﻿C. 
  Barus 
  — 
  Solution 
  of 
  Vulcanized 
  India 
  Rubber. 
  365 
  

  

  scarcely 
  attacked.* 
  In 
  fusing 
  impregnated 
  india 
  rubber, 
  § 
  18 
  

   I 
  frequently 
  noticed 
  that 
  the 
  colder 
  ends 
  of 
  the 
  mass 
  were 
  

   opaquely 
  discolored. 
  Possibly, 
  therefore, 
  the 
  sulphur 
  at 
  200° 
  

   may 
  be 
  gradually 
  segregated 
  by 
  diffusion 
  or 
  evaporation. 
  My 
  

   experiments 
  on 
  this 
  subject 
  failed. 
  

  

  18. 
  Fusion 
  of 
  impregnated 
  rubber. 
  — 
  If 
  vulcanized 
  india 
  

   rubber 
  be 
  impregnated 
  or 
  saturated 
  by 
  digesting 
  it 
  with 
  the 
  

   cold 
  reagent 
  (any 
  solvent 
  of 
  pure 
  rubber), 
  for 
  a 
  suitable 
  time 
  

   (a 
  few 
  minutes 
  to 
  many 
  hours), 
  the 
  swelled 
  mass 
  not 
  only 
  

   shows 
  a 
  relatively 
  low 
  melting 
  point, 
  but 
  it 
  remains 
  liquid 
  

   after 
  cooling, 
  provided 
  the 
  solvent 
  is 
  not 
  allowed 
  to 
  escape. 
  

   This 
  is 
  an 
  observation 
  of 
  practical 
  importance, 
  since 
  the 
  re- 
  

   tortsf 
  can 
  thus 
  be 
  charged 
  with 
  solid 
  or 
  dry 
  rubber, 
  a 
  minimum 
  

   of 
  solvent 
  be 
  used 
  in 
  treating 
  or 
  lost 
  by 
  evaporation, 
  and 
  con- 
  

   centrated 
  solutions 
  be 
  obtained 
  often 
  fit 
  to 
  be 
  used 
  at 
  once. 
  

   The 
  rubber 
  so 
  melted 
  hardens 
  on 
  exposure. 
  Finally 
  the 
  pres- 
  

   sure 
  necessary 
  in 
  this 
  case 
  is 
  the 
  smallest 
  possible, 
  and 
  may 
  be 
  

   below 
  the 
  data 
  given 
  for 
  the 
  divers 
  solvents 
  above. 
  

  

  The 
  quantity 
  of 
  solvent 
  retained 
  by 
  solid 
  rubber 
  is 
  very 
  

   large 
  : 
  Thus 
  elastic 
  sheet 
  rubber 
  will 
  hold 
  7 
  or 
  8 
  times 
  its 
  

   weight 
  of 
  CS 
  2 
  , 
  or 
  1 
  to 
  2 
  times 
  its 
  weight 
  of 
  naphtha. 
  Gray 
  

   rubber 
  (elastic) 
  absorbs 
  more 
  than 
  its 
  weight 
  of 
  naphtha 
  ; 
  etc. 
  

  

  Experiments 
  may 
  be 
  cited 
  as 
  follows 
  : 
  Non-impregnated 
  

   vulcanized 
  rubbers 
  [a 
  to 
  e) 
  do 
  not 
  melt 
  if 
  exposed 
  in 
  a 
  closed 
  

   tube 
  at 
  210°. 
  Only 
  in 
  the 
  case 
  of 
  very 
  slightly 
  vulcanized 
  

   pure 
  rubber 
  gum 
  is 
  there 
  a 
  trace 
  of 
  fusion 
  perceptible 
  at 
  the 
  

   edges, 
  and 
  here 
  it 
  may 
  even 
  be 
  due 
  to 
  a 
  stain 
  of 
  dirt 
  (oil) 
  acci- 
  

   dentally 
  left 
  there. 
  Gray 
  rubbers 
  (b, 
  c) 
  with 
  a 
  superficial 
  coat- 
  

   ing 
  of 
  exuded 
  sulphur, 
  turn 
  black 
  from 
  the 
  formation 
  of 
  a 
  film 
  

   of 
  ebonite. 
  

  

  All 
  the 
  india 
  rubbers 
  {a 
  to 
  e) 
  fuse 
  at 
  210°, 
  when 
  previously 
  

   saturated, 
  or 
  nearly 
  so. 
  with 
  cold 
  carbon 
  disulphide, 
  and 
  exposed 
  

   in 
  a 
  close-fitting 
  glass 
  tube. 
  If 
  the 
  pressure 
  be 
  reduced 
  by 
  a 
  

   capillary 
  aperture 
  at 
  one 
  end 
  of 
  the 
  otherwise 
  closed 
  glass 
  tube, 
  

   or 
  if 
  the 
  tube 
  be 
  only 
  partially 
  filled 
  and 
  the 
  empty 
  end 
  kept 
  

   cool, 
  the 
  impregnating 
  solvent 
  is 
  merely 
  distilled 
  off, 
  and 
  no 
  

   fusion 
  takes 
  place. 
  Whereas 
  at 
  160° 
  fusion 
  scarcely 
  occurs, 
  

   melting 
  seems 
  to 
  be 
  complete 
  in 
  the 
  well 
  impregnated 
  elastic 
  

   rubber 
  (a) 
  at 
  175°. 
  There 
  is 
  therefore 
  an 
  approximate 
  coinci- 
  

   dence 
  of 
  the 
  thermal 
  data 
  in 
  the 
  present 
  and 
  in 
  the 
  above 
  

   paragraphs. 
  

  

  * 
  Fortunately, 
  therefore, 
  steel 
  apparatus 
  is 
  available 
  on 
  a 
  large 
  scale. 
  An 
  

   interesting 
  question 
  occurs 
  as 
  to 
  what 
  becomes 
  of 
  the 
  carbon, 
  in 
  the 
  case 
  where 
  

   sodium, 
  mercury, 
  copper, 
  etc., 
  are 
  attacked 
  by 
  hot 
  liquid 
  CS 
  2 
  and 
  not 
  by 
  cold 
  CS. 
  2 
  . 
  

  

  f 
  The 
  present 
  experiments 
  were 
  made 
  in 
  closed 
  glass 
  tubes, 
  nearly 
  filled 
  with 
  

   the 
  impregnated 
  rubber. 
  After 
  fusion 
  the 
  mass 
  frequently 
  appeared 
  to 
  have 
  

   shrunk. 
  Uf. 
  § 
  2. 
  

  

  