B E N Z E N E I N L I Q U I D TABLE X I EXPERIMENTAL VAPOR-LIQUID EQUILIBRIUM DATA FOR BENZENE-PENTANOL AT ATMOSPHERIC PRESSURE Run D u r a t i o n Temp, of Run °C. (Hrs.) Atm.Press. L i q u i d Phase Vapor Phase mm. Hg R . I . a t 2 5°C M o l . F r . C6 H6 R . I . a t 25°C M o l . F r . C6 H6 1 80.1 760 1.4979 1.0 1.4979 1.0 2 3 80.3 tT 1.4930 0.965 1.4960 0.983 3 3 82.0 tt 1.4796 0.845 1.4931 .0.966 4 3 84.5 tt 1.4679 0.729 1.4912 0.951 5 3 1/2 85.7 tt 1.4620 0.670 1.4900 0.943 6 3 87.7 tt 1.4549 0.600 1.4889 0.934 7 4 90.3 tt 1.4471 0.527 1.4866 0.913 8 3 94.3 tt 1.4395 0.410 1.4827 0.875 9 3 1/2 100.1 tt 1.4319 0.310 1.4768 0.817 10 3 1/2 104.5 tt 1.4273 0 .250 1.4715 0.765 11 4 111.6 tt 1.4210 0.164 1.4612 0.660 12 4 1/2 116.8 tt 1.4175 0.115 1.4525 0.565 13 3 120.4 it 1.4157 0.090 1.4467 0.497 14 3 127.1 tt 1.4128 0.050 1.4336 0.333 15 137.9 tt 1.4095 0 1.4095 0 A l a r g e - s c a l e p l o t o f t h e e q u i l i b r i u m v a l u e s was made and a l s o a p l o t o f t h e t e m p e r a t u r e a g a i n s t t h e l i q u i d and vapor c o m p o s i t i o n s . Reduced graphs o f t h e s e a r e shown i n F i g . 13 and F i g . 14, r e s p e c t i v e l y . The l a r g e graphs i n d i c a t e no p o s s i b l e f o r m a t i o n o f an a z e o t r o p e . 140, X , M O L E F R A C T I O N B E N Z E N E IN LIQUID FIG.14 BOILING POINT DIAGRAM OF BENZENE-PENTANOL S Y S T E M The thermodynamic c o n s i s t a n c y o f t h e system was checked i n a s i m i l a r way t o t h a t o f benzene-propanol system and the r e s u l t s a r e shown i n T a b l e X I I I and F i g . 16. V a l u e s o f A and B f o r l o g ^ and l o g # 2 ? o r x l = 0 and x 2 = 0 were chosen as 0.280 and 0.835, r e s p e c t i v e l y , as t h e ones g i v i n g t h e b e s t p l o t o f the Van L a a r e q u a t i o n s . The vapor p r e s s u r e o f pure p e n t a n o l was t a k e n f r o m t h e work o f B u t l e r , Ramchandanij and Thomson (21) and ar e p r e s e n t e d i n T a b l e X I I and F i g . 15. TABLE X I I VAPOR PRESSURE DATA FOR PENTANOL Temp. °A P r e s s u r e mm. Hg 333.27 26.01 343.45 46.15 348.58 353.74 77.74 363.99 125.8 374.32 198.0 383.35 286.9 393.71 424.1 " 404.04 611.9 410.91 760.0 TEMPERATURE- *C 34 TABLE X I I I ACTIVITY COEFFICIENTS OF BENZENE AND PENTANOL FROM EXPERIMENTAL DATA T°C. P ram. Hg P-^  mm. Hg Hg x l 80 . 1 760 760 - 1.0 1.0 1.000 80.28 » 765 72 0.965 0.983 1.011 5.130 82 .00 810 80 0.845 0.966 1.071 2.060 84.52 880 92 0.729 0.951 1.125 1.497 85.69 912 98 0.670 0.943 1.175 1.340 87.67 960 107 0.600 0.934 1.231 1.245 90.3 1030 121 0.527 0.913 1.300 1.158 94.25 1170 148 0.410 0.875 1.392 1.088 100.1 » 1360 190 0.310 0.817 1.472 1.060 104.5 1525 228 0.250 0.765 1.520 1.042 111.6 1820 303 O . I64 0.660 1.680 1.021 116.8 » 2070 372 0.115 0.565 1.830 1.010 120.4 2270 420 0.090 0.497 1.845 1.002 127.1 2650 534 0.050 0.333 1.909 1.000 137 . 9 _ 760 1.000 >2 o • m E X P E R I M E N T A L —OO-CALCULATED FROM VAN LAAR EQUATIONS X>MOL* F R A C T I O N B E N Z E N E I N L I Q U I D FiQ.lfe A C T I V I T Y C O E F F I C I E N T S F O R B E N Z E N E - P E N T A N O L . S Y S T E M TABLE XIV EXPERIMENTAL AND THEORETICAL ACTIVITY COEFFICIENTS OF BENZENE AND PENTANOL  Mol. F r . C6HD 3Tj_ Expt. Y;i_ C a l c . Y 2 Expt. Y2 C a l c . 0.000 0 1.90 1.000 1.000 0.050 1.909 1.870 1.000 1.000 0.090 1.845 1.865 1.002: 1.002 0.115 1.830 1.835 1.010 1.004 0.164 1.680 1.78 1.021 1.015 0.250 1.520 1.685 1.042 1.025 0.310 1.472 1.630 1.060 1.035 0.410 1.392 1.520 1.088 1.070 0.527 1.30 1.405 1.158 1.147 0.600 .1*231 1.332 1.245 1.230 0.670 1.175 1.256 1.340 1.370 0.729 1.125 1.190 1.497 1.605 0.845 1.071 1.082 2.060 2.230 0;965 1.011 1.006 5.130 4.900 1.000 1.000 1.000 6.700 36 DISCUSSION OF RESULTS A. Benzene-Propanol A plot of the log of the activity coefficients of benzene and propanol gives a reasonably good curve. According to Carlson and Colburn (6) when this so, the system shows some thermodynamic con-sistency. As a further check on consistency, at x = 0.5 the log i 2 curve should f a l l below the log Yj_ curve since the log V 2 curve has a higher end value. A thermodynamic check, on the consistency of the experi-mental values from a theoretical consideration of the Gibbs-Duhem equation showed the theoretical activity coefficients to deviate from the experimental ones. An estimation of the deviation of the values showed an error that ranged from 1% to 17% with the average deviation to be about 10%. Gi l l i l a n d (27) claims an average error of 10% between the experimental and theoretical values of the activity coefficients i s f a i r correlation. A plot of the Margules integration showed no closer correlation so these values have been omitted. The value for the azeotrope of 0.795 mole fraction of benzene in the liquid at 76.2°C. and 740 mm. of pressure for the benzene-propanol system i s in keeping with the value reported by Lecat (4) of 0.791 at 77.1°C. and 760 mm. of pressure. A plot of the vapor-liquid equilibrium compositions gave a smooth curve, as well as the plot of the temperature against the compositions. B. Benzene-Pentanol The benzene-pentanol system showed no tendency toward an azeotrope. The plot of the vapor-liquid equilibrium values gave a. 37 smooth cu r v e as w e l l as t h e t e m p e r a t u r e c o m p o s i t i o n c u r v e . A p l o t o f the l o g o f the a c t i v i t y c o e f f i c i e n t s f o r benzene and p e n t a n o l gave smooth graphs showing thermodynamic c o n s i s t e n c y . The l o g V2 c u r v e f e l l below t h e l o g c u r v e a t x = 0.5 as i t should do. A g a i n , t h e c o r r e l a t i o n o f the t h e o r e t i c a l and e x p e r i -m e n t a l v a l u e s showed an average d e v i a t i o n o f Bfo, the v a l u e s r a n g i n g f r o m l e s s t h a n 1% t o 15%. M a r g u l e s v a l u e s showed no c l o s e r c o r -r e l a t i o n and were o m i t t e d . Van L a a r ( 9 ) based h i s i n t e g r a t i o n o f t h e Gibbs-Duhem e q u a t i o n on t h e thermodynamic changes o c c u r r i n g on the m i x i n g of l i q u i d s . I n d e r i v i n g h i s e q u a t i o n s he made the f o l l o w i n g assump-t i o n s : 1. No change o f e n t r o p y on m i x i n g . j 2. No volume change on m i x i n g . 3. The van d e r W a l l s e q u a t i o n s a p p l y t o each o f t h e components and t o t h e m i x t u r e , b o t h as l i q u i d s and v a p o r s . 4. The van der W a l l s c o n s t a n t s o f the m i x t u r e can be c a l c u l a t e d f r o m the c o n s t a n t s o f pure components. On t h e b a s i s o f h i s d e r i v a t i o n s t h e t h e o r e t i c a l v a l i d i t y o f t h e Van L a a r e q u a t i o n s i s q u e s t i o n a b l e and the q u a n t i t i e s A and B w h i c h were assumed t o be c o n s t a n t i n t h e s e e q u a t i o n s w i l l v a r y somewhat o v e r t h e temperature range i n v o l v e d . Hence the d e v i a t i o n o f t h e e x p e r i m e n t a l and c a l c u l a t e d t h e o r e t i c a l c o e f f i c i e n t i s n o t t o o u n r e a s o n a b l e . EQUILIBRIUM D I A G R A M of BEN z.ENG-n-ALCOHOL SYSTEMS 1 B E . N Z . E N E - M E T H A N O L - TfeO m m . n - E T H A N O L T 5 0 m m . 130) in - PROPANOL - nto m m . T j - BUT A N O L - 7so mm (so) "ST - P E N T A M Q L - 7fco mm. 0.1 O.Z 0.3 0 .4 as o.<b a 7 0 8 X , M O L I F R A C T I O N B E N Z E N E I N L I Q U I D 0.9 l-O 38 . DISCUSSION ON THE BENZENE-n-ALCOHOL SYSTEMS On. F i g . 17 are p l o t t e d the v a p o r - l i q u i d e q u i l i b r i u m c u r v e s f o r the benzene-methanol, b e n z e n e ^ t h a n o l , b e h z e n e - p r o p a n o l , b e n z e n e - b u t a n o l and b e n z e n e - p e n t a n o l systems. The d a t a f o r the benzene-methanol, e t h a n o l , and b u t a n o l systems were t a k e n f r o m t h e l i t e r a t u r e ( 2 9 , 3 0 , 1 0 ) . An e x a m i n a t i o n o f t h e s e c u r v e s shows t h a t t h e f i r s t t h r e e b e n z e n e - a l c o h o l systems cut t h e y = x l i n e and form azeo-t r o p e s , whiba. t h e l a s t two systems m a n i f e s t t h e same g e n e r a l shape of c u r v e somewhat d i s p l a c e d f r o m each o t h e r . A l l the. systems d e v i a t e i n a p o s i t i v e manner f r o m R a o u l t ' s Law. S k o l n i k (31) s a y s t h a t f o u r f a c t o r s c o n t r i b u t e t o such non-i d e a l i t y : i n t e r n a l p r e s s u r e , p o l a r i t y , l e n g t h o f t h e analogous g r o u p s , and a s s o c i a t i o n o f a component, w h i l e Lee (5) says t h a t h eat o f s o l u t i o n and the tendency t o s e p a r a t e i n t o two l a y e r s are c o n t r i b u t i n g f a c t o r s t o n o n - i d e a l i t y . A l l t h e f i v e a l c o h o l s are m i s c i b l e w i t h benzene w i t h m i s c i b i l i t y i n c r e a s i n g as t h e m o l e c u l a r w e i g h t o f t h e a l c o h o l i s i n c r e a s e d , y e t wa t e r w h i c h r e s e m b l e s methanol i n many ways i s o n l y s l i g h t l y m i s c i b l e w i t h benzene. M e t h a n o l may be s a l t e d out from benzene w i t h sodium i o d i d e which shows t h a t t h e degree o f m i s c i b i l i t y o f methanol w i t h benzene v e r g e s on t h a t o f a p a r t i a l l y i m m i s c i b l e system. A p l o t of t h e t o t a l p r e s s u r e o f t h e benzene-methanol vapor p r e s s u r e i s o t h e r m s shows a _ t o t a l p r e s s u r e c u r v e t h a t r e s e m b l e s t h a t o f a p a r t i a l l y i m m i s c i b l e system. I t may be c o n c l u d e d , t h e n , t h a t t h e c o n t r i b u t i n g f a c t o r t o n o n - i d e a l i t y f o r t h e benzene-methanol system i s t h e tendency t o s e p a r a t e i n t o two l a y e r s . T h i s f a c t o r i s l e s s pronounced as the m o l e c u l a r weight of the a l c o h o l i s i n c r e a s e d . E t h a n o l cannot be s a l t e d out f r o m benzene w i t h sodium i o d i d e . Yet the b e n z e n e - e t h a n o l system g i v e s an e q u i l i b r i u m c u r v e t h a t c o u l d be a t t r i b u t e d t o a system showing some i m m i s c i -b i l i t y . Of c o u r s e t h e wide d e v i a t i o n f r o m i d e a l i t y f o r t h e l o w e r benzene a l c o h o l systems may be argued f r o m t h e p o i n t o f v i e w o f the g r e a t d i f f e r e n c e i n p o l a r i t y o f t h e two components. The p o l a r m o l e c u l e s have an a b n o r m a l l y g r e a t a t t r a c t i o n f o r each o t h e r , p r o -d u c i n g g r e a t e r s u r f a c e t e n s i o n , c o h e s i o n , e t c . , and t e n d t o squeeze out n o n - p o l a r m o l e c u l e s f r o m t h e i r m i d s t . As a r e s u l t o f the t e n -dency of a l i q u i d o f h i g h i n t e r n a l p r e s s u r e t o squeeze out a l i q u i d o f l o w i n t e r n a l p r e s s u r e , i t i s e x p e c t e d t h a t t h e p a r t i a l p r e s s u r e would d e v i a t e i n a p o s i t i v e manner f r o m R a o u l t ' s Law. T h i s concept o f a s s o c i a t i o n does not admit any d e f i n i t e p o l y mers l i k e d o u b l e m o l e c u l e s . The p o l a r a f f i n i t i e s a c t w i t h i n the l i q u i d t o f o r m groups o f m o l e c u l e s which become impregnable t o a non-p o l a r m o l e c u l e - l i k e benzene. As t h e l e n g t h o f t h e car b o n c h a i n o f t h e a l c o h o l s i s i n c r e a s e d t h e p o l a r e f f e c t o f t h e OH group i s d e c r e a s e d and f o r systems l i k e b e n z e n e - b u t a n o l and be n z e n e - p e n t a n o l t h e a l c o h o l s would t e n d t o a c t more l i k e s t r a i g h t c h a i n h y d r o c a r b o n s which do not f o r m a z e o t r o p e s w i t h benzene. At a l o w c o n c e n t r a t i o n o f a l c o h o l , m o l e c u l e s a r e s p a r s e l y d i s t r i b u t e d , t o such an e x t e n t t h a t each i s w i t h o u t i n f l u e n c e on t h e o t h e r } hence the a l c o h o l s w i t h benzene would have no r e a s o n t o form an a z e o t r o p e . 40 REFERENCES 1. Othmer, D.F., Ind. Eng. Chem. Anal. Ed., 4, 232 (1932). 2. G i l l e s p i e , D.T.C., Ind. Eng. Chem. Anal. Ed., 7, 349 (1935). 3. Fowler, R.T., J . Soc. Chem. Ind. London, 68, 131 (1949). 4. Lecat, M., "Azeotropisme", B r u s s e l s , Lamertin (1918). 5. .Lee, S.C.., Journal of P h y s i c a l Chem., 35, 3558 (1931). 6. Car l s o n , H.C. and Colburn, A.P., Ind. Eng. Chem., 34, 581 (1942) 7. C l a r k , A.M., Trans. Faraday S o c , 41, 718 (1945). 8. Margules, M., S i t z b e r . Akad. Wiss. Wien. Math, natur. Klassue I I , 104, 1243 (1895). 9.. Laar, J . J . Van, Z. Physik Chem., 72, 723 (1910). 10. Waldichuk, M., M.A. Thesis, U n i v e r s i t y of B r i t i s h Columbia (1950). 11. Wojciechowski, M.^.J.Research Nat. Bureau Stand., 19, 347 (1937) 12. I n t e r n a t i o n a l C r i t i c a l Tables, McGraw-Hill Book Co., 3, 29, 33, 221, 343 (1928). 13. A l l e n , B.B., Lingo, S.P., and F e l s i n g , W.A., J . Phys. Chem., 48, 425 (1928'). 14. "Handbook of Chemistry & P h y s i c s " , 30th ed., P. 2538, Chemical Rubber P u b l i s h i n g Co. 15. Gibbons, L.C., et a l . , J . Am. Chem. S o c , 68, 1130 (1946). 16. Trev, V., and Watkins, M.C., J . Am. Chem. S o c , 152 (1921). 17. Wojciechowski, M.y.J.Research Nat. Bureau Stand., 17, 453 (1936). 18. Brunei, R.F., J . Am. Chem. S o c , 45, 7334 (1923). 19. Denzler, C.G., J . Phy. Chem., 48, 358 (1945). 20. Webb, T.J., and L i n d s l e y , C.H., J . Am. Chem. S o c , 26, 874 (1934). 21. B u t l e r , J.A., Ramchandani, C.N., and Thomson, D.W., J. Chem, S o c , 138, 280 (1935). 22. Timmermans, M.J., J . Chim. Phys., 29, 529 (1932). 23. Simons, I . , B u l l . Soc. Chim. Belg., 38, 47 (1929). 24. S m i t h , A., and M e n z i e s , A.W.C., J . Am. Chem. S o c , 32, 1448 (1910). 25. Gornowski, E . J . , Amick, E.H., and H i x o n , A.N., I n d . Eng. Chem., 39, 1348 (1947). 26. C h e m i c a l E n g i n e e r ' s Handbook, M c G r a w - H i l l Book Co. I n c . (1941). 27. Elements o f F r a c t i o n a l D i s t i l l a t i o n , M c G r a w - H i l l Book Co. (1950). 28. G r a n v i l l e , J.W., and Sage, B.H., Ind. Eng. Chem., 41 , 1272 (1949). ! 2 9 . W i l l i a m s , G.C., and Rosenberg, S., I n d , Eng. Chem. 40, 1273 (1948). 30. I n t e r n a t i o n a l C r i t i c a l T a b l e s , M c G r a w - H i l l Book Co., 3, 313 (1928). 31. S k o l n i k , H., I n d . Eng. Chem., 40, 449 (1948). 

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