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The photochemical and thermal oxidation of hydrogen sulphide Tse, Ronald Siu-Man 1962

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THE  PHOTOCHEMICAL AND  THERMAL  OXIDATION OF  HYDROGEN SULPHIDE  by  RONALD STU-MAN TSE B.A.Sc, University  o f Toronto,  195$  A THESIS SUBMITTED I N PARTIAL FULFILMENT OF THE  REQUIREMENTS FOR THE DEGREE OF  MASTER OF SCIENCE in  t h e Department of CHEMISTRY  We a c c e p t t h i s required  THE  thesis  as conforming  to the  standard  UNIVERSITY OF BRITISH September, 1 9 6 2  COLUMBIA  In presenting  t h i s thesis i n p a r t i a l f u l f i l m e n t of  the r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y  of  B r i t i s h Columbia, I agree t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and for extensive  study.  I f u r t h e r agree t h a t p e r m i s s i o n  c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may  g r a n t e d by the Head o f my  Department o r by h i s  be  representatives.  I t i s understood t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n  Department The U n i v e r s i t y o f B r i t i s h Vancouver 8, Canada. Date  Columbia,  permission.  ii  ABSTRACT  In order t o ^ e l u c i d a t e the mechanism of hydrogen s u l p h i d e o x i d a t i o n , the p h o t o - o x i d a t i o n and thermal o x i d a t i o n of hydrogen s u l p h i d e were s t u d i e d , u s i n g gas chromatography f o r the a n a l y s i s of f i n a l  products.  P h o t o - o x i d a t i o n was s t u d i e d a t 130° and 150°C.  Products  found were sulphur d i o x i d e , hydrogen, water and s u l p h u r . P r o d u c t i o n o f sulphur d i o x i d e was found t o be i n h i b i t e d an i n c r e a s e i n s u r f a c e a r e a .  by  Whether i n photo- o r thermal  o x i d a t i o n , the y i e l d of sulphur d i o x i d e • i n c r e a s e d d r a s t i c a l l y with s l i g h t observed  i n c r e a s e s i n (C^J/fH^S) r a t i o .  T h i s was a l s o  i n the y i e l d o f hydrogen i n p h o t o - o x i d a t i o n .  Thermal  o x i d a t i o n was s t u d i e d at 160°, 170°, 190°, 210°, 225°, and 260°C.  240°,  Products were sulphur d i o x i d e , water, and s u l p h u r .  No hydrogen was found. sulphur d i o x i d e was  An e x p r e s s i o n f o r the p r o d u c t i o n of  obtained:  — 2 -  =  k(H S)~ — 1  9  + 1  (0 ) . 3  ?  4t The o v e r a l l  activation  energy was found to be  21.2±2k.cal./mole.  Comparison w i t h p r e v i o u s l y r e p o r t e d works was made and a mechanism proposed.  iii  A C KNOWLED GEME NT  I wish to express my sincere gratitude and thanks to Professor C.A. McDowell f o r his generous encouragement, supervision and enlightening discussions throughout the course of the work.  I am grateful to the University of B r i t i s h Columbia f o r Teaching Assistantships during the 1959-60, 1960-61, and 1961-62 sessions.  F i n a l l y , I wish to thank the glassblowing, electronic and mechanical workshop s t a f f f o r t h e i r assistance i n the construction of the apparatus.  iv  CONTENTS  1  INTRODUCTION APPARATUS 1.  Vacuum System  7 13  2. Gas Chromatographic System .3. Thermal C o n d u c t i v i t y C e l l  19  4. Mercury Arc  21  5. O p t i c a l Bench  23  6. Photometer a) P h o t o c e l l  24  b) O p e r a t i o n  24  c) Photometric Measurements  29  d) A c t i n o m e t r y  30  7. Furnace5  33  8. Thermocouple  Circuit  33  MATERIAL 1.  Hydrogen  sulphide  3$  2. Oxygen  39  3. Carbon d i o x i d e  39  4.  40  Sulphur d i o x i d e  5. L i g h t f i l t e r  solutions  40  EXPERIMENTAL PROCEDURE 1.  P h o t o l y s i s and p y r o l y s i s of H S alone 2  42  2. P h o t o l y s i s and p y r o l y s i s o f H S w i t h COg as an i n e r t gas  44  3. Bhoto- and Thermal o x i d a t i o n o f H^S  44  2  4. Photo- and Thermal o x i d a t i o n of H^S with CO2 as an i n e r t gas  46  V  RESULTS 1. Photo-oxidation  4#  2. Thermal Oxidation  54  DISCUSSIONS 1. Photo-oxidation  76  2. Thermal Oxidation  78  REFERENCES  84  APPENDIX  36  INTRODUCTION  - 1-  There have been many i n v e s t i g a t i o n s on the o x i d a t i o n of  hydrogen s u l p h i d e by oxygen.  In each o f these  inves-  t i g a t i o n s , a c e r t a i n s p e c i a l aspect o f the r e a c t i o n was s t u d i e d , but no e f f o r t has been made t o c o r r e l a t e these o b s e r v a t i o n s as a whole. the thermal ratios.  Thompson and K e l l a n d  studied  o x i d a t i o n a t f a i r l y high p r e s s u r e s and C^tH^S  The a c t i v a t i o n energy was estimated  range 13-20 k.cal./mole.  The Russian  t o be i n the  group of Emanuel,  1-13 Semenov et a l  has made e x t e n s i v e s t u d i e s on the thermal  o x i d a t i o n o f hydrogen s u l p h i d e by oxygen.  Their  investi-  g a t i o n s were c a r r i e d out a t the temperature around 270° C but they d i d not analyse t h e i r products beyond t a k i n g the a b s o r p t i o n spectrum o f the i n t e r m e d i a t e f i n a l product  S02*  They based most of t h e i r study on the  measurement o f pressure The  changes.  r e s u l t s o f Emanuel et a l are n i c e l y summarised 9  o  i n Semenov s paper . T  At 270  C and an i n i t i a l pressure o f  100 mm. Hg maximum r e a c t i o n r a t e was reached conversion. The  (SO) and o f the  50% conversion was reached  intermediate  at 18-20%  a f t e r two minutes.  SO was i d e n t i f i e d by comparing the ab-  s o r p t i o n spectrum of the intermediate with t h a t o f SO obtained by Schenk/^.  SO was found o 9  temperature f a l l s below 300  C. .  to d i m e r i s e when the Some f u r t h e r study has  been made by Emanuel e t a l on t h i s d i m e r i s a t i o n by meas u r i n g the pressure  c o n t r a c t i o n on cooling"*""*".  They a l s o  -  2 -  found^ t h a t a t 270° C there was an i n d u c t i o n p e r i o d f o r the H S 2  and 0  2  reaction.  During t h i s i n d u c t i o n  period,  which l a s t e d about 20 seconds, o n l y SO was formed. was formed subsequently.  A f t e r 40 seconds the  was found t o be  2  80% H S  —*.  S0  2  conversion  SO  20% H S  S0  2  2  9 Semenov  the  proposed the f o l l o w i n g mechanism, based on 1-13 r e s u l t s o f Emanuel et a l : -  Primary  HgS  +  Chain  S  +  Propagation  0 Chain Branching  —•*  °2  ^  ° 9it  H0  +  SO  SO  +  0'  - 0.8 k . c a l .  +  S  +45  2  HS  —•>  H  —*"  so  2  SO  +  °2  S  -ff-  wall  2°  k.cal.  0  2  Termination :•'  0  wall  Negative i n t e r a c t i o n step SO  +  SO  +  2S0  °2  2  The l a s t step was used t o e x p l a i n the f a c t that maximum r e a c t i o n r a t e occurred  a t 20%  conversion.  N o r r i s h and h i s c o l l a b o r a t o r s s t u d i e d the mechanism of hydrogen s u l p h i d e and  combustion w i t h f l a s h  k i n e t i c spectroscopy ^'  .  An i n i t i a l  photolysis SH  absorption  spectrum was observed which g r a d u a l l y disappeared. disappearance occurred  The  much f a s t e r i n the presence of 0 . 2  In the presence of a l a r g e excess of i n e r t gas, S 0 formed i n a very small amount and S 0 2  2  2  was  was the f i n a l p r o -  - 3 -  d u c t w h i c h was s t a b l e e v e n a t h i g h t e m p e r a t u r e s . inert  g a s was n o t a d d e d , OH s p e c t r u m  appearance and  o f t h e SH s p e c t r u m .  SgOg was a l w a y s  the s p e c t r a o f S 0 2  absent.  These a u t h o r s proposed Initiation  2  irradiation  product both  disappeared temporarily.  the following  mechanism:  :  H S  +  hv  — -  SH  +  H  H  +  H S  —*.  SH  +  H  2  on t h e d i s -  was t h e f i n a l  2  On f l a s h  and o f S 0  2  S0  appeared  When  2  In t h e presence of  a large  (1)  (2)  2  excess of  inert gas, chain  termination :  Flash  SH  +  °2  —»  SO  +  OH  (3)  OH  +  SH  —»  SO  +  H  2  (4)  SO  +  SO  —  irradiation of S  2°2  SO  +  hv  +  SO  S  S  (5)  2°2  2°2  +  SO  —  S  (6)  SO  (5)  2°2  In t h e absence o f i n e r t gas Chain  propagation  SH  +  0  OH  +  H S  2  2  —P. S0 —•»  2  SH  (3)  +  0  +  H 0  +  0  (7)  2  Chain-branching so  +•  o  0  +  H S  so  2  2  2  ~*-0H  C h a i n t e r m i n a t i o n and l i g h t SO  +  0  —*•  +  (g)  SH  (9)  emission  SO*—*. S 0  2  +  hv  (10)  - 4 -  Flash  irradiation  of  S0  2  +  hv  S0  2  +  S0  SO  +  0  0  +  SO  2  S0  2  —  S0 *  —-  SO  (11)  2  S0  2  2  so  +  SO  +  0  slow photochemical  and  oxygen h a v e been s t u d i e d  0  (12)  2  (8)  2  (10)  2  The s l o w p h o t o - d e c o m p o s i t i o n the  +  of hydrogen  s u l p h i d e and  r e a c t i o n between h y d r o g e n  by Darwent and K r a s n a n s k y  18  sulphide  by Darwent a n d R o b e r t s  , respectively.  17  and  By gas b u r e t t e  17 methods, Darwent and R o b e r t s The quantum  yield  was  essentially  independent  analysed o n l y the H  produced.  2  shown t o be c l o s e t o u n i t y and t o be o f temperature,  light  intensity.  found  t o be h e t e r o g e n e o u s  p r e s s u r e , and  The t h e r m a l d e c o m p o s i t i o n r e a c t i o n a t low temperatures  homogeneous o f t h e s e c o n d o r d e r a t 650° C. observed  o f SF^.  The f o l l o w i n g mechanism was  and became  No d e c r e a s e i n  i n t h e p h o t o l y s i s o f E^S  r a t e was  was  i n large  postulated  excess  by D a r -  17 went and R o b e r t s  :  HS  +  hv  •—•»  H  H  +  HS  --4*-  H  —»»  HS +  S  (3)  H  2  +  S  (4)  H  2  +  S  2  2  2HS H  +  HS  2HS Reactions was  —v (1) and  + 2  HS  • +  2  (2) a r e w e l l  f o u n d t o be t h e r m o n e u t r a l .  HS  (2)  (5)  2  established. Reactions  u s e d t o e x p l a i n t h e quantum y i e l d Moreover, r e a c t i o n  (1)  Reaction  (4) and  (3)  (5) were  being bigger than  unity.  (5) c o u l d e x p l a i n t h e o b s e r v a t i o n o f  S  0  - 5 -  bands i n p h o t o c h e m i c a l l y  d e c o m p o s i n g ,H S made b y P o r t e r  19  2  20  and  b y Ramsay  .  The t h e r m a l  Darwent and R o b e r t s 2H S  2H  +  2  S  In studying the photochemical  2  r e a c t i o n o f hydrogen 18  s u l p h i d e w i t h o x y g e n , Darwent and K r a s n a n s k y only f o rH  and used gas b u r e t t e methods.  2  by  as : — .  2  r e a c t i o n was c o n s i d e r e d  analysed  They c o r r e l a t e d  X + HX + H t h e i r r e s u l t s u s i n g t h e f o l2l o w i n g p o s t u l a t e d m e c h a n i s m H  H  °2  H 0  2*  H 0  2*  H 0  2*  +  2*  H 0  M °2  The t h e r m o d y n a m i c a l l y HS  +  0  HS  +  H0  2  H  +  H0  2  H  +  —  HO,  +  M  —•  H  +  20  favourable H  2  H —*>  :-  2  °2  2  reactions +  S0  2  +  S0  2  20H  were f o u n d t o d i s a g r e e w i t h e x p e r i m e n t a l  data. 1-13  It not  should  be n o t e d  t h a t E m a n u e l , Semenov e t a l  did  a t t e m p t t o measure any p o s s i b l e p r o d u c t i o n o f h y d r o 16  gen.  The Z e e l e n b e r g  paths;  proposal  b u t m e a s u r e m e n t s were o n l y made b y k i n e t i c 17  troscopy. H 0 2  included nearly a l l possible  Darwent e t a l  spec-  1$  '  practically  ignored the S0  2  and  produced. Formation  o f s u l p h u r has o n l y been mentioned by  Darwent and K r a s n a n s k y  x o  and h a s n o t been t a k e n  into  account  - 6-  by o t h e r w o r k e r s . mentioned  S u l p h u r was o b s e r v e d  authors as a r e s u l t  or i t s o x i d a t i o n .  Moreover,  o f decomposition  o f H^S  i t h a s l o n g b e e n known t h a t  when H^S a n d SO^ a r e b r o u g h t j  by t h e a f o r e -  together, sulphur i s deposi-  21  ted.  Another  r e a c t i o n which  between hydrogen  i s of interest  and s u l p h u r .  i s t h e one  T h i s r e a c t i o n has been  22 shown t o be m a i n l y h e t e r o g e n e o u s t o have a n a c t i v a t i o n e n e r g y modynamically The late  o f 26 k . c a l .  and t h u s  p r e s e n t i n v e s t i g a t i o n was made i n o r d e r t o c o r r e -  a l l t h e p r e v i o u s d a t a and t o p r e s e n t a  attempt  ther-  favourable.  mechanism f o r t h e p h o t o c h e m i c a l  system  complete  o f HgS a n d Og.  was made t o s t u d y t h e s l o w p h o t o c h e m i c a l  oxidation  o f hydrogen  a clarified  reaction.  An  and t h e r m a l  sulphide, a n a l y s i n g a l l the products  by g a s c h r o m a t o g r a p h y . give  a t low temperatures,  picture  I t was hoped t h a t t h e r e s u l t s o f t h e mechanism o f t h i s  would  complex  APPARATUS  The  Vacuum System  The  vacuum system ( f i g . 1 ) was of c o n v e n t i o n a l  design  with m o d i f i c a t i o n i n order t o avoid mercury i n the sample line.  The t r a p s between the d i f f u s i o n pump and stopcock F  were normally immersed i n l i q u i d n i t r o g e n so that any mercury vapour from the d i f f u s i o n pump, the McLeod Gauge and  the Toepler  cold traps.  pump could be c o l l e c t e d between these  These t r a p s were removable f o r c l e a n i n g .  Whenever stopcock Y i n the sample l i n e was open, the c o l d t r a p preceeding stopcock A, i n the sampling system was immersed i n l i q u i d n i t r o g e n .  One exception  t o t h i s opera-  t i o n was when SO^ was passed through Y i n t o the gas b u r e t t e In such a case, Y would be open f o r o n l y f r a c t i o n s o f a second. sample  Thus v i r t u a l l y no mercury vapour could enter t h e line.  The  vacuum system was c o n s t r u c t e d  w i t h the e x c e p t i o n fused  with pyrex g l a s s  of the r e a c t i o n c e l l , which was made o f  quartz w i t h o p t i c a l l y plane end windows.  The mechani  cal  pump was a Welch No. 1400,  "Duo S e a l " two- oil pump.  The  d i f f u s i o n pump was homemade but of u s u a l design.  A  The  t r a p between the d i f f u s i o n and mechanical pumps was used t o c o l l e c t and d r a i n bounced o f f mercury drops.  The main  vacuum l i n e was 22 m i l l i m e t r e s i n diameter and the sample l i n e 12 m i l l i m e t r e s .  The l e a d t o the s p i r a l gauge was o f  2 m i l l i m e t r e s c a p i l l a r y and those from the c e l l gas  chromotograph system were a l s o c a p i l l a r y  t o the  tubing.  To  gas  chromafograph  00  11"  ch no ma+ograph  IB"  3*t CC  IS  fig-, i.  Main Vacuum  System  - 9  -  S t o p c o c k s were g e n e r a l l y l u b r i c a t e d w i t h A p i e z o n L g r e a s e . Those c l o s e t o t h e f u r n a c e were l u b r i c a t e d w i t h A p i e z o n N grease.  I t was f o u n d u n n e c e s s a r y t o u s e h i g h  grease.  In t h i s  at  temperature  s y s t e m a vacuum o f 10 ^ m i l l i m e t r e  t h e M c L e o d gauge c o u l d r e a d i l y be o b t a i n e d .  charge o f the T e s l e r c o i l  was e a s i l y r e a c h e d  e x c e p t i n t h e s p i r a l gauge  leads.  The t o t a l v o l u m e was 148 c c .  e n c l o s e d i n p y r e x was p l a c e d i n s i d e w h i l e a Scientific  Dark d i s -  elsewhere  The m i x i n g v e s s e l was made o u t f r o m a 125 Erlenmeyer f l a s k .  Hg  millilitre A magnet  Precision  Co. "Mag-mix" was p l a c e d u n d e r t h e f l a s k .  speed o f s t i r r i n g  c o u l d be c o n t r o l l e d on t h e  The  "Mag-mix".  The s p i r a l gauge had a s e n s i t i v i t y o f 0.840 m i l l i metres  on t h e s c a l e / l m i l l i m e t r e Hg and c o u l d w i t h s t a n d  1 a t m o s p h e r e on b o t h s i d e s .  The c a l i b r a t i o n c u r v e f o r t h e  s p i r a l gauge i s shown on f i g . w i t h a s m a l l e r range fragile. spiral  2.  More s e n s i t i v e  h a d been t r i e d  spirals  b u t f o u n d t o be t o o  I t was p o s s i b l e t o r e a d 0.5 m i l l i m e t r e o n t h e  gauge  scale.  O p t i c a l l y p l a n e w i n d o w s were f u s e d t o t h e e n d s o f the  unpacked quartz c e l l .  The i n t e r n a l m e a s u r e m e n t s were  100 m i l l i m e t r e s i n l e n g t h and 37 m i l l i m e t r e s i n d i a m e t e r . The v o l u m e was 107.5 cc,-. to  the c e l l  and t h e dead volume i n t h e l e a d  was 3.5 c c c .  The i n t e r n a l d i m e n s i o n s o f t h e p a c k e d millimetres  cell  was  100  i n l e n g t h a n d 28 m i l l i m e t r e s i n d i a m e t e r .  It  was p a c k e d w i t h 100 q u a r t z r o d s o f 83 m i l l i m e t r e s l o n g and  - 11 -  2  millimetres  i n diameter.  The  free  volume was 3 5 . 4  The dead volume i n t h e l e a d was 3 . 6 cc.:. volume r a t i o the  was 4 * 3 e x c l u d i n g  ccx;.  The s u r f a c e t o  d e a d s p a c e and 4 . 5 i n c l u d i n g  d e a d volume. Referring to the admission  matograph  (fig.3  system o f t h e gas chro-  ) t h e volume o f t h e g a s b u r e t t e  I t was f o u n d t h a t a f t e r 3 o p e r a t i o n s 94% o f t h e m a t e r i a l ferred  of the Toepler  i n the reaction c e l l  t o t h e gas b u r e t t e .  volume o f t h e sample l i n e , R,S,T,U,V,W, was 109.5  was  28.7ccc.  pump,  c o u l d be t r a n s -  I t was a l s o f o u n d t h a t t h e defined  by s t o p c o c k s N,0,P,Q,  ccc.; t h e volume d e f i n e d  by V,X,Y  5 . 6 c c c ; t h a t d e f i n e d by Y,Z,AA,A' was 20.4 c f t c ; t h e volume d e f i n e d  by C ' J D ^ E ' J F  1  was 4.3  ccc  was  13  -  The Gas Chromatographic  -  system  The gas chromatographic  system i s r e p r e s e n t e d i n  f i g . 3 « From the rotameter onwards, i t was c o n s t r u c t e d w i t h pyrex. first  C a r r i e r gas from commercial  c y l i n d e r s was  reduced to 20 p . s . i . g . before e n t e r i n g a Matheson  pancake type low p r e s s u r e r e g u l a t o r i n which the p r e s s u r e was  f u r t h u r reduced to 5 p . s . i . g . f o r helium and 9 p . s . i . g .  for  nitrogen.  Trap 3 was u s u a l l y immersed i n d r y i c e t o  c o l l e c t any water from the c y l i n d e r s . G 9 1 4 2 B manufactured  by the Monostat  A rotometer (No. Corp., New York)  p l a c e d between the low p r e s s u r e r e g u l a t o r and the t h e r mal c o n d u c t i v i t y c e l l , was used to i n d i c a t e the f l o w . The thermal c o n d u c t i v i t y c e l l was i d e n t i c a l w i t h the 23  one designed by Ryce, Kebarle and Bryce  .  The only  d i f f e r e n c e was t h a t the f i l a m e n t s were a p a i r of matched tungsten c o i l s o f 20Aeach made by Gow-mac Instrument Co., Madison,  N.J. I t was found t h a t t h e tungsten f i l a m e n t s  were even more s t a b l e and more s e n s i t i v e than platinum filaments.  The c e l l b l o c k was wrapped with h e a t i n g tape  and p l a c e d i n an i n s u l a t e d can. about 40°C.  Temperature  was kept a t  The c e l l b l o c k i t s e l f was grounded.  - 14 -  The gas b u r e t t e was made of 15 m i l l i m e t r e s t u b i n g to  ensure quick m i x i n g .  metres  i n diameter.  The leads were u s u a l l y & m i l l i -  The l e a d from the columns t o the  thermal c o n d u c t i v i t y c e l l were wrapped w i t h h e a t i n g t a p e . The chromatographic and No.  feet long.  columns were made o f 6 m i l l i m e t e r s t u b i n g These were connected t o the system  12 b a l l j o i n t s , l u b r i c a t e d w i t h Apiezon L grease o r  s i l i c o n e grease a c c o r d i n g t o temperature. the  through  chromatographic  Temperature o f  columns was c o n t r o l l e d by h e a t i n g c o i l s  p l a c e d i n s i d e a l a r g e g l a s s tube.  An even l a r g e r  tube f i t t e d over the f i r s t one p r o v i d i n g adequate tion.  glass insula-  Ends o f t h i s d o u b l e - l a y e r tube were plugged with  g l a s s wool t o prevent c o n v e c t i o n . A few chromatographic packing materials had been t r i e d , namely, s i l i c a  Gel, Perkin-Elmer Column W m a t e r i a l , T.C.P.  on C e l i t e 545, a c t i v a t e d c h a r c o a l , and P-0190 on a c i d washed chromosorb manufactured p o r a t i o n , Wilmington,'Delaware. silica  by F & M S c i e n t i f i c  Cor-  At room temperature,  g e l separated v e r y w e l l R^S from 0^ but p o o r l y  H^S from SOg..  I t a l s o i r r e v e r s i b l y absorbed H^O. The  Perkin-Elmer m a t e r i a l was supposed t o give  symmetric  peaks f o r p o l a r m a t e r i a l s such as HgO but i t s s e n s i t i v i t y was  lower than t h a t o f the F. & M. m a t e r i a l .  Celite  T.C.P. on  545 would be good i n s e p a r a t i n g organo-sulphur com-  24 pounds ^ but d i d not g i v e a good H 0 peak. 9  In t h i s i n -  — 15 —  HS 2  O  z  Time Column : F i  M  P-OI90.  Temperature  :  90°C.  C a r r i e r gas-. He  -*  Time  Column: B. D.H. activated charcoal, 5 0 - 2 0 0 mesh. Temperature : Room. C a r r i e r gas : N  fig.  4  2  -Inv e s t i g a t i o n the u s e f u l property of the T.C.P. m a t e r i a l  was  not needed. A f t e r a few t r i a l s , the F. &. M Corp. P-0190 m a t e r i a l with helium c a r r i e r gas was used to analyse SOg and Operating temperature was 5.05  centimetres  HgO.  set at about 90°C, f l o w rate at 32.0  of the rotameter equivalent to  ml./minutes, and pressure at 5 p . s . i . g .  Under these con-  d i t i o n s hydrogen could be separated from oxygen and oxygen peak u s u a l l y overlapped the H^S and HgO  peaks were f a r separated  peaks, ( f i g . 4 ) .  peak.  from the H^S  the  The and  With a chart speed of 30 inches  SOg 0^ per  hour, Og appeared at IS m i l l i m e t r e s , HgS at 25 m i l l i m e t r e s , SOg  at 23 centimetres.  at 56 m i l l i m e t r e s , and HgO  t a i l f o r the HgO  peak was  considerable.  The  The  sensitivity  _5  of a n a l y s i s  was  1.095  x 10  gm.  mole of 30^ i n the  packed c e l l per square inch on the recorder chart.  unIt  2  was p o s s i b l e to measure to 0.01 dency of HgO  inches .  Due  to the t e n -  adhering t o the w a l l s of tubings, the  b r a t i o n f o r HgO  cali-  i n t h i s column was not c o n s i s t e n t .  the value was about 3.28  x 10"^ gm.  But  mole i n the unpacked  c e l l per square inch on the recorder  chart.  The a c t i v a t e d charcoal used to analyse hydrogen with nitrogen as c a r r i e r gas was 50-200 mesh.  B.D.H. AR grade charcoal of  The optimum operating conditions were found  to be the f o l l o w i n g : pressure= 9 p . s . i . g . ; temperature^ room temperature, but column i n i n s u l a t i n g enclosure the F. & M. P-0190 column; flow rate= 4.0  centimetres  as on  - 17  the  r o t a m e t e r , e q u i v a l e n t t o 9.8  Higher temperature would  charcoal.  columns  s e n s i t i v i t y o f 4.88  10 the  —4  gm.  The  —4  x 10"  6  gm.  gm.  mole/inches  —6 x 10" gm.  mole/inches  mole/inches  l o n g c o l u m n was  2  The  size  2  f o r oxygen.  u s u a l l y used.  2  of  85  l o n g column  mole/inches 2  sen-  relatively high  w e r e f o u n d s u i t a b l e , one  l o n g and t h e o t h e r 5 f e e t l o n g .  h a d 6.99  per minute.  n e e d e d due t o t h e f i n e p a r t i c l e  Two  a n d l . 7 2 5 x 10  millilitres  s p e e d up t h e s e p a r a t i o n b u t  s i t i v i t y would drop c o n s i d e r a b l y . p r e s s u r e was  -  feet  gave a  f o r hydrogen  f o r oxygen.  The  f o r hydrogen  and 2.87  For better  short  one x  sensitivity,  W i t h t h e same r e c o r d e r  c h a r t s p e e d o f 30 i n c h e s p e r h o u r , h y d r o g e n  appeared oxygen  at  37 m i l l i m e t r e s ,  H e l i u m a t 34 m i l l i m e t r e s and  at  91 m i l l i m e t r e s .  H y d r o g e n and h e l i u m p e a k s o v e r l a p p e d e a c h  o t h e r , b u t i n any r u n , t h e h e l i u m f r o m a p r e v i o u s a n a l y s i s c o m p l e t e l y d r i v e n out by t h e n i t r o g e n c a r r i e r gas b e f o r e a n y h y d r o g e n was  admitted to the  system.  was  0 . 4 7 - A w. w.  I % w.w.  _ iso-a 2S0-0. • k-n.  5oo-fl.  loojiw.w. "FINE"  "X"  20 -a  l O O A . KA/.W.  sw  fig. 5  Thermal  Circuit Diagram  Conductivity  Cel  for  lOJL I % u/.iv.  - 19  -  Thermal C o n d u c t i v i t y C e l l D e t e c t o r  Fig. cuit  5 i s a schematic  f o r the  tographic  thermal  system.  System  diagram of the  : -  electrical  c o n d u c t i v i t y d e t e c t o r of the  The  m a t c h e d 20-&.  tungsten  gas  composed o f a p a i r o f p r e c i s i o n ,  constant  10-ft. w i r e - w o u n d r e s i s t o r s and  c o n t r o l purposes.  6 v o l t s D.C.  used to unbalance the  circuit  r a n g e o f i n e q u i l i b r i u m c o u l d be o f a 1 0 0 S L and  w e r e made up parallel,  the  the  "COARSE" c o n t r o l .  the  base l i n e  the  chart.  of the  In place and on  0.47-**. W.W.  controlled.The  resistor enough  controls  variable resistor  " F I N E " c o n t r o l and  in  the  place  recorder.  Various  potentials could  This multiple switch provided  0 , 1 , 2 , 4 , 1 0 , 2 0 , 5 0 , 1 0 0 , 2 0 0 , 4 0 0 and  b e i n g t h e most s e n s i t i v e .  Chart  on  w i r e wound r e s i s t o r s w e r e m o u n t e d  The  800,  r e c o r d e r used  a Leeds & N o r t h r o p S e r i e s 60000 type w i t h a range o f m.v.  l-O.  o f t h e g a l v a n o m e t e r , a number o f 1% p r e c i s i o n  of s e n s i t i v i t y l a s t one  The  for  was  recorder at a d e s i r a b l e p o s i t i o n  a multiple,switch plate. to the  other r e s i s t o r s  T h e s e c o n t r o l s were u s e d t o  temperature constant  taken  other  temperature  so t h a t a w i d e  a 1SL  100-ft. b e i n g t h e  The  f r o m an a c c u m u l a t o r  u s u a l l y a p p l i e d across the b r i d g e . was  chroma-  filaments  formed h a l f of a c o n v e n t i o n a l Wheatstone b r i d g e . h a l f "was  cir-  s p e e d was  s e t a t 30  inches/hour.  be steps the was 0-10  - 21 -  The Mercury Arc The lamp ( f i g . 6) used f o r p h o t o l y s e s was a U-shaped Hanovia D - 8 8 A - 4 5 low pressure mercury a r c . 9U% o f the i n t e n s i t y was the unreversed was  Approximately  2537A°.  No f i l t e r  necessary. The a r c was put i n s i d e a t u b u l a r h o u s i n g .  A hole  o f about 1 centimetre i n diameter allowed the l i g h t t o pass  i n t o the o p t i c a l system.  The s i z e of t h i s hole could  be v a r i e d by r o t a t i n g a d i s c i n which there were a s e t of h o l e s of v a r i o u s lamp housing.  s i z e and which covered the hole on the  The lamp was so a l i g n e d t h a t t h i s h o l e and  the two limbs o f t h e U-shaped a r c were l i n e a r to a l l o w maximum emitted i n t e n s i t y i n t h i s  direction.  In o r d e r t o keep the lamp temperature 2537A  0  low f o r maximum  r a d i a t i o n , the lamp housing was wrapped w i t h  t u b i n g i n which c o l d water was passed.  copper  Cold a i r was blown  from the bottom of the lamp housing and was allowed t o escape mainly from the top. was  In such an arrangement, t h e r e  a danger o f mercury condensing  around the area oppo-  s i t e the opening t o the o p t i c a l system.  To prevent  this,  a small amount o f hot a i r was blown through a j e t d i r e c t l y at t h i s a r e a . letting  Flow r a t e of c o l d water was r e g u l a t e d by  f r e e f l o w from a can p l a c e d a t a constant h e i g h t .  Power supply t o the lamp t e r m i n a l s was through a Sorensen  voltage r e g u l a t o r .  arrangement, approximately  With the above mentioned  0 . 5 % s t a b i l i t y over a few hours  —  —  0 0 0 0 0 0  c c c 0 0  fig.  22  I- o 0  o o  ^  Aperture  L o w Pressure Hg Arc  G  6  o 0 0 0  ^ Hot- a i r 0  0  o  0 0  0 0 0  g—Cooling  8  Hanovia  D - 8 8 A - 4 5  water with  Housing  compressed air  Medium P r e s s u r e H g A r c  Hanovia  wi+h  SH-100  Housing  Aperture  fig.  7  - 23 -  was always obtained.  I t was found that i n t e n s i t y  greatly  depended on the temperature of the mercury a r c . In the p r e l i m i n a r y experiments, r a d i a t i o n of 3130 A° was t r i e d .  For t h i s wave length, a Hanovia SH 100 U-shaped  high pressure mercury a r c was used. lamp i s shown i n f i g . 7.  The housing f o r t h i s  Cold a i r was blown from the  bottom of the housing t o keep the lamp and environment from excess heat. A f i l t e r combination f o r 3130 A described by Kasha 25a and by Hunt & Davis 25b was used i n 0  y  conjunction with t h i s lamp. The O p t i c a l Bench F i g . S shows s c h e m a t i c a l l y the arrangement of the o p t i c a l bench.  Radiation from the mercury lamp was c o l i -  mated by two plano-convex lenses.  The f i r s t one, w i t h a  f o c a l length of 7.5 centimetres was placed 11.0 centimetres from the opening i n the lamp housing.  The second one,  mounted on the furnace, was 23.55 centimetres from the f i r s t one. The f o c a l l e n g t h of t h i s second lens was 10.0 centimetres.  The l i g h t beam was thus made approximately  p a r a l l e l . . Another plano-convex lens of 7.5 centimetres f o c a l length was placed at the other end of the furnace and focussed the beam t o a p h o t o c e l l .  When f i l t e r s were  used, they were placed on a stand immediately behind the f i r s t lens.  A s h u t t e r , made o f aluminum sheet and operated  by manually l i f t i n g i t , was mounted on t h i s stand. The  -  The w h o l e  optical  s h e e t s a n d was  The  f.,_.  circuit  9 a)  Cintel  Photocell.  It  was  intensity  relative  of  quartz  light  to  also  be  the  photometer  shone  vs.  aluminum  on i t .  wavelength  of  with this  :ic  at  Operation.  The  photocell  current  with  applied  the by  the  and the  1 x  to  10~ The  resistor  voltage any  of  tapped  values-  An  S^.  circuit  from the  between  the  A  0  U.V. to  representing radiation  No.  was  passed voltage  r ' . '•-  935  circuit,  photocell  but  very  the  poor.  through was  opposing  the  tapped  v o i a g e was  consisting  decades R 5-12.  of  B^ w a s  potentiometer  0 and 2V w i t h a n  difference  between  the  c h a i n R 1-4  and the  opposing  was  value  second  voltage  for  the  The  variation.  applied  to  triode The  the unit  output  of  voltage  normally was  ad-  accuracy  tapped  voltage  double  compensated the  from  from  triode  the  the  amplifier  for  then  battery  volts.  k  potentiometer 7.  dual  2537  required  switch  potentiometer  series  2V a n d t h e justable  selector  British  incident  photometer  i n f i g . 9.  proportional  ."'..•-.-'„!.  photocell  and the  a  of  this  R\-k  shown  II'. rj:-  chain  was  A curve  of  resistor  is  designed  an output  1 0 . a.-;.J r:::  used  used  envelope  give  \':  sensitivity  of  of  shown on f i g .  could  off  in thin  tight.  The p h o t o c e l l  claimed  sensitivity  }:::•.-!  b)  enclosed  light  diagram  QVA 3 9 w i t h a  range.  is  almost  was  Photometer  The  the  system  -  24  supply  a m p l i f i e r was  then  f.g. 8  The  Optical  Bench  — 26  —  S.c  R-, ~  Accumulator B  120v. h . t . b a t t e r y  9  R  14  G  C a l variometer  S.C.  Standard  Cell  1  R  5!* h . s . c . l w .  16  f  R,  1 . 5'"': h . s . c . l w .  17  l  18  f  19 20  15  v  500k  h.s.c  1u w.  R.  150k h . s . c . Iv;.  1L  R  10k d u a l  decade  R  lk  decade  •+  , 5 ,o  c  R7 R  •, 100 9,10 ^1.1 "i ? N  n  dual dual  decade  dual  decade  f i g . .9.  21  "22  23 R 24 R, 25  R  2.5k  w.w.  pot.  2k  w.w.  pot,.  5CK  w.w.  lw.  50k  w.w.  lw.  2.2k w.w.  1w.  IM  |w.  100k. w.w. 33k w.w.  lw. lw.  10k. w.w.  lw.  3.3k  w.w.  1w.  1k  w. w.  1 w.  330  w.w.  lw.  10k w.w.  PHOTOMETER CIRCUIT  lw.  150  -  Relative  IOO  fig.io.  Spectral Sensitivity  f-  50 U  3 0 0 0  50OO  40OO.  Wavelength  in A  6 0 O O  of  Oprical Density  - 29 -  fed into the galvanometer G v i a the altenuator R-^  The  galvanometer used was a.Rubicon Catalogue No. 3402 and had a s e n s i t i v i t y of 0.046mA./mm. d e l f e c t i o n .  The high  tension of the unit was derived from a 120 V. battery. Filament current of the value 6SC7 was supplied by a 6v accumulator  f o r maximum s t a b i l i t y ,  c)Photometric measurements. In the actual apparatus, switches Sg.  and  and the  switch f o r the filament current were mounted on a single 4-deeked switch.  S-^ was set at the 4 p o s i t i o n .  was  u s u a l l y set at p o s i t i o n 3« In order to operate the photometer, the instrument was turned on by closing the main switch and was allowed to warm up f o r r about 15 minutes. With no l i g h t f a l l i n g on the photocell and the dualdecade potentiometer reading zero, the dark current from the photocell was balanced by adjusting R-^ and R-^ f o r zero galvanometer current.  The c i r c u i t must be rebalanced  f o r each position of the selector switch S-^. was then closed, thus applying a standard voltage across the r e s i s t o r chain R-^ ^.  The potentiometer voltage  was then increased u n t i l the galvanometer showed zero deflection and the potentiometer reading taken. t i o n was carried out to ensure that voltage.  This opera-  gave a constant  The standard c e l l used was a SRIC miniature  Eppley standard c e l l manufactured by the Sensitive Research Instrument  Corporation, New Rochelle, N.Y.  t h i s standard c e l l was 1.0192 volts at 25°C.  The e.m.f. of  -  30  -  Sg was then opened and l i g h t was allowed to f a l l on the p h o t o c e l l . galvanometer  The potentiometer was adjusted so that the  showed zero d e f l e c t i o n and the potentiometer  reading taken.  Assuming t h a t the p h o t o c e l l c h a r a c t e r i s t i c  was l i n e a r , t h i s potentiometer readingwas p r o p o r t i o n a l to the l i g h t i n t e n s i t y . This u n i t was used to monitor the amount of l i g h t passing the r e a c t i o n c e l l , both when empty and when f i l l e d . d) Actinometry A potassium f e r i o x a l a t e actinometer was used according 29 to Hatchard and Parker . (1) C a l i b r a t i o n f o r Ferrous Ion. Four ml of the standardized 0.1M  Ferrous sulphate  s o l u t i o n was d i l u t e d to 500 ml w i t h 0.1N The r e s u l t i n g s o l u t i o n contained 0.8 x 10 per c c .  sulphuric acid. -6 moles Fe  Next, 0,1,2,4, and 6 ml a l i q u o t s of t h i s s o l u t i o n  were added to i n d i v i d u a l 50 ml volumetric f l a s k s . cient volume of 0.1N  A suffi-  s u l p h u r i c acid was then added to each  f l a s k to make the t o t a l volume of a c i d equal to 25 ml. Five ml of the 0.1% 1:10 phenanthroline s o l u t i o n and 12.5  ml  of the b u f f e r solution(600 ml of IN sodium acetate and 360 ml IN s u l p h u r i c a c i d d i l u t e d to 1 l i t r e . ) were then added to each f l a s k .  The fasks were d i l u t e d to volume with  d i s t i l l e d water and allowed to stand f o r  g hour.  At the  end of t h i s time, the o p t i c a l d e n s i t i e s of the developed s o l u t i o n s were measured at 510 m spectrophotometer.  on a Unicam Sp.  600  A p l o t of the r e s u l t i n g o p t i c a l densi-  t i e s against the f e r r o u s ion concentration i s shown i n f i g . 12.  Heating coils  To vacuum  Thermocouple  Insulation  0 0 0 0 0 0 0 0 "  Lens  Reaction Procelain  To optical  fig.13  bench  Furnace  cell  1  - 32 -  (2) C a l i b r a t i o n ' o f Photometer Both t h e lamp and photometer were warmed up. An i n t e n s i t y r e a d i n g was made by the photometer. was  then r e p l a c e d by a 1 cm. t h i c k quartz c e l l o f about  10 ml c a p a c i t y c o n t a i n i n g standard potassium solution.  ferrioxalate  T h i s c e l l was covered with b l a c k tape  the windown f a c i n g the o r i g i n o f l i g h t . i r r a d i a t e d f o r about s i x hours. was  The p h o t o c e l l  except  T h i s s o l u t i o n was  At t h i s time  the p h o t o c e l l  r e p l a c e d and another r e a d i n g of l i g h t i n t e n s i t y  From the i n i t i a l and f i n a l  r e a d i n g s , an average  taken.  value was  obtained. A f t e r i r r a d i a t i o n , the actinometer s o l u t i o n was t r a n s f e r r e d t o a 50 ml r e d coloured f l a s k and 5 ml o f the phenanthroline were added.  s o l u t i o n and 5 ml o f the b u f f e r s o l u t i o n  The volume was then made up t o 50 ml with  dis-  t i l l e d water and t h e f l a s k was allowed to stand f o r g hour. T h i s o p t i c a l d e n s i t y o f the r e s u l t i n g s o l u t i o n was then measured on the U n i c a l a t a wavelength o f 510 m\L  . The  r e s u l t i n g o p t i c a l d e n s i t y was then converted t o micro moles o f f e r r o u s MI produced.  The above procedure was  c a r r i e d out i n d u p l i c a t e and blanks were run a l o n g with each d e t e r m i n a t i o n . This c a l i b r a t i o n produced  a value o f 6.13 x 10"*"^  -12 quanta per ohm-second o r 6.11 x 10  feinsteins  per Ohm-  -12 minute f o r the No. 935 phototube and 2.42 x 10 per Ohm-minute f o r t h e QVA 39  phototube.  ieinsteins  -  The  3 3  -  Furnace  F i g . 1 3 shows schematic diagram o f the f u r n a c e arrangement.  The furnace b l o c k i t s e l f was a h o l l o w por-  c e l a i n c y l i n d e r o f 5 . 5 cm i n t e r n a l diameter.  On the o u t s i d e  of t h i s c y l i n d e r were grooves over which c o i l e d elements were around.  heating  The b l o c k was s p l i t t r a v e r s e l y i n  i t s c e n t r e t o f a c i l i t a t e easy removal o f t h e r e a c t i o n The h e a t i n g c o i l s were made o f nichrome w i r e s .  The room  temperature r e s i s t a n c e o f each h a l f was about 28-£L . furnace b l o c k r e s t e d on asbestos and V e r m i c u l i t e m a t e r i a l which  cell.  This  insulation  i n t u r n was put i n s i d e a r e c t a n g u l a r metal  box w i t h c i r c u l a r openings on each end over wiich p l a n o convex l e n s e s were mounted.  Glass wool was used as i n s u -  l a t i o n over the f u r n a c e b l o c k .  An aluminum sheet formed  the cover o f the e x t e r n a l metal box. maintain  I t was found easy t o  * 0.5°C a t 150°C over a p e r i o d o f a few hours  w i t h a v a r i a c s e t t i n g o f about 30V a p p l i e d t o each h a l f o f the f u r n a c e h e a t i n g c o i l s .  The thermocouple t i p was glued  to the r e a c t i o n v e s s e l with G. E . G l y p t a l cement.  The whole  f u r n a c e b l o c k was mounted on standard o p t i c a l bench e q u i p ment and p l a c e d i n the o p t i c a l path as p r e v i o u s l y d e s c r i b e d i n the s e c t i o n on the O p t i c a l Thermocouple  system.  Circuit  Temperature  measurements were made w i t h copper-  eonstantan thermocouples.  A common c o l d j u n c t i o n was  p l a c e d i n a s l u s h o f i c e and water i n a Dewar f l a s k .  To  F r o m cylinder  S|  Mercury  Cold t r a p  ..fig. 14  Gas  admission  system  for  oxygen  on v a c u u m line  - 35 -  E.M.F. measurements were made w i t h a Rubicon Type S potentiometer with a homemade chassis of c o n t r o l s as shown i n f i g . 15. In t h i s potentiometer, two ranges were provided namely, 0-1.6 v o l t s and 0-16 m i l l i v o l t s .  Each range was  coveredby two measuring d i a l s , the f i r s t of which was composed of a 16 p o s i t i o n switch c o n t r o l l i n g 15 f i x e d • 10-0. standard r e s i s t o r s , and the second of which was comprised of a 14-inch s l i d e wire with 200 d i v i s i o n s .  On  the upper range, 15 increments of 0.1 v o l t each were developed across the f i r s t d i a l r e s i s t o r s , the s l i d e wire affording  continuous v a r i a t i o n throughout a t 0.1 v o l t  i n t e r v a l s w i t h 0 . 0 0 0 5 vilt each.  On the lower range, the  corresponding values were 1/100 of the foregoing,  Thus  i t was p o s s i b l e t o measure down t o 0.001 of a m i l l i v o l t . C a l i b r a t i o n of the potentiometer was made by s e t t i n g switch $2 t o the standard c e l l p o s i t i o n and c l o s i n g S-^. Range connection was made t o 1.6 v o l t and d i a l s A and B were set t o the standard c e l l value.  Key k-^ was tapped and the  "COARSE" and "FINE" r e s i s t o r s were adjusted t o give a zero galvanometer readings calibration.  was then tapped f o r a f i n e r  To make thermocouple e.m.f. measurement,  the switch S was set t o the E.M.F. p o s i t i o n and the range 2  connection was made t o the 0.016 v. t e r m i n a l .  Having  p r e v i o u s l y connvected a l l the cold sides of the thermocouples to the t e r m i n a l marked " - ", the s e l e c t o r switch was then set t o the +  t e r m i n a l of the thermocouples i n question.  K-, was tapped and d i a l s A and B on the potentiometer ad-  — 56^—  Rixbicon  Type S  Potentiometer  "Fine" loo-a Control  *ig. is  Thermocouple  Box  Potentiom+er  Circuit  - 37 -  j u s t e d t o give a zero galvanometer r e a d i n g . tapped t o give a  Then Kg was  more a c c u r a t e r e a d i n g .  Values o f e.m.f. v s . temperature was taken from 26  the Handbook o f P h y s i c s and Chemistry, the 41st  edition  No a c t u a l c a l i b r a t i o n was done s i n c e temperature measurements were made t o + 0 . 5 ° C  MATERIAL  - 38 -  Hydrogen  Sulphide  H y d r o g e n S u l p h i d e was d e r s by M a t h e s o n Co. was  Only  obtained from CP  g r a d e was  commercial  available.  The  gas  s u b j e c t e d t o p u r i f i c a t i o n as f o l l o w s :  A needle  v a l v e was  bing with system.  a BIO The  fitted  come was  tygon  gas was  twice  tubing.  Having  along the  in a  filled  away any  filled  any  cylinder,  and  gauge.  2 was- immersed  Stopcock and  M was  t r a p 1 was  gas  in liquid  again evacuated.  a l l stopcocks  liquid  Ng  and  2,  w i t h the  4  bulb-to-bulb d i s t i l l a t i o n s  warm s i d e i n a d r y  T h i s was  cold  ice-acetone  was Trap HgS. was  side i n  were p e r f o r m e d .  A f t e r b u l b - t o - b u l b d i s t i l l a t i o n , no  Usually The  c o n t a i n e d a s m a l l amount o f a i r a s  amount o f i m p u r i t y was  distillation.  3  the  slosh.  impurity.  originally  was  inten-  distillation  d r i e d HgS  t h e HgS  by  cylinder  originally  g e l and  trap 1  evacuated.  Bulb t o bulb  between t r a p s 1 and  silical  tygon  n i t r o g e n f r e e z i n g out a l l the  performed  using  the  i n the  storage bulb  closed, the warmed and  gently then  M,N,S, & U,  The  vacuum  T h i s was;.--  acetohe.  water vapour.  by  and  L.  undesired  c l o s e d except  i n the  t o a b o u t 1 afc.ni. p r e s s u r e , m o n i t o r e d  disconnected,  such  Sg  a $ygon t u -  w i t h HgS  stopcock  s l u s h o f d r y i c e and  was  3 was  to socket  system evacuated  sample l i n e  t o t r a p out  Bulb  the  c y l i n d e r and  v a l v e on t h e  to d r i v e  ded  spiral  joined  pumped away by o p e n i n g  repeated  cooled  to the  t u b i n g was  r e l e a s i n g the needle  of  cylin-  found  by  chromatographic  F & M P-0190 c o l u m n s . filled  was  observable  left after  analysis,  Usually only g such  bulb-to  bulb  - 39 -  Oxygen  Oxygen was  o b t a i n e d from commercial c y l i n d e r s manu-  f a c t u r e d by A i r c o . The  I t was  found to be remarkably  pure.  apparatus used f o r f i l l i n g oxygen i n both storage bulb  i s shown i n f i g . 1 4 . The in  vacuum system was  the sample l i n e  s p i r a l t r a p was filling  evacuated  and a l l stopcocks  c l o s e d except L and K.  The p o r t a b l e  immersed i n a dry ice-acetone s l o s h .  system was  f l u s h e d with oxygen.  Trap 1 was  The immersed  i n a d r y ice-acetone slosh,' and t r a p 2 i n l i q u i d n i t r o g e n . Stopcock  K was  c l o s e d and M opened.  L i q u i d oxygen was  thus  condensed i n t r a p 2.  The p r e s s u r e i n the p o r t a b l e t r a p  system was  above atmospheric,  maintained  vapour could creep i n t o the system. i n d i c a t e d by the mercury l e v e l  so t h a t no water  T h i s pressure  was  i n the T tube.  A f t e r enough oxygen had been condensed i n t rap 2, stopcock M & L were c l o s e d , K opened and the c y l i n d e r the p o r t a b l e t r a p system d i s c o n n e c t e d . evacuated,  After trap 1  bulb to bulb d i s t i l l a t i o n was  Storage bulb 2 was  finally filled  t o r e d by the s p i r a l gauge.  moni-  oxygen was  by the chromatography with molecular s i e v e s No. F & M P-0190 columns but no observable  was  performed.  to about 1 atm.,  The p u r i f i e d  and  analysed  5 and  i m p u r i t y was  det§gtid.  Carbon Dioxide  "Bone d r y " carbon-dioxide was  o b t a i n e d from  manufactured by the Matheson Company.  The  cylinders  same f i l l i n g  and  - 40 -  p u r i f i c a t i o n t e c h n i q u e s was e m p l o y e d a s i n t h e c a s e gen.  f o r oxy-  The F & M P-0190 c o l u m n was u s e d t o a n a l y s e f o r  purity. Sulphur  No d e t e c t a b l e amount o f i m p u r i t y was  found.  Dioxide  M a t h e s o n " a n h y d r o u s " s u l p h u r d i o x i d e i n c y l i n d e r was used f o r c a l i b r a t i o n o f the chromatographic  chart  areas.  S i n c e a s m a l l amount o f i m p u r i t y w o u l d n o t a l t e r t h e r e s u l t s a p p r e c i a b l y , t h e g a s was u s e d w i t h o u t  further puri-  fication. Light F i l t e r  Solutions  F o r r a d i a t i o n a t 3 1 3 0 A , a H a n o v i a SH 1 0 0 lamp i n 0  combination was  used.  Kasha  25a  This f i l t e r  0  Potassium  s o l u t i o n s and a g l a s s  combination  and b y Hunt & D a v i s  a b o u t 200 A a.  with 2 light f i l t e r  25b  was recommended b y  t o i s o l a t e a wave band o f  width. Hydrogen P h t h a l a t e .  0.500 gm. o f A.R. p o t a s s i u m  p h t h a l a t e was d i s s o l v e d  i n w a t e r a n d made up t o 250 m l . was  u s e d i n a 1 em. t h i c k  This concentration  quartz f i l t e r  cell.  s o l u t i o n was n o t s t a b l e t o p h o t o l y s i s . necessary  a n d change  i n the f i l t e r o c c a s i o n a l l y .  Chromate  0.246 gm. o f A.R. p o t a s s i u m  Chromate was d i s s o l v e d i n  w a t e r t o make up 500 m l . o f s o l u t i o n . in  This  I t was  t o s t o r e the s t o c k i n the dark  the s o l u t i o n b. P o t a s s i u m  filter  a 1 em. t h i c k  quartz f i l t e r  cell.  T h i s was u s e d  T h i s s o l u t i o n was q u i t e  - 41 -  stable c.  Glass  to  photolysis,  Filter  A 2 mm. t h i c k with  the  C o r n i n g 9863 f i l t e r w a s  above-mentioned  filter  used  solutions.  in  series  EXPERIMENTAL PROCEDURE  - 42 -  Experimental Procedure  At the b e g i n n i n g o f each experiment, the vacuum system was  evacuated so t h a t a dark d i s c h a r g e was o b t a i n e d i n t h e  sample l i n e near the r e a c t i o n v e s s e l .  The lamp and the photo-  meter were allowed to warm up f o r a t l e a s t f i f t e e n The gas chromatographic  minutes.  system was allowed a t l e a s t t h i r t y  minutes f o r e q u i l i b r i u m to be reached.  The f u r n a c e was  never turned o f f except f o r r e p a i r s and f o r removal o f the reaction c e l l .  Most o f t h e photochemical experiments were  made a t 150°C with a few at lower temperatures and a few at  160°C.  1. P h o t o l y s i s  and p y r o l y s i s o f HgS alone...  Transmitted i n t e n s i t y I« was measured when the r e a c t i o n c e l l was empty.  The s p i r a l gauge s c a l e r e a d i n g f o r an empty  sample l i n e was taken.  Then with the l i g h t  shutter  open  and w i t h a l l t h e stopcocks c l o s e d except U and W, HgS was metered  i n t o the sample l i n e and the r e a c t i o n v e s s e l .  timer was immediately made to r u n .  The  The value o f t r a n s m i t t e d  i n t e n s i t y measured^the r e a d i n g o f the s p i r a l gauge t a k e n and the  stopcock X closed.Under the experimental  the  conditions,  gas was warmed up i n a n e g l i g i b l e amount o f time so  t h a t the s p i r a l gauge r e a d i n g corresponded to the a c t u a l pressure o f the gas i n the r e a c t i o n v e s s e l .  Periodic  measurements o f the i n t e n s i t y were made throughout the experiment. Experiments on the thermal r e a c t i o n alone were c a r r i e d out  i n a s i m i l a r manner.  In t h i s case, no l i g h t was shone  - 43 -  through the r e a c t i o n c e l l and no measurement o f i n t e n s i t y was  necessary. At the end o f the experiment, the r e c o r d e r f o r t h e  gas chromatographic  system was turned on and t r a p 3 was  immersed i n l i q u i d n i t r o g e n .  In the meantime, the c h a r c o a l  column i n the chromatographic  system was prepared and n i t r o g e n  was  passed through.  T h i s c a r r i e r gas was allowed t o pass through,  one a f t e r the other, the by-pass and the gas b u r e t t e , so that any unwanted helium l e f t  over from a p r e v i o u s a n a l y s i s  could be d r i v e n away from the bores o f the stopcocks.  i  he  c a r r i e r gas f i n a l l y was d i r e c t e d t o f l o w through the bypass and t h e g a s - b u r e t t e evacuated. c l o s e d except Y, C was  closed.  f  and E'.  A l l stopcocks were  The s h u t t e r on t h e l i g h t  path  F i n a l / r e a d i n g s o f time and i n t e n s i t y were made.  Stopcock X was opened t o a l l o w the condensable gasses t o condense i n t r a p 3 and the Hg(product) t o pass t o the gas burette.  G  r  was then c l o s e d , A  r  and F  f  opened.  l e v e l i n the Toeppler pump was allowed to r i s e . few o p e r a t i o n s o f the Toeppler pump, the hydrogen be e x h a u s t i v e l y t r a n s f e r r e d t o th© gas b u r e t t e . stopcocks G  r  and H  f  The mercury After a could • By t u r n i n g  s i m u l t a n e o u s l y , the c a r r i e r gas was  d i r e c t e d t o swee|>p through the gas b u r e t t e , c a r r y i n g the hydrogen  i n t o t h e c h a r c o a l column.  When the stopcocks G' and H  T  were turned, a k i c k on  the r e c o r d e r c h a r t was r e g i s t e r e d , marking the s t a r t i n g point.  The chart was t u r n e d o f f o n l y a f t e r the expected  peak o r peaks had emerged. 2. P h o t o l y s i s o r p y r o l y s i s o f HgS w i t h COg as an i n e r t gas.  - 44 When COg was u s e d procedure  was s l i g h t l y  as an i n e r t altered.  With  except  P,U, a n d W, HgS was a d m i t t e d  cocks.  The p r e s s u r e was m e a s u r e d .  m i x i n g v e s s e l was immersed HgS c o u l d be irozen h e r e . sample l i n e  admitted cock  into  t h e sample l i n e so t h a t  c o u l d be c o n d e n s e d  to  Liquid  warm, w h i l e  magnetic so t h a t  n i t r o g e n thus a l l the  P was c l o s e d a n d t h e were e v a c u a t e d  by o p e n i n g  a g a i n and COg was  and t h e r e a c t i o n  cell.  a l l t h e COg i n t h e l i n e  w i t h t h e HgS.  Stopcock  P was  Stop-  and  cell  closed allowed  s t i r r i n g was a p p l i e d b y t u r n i n g on t h e  the line  admitted  the stop-  n i t r o g e n was removed and t h e m i x t u r e was  stirrer.  measured.  cell  closed  The s i d e a r m o f t h e  T h e n s t o p c o c k 0 was c l o s e d  P was o p e n e d  again.  Stopcock  a l l stopcocks  by t u r n i n g  in liquid  plus the r e a c t i o n  s t o p c o c k 0.  gas, the gas-metering  I n t h e meantime, s t o p c o c k 0 was and c e l l  Stopcock  c o u l d be e v a c u a t e d .  0 was c l o s e d .  to the c e l l  by opening  opened  Intensity  The warmed m i x t u r e  s t o p c o c k P.  was  was  '^he l i g h t  s h u t t e r was opened, t h e t i m e r s e t t o r u n , t h e p r e s s u r e m e a s u r e d , and t h e s t o p c o c k X c l o s e d . two  of the  p r e s s u r e s gave t h e p r e s s u r e o f COg. The  procedure 3.  The d i f f e r e n c e  analysis part as i n part  Photochemical The  previous  of this  experiment  f o l l o w e d t h e same  (a) above.  & T h e r m a l " O x i d a t i o n o f HgS  a d m i s s i o n o f HgS was t h e same a s d e s c r i b e d i n t h e section.  With  was l e t i n t o t h e s y s t e m was r e c o r d e d .  The H S 0  o n l y s t o p c o c k s P,V and W open, HgS by t u r n i n g  s t o p c o c k s S.  was t h e n f r o z e n  into  The p r e s s u r e  t h e s i d e arm o f  - 45 -  the m i x i n g v e s s e l . was  Stepceck  P was c l o s e d .  t h e n opened t o e v a c u a t e  cell.  W, 0 were t h e n  a d m i t t e d by t u r n i n g  Stopcock  t h e sample l i n e  and t h e r e a c t i o n  c l o s e d , and P o p e n e d .  s t o p c o c k R.  Oxygen was  P was n e x t  closed.  Liquid  n i t r o g e n was removed f r o m t h e s i d e arm o f t h e m i x i n g and  t h e magnetic  s t i r r e r turned on.  s t o p c o c k 0 was opened t o e v a c u a t e reaction and  cell.  the l i g h t  opened,  Initial  t h e sample l i n e  open.  Stopcock  2  then closed.  was  made a t a p p r o p r i a t e i n t e r v a l s .  cell  pressure  Stopcock  P e r i o d i c measurements o f i n t e n s i t y  D u r i n g t h e r u n , t h e vacuum reaction  0 was c l o s e d , P  i n the c e l l .  was  and t h e  I© , was t a k e n  The t i m e r was s e t t o r u n and t h e t o t a l  r e a d i n g s gave t h e p r e s s u r e o f 0  chamber  I n t h e mean t i m e ,  reading of intensity,  shutter l e f t  0  system  was c o n s t a n t l y pumped.  W  1^  other than the Chromatographic  Column F & M P-0190 w i t h h e l i u m a s c a r r i e r g a s was p r e p a r e d . At  t h e end o f t h e e x p e r i m e n t ,  were c l o s e d lowered,  and  f  and E  r e a c t i o n time  Y was t h e n to  and C  f  f  noted,  opened f o r a b o u t  and H  T  T  opened.  to a l l o w the products  Stopcocks  C  and E  r  were  closed  t u r n e d s i m u l t a n e o u s l y , so t h a t t h e p r o d u c t s  i n liquid  condensable  s h e l t e r was  and s t o p c o c k X was o p e n e d .  were swept i n t o t h e c h r o m a t o g r a p h i c immersed  The l i g h t  a second  flow t o t h e gas b u r e t t e . G  s t o p c o c k s V, Y, A', B , D' & F '  column.  Trap  n i t r o g e n and s t o p c o c k Y opened. A l l  p r o d u c t s and r e a c t a n t s were t h u s  A f t e r t h e 0 , H^S, S 0 2  3 was  2  & HgO h a d p a s s e d  t h e F & M P-0190 column, t h e c h r o m a t o g r a p h i c swept w i t h n i t r o g e n and t h e c h a r c o a l column  condensed. through s y s t e m was  prepared.  - 46 -  The  hydrogen  f r o m t h e r e a c t i o n c e l l was T o e p p l e r -  pumped i n t o t h e g a s b u r e t t e b y t h e f o l l o w i n g s e q u e n c e o f o p e r ations.  S t o p c o c k s A', B  opened.  C  and D  T  were c l o s e d and t h e n  T  was c l o s e d a n d A' o p e n e d .  The m e r c u r y  C  T  level  i n t h e T o e p p l e r pump was a l l o w e d t o r i s e b y l e t t i n g a i r into the r e s e r v o i r through I i n t o t h e gas b u r e t t e . to  Stopcock  . The h y d r o g e n  Repreated  t r a n s f e r t h e hydrogen  gas b u r e t t e .  T  D  o p e r a t i o n s were  practically f  was f o r c e d performed  completely into the  was t h e n c l o s e d a n d G  turned s i m u l t a n e o u s l y t o a l l o w t h e hydrogen  T  and H  f  t o be swept  into  the c h a r c o a l column. The  reaction cell  intensity  measured.  The  procedure  and l e a d s were e v a l u a t e d a n d t h e  f o r t h e r m a l o x i d a t i o n was t h e same  e x c e p t t h a t no i r r a d i a t i o n was  involved.  4. P h o t o c h e m i c a l a n d T h e r m a l o x i d a t i o n o f HgS w i t h COg a s an i n e r t g a s . The  only difference  was t h e a d m i s s i o n o f . C O g . arm  i n procedure  f r o m t h e above  HgS was f i r s t  section  frozen i n the side  o f t h e m i x i n g v e s s e l a n d s t o p c o c k P was c l o s e d .  The  s a m p l e l i n e was e v a c u a t e d a n d a l l s t o p c o c k s w e r e c l o s e d . was a d m i t t e d t o t h e s a m p l e l i n e b y t u r n i n g s t o p c o c k The  s p i r a l gauge r e a d i n g was n o t e d .  a n d t h e COg a l l o w e d t o g r e e z e s e l w i t h t h e HgS.  Stopcock  COg  Q.  P was o p e n e d  i n the sidearm of the mixing ves-  Oxygen was a d m i t t e d i n t h e same way a s  i n the preceeding section.  The f i n a l p r e s s u r e o f COg i n t h e  r e a c t i o n v e s s e l was c a l c u l a t e d f r o m t h e v o l u m e m e a s u r e m e n t s  - 47 -  of the sample l i n e , reaction vessel and mixing vessel, assuming perfect gas behaviour.  The pressure of oxygen  was found from the difference i n t o t a l pressure and the pressures of HgS and  COg.  The subsequent experimental procedure and analysis were the same as i n the preceoding section.  RESULTS  -  48  -  Photo-oxidation Photo-oxidation of hydrogen sulphide was studied at temperatures of 1 3 0 ° G and 1 5 0 ° e .  P h o t o l y s i s of hydrogen  sulphide alone gave hydrogen and deposits of sulphur, fhe products of p h o t o l y s i s of a mixture of hydrogen sulphide and oxygen were SOg, Hg, and HgO  and sulphur.  Great d i f f i c u l t y was encountered i n o b t a i n i n g reprodu c i b l e q u a n t i t a t i v e data.  This might a r i s e from a number  of reasons. 1. HgS absorption under experimental c o n d i t i o n s was about 1%. order.  F l u c t u a t i o n s i n lamp i n t e n s i t i e s was of t h i s  Thus i t was d i f f i c u l t to measure a c c u r a t e l y the l i g h t  absorbed.  This was p a r t i a l l y remedied by c a l c u l a t i n g the  l i g h t absorbed from a pre-determined  absorption c o e f f i c i e n t .  The absorption of HgS at 2537 2 and 1 3 0 ° G i s shown on f i g . 16. I t i s seen that the Beer-Lambert Law i s not s t r i c t l y f o l l o w e d . For the experimental pressures, however, the p o r t i o n of the p l o t i s s t r a i g h t and the absorption c o e f f i c i e n t f o r c a l c u l a t i n g l i g h t absorbed has been obtained from t h i s r e g i o n . I  ,  l o g y^. = 7 . 0 3 x l O " ^ P  t  :  at P = 0-60  mm.Hg.  2. The extent of the r e a c t i o n between SDg and was not known.  Thus  HgS  The amount of SOg measured could be d i f f e r e n t  from the amount produced.  3.  The  in  a packed  The  product  c o u l d be nature  effect cell  of the  d i d not  i n s u c h an  due  to the  o f the  s u r f a c e was  r e v e a l any  s u r f a c e was  the  effect  i n the  in  1.  Table  The  ratio  of  A  clean  quartz  w h i c h was  of  of  was  observed  S0  and  2  Hg  (Og)/(HgS).  a few  This and  o f Hg  reaction  i n the  gave h y d r o g e n . o x y g e n was after  700  and  the  low  t h i s temperature(150°C) the  been a p p r e c i a b l e . cell  are  Results  shown i n T a b l e  Whether i n t h e o x i d a t i o n was to  production  r e a c t i o n o r the r e a c t i o n was Appendix.  the  2. cell  r e d u c e d when was  (0g)/(HgS)  a  packed  to the  not  observed  ratio s m a l l amount  i n t e n s i t y absorbed.  of photo-oxidation  i n the  of  However, have  packed  3. or the  a t 150°C.  q u a n t i t y of the  photo-oxidation.  negligible.  chainn  thermal r e a c t i o n should  large c e l l  appreciable  differentiate  i n the  o f SOg  T h i s m i g h t have a r i s e n due  reactants photolysed at  The  minutes of r a d i a t i o n with  e x c e e d i n g 2.  alone  q u a n t i t y o f h y d r o g e n was  introduced.  was  T h i s i s shown i n T a b l e  of hydrogen s u l p h i d e The  with  i s shown  i n a l l p h o t o l y s i s experiments, i n d i c a t i n g a SOg.  observ-  increased  a b o u t 20  Photolysis  surface  deposited  quantum y i e l d s o f SOg  of  The  cell.  yield  production  this  packed c e l l .  in reproducibility,  i n i t i a l ratio  The  h a r d l y m e a s u r a b l e and  t h a n one  to the  Experiments  information.  However, s u l p h u r  difficulty  a t i o n s were d e f i n i t e . increase  known.  pertinent  a l s o unknown.  colder leads  Despite  not  e x p e r i m e n t was  f i n e l y divided sulphur.  only at the  -  s m a l l f r e e volume o f t h e  w o u l d have a d i f f e r e n t with  49  At  packed  I t was product  cell  often due  thermal difficult  to the  130°C, however, t h e  Complete r e s u l t s a r e  shown i n  thermal thermal the  Table 1. PhotoQoxidation r e s u l t s showing the effect of P  Expt.No. Temp.°G  Reaction Time min.  ?  H  92  S  m mm.  m  P  0  P  2 mm. o  134 132 136 129 169 165 159 151  149 149 152 152 149 152 152 154  75 47 66 45 65 244 104 265  890 930 870 1080 740 550 770 820  5.5 5.5 5.9 6.8 6.4 5.9 6.4 5.5  92.1 90.9 90.4 96.7 62.5 32.0 25.2 21.6  273 272 271 269 268  149 149 149 147 147  150 178 210 203 200  2010 2050 2250 2090 1940  15.1 18.5 •1.5.9 13.4 15.4  40.3 33.6 26.0 12.6 7.1  322 324 326 325 323 327  148 147 146 145 147 147  169 235 415 198 294 149  3590 3416 3270 3140 3170 3054  18.5 16.8 17.6 20.6 23.5 22.2  110 99.4 96.1 97.4 105.8 91.5  G0  o  2 mm.  145  n  : P„  q  r a t i o on 5 q  W 16.7 16.5 15.5 14.0 9.78 5.40 3.94 3.92  *so  x 1 0 2  7.86 7.15 7.44 7.70 6.15 3.68 2.05 2.04  n  & *i  "'  -  —  -  -  —  —  2.67 1.81 1.63 0.94 0.458  0.994 0.348 0.229 0.138 0.046  55.0 16.4 11.4 7.1/ 5.3:  •6.0 5.9 5.5 4.7 4.5 4.1  0.188 0.258 0.187 0.068 0.090 0.086  9.2 9.S 7.0 6.2 5.6 5.4  Table 2. P h o t o - o x i d a t i o n r e s u l t s showing c o n s i s t e n c y of l Expt.No.  Temp. °C  256 269 271 272 273 322 323 324 325 326 327 263 2662744 275 273 233 236 292 296 307 315 313 323 329 331 334 336 343 359 363 333 344  151 147 149 149 149 143 147 147 145 146 147 143 143 143 146 147 145 134 136 136 150 152 147 143 146.3 151 149 149 150 161 169 152 151  Reaction Time min. 243 203 210 173 150 169 294 235 193 415 149 175 132 123 120 112 135 121 123 120 255 331 99 230 190 211 173 204 209 35 34 234 313  -r o  a  2340 2090 2250 2050 2010 3530 3170 3416 3140 3270 3054 2000 1360 2100 2020 2060 1670 1640 2400 1520 297 330 3552 3014 2362 2930 2327 3350 3270 2560 1700 3170 3290  Prr o 2 mm. 24.4 13.4 15.9 13.5 15.1 13.5 23.5 16.3 20.6 17.6 22.2 15.5 14.3 12.2 15.5 14.7 21.3 15.1 26.6 19.3 16.3 20.2 15.1 20.2 17.6 22.1 13.9 14.3 24.0 10.9 11.3 19.3 16.3  P  ^2 mm. 44.9 12.6 26.0 33.6 40.3 110 106.3 99.4 97.4 96.1 91.5 44.5 47.0 47.9 39.4 33.6 59.6 63.4 76.4 65.9 173.5 114 104 37.3 32.3 75.5 73.4 61.7 45.3 90.6 33.1 43.6 39.4  o/ H S P  2  1.34 0.94 1.63 1.31 2.67 6.0 4.5 5.9 4.7 5.5 4.J  2.37 3.29 3.93 2.54 2.62 2.73 4.53 2.94 3.41 10.6 5.59 6.9 4.3 4.7 3.4 5.3 4.3 1.9 3.31 7.32 2.3 2.3  q  n  /I * s o  x 2  l  o  " °  0.20 0.133 0.229 00.343 0.994 0.133 0.090 0.253 0.063 0.137 0.036 0.737 1.14 0/252 0.206 0.516 0.357 1.39 0.222 0.335 13.7 1.16 0.104 0.132 0.062 0.090 0.132 0.215 0.033 9.93 14.1 0.042 0.072  % 0.723 7.14 11.4 16.4 55.0 9.2 5.6 9.3 6.2 7 5.4 31.4 53.1 9.75 13.3 23.6 15.3 52.7 10.4 32 304 53 4.6 7.2 2.6 5.3 6.9 11.3 4.6 516 710 3.5 4.3  *  S 0  2  / %  27.4 19.4 20.1 21.2 13.6 20.2 16.0 26.4 11.5 23.6 16.1 25.1 21.5 25.3 15.5 13.1 22.6 26.4 21..3 26.1 23.3 19.2 23 13.2 23.0 15.3 19 13.3 19 19.3 20.0 24 16.7  2  Table 3  cpt. No. Temp. °C 379 380 381 382 383 384 385 3S8 389 390 391 392 393  149.3 150.2 149.0 i54.1 153.1 151.0 150.6 150.6 152.2 152.2 152.2 152 149.5  P h o t o - o x i d a t i o n i n packed c e l l . —1 Volume = 3 5 . 4 c.c. Surface/volume r q t i o = 4 . 3 cm. Reaction 0 /H S H S 0 *so 2 mm. 2 2 Time min. 2 mm. P  0  205 322 182 433 641 650 645 612 670 575 406 539 559  450 620 655 630 600 650 605 650 660 640 650 610 »4  7.1 21.0 11.3 12.6 18.9 10.9 10.9 28.2 20.2 15.1 25.2 24.8 18.9  P  P  P  x l c r 3  u  88.2 92.0 77.6 78.5 68.1 84.8 86.5 0 126 135.6 0 73.9 125.1  2  12.4 4.38 6.87 6.23 3.61 7.78 7.94  0 0 0 0 0 0 0  6.25 8.98  0 0  —  mm  2.98 6.62  0 0  —  -  20.2 6.2 e 0 0 31.2 22.8 8.8 1.4 2.2 9.2 3.4 0  -  54  -  Thermal Oxidation Thermal oxidation of hydrogen sulphide was studied at temperatures  of 160°, 170°, 190°, 210°, 2 2 5 ° , 240° and 260°G.  Products were SOg, HgO and sulphur© -8 About 3x10"  No hydrggen was  found.  gm.mol.e of hydrogen could be detected on the char-  coal column.  The amount of S0  2  usually produced was of the order  —6 of 5x10"  gm.mole.  The y i e l d of SOg increased d r a s t i c a l l y with  s l i g h t incfease i n (0g)/(HgS) r a t i o . at 260°C, 19 mm. (ratio = 1.33)  Under certain conditions  of hydrogen sulphide and 26 mm.  of oxygen  led to a small explosion with a l i g h t emission  about 5 seconds a f t e r introduction of the mixture into the reaction vessel.  Increased pressure, with the r a t i o of  (0 )/(H S) 2  2  kept constant also increased the y i e l d , as shown on Table 4 and f i g .  17.  Runs were made (a)holding the oxygen pressure constant and (b)holding the hydrogen sulphide pressure constant.  Initial  rates were calculated at l e s s than 10% completion, l o g d n i t i a l rate) was plot against log(H S) or log(Og) as the case might 2  be.  The order of reaction was calculated from the slope.  The plot showing runs with (0 ) held constant at 258.5°C 2  i s shown i n Table 5 and f i g . 18.  It i s seen that the order  with respect to (HgS) varies with (HgS) from 1 to 0 to -1 and again to 0.  The plots f o r runs with (HgS) held constant  at seven temperatures 19-25. i s 3.  are shown i n Tables 6-12  and gigs.  It i s obvious that the order with respect to (0g) Overall results could be expressed as Rate = k(HgS)" " " ^ ( O g ) . 1  3  The slopes and intercepts of these l i n e s were calculated by the least squares method.  The i n i t i a l rates f o r  (H S)  - 55 = 9.75x10"^ gm. mole i n the r e a c t i o n c e l l and (0 ) = 1.00x10"^ 2  gm. mole f o r seven temperatures were c a l c u l a t e d 1/T.  and p l o t  against  T h i s p l o t , shown on Table 13 and f i g . 26, t u r n e d out  to be a smooth curve, but the c l o s e s t l e a s t squares l i n e gave anc o v e r a l l a c t i v a t i o n energy o f 21.2t2k.cal./mole. The e f f e c t o f i n e r t g a s ( C 0 ) at 260°C was s t u d i e d . 2  The e f f e c t of C 0 up t o 3 times the t o t a l p r e s s u r e o f 2  hydrogen  s u l p h i d e and oxygen t o g e t h e r was not a p p r e c i a b l e .  Complete  r e s u l t s are shown i n the Appendix.  i  Table 4. Thermal Oxidation - E f f e c t of t o t a l pressure - 256.6°C. Reaction p p p p p T .^j..jai Temp. °G. Time min. V m m . °2 mm. ^otalmm. \ / \ s r  EjcptJio.  530 531  258.1 257.9 257.0 255.6 256.9 257.4 258.3 256.3 255.3 256.7  2.0 2.1 1.9 2.3 2.5 2.4 2.2 4.6 1.9 2.4  15.5 21.0 15.1 21.4 22.2 19.7 31.9 50.0 33.6 45.4  13.9 13.1 10.5 13.1 19.7 16.3 26.9 44.1 29.0 32.3  29.4 39.1 25.6 39.5 41.9 36.5 53.3 94.1 62.6 77.7  0.392 0.360 0.694 0.343 0.837 0.351 0.342 0.333 0.362 0.713  0.35 2.71 0.474 2.16 3.63 2.10 4.73 5.33 6.0 5.91  510 514 517 527 528  256.9 254.0 259.0 255.7 254.4  2.4 4.3 2.3 3.2  3.3  25.6 24.4 23.1 26.4 33.2  24.3 23.1 22.2 24.3 37.0  50.4 47.5 45.3 51.2 75.2  0.967 0.943 0.964 0.936 0.967  5.33 2.56 3.04 3.42 6.13  513  254.3 255.2 259.0 255.6  3.1 1.3 2.3 2.3  19.7 27;3 23.1 22.7  21.3 23.1 25.2 23.5  41.5 55.4 43.3 46.2  1.11 1.03 1.09 1.04  509 519 520  523  524 525 526 529  515 516 522  j'j  •  3.97 10.4 6.65 6.43  g m  .  m o l e / m i :  -Sa5.  lable  Thermal Oxidation at 258.3°C. (0 ) = 1.26x10""^ gm. mole i n the reaction 2  cell.  r = A ( S 0 ) / * t = i n i t i a l rate i n gm.mole/min. 2  Reaction Expt. No. The  Temp. °C  Time min.  straight portion of the p l o t :  474 477 432 433 434 504 505 506 507  Thus The  253.5 256.3 255.4 256.1 257.1 259.9 260.0 260.0 260.0  3.3 3.3 - 1.4 1.3 1.4 2.3 2.0 2.1 2.5  log(H S) 2  log r  -4.733 -4.450 -4.333 -4.163 -4.131 -40090 -4.206 -4.312 -4.432  -5.623 -5.306 -5.025 -4.390 -4.333 -4.754 -4.327 -4.992 -5.133  -3.993 -3.979 -3.921  -4.396 -4.362 -4.357 -5.133 -5.134  l o g r = 1.27xlog(H S) + 0.44 2  curved portion of the p l o t :  435 436 437 433 439 490 491 492 493 495  496 497 493 499 500 501 502 503  256.3  255.1 253.5  253.9 259.0 259.6 254.4 260.6 256.1 263.1 263.0  253.7 259.5 260.2 260.7 257.6 257.6  2.0 1.7 1.7 2.2 1.7 3.1 3.2  2.6  3.3  3.7 3.1  2.2 2.1 2.0 1.5 1.7 2.1, 2.5  -5.320  -3.697 -3.590 -3.527 -3.434 -3.340 -3.270 -3.234 -3.955 -3.352 -3.961 -3.321 -3.913 -3.357 -3.772  -5.336  -5.430 -5.434 -5.545 -5.579 -5.532 -4.961 -5.107 -if.911 -4.904 -4.327 -5.034 -5.253  - 60 Table 6. Thermal Oxidation at 162.0°C. (HgS) = 9.59x10"-' gm.mole i n reaction c e l l r• Expt. No. 573 574 575 576 57$ 579 581 582 583 584  Thus  Temp. °G 162.4 162.5 162.1 161.5 161.5 163.4 161.8 160.9 161.4 164.2  (SOg )/*t = i n i t i a l rate i n gm.mole/min, Reaction Time min. log(Og) log r 55-1 52.0 103.9 93.3 58.5 33.3 84.6 50.8 24.0 19.5  l o g r = 2.90xlog(Og) + 4.31  -4.627 -4.398 -4.206 -4.074 -3.818 -3.629 -3.950 -3.772 -3.618 -3-556  -9.750' -9.424 -7.864 -7.444 -6.714 -6.179 -7.125 -6.684 -6.578 -6.218  - 62 Table 7. Thermal O x i d a t i o n a t 171.4°C. ( H S ) = 9.30x10"^ gm.mole i n r e a c t i o n 2  cell  r =^(SO ,)/^t = i n i t i a l r a t e i n gm.mole/min. c  Expt. No.  Temp. °C  585 586  172.0  587 583  170.7 171.6  539 590 591  Thus  Reaction Time min.  log(0 ) 2  log r  137 73.3  -4.363  -7.666  -3.993  -6.371  36.2 37.3  -3.745 -3.336  -6.044 -6.256  170.7 172.6  67.0  -4.114  -7.242  27.3  172.6  13.0  -3.631 -3.640  -5.351 -5.902  169.6  l o g r = 2.96xlog(0 ) + 4.91 2  -  63  -  - 64 Table 8.. Thermal Oxidation at 191.0°C (HgS) = 9.24x10  gm.mole i n reaction c e l l  r =*(S0 )A>t = i n i t i a l rate i n gm.mole/min. 9  Expt. No.  Temp. °C  Reaction Time min.  log(0 ) 2  log r  566  139.6  35.6  -4.330  -3.354  567 563  139.6  34.4  -4.523  190.6  -4.223  569 570  191.3  29.5 11.1  -7.393 -6.933  -4.004  -6.130  191.3  9.1  -3.955  -6.016  571 572 .  191.3  4.1  -3.757  -5.632  192.3  4.1  -3.605  -5.296  Thus  log r = 2.96xlog(0 ) + 5.55 2  - 66 -  Table 9 . Thermal Oxidation at 209.5°C (H S) = 9.30x10"*'' gm.mole i n reaction c e l l 2  r = ( S 0 2 ) / t = i n i t i a l rate i n gm.mole/min. A  Expt. No.  Temp.  C  A  Reaction Time min.  i crln n  g v  )  2'  log r  556  211.2  29.7  -5.050  -3.775  557 553  210.3  37.7  -4.575  -7.424  203.3 209.6  17.7  -4.333 -4.206  -6.995 -6.423 -6.460 -5.354 -5.163  207.6  10.3 10.1  561  209 j 6  2.8  -4.217 -3.900  562  203.2  4.0  -4.074  563  210.3  2.0  564  212.6  -3.794 -3.772  565  209.2  559 560  Thus  log  2.2 2.2  r = 2.89xlog(B $)+ 5.73 2  -3.733  -5.430  -5.150 -5.073  - 63 Table 10. Thermal Oxidation  at 225.0°C.  (HgS) = 9.91x10 ^ gm.mole i n reaction c e l l r = * ( S 0 ) / o t = i n i t i a l rate i n gm.mole/min. 9  Expt. No.  Temp. G U  Time min.  J  -  U f e V U  2  7  log r  546  225.3  20.3  -4.733  -7.700  547 543  224.5 223.7  24.5 13.6  -4.634 -4.333  -7.437 -6.673  549 550  223.3 227.8  10.0  -4.250  4.2  551 552  227.1 225.6  3.9  -4.097 -3.921  -6.444 -5.302  553 554  224.1 224.3  555  224.1  Thus  -5.212  3.5 2.6  -3.333  -4.921  -3.732  -4.936  1.4  -3.740  1.7  -3.634  -4.673 -4.660  l o g r = 2.91xlog(0g) + 6.15  - 70 Table 11. Thermal Oxidation 1 aat 1 240.5°C. .-5 (H^S) = 9.24x10 gm.mole i n reaction c e l l . r = •^(SOgJ/^t = i n i t i a l rate i n gm.mole/min, Expt. No. 537 538 539 540 541 542 543 544 545 Thus  Temp. °G  Reaction Time min.  -,  x o g  / \ ^ 2 n  u  ;  log  243.6  4.6  -4.330  -7.622  243.5 240.9 240.6  21.9 10.9 3.3  -4.634 -4.432  -7.396  239.3 239.0 239.8  10.4 2.6  -4.031  1.4 1.7 1.2  -3.951 -3.333 -3.660  239.8 239.1  l o g r = 2.93xlog(0 ) + 6.34 2  -4.136 -4.363  -6.767 -5.917 -6.616 -5.335 -4.962 -4.307 -4.514  - 72 'Table 12. Thermal O x i d a t i o n a t 258.5°C. (HgS)  = 1.12x10"^ gm.mole i n r e a c t i o n  cell  r = * (SOg)/*t = i n i t i a l r a t e i n gm.mole/min. Expt. No. 455 447 442 434 431 430 448 449 450 451 453 454 455% 456 457 453 459 460 462 463 464 465 466 467 Thus  Temp. °C. 259.0 253.0 260.5 262.3 260.9 260.9 253.0 253.0 253.0  253.0  256.3 257.7 256.1 256.2 257.0 259.2 257.9 257.9  255.9  257.7 256.9 259.7 260.9  259.9  React Time \  \.  0.2 4.5 4.6 3.0 6.1 5.1 4.1 3.9 6.4 4.1 4.4 5.1  1.3 2.0  3.3  4.0 4.1 5.1 4.6 4.4 4.2  3.2  12.6 20.5  l o g r = 2.56xlog(Og) + 4.72  1  °g  ( Q  2  )  -4.114 -4.052 -3.961 -3.917 -3.961 -3.979 -3.817 -3.921 -3.830 -3.927 -3.666 -3.740 -3.673 23.733 -3.827 -3.376 -3.993 -4.097 -4.114 -4.166 -4.298 -4.333 -4.654 -4.923  log r -5.734 -5.674 -5.405 -5.334 -5.463 -5.403 -4.934 -5.296 -5.173 -5.136 -4.369 -4.952 -4.536 -4.624 -4.980 -5.223 -5.457 -5.330 -5.320 -5.905 -6.203 -6.438 -7.146 -7.900  -  73  -  - 74 -  Thermal Oxidation  Table 13. - Dependence of i n i t i a l rate on Temperature.  r =4 (S0 )/*t = i n i t i a l rate when 9  (H S)  9.75x10 ' gm.mole i n reaction  9  (0~) Temp. °C. 258.5 240.5 225.0 209.5 191.0 171.4 162.0  —L  = 1.00x10  1/T x l O  3  gm.mole i n reaction  log r  1.881  -5.52  1.947 2.007 2.072  -5.38 -5.49 -5.73  2.154 2.249 2.298  -6.29 -6.93 -7.29  Thus l o g r = -4.66X10VT +3.62 Therefore, o v e r a l l a c t i v a t i o n energy = 21.2*ik.cal./mole.  cell cell.  D I S C U S S I O N  - 76 Photo-oxidation In the ility  photo-oxidation, d i f f i c u l t y i n obtaining reproducib-  made q u a n t i t a t i v e m e a s u r e m e n t s  possible  e x p l a n a t i o n f o r t h i s d i f f i c u l t y have been  e a r l i e r under " R e s u l t s " . factors fact  It  s h o u l d be e x p e c t e d  mentioned played a p a r t .  The  described  that a l l  I n a l l p r e v i o u s work  s u l p h u r was n e g l e c t e d .  important f a c t o r  in affecting  s u l p h u r was d e p o s i t e d , the v e s s e l .  T h i s c o u l d have  the  the  t h a t hydrogen s u l p h i d e r e a c t e d w i t h s u l p h u r d i o x i d e  deposit  of  of l i t t l e v a l u e .  been the  to most  r e p r o d u c i b i l i t y , s i n c e when a n y  a new s u r g a c e  was f o r m e d o n t h e  walls  t h a t the v e s s e l  c o u l d be  T h e r e was no e v i d e n c e  "seasoned". SgOg was n o t f o u n d a t a l l b y gas be e x p e c t e d w o u l d have  t £ a t under the  chromatographic  decomposed b e f o r e  The f a c t sulphide alone  that  chromatography.  r e a c h i n g the  Hg was f o u n d i n t h e  It  c o n d i t i o n s , the  SgOg  detector.  p h o t o l y s i s of  agreed w i t h the g e n e r a l l y  should  accepted  hydrogen  initiation  steps: HgS  —  H + H S  —  2  In the presence as  of  SH + H H  oxygen,  2  + SH  t h e s e were t h e  initiation  steps  well.  17 Darwent and h i s c o - w o r k e r s  1$ '  d i d n o t measure  d i o x i d e a s a p r o d u c t and t h e i r c o n c l u s i o n s without considering the present  work, the  c o u l d n o t be  sulphur dioxide production.  sulphur complete  In the  quantum y i e l d o f h y d r o g e n i n c r e a s e d w i t h t h e  a d d i t i o n o f oxygen and w i t h the  increase  i n (Og)/(HgS)  ratio.  T h i s c o u l d be due t o o x y g e n i n h i b i t i n g t h e t e r m i n a t i n g r e a c t i o n : H + SH *. HgS*  - 77 to the same e f f e c t .  More important,  however, could be oxygen  as a t h i r d body p r e v e n t i n g c o l l i s i o n of hydrogen s u l p h i d e w i t h sulphur d i o x i d e i n the o v e r a l l r e a c t i o n : 2H S +-S0 2  3S + 2 H 0  2  2  S i m i l a r r e s u l t s were obtained by Thompson and K e l l a n d but no p l a u s i b l e explanations were made.  The same r e s u l t s 17  were not observed  23  by hoth Darwent and h i s co-workers  18  '  and  15 lcS  N o r r i s h and h i s c o l l a b o r a t o r s  ' 20 i n d i c a t e s t h a t sulphur  The common r a t i o of IgQ / I ^  d i o x i d e must be produced by a complicated  chain r e a c t i o n . I t  i s l i k e l y the sulphur d i o x i d e i s produced i n more than one reaction.  T h i s o b s e r v a t i o n was not made by e i t h e r Darwent and  h i s co-workers"^'"^ nor by N o r r i s h and h i s c o l l a b o r a t o r s " ^ s i n c e they d i d not measure the quantum y i e l d s of both  t  sulphur  d i o x i d e and hydrogen. The f a c t t h a t sulphur d i o x i d e has not been found i n the p h o t o - o x i d a t i o n i n the packed c e l l i n d i c a t e s t h a t t e r m i n a t i o n steps i n the c h a i n r e a c t i o n producing be heterogeneous.  sulphur d i o x i d e must  The p r o d u c t i o n of hydrogen was not i n h i b i t e d  by the i n c r e a s e i n s u r f a c e a r e a . be i n agreement w i t h t h i s  fact.  Any proposed mechanism must  -  78 -  Thermal O x i d a t i o n In the thermal o x i d a t i o n , i t was s i g n i f i c a n t t h a t hydrogen was not found,  i n d i c a t i n g that  H S +• M - — - H + SH + M £  was not the i n i t i a t i o n step, as p o s t u l a t e d by N o r r i s h and h i s 15 co-workers  .  A more reasonable H S + 0 2  w i t h the H 0  2  2  suggestion would be  - SH + H0  2  r a d i c a l d i s a p p e a r i n g subsequently  a t the w a l l .  The v a r i a t i o n s i n the order f o r (HgS) w i t h H^S could be e x p l a i n e d i n the f o l l o w i n g way.  The f i r s t  pressure part of  the p l o t with order = 1 was probably the genuine H^S + Og reaction.  In the r e g i o n where order = -1, a r e t a r d a t i o n by  HgS was i n d i c a t e d and t h i s was probably due t o the r e a c t i o n 2H S + S 0 2  2  — * . 3 S + 2H 0 2  In the r e g i o n where the r a t e i s independent o f H S p r e s s u r e , 2  the hydrogen sulphide was i n such a l a r g e excess t h a t (H S) 2  could be c o n s i d e r e d as constant.  ^2^2  w  a  s  n  0  ^ ^  o  u  n  ^  a  s  -*- ^ n t  l e  case o f p h o t o - o x i d a t i o n . I t i s d i f f i c u l t to comprehend the r a t e being dependent on t h e t h i r d o r d e r w i t h r e s p e c t t o oxygen. c h a i n r e a c t i o n must take p l a c e .  A complicated  To e x p l a i n the o v e r a l l r a t e  expression of Rate = k(H S)"" 2  1  """^(O^  the f o l l o w i n g mechanism i s p o s t u l a t e d :  3  Initiation:  Chain branching:  Termination :•  +  °2  SH  + HO  SH  +  °2  SO  + HO  (2)  HO  +  HS  H 0  + SH  m  SO  +  °2  so  0  +  so  + 0  S0| -  so  + SO  S  + 0„  2S0  = 0,  For  2  2  ;H  H S 2  = 0,  = 0,  F  o  r  d  ^ 2°2 S  )  (5)  -  S 0  (7)  2°2  0  wall  (10)  SH  wall  (11)  HO„  wall  (12)  considerations,  1  2  2  k (0 )(SH) 2  - k ( 0 ) ( S H ) + k (H S)(HO) 2  2  3  2  + k (H S)(0)  - k (W)(SH) - r = 0 .  -kk (0 )(S0)  - k '(S0)(0)  2  4  1;L  2  2  - k (W)(0)  6  1 Q  + k _ ( S 0 ) =* 0 . 2  7  2  k ( 0 ) ( S H J ) k k (H .S)(H0) - k ( W ) ( H 0 ) 2  2  3  k (0 )(S0) 4  2  = 0,k (S0) ?  (6)  2  (9)  ?  For  HO  wall  - k (S0) For ^ | ^ - = 0 ,  (4)  HO  k (H S)(0 )  2  0  (3)  2°2  5  For  2  (.11  2  2  S  By s t a t i o n a r y s t a t e  -  HS 2  Chain p r o p a g a t i o n :  79  2  g  9  - k (H S)(0) 5  - k^S^)  2  -  k  k (H S)(0)  +  5  2  - k "(S0)(0) - k (W)(0) 6  ^° ^ 2  S  2°2  1 Q  )  =  °*  =0  - 80 -  An e x p r e s s i o n f o r (SO) can be obtained from the above equations u s i n g the f o l l o w i n g assumptions f o r s i m p l i f i c a t i o n s k (¥)  <<  9  k (H S) 3  2  k ( S 0 ) <-< k ( H S ) 6  5  2  k ( ¥ ) <C k ( H S ) 1 Q  5  2  then a(S0)  + b(S0) + c = 0  2  where _ k  i : L  (W){k CK_ 7  7  + k (0 )] + k k k Ck_ + a  2  2  k  4  6  2  ?  i  7  5  7  n  ?  9  2  4  2  2  k Ck_ + k g ( 0 ) ] ( 0 )  k, k b = -k, Ck,k (H S) + k,](0 ) + J L - i i ( w ) k 4  kg(0 )](0 )+k k k_ (H S)}  ?  2  2  +  2  k, k ^ k - . , (W) 4  1  0  l  h  k (H S) 5  2  c = k (H S)(0 ) 1  2  2  The s o l u t i o n i s  (SO) =  -b + =  b* - 4 a c y  2a  I t i s c l e a r t h a t the s o l u t i o n cannot be e x p l i c i t l y but  expressed,  w i l l have the form (SO) = a ( 0 ) x  where a-,, a , a , 9  2  2  + a ( 0 ) +• 2  2  , a r e c o e f f i c i e n t s o f terms of ( 0 ) . ?  5  7  ?  2  - 81 -  Therefore, (0) = -it—£ k (H S) r  (SO)  2  = a (0 ) 4  -* a ( 0 )  3  2  k (S0)  5  + a (0 ) +  2  2  6  a  2  ?  2  7  (  S  o ) = -L k_  +  ?  kg(0 ) 2  = a (0 ) G  9  + a  2  2  1 0  (0 ) *  a  2  u  (4),  Thus from reaction  Rate =  + a (0 )  3  2  d ( S Q  "Tt  2  = k,(S0)(0 )  )  9 2  4  3  = a12: 0°2 0 ) l 10  I  ()  0)  3  +  + 1 a3. 2 ( 0' ) '+14a-,, {OJj + a-. 2?' ' °15 cl  w 0  a  l3 °2  0  2  a  w  From reaction ( 6 ) , Rate = k (S0).(0) 6  " l6 a  ( 0  2  ) 5  +  a  i5 2 ( 0  ) 4  * 20 2* a  (0  +  +  (  a  ) 3  +  a  19 °2 (  ):  21  From reaction (#), Rate = k g ( S 0 ) ( 0 ) a  22  ( 0  2  2  2  ) 4  2  + a  +  23 °2 (  a  26  ) 3  * 24 °2 a  (  ) 2  + 25 °2 a  (  )  - 82 -  Since r e a c t i o n ( 6 )  i s a r a d i c a l - r a d i c a l c o l l i s i o n process and  r e a c t i o n (8) i s an i n t e r m e d i a t e - r e a c t a n t p r o c e s s , both  cannot  be important.  these  Moreover, the r a t e expressions from both  r e a c t i o n s c o n t a i n terms of h i g h e r order than ( © 2 ' o the experimental  e x p r e s s i o n i s o n l y t o (Og) .  whereas  Thus the r e a c t -  i o n mainly r e s p o n s i b l e f o r sulphur d i o x i d e p r o d u c t i o n must be r e a c t i o n (4), and the r a t e i s t h i r d order with r e s p e c t to oxygen p r e s s u r e . The above mechanism i s very s i m i l a r t o t h a t proposed by 15 Norrish and  steps  .  The major d i f f e r e n c e s l i e i n the i n i t i a t i o n (7) and ( 8 ) ,  Without these two steps, no terms i n  t h i r d order o f (Og) can be o b t a i n e d . been found,  step  Though SgCv, has not  i t i s assumed to be an i n t e r m e d i a t e .  f o r m a t i o n i s not accounted  Suphur  f o r , s i n c e i t i s a t t r i b u t e d to  the r e a c t i o n 2H S + S 0 2  2  the mechanism o f which i s unknown.  -  3S + 2H 0 2  N o r r i s h and h i s co-workers  were able t o i d e n t i f y the r e a c t i n g s p e c i e s , except  atomic  oxygen, but u s i n g k i n e t i c spectroscopy, they could not o b t a i n data f o r the r a t e dependence on order w i t h r e s p e c t t o each r e a c t a n t , and they were unaware o f the d i f f e r e n t  initiation  step i n thermal o x i d a t i o n . Another p l a u s i b l e mechanism which on s t a t i o n a r y s t a t e c o n s i d e r a t i o n s g i v e s f o r the r a t e e x p r e s s i o n one term out of about t e n i n ( 0 ) , i s as f o l l o w s : ?  - 83 Initiation:  HS  +0  Chain propagation:  SH  +• 0  HO  + HS •  se  +• so  2  Termination:  S  it  (O^,)  2  •  SH  +  HO,  (1)  •  SO  +  HO  (2)  H0  + SH  (3)  2  2°2  •  +  2  S  +  2  2  (5)  2  H0  HS  (4)  2°2  2S0  °2  +  SO  Since the  2  S  (6)  2  SH  wall  (7)  HO  wall  (dj  wall  (9)  term i n t h i s mechanism i s not  i s believed unlikely.  important,  T h i s mechanism, however, i n d i c a t e s  sulphur to be a d i r e c t product of HgS  oxidation i n addition  to b e i n g a product formed from the primary product  reacting  with the o r i g i n a l r e a c t a n t . In f a c t , involved, 0  36 2  i n order to e s t a b l i s h whether atomic oxygen i s should be used  i n mixture with 0  32 2  .  From the  exchange r e a c t i o n of 0 O^  4  1 6  +  0 34  0  1&  should be able to be determined m a s s - s p e c t r o m e t r i c a l l y .  Again, the amount of 0  2  produced may  be too low t o be d e t e c t e d .  The o v e r a l l a c t i v a t i o n energy found, was  i n good agreement w i t h the very rough  21.2±2k.cal./mole, estimate o f l£-20  28 k.cal./mole made by Thompson and  Kelland  .  These authors d i d  not study the thermal o x i d a t i o n t o as low a temperature present work and the estimate was  v e r y approximate  as the  indeed.  - 84 -  I f the f o l l o w i n g values of bond energies are used, S-H  81.1  S-0  k.cal./mole  32  118.5 k . c a l . / m o l e  0 - 0 peroxide  3 3 . 2 k.cal./mole  30  32 32  0 - 0 molecule  118.3  k.cal./mole  0-H  110.6  k.cal./mole  32  H-OH  113  k.cal./mole  31  the enthalpies of the r e a c t i o n s ( l ) - ( 5 ) can be estimated to be Reaction (1)  H = +56 k.cal./mole  Reaction (2)  H = - 3 k.cal./mole  Reaction (3)  H = - 3 7 k.cal./mole  Reaction (4)  H = +27 k.cal./mole  Reaction (5)  H = - 3 0 k.cal./mole.  The o v e r a l l a c t i v a t i o n energy of 21.2t2k.cal./mole i s smaller than the enthalpy f o r r e a c t i o n (1) and i n d i c a t e s that a term — —— may be very important i n the o v e r a l l r a t e }  k  2  constant e x p r e s s i o n ( g i v i n g an expected value of 22 k.cal./mole.) This cannot be v e r i f i e d due to the complexity of the rate equation.  - 8 4REFERENCES  (1)  N.M. Emanuel, D.S. Pavlov & N.N. Semenov, Compt. rend. acad. s c i . U.R.S.S., 23 613-20 (1940)  (2)  N.M. Emanuel, J . Phys. Chem. (U.S.S.R.), 14 863-76 (1940)  (3)  N.M. Emanuel, Compt. rend. acad. s c i . U.R.S.S., 35 250-5 (1952)  (4)  N.M. Emanuel, i b i d . , 36 145-9 (1942)  (5)  D.S. Pavlov, N.N. Semenov & N.M. Emanuel, B u l l . acad. s c i . U.R.S.S., Classe s c i . chem., 93-105 (1942)  (6)  N.M. Emanuel, i b i d . , 221-3 (1942)  (7)  N.M. Emanuel, Acta Physiochem. U.R.S.S., 19 360-73 (1944)  (8)  N.M. Emanuel, Zh. F i z . Khim., 19 15-47 (1945)  (9)  N.N. Semenov. B u l l . Acad. S c i . U.R.S.S. Classe. s c i . chem., 210-22 (1945) N.M. Emanuel, Compt. rend. acad. s c i . U.R.S.S., 43 438-90 (1945) ~~ V.G. Marhovich & M.M. Emanuel, Zh. F i z . Chem., 21 1251-3 (1947)  (10) (11) (12)  V.G. Marhovich & M.M. Emanuel, i b i d . , 21 1259-62 (1947)  (13)  N.M. Emanuel, Dokl. Acad. Nauk. U.S.S.R., 59 1137-40 (1943)  (14)  P.W.  (15)  R.G.W. Norrish and A.P. Zeelenberg, Prox. Roy. Soc. Lond., A 240 293 (1957) A.P. Zeelenberg, 7th Symposium on Combustion, Butterworths, 1959, p. 63  (16)  Schenk, Z. Anorg. Chem., 211 150 (1933)  -  (17)  35 -  B. de B. Darwent and R. Roberts, Proc. Roy. Soc. Lond., A216  (13)  344(1953).  B. de B. Darwent and V.J. Krasnansky, 7th International Symposium on Combustion, Butterworths,  1959, p. 3. (19)  G. Porter, Disc. Far. S o c , 9 60(1951).  (20)  D.A. Ramsay, J . Chem. Phys., 20 1920(1952).  (21)  e.g. N.V. Sedgwick, The Chemical Elements and Their Compounds, Oxford, 1950, p.930.  (22)  R.G.W. Norrish and E.K. Rideal, J . Chem. Soc. Lond.,  696 (1923). (23)  S.A. Ryce and W.A. Bryce, Anal. Chem., 29 925(1957).  (24)  S . A . Ryce, P. Kebarle, and W.A. Bryce, Anal. Chem., 29  1336(1957).  (25a)  M. Kasha, J . Optical Soc. Am., 33 929-34(1947).  (25b)  R.E. Hunt and W.J. Davis, J . Am. Chem. S o c , 6 9 1415(1952).  (26)  Handbook of Chemistry and Physics, 41st E d i t i o n , 1959-60, Chemical Rubber Publishing Co., Cleveland.  (27)  A.V. Jones, J . Chem. Phys., 13 1263(1950).  (23)  H. Thompson and N. Kelland, J . Chem. S o c , Lond., 1 3 0 9 ( 1 9 3 1 ) .  (29)  C.G. Hatchard and C.A. Parker, Proc. Roy. Soc. Lond.,  (30)  R.M. Reese, V.H. Dibeler and J.L. Franklin, J . Chem. Phys.,  A235 29  (31)  513(1956).  330(1953).  S.W. Benson, Foundations of Chemical Kinetics, McGraw-Hill, I960).  (32)  L. Pauling, Nature of the Chemical Bond, Cornell, I960.  A P P E N D I X  -  86  -  !  Other results on Photo-oxidation Expt. No. Temp. C G  242 243 244 245 246 247  248 249 265 276 277 279 230 231 232 234 235 237 238 239 290 291 293 295 297 293 303 310 319 320 321 330 332  335 337 339  340 341  343 345  150.4 150.4 135 135 134.6 135 133 133 149.1 147.4 146.1 146.3 147.3 147.5 143.3 147.5 147.5 134.0 134.6 137.0 137.0 136 136.6 135.7 140.2 140 149.6 147.2 143.3 150.7 149.0 147.0 149.3 143.2 152.0 143.7 149.6 147.3 149.1 143.3  Reaction Time min. 103  107 65 75 102 42 212 50 316 124 123 66 199 200 252 152 352 127 163 135 112 129 333 125 123 335 427 120 127 232 110 203 131 177 130 130 253 237 233 230  P  H S 0  2  2932 2930 2960 2940 2920 2380 2550 2670 1060 1930 1760 1960 1930 2100 1360 1370 1540 1350 970 2100 2060 1440 2210 1340 2440 1570 413 256 3730 3630 2330 3365 3430 3260 2930 2565 3020 2330 2930 2970  mm.  3.3 7.1 7.1 0.93 7.6 7.1 3.4 13.4 15.5 13.0 14.3 12.2 16.3 14.3 12.2 20.6 15.5 14.3 16.0 13.9 26.0 26.0 27.3 17.2 29.4 23.1 19.3 16.3 21.0 13.5 20;5 23.5 21.0 16.4 19.7 1-9.7 22.2  21.0 19.3 13.5  P  0 2 mm. 23.1 75.1 43;6 45.4 44.5 45.3 79.4 117.3 30.6 37.0 37.4 56.2 46.1 3.0 41.1 56.6 4.6 63.0 63.0 69.7 64.3 63.0 74.0 63.9 76.0 70.5 197.5 170.0 121 122.4 113 79.4 67.6 63.0 42.0 50.3 45.3 46.1 37.3 26.0  P  o/ H S P  2  2.62 10.6 6.14 3.13 5.35 6.45 9.45 10.3  -  2.34 2.62  4.61 2.75 0.56 3.33 2.75 0.30 4.75 4". 25 5.0 2.47 2.42 2.71 4.0 2.53 3.0 10.4 10.1 5.3 6.6 5.5 3.4 3.2 3.3 2.1 216 2.0 2.2 2.0 1.4  1.3 2.4 0.73 5.0 1.4 266  -  734 336 232 79 0 2210 630 59 1395 3245 2690 2250 1172 606 ' 1020 354 1020 0 2465 109 363 36 74 64.6 99 30.6 39.4 32.7 22 24 16  -2.6  C4.27 0.26  39.24  33.46 32.4  4.45 40.9 14.0 4,55 50.2 57.1 37.9 9.5 3.0 10.7 23 12 22 117 57 2.6 10.2 11.2 6.4 5.6 11.7 7.7 6.6 6.5 7.3 5.9 6.0  - 88 ~  Thermal Oxidation - E f f e c t of Inert Gas at 257°C.  r = A ( S 0 ) / A t = i n i t i a l rate i n gm.mole/min. 2  Expt .-No,  2  mm.  2 mm.  2 mm.  log r  536  18.5  10.9  0  -6.395  532  13.9  15.1  22.6  -6.100  533 .  19.3  15.0  30.3  -6.306  534,  21.4  13.7  37.6  -6.246  535  17.2  4.5  67.2  -6.136  

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