﻿C. 
  Bar 
  us 
  — 
  Solution 
  of 
  Vulcanized 
  India 
  Rubber. 
  361 
  

  

  15 
  atm., 
  but 
  need 
  not 
  exceed 
  30 
  or 
  40 
  atm. 
  Inasmuch 
  as 
  CS 
  2 
  

   thus 
  unites 
  with 
  rubber 
  in 
  any 
  proportions, 
  clear 
  brown 
  solu- 
  

   tions 
  of 
  any 
  viscosity 
  may 
  be 
  obtained. 
  Diluting 
  such 
  (thick) 
  

   solutions 
  with 
  cold 
  CS 
  2 
  , 
  the 
  solvent 
  is 
  first 
  greedily 
  absorbed; 
  

   but 
  the 
  final 
  complete 
  solution 
  of 
  the 
  unagitated 
  syrupy 
  rubber 
  

   takes 
  places 
  very 
  slowly. 
  Finally, 
  by 
  exposing 
  any 
  of 
  the 
  

   solutions 
  to 
  air, 
  the 
  CS 
  2 
  evaporates, 
  and 
  the 
  dissolved 
  vulcan- 
  

   ized 
  rubber 
  is 
  regained 
  without 
  sacrifice 
  of 
  its 
  original 
  non- 
  

   viscid 
  quality. 
  Similarly 
  fissured 
  brittle 
  sheet 
  rubber 
  or 
  tub- 
  

   ing 
  (V), 
  which 
  has 
  become 
  useless 
  for 
  practical 
  purposes 
  by 
  age, 
  

   is 
  quite 
  soluble 
  in 
  CS 
  2 
  at 
  200°, 
  so 
  far 
  at 
  least 
  as 
  its 
  undecom- 
  

   posed 
  portion 
  is 
  concerned. 
  Elastic 
  gray 
  rubber 
  (&), 
  dissolves 
  

   completely 
  to 
  a 
  gray 
  liquid, 
  in 
  which 
  the 
  pigment 
  is 
  suspended. 
  

   § 
  16. 
  The 
  concentrated 
  solution 
  hardens 
  at 
  once 
  on 
  exposure 
  

   to 
  air, 
  reproducing 
  a 
  rubber 
  of 
  nearly 
  the 
  qualities 
  (b). 
  The 
  

   same 
  is 
  true 
  of 
  the 
  non-elastic 
  sample 
  (<?). 
  Treatment 
  at 
  310° 
  

   resulted 
  in 
  a 
  decomposition 
  of 
  the 
  rubber. 
  

  

  Commercial 
  ebonite 
  (d) 
  is 
  first 
  partially 
  devulcanized 
  at 
  200°, 
  

   (excess 
  of 
  rubber) 
  and 
  eventually 
  dissolves 
  in 
  excess 
  of 
  solvent. 
  

   The 
  partially 
  devulcanized 
  product 
  is 
  elastic 
  on 
  drying, 
  but 
  

   finally 
  hardens 
  to 
  a 
  tough 
  solid 
  having 
  a 
  leathery 
  quality. 
  

   The 
  solution 
  leaves 
  a 
  black 
  stain, 
  with 
  free 
  sulphur 
  apparent 
  

   after 
  evaporation. 
  § 
  15. 
  Gases 
  are 
  frequently 
  evolved 
  during 
  

   solution 
  of 
  highly 
  vulcanized 
  rubber 
  in 
  CS 
  2 
  . 
  §§17 
  and 
  19. 
  

   - 
  As 
  a 
  whole 
  my 
  experiments 
  show 
  that 
  excess 
  of 
  sulphur 
  is 
  

   first 
  removed 
  by 
  the 
  solvent, 
  after 
  which 
  the 
  vulcanized 
  rub- 
  

   ber 
  itself 
  passes 
  into 
  solution. 
  § 
  15. 
  

  

  4. 
  Solution 
  in 
  liquids 
  of 
  the 
  parajjine 
  series. 
  — 
  The 
  elastic 
  

   rubbers 
  {a 
  and 
  e) 
  dissolve 
  easily 
  in 
  liquid 
  mineral 
  oils, 
  at 
  200°. 
  

   The 
  pressure 
  necessary 
  will, 
  of 
  course, 
  vary 
  with 
  the 
  boiling 
  

   point 
  of 
  the 
  oil 
  used, 
  and 
  may 
  be 
  as 
  high 
  as 
  50 
  atm. 
  in 
  the 
  

   very 
  volatile 
  gasolenes. 
  Commercial 
  gasolene, 
  though 
  a 
  good 
  

   solvent 
  of 
  the 
  rubbers 
  a 
  and 
  e, 
  is 
  less 
  powerful 
  in 
  case 
  of 
  b 
  and 
  

   c, 
  unless 
  excess 
  of 
  solvent 
  be 
  used. 
  On 
  exposure 
  to 
  air, 
  the 
  

   gasolene 
  evaporates, 
  leaving 
  a 
  residue 
  which 
  soon 
  hardens. 
  

   Mineral 
  oils 
  of 
  a 
  higher 
  carbon 
  order 
  than 
  gasolene, 
  petroleum,* 
  

   for 
  instance, 
  dissolves 
  the 
  rubbers 
  a 
  and 
  e 
  even 
  more 
  easily. 
  

   The 
  solution, 
  however, 
  dries 
  only 
  after 
  much 
  time 
  and 
  proba- 
  

   bly 
  only 
  in 
  thin 
  films. 
  Solubility 
  seems 
  to 
  increase 
  as 
  the 
  oil 
  

   lies 
  higher 
  in 
  the 
  carbon 
  series. 
  §§ 
  12, 
  18. 
  

  

  * 
  Looking 
  up 
  the 
  literature 
  of 
  the 
  subject, 
  I 
  found 
  that 
  John 
  J. 
  Montgomery 
  

   (Cf. 
  Letters 
  Patent 
  No. 
  308,189, 
  November, 
  1884, 
  U. 
  S. 
  Patent 
  Office), 
  describes 
  

   a 
  process 
  for 
  the 
  solution 
  of 
  vulcanized 
  rubber. 
  His 
  statement 
  of 
  the 
  tempera- 
  

   ture 
  and 
  pressure 
  necessary 
  are 
  substantially 
  correct, 
  although 
  he 
  confines 
  his 
  

   experiments 
  to 
  a 
  petroleum 
  oil 
  boiling 
  at 
  200° 
  or 
  higher. 
  The 
  oil 
  is 
  subsequently 
  

   driven 
  off 
  by 
  injections 
  of 
  steam. 
  This 
  is 
  the 
  nearest 
  approach 
  to 
  an 
  available 
  

   and 
  true 
  solution 
  (a 
  solution 
  which 
  does 
  not 
  remain 
  permanently 
  sticky 
  like 
  the 
  

   turpentine 
  and 
  other 
  solutions) 
  which 
  I 
  have 
  found. 
  The 
  essential 
  peculiarity 
  of 
  

   the 
  methods 
  in 
  the 
  above 
  text 
  is 
  solution 
  in 
  volatile 
  solvents. 
  

  

  