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UBC Theses and Dissertations

The surface reaction of chlorine and activated carbon at low pressures Boyd, Alan William 1947

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THE SURFACE REACTION OF CHLORINE AND ACTIVATED CARBON AT LOW PRESSURES  by  A l a n W i l l i a m Boyd  A t h e s i s submitted i n p a r t i a l f u l f i l m e n t of t h e r e q u i r e m e n t s f o r t h e Degree o f MASTER OF ARTS i n t h e Department of CHEMISTRY  The U n i v e r s i t y o f B r i t i s h October 1 9 4 7 .  Columbia  ACKSOWLEDdmjmaT  I w i s h t o thank Dr. M. J . M a r s h a l l , who d i r e c t e d t h i s r e s e a r c h , f o r h i s many s u g g e s t i o n s and h i s h e l p i n b u i l d i n g t h e a p p a r a t u s .  TABLE OF CONTENTS Page 1  I. Introduction I I . Theoretical Considerations  4  I I I . A p p a r a t u s , P r o c e d u r e and C a l i b r a t i o n Data Figure Figure  I  Diagram o f A p p a r a t u s : F a o i n g  6 6  I I C a l i b r a t i o n Curve f o r F i b e r Gauge:  Facing  17. R e s u l t s  12 14  Figure I I I  Isosteres  Figure  17  Isosteres  Figure  7  Figure  71  F i g u r e 711  Facing  Integral 0esorption Isobars D i f f e r e n t i a l Besorption Isobar I D i f f e r e n t i a l Resorption Isobar I I  Figure T i l l D i f f e r e n t i a l  7. D i s c u s s i o n o f R e s u l t s and C o n c l u s i o n s  711. B i b l i o g r a p h y  *  15  "  16  «  17  »  17  "  17  Besorption  Isobar I I I  71. A b s t r a c t  14  18 20  1.  THE SURFACE REACTION OF CHLORINE AND ACTIVATED CARBON AT LOW PRESSURES  I . INTRODUCTION  The purpose o f t h i s b r i e f i n t r o d u c t i o n , w i l l be t o r e v i e w t h e o b s e r v a t i o n s a l r e a d y made on t h e b e h a v i o u r o f c h l o r i n e w i t h c h a r c o a l and t o s t a t e t h e aim o f t h i s i n v e s t i g a t i o n . We might l i s t t h e work done i n t h i s f i e l d under t h e f o l l o w i n g headings; general q u a l i t a t i v e observations,  activation  of c h a r c o a l by c h l o r i n e , h e a t s o f a d s o r p t i o n , f o r m a t i o n o f oarbon. t e t r a c h l o r i d e and q u a n t i t a t i v e measurements o f i s o t h e r m s and i s o b a r s . A l l q u a l i t a t i v e o b s e r v a t i o n s i n d i c a t e t h a t something more t h a n o r d i n a r y p h y s i c a l a d s o r p t i o n i s i n v o l v e d .  Berthelot  IL  and P e t i t , t h e e a r l i e s t i n v e s t i g a t o r s , found t h a t t h e y  could  p r e p a r e p u r e r c h a r c o a l by t r e a t i n g i t w i t h c h l o r i n e and removing  the l a t t e r a t higher temperatures.  M i x t e r found t h a t even  a t r e d heat n o t a l l t h e c h l o r i n e was removed though a l l o f i t came o f f a t w h i t e h e a t .  He b e l i e v e d i t combined w i t h t h e  hydrogen i n t h e c h a r c o a l and came o f f a s hydrogen c h l o r i d e .  2. R a f f , R i m r d t t and Zeumer f o u n d t h a t h e a t i n g o h a r o o a l o h l o r i n e on i t a t 600° - 800° and k e e p i n g  with  the pressure l e s s  t h a n 1 mm* removed v e r y l i t t l e and b o i l i n g w i t h t e n p e r c e n t a l k a l i removed none,  A l e k s e e v s k i and L i k h a r e v ' f o u n d a con-  s i d e r a b l e p a r t o f t h e c h l o r i n e c o u l d n o t be removed by h e a t i n g i n vacuo, b o i l i n g w i t h a l k a l i e s o r e l e c t r i c d i a l y s i s .  Others  who h a d t r o u b l e i n removing o h l o r i n e f r o m o h a r o o a l a r e H e n g l e i n and O r z e n k e w s k i . An i n c r e a s e i n t h e a d s o r p t i v e power o f o h a r o o a l a f t e r treatment  w i t h o h l o r i n e and r e m o v a l o f i t a t h i g h temper-  a t u r e s h a s been found by s e v e r a l w o r k e r s .  Among them a r e  W i n t e r and B a k e r , K l a r and M u l l e r , B o h a r t and Adams and P u t t i and M a g l i f  6  II  Keyes and M a r s h a l l have r e p o r t e d t h e v a l u e o f 32,000 c a l o r i e s p e r mole f o r t h e heat o f a d s o r p t i o n o f o h l o r i n e on o h a r o o a l a t 0° and zero c o n c e n t r a t i o n .  T h i s v a l u e i s seven  t i m e s t h e heat o f v a p o r i z a t i o n o f o h l o r i n e and even B e r t h e l o t and G u n t z * s ^ v a l u e o f 13000 c a l / m o l f o r p r e s s u r e s up t o one atmosphere i s t h r e e times t h e heat o f v a p o r i z a t i o n , Stook c l a i m s t o have formed oarbon t e t r a c h l o r i d e by u s i n g c h a r c o a l and c h l o r i n e a t 400°C and 2.3 atmospheres and 7 H a r r i s working a t t h i s U n i v e r s i t y obtained a l i q u i d whioh b o i l e d w i t h i n a degree o f t h e b o i l i n g p o i n t o f t h i s compound. He u s e d c h a r c o a l and o h l o r i n e a t 360  0  and about one atmosphere  pressure. Isotherms a t r e l a t i v e l y h i g h p r e s s u r e s f o r c h l o r i n e • 2.  and o h a r o o a l have been measured by K l o j * and M u l l e r and Reyersan  and Wishartj and at lower pressures by A r i l ,  The f i r s t found  d i f f e r e n t i a l heats twice that of chlorine on s i l i c a g e l , the second hysteresis i n desorption and the l a s t , that the pressure dropped slowly over a long period,  to Godson working at t h i s University determined desorpt i o n isobars f o r chlorine from charcoal using the low pressure of 5 x 10~2 1200°C.  and r a i s i n g h i s temperature i n steps from 20° to  He found a large amount desorbed at f i r s t then instead  of the amount coming o f f steadily decreasing with r i s i n g temperature, i t rose to a maximum about 1000° and decreased above that. The purpose of this investigation i s to determine desorption isosteres f o r varying amounts of chlorine on charcoal i n the pressure range 10"-5 and from -18?°  to 1200°,  to 10""^ mm,  of mercury  From these isosteres, desorption  isobars and heats of adsorption w i l l be found and from these more l i g h t on the surface reaction of chlorine with oharooal.  4.  I I . THEORETICAL  CONSIDERATIONS PUMtTltHS  I n t h i s i n v e s t i g a t i o n two d i f f e r e n t a d s o r p t i o n ^ a r e d e t e r m i n e d - i s o s t e r e s and i s o b a r s . obtained  The i s o s t e r e s a r e n o t  i n t h e c o n v e n t i o n a l way, t h a t i s by a d d i n g  i n c r e m e n t s o f t h e a d s o r b a t e and f i n d i n g p r e s s u r e  small  and t e m p e r a t u r e  v a l u e s , b u t a r e f o u n d b y a d d i n g a l a r g e amount o f c h l o r i n e , r e a d i n g t h e t e m p e r a t u r e s and p r e s s u r e s  ( o v e r t h e somewhat  l i m i t e d range o f t h e gauge u s e d ) , t h e n removing some c h l o r i n e and f i n d i n g a n o t h e r s e t o f p r e s s u r e ships.  and t e m p e r a t u r e r e l a t i o n -  The I s o b a r s a r e f o u n d d i r e c t l y f r o m t h e i s o s t e r e s . L e t u s f i r s t d i s o u s s t h e i s o b a r s and t h e i r  relation-  s h i p t o t h e n a t u r e o f t h e s u r f a c e r e a c t i o n between c h l o r i n e and c h a r c o a l .  I f c h l o r i n e a d s o r b s on c h a r c o a l i n a p h y s i c a l  way o n l y , t h a t i s i f t h e f o r c e s between t h e c h l o r i n e and c h a r c o a l a r e n o n - s p e c i f i c /then as we r a i s e t h e  temperature,less  and l e s s and o h l o r i n e w i l l be l e f t on t h e s u r f a c e on t h e adsorbent.  I n o t h e r words t h e d e s o r p t i o n  i s o b a r would show a  l a r g e amount of c h l o r i n e coming o f f a t l o w t e m p e r a t u r e s and l e s s and l e s s a t h i g h t e m p e r a t u r e s .  B u t i f any o f t h e o h l o r i n e  forms a c h e m i c a l compound o r compounds w i t h t h e c a r b o n t h e n suoh would n o t be t h e oase - assuming t h a t t h e d e c o m p o s i t i o n t e m p e r a t u r e range o f t h e c a r b o n - o h l o r i n e  oompounds does n o t  c o i n c i d e w i t h t h e range i n w h i c h t h e b u l k o f t h e p h y s i c a l l y adsorbed o h l o r i n e i s e v o l v e d .  I n s t e a d o f l e s s and l e s s  o h l o r i n e coming o f f a s t h e temperature r a i s e d more w i l l be  e v o l v e d a t a h i g h e r temperature  than a lower.  I f t h e desorp-  t i o n i s o b a r shows f o r example, more o h l o r i n e oan be removed at t h e same p r e s s u r e a t 1000® t h a n a t 800* o r more a t 700° t h a n 500° then t h e o h l o r i n e must adsorb  t o some e x t e n t ohemic-  a l l y on t h e o h a r o o a l . 3?he i s o s t e r e s themselves  w i l l show l i t t l e about t h e  n a t u r e o f t h e r e a c t i o n between o h l o r i n e and o h a r o o a l .  But  f r o m them, u s i n g t h e f o l l o w i n g form o f t h e C l a u s i u s - C l a p e y r o n equation,we oan c a l c u l a t e t h e heat o f a d s o r p t i o n ,  What s h o u l d t h e v a l u e o f t h i s f u n c t i o n be f o r a c h e m i c a l r e a c t i o n a t t h e s u r f a c e and what v a l u e s h o u l d i t have f o r purely physioal adsorption?  F o r t h e l a t t e r t h e r e a r e two  v a l u e s w h i o h g i v e an i d e a o f what s h o u l d be e x p e c t e d .  The \2  heat o f c o n d e n s a t i o n o f o h l o r i n e i s 4;420 o a l o r i e s and Magnus r e p o r t s a heat o f 7100  oalories f o r the adsorption of ohlorine  on s i l i c a g e l a t 10°C.  From t h e s e f i g u r e s we might assume any  v a l u e above 1 0 , 0 0 0 c a l o r i e s a t 10°C w o u l d i n d i o a t e a c h e m i c a l reaction taxing place. 2C1  2  + C  —*  The heat o f r e a c t i o n f o r  CCI4 i s g i v e n a s 2^,000  c a l o r i e s a t 20°C b y  B o d e n s t e i n and Gunther b u t s l n o e a l l we know about t h e f o r m u l a o f t h e compound formed i s t h a t i t i s C C 1 X  V  t h i s t e l l s us l i t t l e .  6  I I I . APPARATUS. PROCEDURE AND CALIBRATION DATA  A. APPARATUS The a p p a r a t u s u s e d i s shown i n t h e diagram f a e i n g page 6> •  The McLeod gauge was u s e d f o r o a l i b r a t i n g t h e  q u a r t z f i b e r gauge and r e a d i n g t h e p r e s s u r e s over t h e o h a r o o a l d u r i n g t h e o u t g a s s l n g , and t h e q u a r t z f i b e r gauge u s e d f o r , measuring t h e p r e s s u r e o f t h e o h l o r i n e on t h e o h a r o o a l .  To  s e t t h e f i b e r i n t h i s gauge s w i n g i n g a g l a s s t u b e w i t h i r o n s e a l e d i n i t was p u l l e d from one s i d e t o t h e o t h e r w i t h a magnet.  The time t a k e n f o r t h e f i b e r t o d e c r e a s e  a m p l i t u d e was measured w i t h a m i c r o s c o p e e y e p i e c e and a stopwatch.  to half  with a seale i n the  The q u a r t z b u l b was  specially  c o n s t r u c t e d so t h a t t h e o h l o r i n e w h i o h was c o n t a i n e d i n t h e b u l b B o o u l d be a d m i t t e d t o t h e o e n t r e o f t h e o h a r o o a l .  The  U-tube f o r t h e p o t a s s i u m was f i t t e d w i t h ground g l a s s j o i n t s w h i o h were s e a l e d w i t h P i o e i n , a l o w p r e s s u r e cement,and t h e s t o p c o c k s were g r e a s e d w i t h A p i e z d n i *  To r e d u c e t h e chance  o f a l e a k a l l s t o p c o c k s i n oontaot w i t h t h e c h l o r i n e a t r e l a t i v e l y h i g h p r e s s u r e s were meroury s e a l , vaouum end s t o p cocks.  A p l a t i n u m r e s i s t a n c e f u r n a c e w i t h an alundum c o r e was  u s e d t o h e a t t h e o h a r o o a l and t h e t e m p e r a t u r e  was k e p t a t a  c o n s t a n t v a l u e by a C a p a o i t r o l . T h i s i n s t r u m e n t w h i c h r e g u l a t e d t h e temperature  w i t h i n + 2° has a c a p a c i t y r e l a y  a c t u a t e d b y an e l e c t r o n tube and u t i l i z e s a  chromel-alumel  7. thermocouple. thesis*  The wiring diagram may be found i n my  To f i n d the temperature  B.A.  of the oharooal more accur-  ately another thermocouple i n conjunction with a potentiometer was used.  A single stage mercury d i f f u s i o n pump backed  by a Geneo Hyvao served to outgas the oharooal and to p u l l o f f the ohlorine. Lower temperatures  than 0°C were obtained by  means of l i q u i d oxygen and freezing mixtures of chloroform, ether and toluene.  The l a s t mentioned, but a very e s s e n t i a l  part of the apparatus, was a small nichrome heater to keep the potassium hot enough to react with the chlorine*  B. PROCEDURE AND TECHNIQUES F i r s t the quartz f i b e r gauge was calibrated using the MoLeod gauge and a i r as primary standards.  Mercury vapour  was removed from the gauge by immersing the U-tube below i t i n l i q u i d oxygen.  C a l i b r a t i o n data f o r both gauges i s given  i n the next seotion. Next the oharooal, which was the same as that used by Godson, was outgassed thoroughly at 1100°C.  Actually i t  was outgassed f o r a t o t a l of 81 hours, 44 of them at 1100°• The f i n a l pressure over the oharooal before admission of the ohlorine was 2 x 1 0 m m . at 1000° •  at 1100° and l e s s than 5 x 10"<5mm.  Before the ohlorine was l e t i n a l l mercury vapour  was removed from the bulb and quartz f i b e r gauge by outgassing f o r several hours with the U-tube tetween the pump and the bulb immersed i n l i q u i d oxygen.  The faot that potassium was always  8. i n t h e TT-tube a f t e r t h i s p r e v e n t e d any more mercury v a p o u r g e t t i n g i n t o the o h a r o o a l o r gauge* The c h l o r i n e w h i c h was a d m i t t e d t o t h e o h a r c o a l came from a t a n k s u p p l i e d by t h e C a n a d i a n I n d u s t r i e s L i m i t e d . In  o r d e r t h a t t h e t o t a l amount o f c h l o r i n e g o i n g on t h e ohar-  o o a l m i g h t he known a f i v e hundred m i l l i l i t r e b u l b w i t h a s t o p c o c k was weighed  e v a c u a t e d , weighed, f i l l e d w i t h o h l o r i n e and  a g a i n , and f i n a l l y s e a l e d on t o t h e a p p a r a t u s .  The  o h l o r i n e was f r e e d f r o m w a t e r vapour by c o n t a c t w i t h phosphorus pent o x i d e and from a i r by condensing i t w i t h l i q u i d oxygen and pumping o f f t h e r e s i d u a l  gas.  The o h a r o o a l b e i n g outgassed i t was h e a t t e d t o and t h e o h l o r i n e a d m i t t e d .  Then t h e o h a r o o a l was  1100°  oooled to  560° where i t was k e p t f o r f i v e hours and t h e n down t o - I 8 3 t h e p r e s s u r e went b e l o w 10"^  a t whioh temperature  mm.  To  0  ob-  t a i n d a t a f o r t h e f i r s t i s o s t e r e t h e q u a r t z b u l b and t h e f i b e r gauge were shut o f f from the c h l o r i n e b u l b and t h e  temperature  v a r i e d u n t i l r e a d i n g s w i t h i n t h e l i m i t s o f t h e gauge were o b t a i n e d (10*^  - 10"  2  mm.).  F o r t h e f i r s t i s o s t e r e , i t was  n e c e s s a r y t o use l i q u i d oxygen and f r e e z i n g m i x t u r e s o f c h l o r o form and t o l u e n e . At t h i s p o i n t i t might be w e l l t o d e s c r i b e the U-tube, p o t a s s i u m and a n a l y s i s t e c h n i q u e i n some d e t a i l .  The  potassium  w h i c h was u s e d f o r c o l l e c t i n g t h e o h l o r i n e t a k e n o f f t h e oharo o a l was put i n t h e IT-tube i n t h e form o f s m a l l p e l l e t s e n c l o s e d i n s h o r t l e n g t h s o f 9 o r 10 mm.  glass tubing.  Following a  procedure used by Hughes and P o i n d e x t e r , t h e p o t a s s i u m  was  cleaned, o f most o f t h e o i l , from t h e c o n t a i n e r i n w h i c h i t came, w i t h b e n z e n e t h e n ;  h e a t e d i n a l a r g e t u b e , s e a l e d a t one  end and drawn- down a t t h e o t h e r , u n t i l t h e r e m a i n i n g hydrocarbons were o x i d i z e d and t h e p o t a s s i u m m o l t e n .  Another  s i m i l a r tube and an a p p a r a t u s suoh as t h a t shown, had been p r e p a r e d , and t h e p o t a s s i u m was pjured i n t o t h e o t h e r l a r g e tube and t h e n t h i s  was  q u i c k l y s e a l e d on t o t h e a p p a r a t u s . The p o t a s s i u m was heated and o u t gassed and t h e n m e l t e d and t h e apparatus t i p p e d a l l o w i n g the l o n g tube w i t h t h e c o n s t r i c t i o n s t o be f i l l e d w i t h potassium.  In order to  o b t a i n a charge o f p o t a s s i u m f o r t h e U-tube a f i l e mark was made a t one o f t h e c o n s t r i c t i o n s and the c a p s u l e b r o k e n o f f . T h i s tube was k e p t i n vacuo t o prevent, o x i d a t i o n o f t h e exposed About 10 c a p s u l e s each around 15 mm. one t u b e .  potassium.  l o n g were o b t a i n e d from  Once i n t h e U-tube and s e a l e d onto t h e r e s t of t h e  a p p a r a t u s t h e p o t a s s i u m was o u t g a s s e d and h e a t e d so t h a t i t f l o w e d out o f t h e e a p s u l e and formed a m i r r o r up t h e s i d e s o f t h e U-tube. 1^0  Q  I t was f o u n d n e c e s s a r y t o h e a t i t t o around  - 250°C b e f o r e i t would r e a c t w i t h t h e o h l o r i n e .  amount o f p o t a s s i u m c h l o r i d e formed was f o u n d , by  The  removing  t h e U-tube d i s s o l v i n g t h e c o n t e n t s i n w a t e r and a n a l y s i n g f o r c h l o r i d e , by t h e V b l h a r d method.  10. To r e t u r n t o t h e d e t e r m i n a t i o n o f i s o s t e r e s , i n o r d e r t o o b t a i n a s i g n i f i c a n t number o f , y e t n o t t o o many i s o s t e r e s , i t was d e c i d e d t o t a k e o f f enough c h l o r i n e eaoh t i m e , so t h a t t h e r e would be around 100°  temperature  ence between t h e same p r e s s u r e s on t h e i s o s t e r e s . t h e o h l o r i n e t h e o h a r o o a l was heated around 100°  differ-  To remove h i g h e r than  t h e h i g h e s t temperature a t w h i c h t h e gauge o o u l d be r e a d (9 x 1Q~  2  mm.)  and opened t o t h e TT-tube b u t n o t t o t h e pumps.  A f t e r t h e m a j o r i t y o f t h e o h l o r i n e had r e a c t e d w i t h t h e p o t a s sium and t h e r e was no l o n g e r any danger o f i t g e t t i n g p a s t t h e TT-tube, t h e o h a r c o a l was opened t o t h e pumps, u n t i l t h e p r e s sure became c o n s t a n t o v e r a f i v e t o ten. minute p e r i o d .  This  g e n e r a l l y t o o k about h a l f an hour and t h e p r e s s u r e r e a c h e d about 3 x I Q " . 2  was  I n t h e f i r s t removal o f o h l o r i n e , i t was  condensed out w i t h l i q u i d a i r i n t h e tube T, and t h e n a d m i t t e d t o t h e XT-tube b u t t h i s method was not f o u n d s a t i s f a c t o r y t h e above p r o c e d u r e was used i n a l l t h e o t h e r r u n s .  and  To d e t e r -  mine eaoh i s o s t e r e t h e c h a r c o a l was e o o l e d u n t i l t h e p r e s s u r e went down t o around 10"^ 30 - 30°  and t h e n t h e t e m p e r a t u r e r a i s e d i n  i n t e r v a l s u n t i l t h e p r e s s u r e became 9 x 10~ #  sure r e a d i n g s w e r e o f c o u r s e , t a k e n a t eaoh i n t e r v a l . /  t h e IT-tube was removed, a new moved and a new  Pres-  2  one put i n , more o h l o r i n e r e -  i s o s t e r e found.  reached was l l 8 o ° C .  Then  The h i g h e s t temperature  E x c e p t a t -183?, where t h e p r e s s u r e con-  t i n u e d t o drop f o r 24 h o u r s , e q u i l i b r i u m was an hour a t any g i v e n t e m p e r a t u r e .  reached i n about  11. C. CALIBRATION DATA MoLeod Gauge L a r g e s t R a t i o - 15*00 om. f r o m e t c h e d mark 1.034 x 10~3 S m a l l e s t R a t i o -.93  om. above e t c h e d mark  7*57 * 10"* Volume o f Large B u l b and C a p i l l a r y 316*1 c.c* Average C r o s s S e c t i o n o f C a p i l l a r y ( e x c l u d i n g t i p ) •0361 cm. Q u a r t z F i b e r Gauge. The e q u a t i o n f o r t h e q u a r t z f i b e r gauge i s e » HE log a i a  r— p JM  - b  2  where p i s t h e p r e s s u r e . M t h e m o l e c u l a r w e i g h t o f t h e g a s , t t h e time t a k e n f o r t h e s w i n g i n g f i b e r t o drop f r o m a m p l i t u d e ax t o a m p l i t u d e ag and 0 and b a r e c o n s t a n t s f o r a g i v e n gauge and t e m p e r a t u r e . ~ 2 a  I n o u r case ag was always h a l f a ^ i . e . l o g  was a c o n s t a n t so t h a t i t s i m p l i f i e s t o p j l l = A "t  -  b  The c a l i b r a t i o n c u r v e g i v e n i n F i g u r e I I and t h e t a b l e below were o b t a i n e d a s f o l l o w s .  By u s i n g t h e HcLeod  gauge and a i r , v a l u e s o f p and t were f o u n d o v e r t h e range 7 x 10~-5  t o 1.4 x 10*"  1  mm.  (for air).  To c o n v e r t t h e p r e s s u r e s  f o r a i r t o t h o s e whioh o h l o r i n e would have f o r t h e same v a l u e o f t t h e y were m u l t i p l i e d by  JM jf a  r  JHC1  2  »  J28.96 (70.91  3.38 8.42  Si* fed  \  J  *  \  <  $  \*  12. Then these converted pressures now covering the range 4 x 10"*^ to 9 x 10  were plotted against the r e c i p r o c a l of t .  Two  d i f f e r e n t scales were used f o r convenience and accuracy.  To  f i n d pressures f o r whioh t i s greater than one minute take i t s r e c i p r o c a l and read d i r e c t l y o f f Figure I I and to f i n d pressures f o r which t i s l e s s than 60 seconds read o f f the following table.  These pressures w i l l be of course f o r ohlorine.  The values of the constants A and b may be found from the slope and the intercepts of the l i n e i n Figure I I . The equation f o r the gauge used here i s p JM~= 7.^3  -  3,8b* x 10'  4  where t i s the time taken to drop to h a l f amplitude! Values of the pressure f o r chlorine f o r values of t from 1 - 6 0 t  p x 10"?  seconds.  t  p x 10"-  t  5  p x 10  1  91  16  3.8  31  3.0  2  43  17  5.4  32  2.9  3  30  18  5  33  2.8  4  24  19  4.8  34  2.7  3  18  20  4.6  33  2.6  6  13  21  4.4  37  2.5  7  13  22  4.2  38  2.4  8  11  4.0  39  2.3  9  10  24  3.8  42  2.2  10  9  23  3.7  45  2.1  11  8  26  3.6  48  2.0  13. t  p x 10*3  12  t  p x 10^  t  p x 1Q-3  7.5  27  3.4  50  1.9  7  28  3.5  53  1.8  14  6.5  29  3.2  56  1.7  15  6  30  3.1  59  1.6  13  •  Weight of the oharooal i n vacuo  19.90 grams.  1  1  ?  <?  .  > i  <i K  \ *  . Y  <  . 1  c  14.  0  IV. RESULTS  The following table ^ i v e s a l l the data obtained i n the run, as w e l l as values f o r the heat of adsorption calculated from the isosteres using the Clausius-CTapeyron  equation.  To obtain these values ol A K the logs of the pressure values were plotted against the reciprocals of the corresponding absolute temperatures f o r each isostere, and the slope of the curve,thus obtained, (taken at the oentre of the straight l i n e portion of the curve) found. Figures I I I and IV.  These curves are shown i n  In the oase of isostere Ho. 6 since there  was no straight l i n e portion, no attempt was made to calculate A H. y refers to the amount of ohlorine on the oharooal f o r a given isostere, and x refers to the amount of chlorine removed from the charcoal p r i o r to a given i s o s t e r e .  Both are given  i n micromeles of ohlorine per gram of charcoal. No.  i 2  y_  x  876  603  T°G  -183 -98° -82° -64° 271  P-mm.  533  73.5  i<r£  5 6 9 2  x 10" x 10"? x 10"  -47° 0° 30° . 76° 96 118°  3 1.8 8 2.4 4.5 9  x x x x x  0° 29° 37° 79° 113° 133°  8 1.7 7.8 3.2 2.4 9  x x x x x  0  0  3  A H-oalories  x  2390 o -183 o to -64  1  x 10"^ 10"|  lO'*  10~ 10"  7830 -47°o to 118 e  2  2  1(T  2  x 10~2 10"; 10"* 10"^ 10" 10~ 2  2  10,600 0° to 133'  15. Ho. 4  P-mm.  371  162  9 X 10-5 1.9 x 10" 1.7 X 10-3 X 10" 3 X 10 -1 1  14,100 at 81° 21,400 , at 179°  133° 208° 263° 313° 132° 232° 303; 357° 455°  3.2 X 10 4 1.26x 8 X l l 9 X 10  24,300 at 288°  257°  1.3 7.7 2.2 8 9  61°  81°  121°  179° 200°  5  6  7  232  193  173  13?  39  20  462° 565 616° 0  164  9.5  360° 512° 612° 720° 749°  133  8.43  464°  612°  710° 802° 881°  10  144  11.2  606° 846° 916°  978° 1017° 11  134  9.9  AH-oalorie8  759°  998°  1043° 1099° 1130°  4  2  :  1  9 1.6 3.4 7.5 9  X X X X X X X X X X X  6.3 2.1 2.4 9 3.1 6.8 1.6 7 9 4.5 8 6.8 5 2.4 9 3 3.8 3.2 7 2.4 9  X X X X X X X X X X X X X X X X X X X X X  0  2  10-2 10-3 1010-4 10-* 10"? 2  icrf  10  11,300 257* to 365'  2  10io;4 10 10 10 -2  26,900 612° to 720°  10-  50,200 at 802°  4  I 2  4  10-J  10-3 io-3 1010-5 10-5 lO' 10-3 2  4  J  68,300 600* to 1017°  1Q  10  2  10lo;3 10-3 lO" 10" 4  2  2  57.500 900° to 1100°  16. Ho.  y  12  122  x  T°C  12.3  P-mm.  897° 990° 1095° 1175°  . 4.5 x 7.6 x 6 x 2.4 x  H-oalories  10"* 10" 10"*  73,500 a t 1000°  4  IO"  2  13  107  15.4  1015° 1112° 1178°  1.5 x 1 0 " 2.1 x 10*3 6.5 x 10-3  82,300 1000° t o 1180°  14  101  5.6  1020° 1123° 1178°  1.2 x 1 0 " 1.24x 10-3 3.2 x 10-3  72,000 1000° to 1180°  4  4  From t h e s e i s o s t e r e s i n t e g r a l d e s o r p t i o n i s o b a r s were obtained.  T h i s was done by p l o t t i n g t h e i s o s t e r e s (°C a g a i n s t  l o g p) and r e a d i n g o f f t h e t e m p e r a t u r e s on t h e d i f f e r e n t i s o s t e r e s f o r t h e same p r e s s u r e .  Three d i f f e r e n t  pressures  were u s e d and t h u s t h r e e d e s o r p t i o n i s o b a r s o b t a i n e d .  The  p r e s s u r e 3 x 10"* was u s e d by Godson and t h e p r e s s u r e 4.1 x 10" by m y s e l f i n my B.A. t h e s i s . oomparison p u r p o s e s .  These t h r e e i n t e g r a l d e s o r p t i o n i s o b a r s  a r e p l o t t e d i n F i g u r e V. differential  The o t h e r p r e s s u r e was u s e d f o r  By t a k i n g t h e s l o p e s o f t h e s e  d e s o r p t i o n i s o b a r s were o b t a i n e d .  three  These a r e shown  i n F i g u r e s 71 - T i l l and t h e v a l u e s f o r t h e i n t e g r a l and differential  c u r v e s a r e g i v e n i n t a b u l a r f o r m below,  x refers  t o t h e amount removed i n mieromales p e r gram,j£x t o t h e t o t a l amount o f o h l o r i n e removed and dx/dT t o t h e s l o p e o f t h e i n t e g r a l curve a t t h a t p o i n t .  I  /  l  1  $  1 \  \l  L  \ \ \  & •  A /\  /  i  /  §  14  /  '  \  i  '  V$ /  /j ,_  —^^S  «  >>  —  —'  —  —  L  • •  v s,  <a  <  2  > /  W —  ^  °/ /> X  N  ,  Q p>  N* i.  -  it • I V  /  /  /  «  ^ «l  i  u:  k  \, •  /  •  : .  SI-  /  suss  7  0  fcl-  o  '•  (  .1  i  1  •  —  >  v  -Jfi/*  ,  Table f o r Figure TI T°C -2 38° 92° 170° 205° 330° 475° 513° 825° 910° 960° 1050° 1075° U  Pressure = 4,1 x 10*"  4  X  271 73.5 162 139 39 20  I'*  8.5 11 10 12.3 15.4 5.6  Ex  X  40° 80° 130° 225° 295" 480° 640° 750° 900° 995° 511055° 1125° 1170° u  271 73.5 162 139 39 20  I' 8.5  5  11 10 12.3 15.4 5.6  Table f o r Figure T i l l T°C 120 155° 200° w  460° 620° 750 885° 1020° 1135°  X  271 73.5 162 139 39 20  0  8.5 11 10  dx/4T 1.285 3.00 2.44 1.66 .93 .102 .120 .14 .07 .15 .194 .222 .192  Pressure • 3 x 10*3  Table f o r Figure T i l T°C  Ex 271 344.5 506.3 646.5 684.5 704.5 714 722.5 733.5 743.5 755.5 770.5 776  271 344.5 506.5 646.5 684.5 704.5 714 722.5 733.5 743.5 755.5 770.5 776  mm.  dx/dT  1.46 2.80 2.50 1.03 .216 .0741 .0655 .0824 .082 .152 .211 .15 .104  Pressure = 1 x 10 Ex 271 344.5 506.5 646.5 684.5 704.5 714 722.5 733.5 743.5  mm.  dx/dT  6.83 1.55 .595 .192 0O875  .0705 .067 .100 .0595  mm.  18. The broken l i n e on Figure VI i s the one obtained i n my B . A , thesis and the broken l i n e on Figure VII was obtained by Godson.  V. DISCUSSION OF RESULTS AMD CONCLUSIONS OF  The value s/\the heat of adsorption obtained from the isosteres are i n many oases quite inaccurate and only the most general sort of conclusions can be drawn from them.  The small  values obtained i n the f i r s t three isotherms are probably due to the fact that true equilibrium was not established. The large values a t high temperatures though, would seem to i n d i cate three things.  F i r s t ohlorine does react chemically with  the surface of oharooal at low pressures.  Second that the heat  of adsorption increases with decreasing conoentration and f i n a l l y t h i s heat increases with increasing temperature. The three d i f f e r e n t i a l desorption isobars obtained a l l indicate that the bulk of the p h y s i c a l l y adsorbed chlorine comes o f f i n the range 40° - 160°C and that the optimum temperature f o r desorption of the ohemioal surface complex i s  1050°.  The q u a l i t a t i v e agreement of these r e s u l t s with Godson's  would seem to indicate that l i t t l e doubt oan be held regarding the chemical reaction of ohlorine with the surface of activated carbon.  1?. The extreme s t a b i l i t y of t h i s compound i s shown by the fact that some chlorine i s s t i l l on the charcoal a f t e r the pressure has been reduced to 3 x 10*3 at 1 1 8 0 ° ,  Just how  much i s impossible to say f o r although the t o t a l amount of ohlorine i n i t i a l l y put on the•oharooal was known, some of the ohlorine may have oome o f f as a earbon complex or even carbon tetrachloride and may not have been picked up by the potassium.  20.  71. ABSTRACT  The nature of the surface reaction of chlorine with activated carbon was investigated i n the following way,  A  measured amount of ohlorine was admitted to outgassed oharooal and pressure and temperature readings taken over the pressure range 10"* - 10" mm. 2  Chlorine was removed i n increments u n t i l  a series of isosteres were obtained i n the temperature range -183° to 1180°C.  Prom these functions desorption isobars and  heats of adsorption were calculated.  Conclusions were drawn  from the values of these as to the nature of the surface reaction of the chlorine and activated carbon.  711. BIBLIOGRAPHY 1. Alekseevski and Likharetf; J.Gen.Chem.(USSR) 12,306-19(1942) 2. A r i l , K.; Bull.Inst.Phys.Chem.Research (Tokyo) 19,148-59 (1940) 3 . Berthelot and Guntz; C ampt.Rend 99, 1 (1884) Ann.Chim.Phys.(7l) 7,138  (1886)  4. Berthelot and P e t i t ; Ann.Chim.Phys. (7),18,80(1889) 5 . Bodenstein and Gunther; Tr.Am.Elee.Chem.Soc. 17,717, (1938) 6. Bahart, C S . and Adams E.Q,.; J.Am.Chem.Soc. 42,533-44 (1920) 7. Harris, I. Thesis, Univ. of B r i t . C o l . 8 . Henglein, F.A. and Grzenkowski, M.; Z.Angewond.Chem. 38, 1186  (1925)  9. Hughes, A.U. and Peindexter, F.E. Phil.Mag. 5 0 , 423-439(1925) 10. Godsan, W.L.; Thesis, Univ. of B r i t . C o l . 11. Keyes, F.G. and Marshall, M.J.; J.Am.Chem.Soo. 49,156-73 (1927) 12. Klar, R. and Muller, A; Z, physik Chem. 169,297-304 (1934) 13. Magnus, A.; Z. physik.Chem. Abt.A. 142,401 (1929) 14. Mixter; Am.Jour.Soi. (3) 45, 363 (1893) 15. P u t t i , A. and Magli, Rend.Aocad.Sci.(Napali) 14,(3) 68-74 (1908) 16. Reyersan, L.H. and Wishart, A.W.; J.Phys.Chem. 42,679-85 (1938) 17. Ruff, 0 . , .Rimratt, E. and Zeumer, H.; K o l l o i d Z. 37 270-4 (1925) 18. Stock; Z. f u r Anorg.Chem. 195, 149-57 (1931) 19 • Winter, R.M. and Baker, H.B.; J . Chem.Soo. 117,  319-20 (1920)  

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