﻿364 
  0. 
  Barus 
  — 
  Solution 
  of 
  Vulcanized 
  India 
  Rubber. 
  , 
  

  

  nite, 
  on 
  treating 
  at 
  200° 
  either 
  in 
  CS 
  3 
  alone, 
  or 
  in 
  mixtures, 
  

   § 
  16, 
  of 
  this 
  liquid 
  with 
  gasolene, 
  benzol, 
  etc. 
  In 
  most 
  cases 
  

   these 
  harden 
  very 
  quickly 
  to 
  a 
  jet-black 
  enamel. 
  With 
  less 
  

   sulphur 
  the 
  color 
  is 
  brown 
  in 
  thin 
  films. 
  

  

  16. 
  Solution 
  in 
  mixtures 
  of 
  solvents, 
  and 
  solution 
  of 
  mixed 
  

   gums. 
  — 
  By 
  acting 
  on 
  vulcanized 
  rubbers 
  with 
  mixed 
  solvents 
  

   of 
  the 
  above 
  kind, 
  I 
  obtained 
  very 
  satisfactory 
  results. 
  All 
  

   the 
  rubbers 
  mentioned 
  {a 
  to 
  e\ 
  ebonite 
  excepted, 
  pass 
  easily 
  

   into 
  true 
  solution 
  by 
  such 
  treatment. 
  Thus 
  the 
  gray 
  elastic 
  

   rubber 
  (b) 
  dissolves 
  at 
  once 
  in 
  a 
  mixture 
  of 
  CS 
  2 
  with 
  gasolene, 
  

   or 
  benzol, 
  or 
  ether, 
  etc. 
  ; 
  or 
  of 
  benzol 
  and 
  toluol 
  ; 
  or 
  less 
  

   easily 
  in 
  mixtures 
  of 
  benzol 
  and 
  gasolene 
  ; 
  etc. 
  Ebonite 
  is 
  

   partially 
  de 
  vulcanized, 
  and 
  would 
  probably 
  be 
  dissolved 
  in 
  

   large 
  excess 
  of 
  solvent. 
  § 
  3. 
  ~No 
  gas 
  was 
  evolved 
  in 
  any 
  

   case, 
  § 
  19, 
  which 
  is 
  an 
  advantage 
  of 
  this 
  method. 
  In 
  all 
  

   cases 
  the 
  solutions 
  hardened 
  rapidly 
  on 
  exposure 
  to 
  air, 
  yield- 
  

   ing 
  the 
  pigmented 
  rubber 
  if 
  the 
  solution 
  be 
  shaken, 
  or 
  a 
  

   purer 
  rubber, 
  if 
  the 
  sediment 
  be 
  removed 
  by 
  subsidence 
  and 
  

   decantation. 
  

  

  Equally 
  feasible 
  is 
  the 
  solution 
  of 
  mixed 
  gums 
  in 
  a 
  suitable 
  

   solvent 
  at 
  200°. 
  Thus 
  I 
  made 
  solutions 
  of 
  mixed 
  vulcanized 
  

   rubber 
  and 
  gutta 
  percha 
  in 
  CS 
  2 
  , 
  which 
  dried 
  at 
  once 
  on 
  ex- 
  

   posure 
  to 
  air 
  ; 
  mixtures 
  of 
  rubber 
  and 
  shellac 
  dissolved 
  in 
  CS 
  2 
  , 
  

   drying 
  more 
  slowly; 
  mixtures 
  of 
  vulcanized 
  rubber 
  and 
  rosin 
  

   dissolved 
  in 
  CS 
  2 
  and 
  in 
  gasolene, 
  which 
  dried 
  in 
  thin 
  films 
  only 
  

   after 
  long 
  exposure 
  ; 
  etc. 
  

  

  IT. 
  Direct 
  devulcanization. 
  — 
  When, 
  by 
  any 
  of 
  the 
  above 
  

   methods 
  a 
  solution 
  of 
  vulcanized 
  rubber 
  is 
  obtainable, 
  direct 
  

   devulcanization 
  may 
  be 
  attempted 
  by 
  mixing 
  the 
  charge 
  with 
  

   some 
  sulphur 
  absorbent. 
  Such 
  material 
  must 
  be 
  chosen 
  which 
  

   at 
  200° 
  acts 
  neither 
  on 
  the 
  rubber 
  nor 
  the 
  solvent. 
  Metallic 
  

   filings 
  do 
  not 
  appear 
  to 
  be 
  available. 
  Treating 
  ebonite 
  with 
  

   CS 
  2 
  , 
  C 
  6 
  H 
  6 
  > 
  or 
  gasolene, 
  to 
  which 
  copper 
  filings 
  had 
  been 
  added, 
  

   I 
  found 
  the 
  charge, 
  after 
  exposing 
  to 
  200°, 
  to 
  be 
  disintegrated, 
  

   while 
  an 
  enormous 
  amount 
  of 
  gas 
  was 
  evolved. 
  Scarcely 
  

   any 
  of 
  the 
  solvent 
  was 
  left 
  in 
  the 
  tube 
  The 
  direct 
  action 
  of 
  

   copper 
  or 
  of 
  sulphur, 
  on 
  CS 
  2 
  , 
  etc., 
  at 
  200° 
  is 
  insufficient 
  to 
  

   account 
  for 
  this 
  reaction. 
  § 
  19. 
  The 
  gas 
  must, 
  therefore, 
  be 
  

   produced 
  at 
  the 
  expense 
  of 
  the 
  ebonite, 
  or 
  of 
  the 
  reagent 
  in 
  

   presence 
  of 
  ebonite 
  ; 
  and 
  since 
  all 
  the 
  solvents 
  used 
  behave 
  

   alike, 
  at 
  the 
  expense 
  of 
  the 
  ebonite. 
  This 
  may 
  furnish 
  some 
  

   clue 
  as 
  to 
  the 
  chemical 
  character 
  of 
  the 
  rubber 
  as 
  related 
  to 
  the 
  

   gases 
  evolved. 
  Gaseous 
  decomposition 
  frequently 
  sets 
  in 
  on 
  

   exposure 
  of 
  highly 
  vulcanized 
  rubber 
  solutions 
  even 
  to 
  ordinary 
  

   room 
  temperatures, 
  whereas 
  at 
  0° 
  and 
  under 
  slight 
  pressure 
  (1 
  

   or 
  2 
  atm.) 
  the 
  gas 
  remains 
  in 
  combination. 
  Bright 
  steel 
  is 
  

  

  