﻿C. 
  Barus 
  — 
  Solution 
  of 
  Vulcanized 
  India 
  Rubber. 
  363 
  

  

  13. 
  Treatment 
  with 
  keto?ies. 
  — 
  India 
  rubber 
  (a) 
  treated 
  with 
  

   liquid 
  acetone 
  at 
  200°, 
  is 
  converted 
  into 
  a 
  sticky 
  paste 
  from 
  

   which 
  it 
  hardens 
  at 
  once 
  on 
  exposure 
  to 
  air. 
  Pressure 
  should 
  

   exceed 
  15 
  atm., 
  but 
  need 
  not 
  be 
  greater 
  than 
  30 
  or 
  40 
  atm. 
  

  

  14. 
  Treatment 
  with 
  water 
  and 
  mineral 
  acids. 
  — 
  In 
  no 
  case 
  

   was 
  there 
  a 
  trace 
  of 
  true 
  solution 
  at 
  210°. 
  Water 
  probably 
  

   enters 
  the 
  physical 
  pores 
  of 
  the 
  elastic 
  rubber 
  (a), 
  as 
  this 
  sub- 
  

   stance 
  becomes 
  superficially 
  rough 
  and 
  warty 
  on 
  drying 
  in 
  

   steam 
  at 
  200°, 
  after 
  being 
  treated 
  with 
  liquid 
  water 
  at 
  the 
  

   same 
  temperature. 
  It 
  does 
  not 
  melt. 
  § 
  18. 
  Strong 
  hydro- 
  

   chloric 
  acid 
  (1 
  : 
  2) 
  has 
  no 
  obvious 
  effect, 
  while 
  strong 
  sulphuric 
  

   acid 
  (1:3) 
  seems 
  only 
  to 
  char 
  the 
  rubber. 
  Treating 
  gray 
  rub- 
  

   ber 
  (b), 
  with 
  HC1, 
  I 
  found 
  its 
  solubility 
  in 
  CS 
  2 
  , 
  C 
  6 
  H 
  6 
  and 
  gas- 
  

   olene 
  to 
  have 
  decreased. 
  

  

  15. 
  Treatment 
  for 
  vulcanization. 
  Liquid 
  ebonite. 
  — 
  Liquid 
  

   ammonic 
  polysulphide 
  at 
  185° 
  or 
  200° 
  does 
  not 
  change 
  the 
  

   appearance 
  of 
  gray 
  rubber 
  (b) 
  markedly 
  ; 
  but 
  the 
  sample 
  loses 
  

   its 
  elasticity 
  and 
  shows 
  a 
  semi-plastic 
  consistency. 
  This 
  I 
  be- 
  

   lieve 
  to 
  be 
  due 
  to 
  additional 
  vulcanization 
  induced 
  by 
  the 
  poly- 
  

   sulphide. 
  If 
  now 
  the 
  sample 
  be 
  treated 
  with 
  liquid 
  CS 
  2 
  at 
  

   200°, 
  the 
  solvent 
  is 
  decomposed 
  with 
  the 
  evolution 
  of 
  much 
  

   gas, 
  and 
  the 
  rubber 
  restored 
  to 
  its 
  original 
  elastic 
  quality. 
  The 
  

   gas 
  is 
  liberated 
  throughout 
  the 
  mass 
  of 
  the 
  rubber, 
  and 
  the 
  

   sample, 
  when 
  taken 
  out 
  of 
  the 
  tube, 
  has 
  the 
  form 
  of 
  an 
  enor- 
  

   mously 
  inflated 
  cellular 
  sack, 
  which 
  issues 
  from 
  the 
  glass 
  tube 
  

   explosively, 
  but 
  soon 
  collapses 
  on 
  exposuie 
  to 
  air. 
  As 
  a 
  whole 
  

   these 
  results 
  agree 
  with 
  the 
  behavior 
  found 
  for 
  ebonite 
  in 
  § 
  3. 
  

   In 
  both 
  cases 
  it 
  is 
  possible 
  to 
  pass 
  from 
  a 
  more 
  vulcanized 
  to 
  a 
  

   less 
  vulcanized 
  solvent 
  by 
  treating 
  an 
  excess 
  of 
  rubber. 
  It 
  

   will 
  be 
  shown 
  below, 
  § 
  19, 
  that 
  the 
  gas 
  evolved 
  is 
  probably 
  due 
  

   to 
  the 
  double 
  decomposition 
  of 
  water 
  and 
  CS 
  2 
  . 
  

  

  More 
  interesting 
  is 
  the 
  direct 
  vulcanization 
  of 
  a 
  rubber 
  solu- 
  

   tion, 
  to 
  liquid 
  ebonite, 
  by 
  aid 
  of 
  a 
  solution 
  of 
  sulphur. 
  In 
  case 
  

   of 
  elastic 
  sheet 
  rubber 
  (a), 
  this 
  even 
  begins 
  at 
  160° 
  ; 
  but 
  it 
  is 
  

   more 
  complete 
  at 
  185° 
  and 
  210°. 
  In 
  case 
  of 
  pure 
  (non-vulcan- 
  - 
  

   ized) 
  rubber 
  dissolved 
  in 
  CS 
  2 
  with 
  excess 
  of 
  sulphur, 
  scarcely 
  

   any 
  change 
  of 
  the 
  flesh 
  color 
  is 
  observed 
  at 
  lfi0°, 
  and 
  the 
  sul- 
  

   phur 
  crystallizes 
  out 
  of 
  the 
  solvent 
  in 
  needles, 
  on 
  exposure. 
  

   At 
  185° 
  and 
  210°, 
  however, 
  the 
  charge 
  turns 
  black, 
  showing 
  

   complete 
  vulcanization. 
  If 
  equal 
  masses 
  of 
  vulcanized 
  rubber 
  

   (a) 
  and 
  sulphur 
  be 
  treated, 
  the 
  product, 
  after 
  heating 
  to 
  210°, 
  

   is 
  not 
  dissolved 
  nor 
  soluble, 
  until 
  the 
  excess 
  of 
  sulphur 
  is 
  re- 
  

   moved. 
  §§ 
  3, 
  15. 
  Gas 
  is 
  often 
  evolved. 
  §§ 
  17, 
  19. 
  In 
  pro- 
  

   portion 
  as 
  less 
  sulphur 
  is 
  used 
  relatively 
  to 
  the 
  rubber, 
  the 
  

   product 
  becomes 
  more 
  immediately 
  soluble 
  and 
  less 
  gas 
  is 
  

   evolved. 
  Adding 
  about 
  20 
  per 
  cent 
  of 
  dissolved 
  sulphur 
  to 
  

   the 
  elastic 
  rubber 
  (a), 
  I 
  obtained 
  serviceable 
  solutions 
  of 
  ebo- 
  

  

  