﻿366 
  0. 
  JBarus 
  — 
  Solution 
  of 
  Vulcanized 
  India 
  Rubber. 
  

  

  Similar 
  results 
  were 
  obtained 
  with 
  benzol, 
  with 
  gasolene 
  and 
  

   higher 
  petroleum 
  oils, 
  etc. 
  Fusion 
  is 
  absent 
  or 
  only 
  incipient 
  

   at 
  160°, 
  and 
  more 
  than 
  complete 
  at 
  210°, 
  provided 
  the 
  gasolene 
  

   be 
  not 
  too 
  volatile. 
  §§4, 
  12. 
  In 
  general 
  the 
  gray 
  rubbers 
  

   (6, 
  c) 
  fuse 
  to 
  a 
  more 
  viscous 
  mass 
  than 
  the 
  gum 
  rubbers 
  (a), 
  the 
  

   consistency 
  of 
  cold 
  solutions 
  in 
  the 
  latter 
  case 
  about 
  that 
  of 
  

   treacle. 
  

  

  The 
  occurrences 
  of 
  this 
  paragraph 
  therefore 
  would 
  resemble 
  

   the 
  fusion 
  of 
  a 
  salt 
  in 
  its 
  water 
  of 
  crystallization, 
  but 
  for 
  the 
  

   exceptional 
  behavior 
  that 
  impregnated 
  vulcanized 
  rubber 
  after 
  

   fusion 
  retains 
  a 
  consistency 
  which 
  is 
  liquid 
  relatively 
  to 
  the 
  

   original 
  non-impregnated 
  charge. 
  The 
  analogy 
  with 
  the 
  solu- 
  

   tion 
  of 
  starch, 
  or 
  of 
  gluten, 
  is 
  thus 
  more 
  close 
  and 
  immediate. 
  

   In 
  all 
  these 
  cases 
  the 
  solid 
  swells 
  up 
  when 
  impregnated 
  with 
  

   the 
  solvent, 
  and 
  fuses 
  to 
  a 
  relatively 
  less 
  viscous 
  consistency, 
  

   or 
  to 
  a 
  thin 
  solution, 
  when 
  a 
  certain 
  temperature 
  (below 
  

   100° 
  in 
  case 
  of 
  starch 
  and 
  gluten 
  and 
  above 
  160° 
  in 
  case 
  of 
  

   vulcanized 
  india 
  rubber) 
  has 
  been 
  reached. 
  Hence 
  it 
  is 
  not 
  

   unreasonable 
  to 
  suspect 
  that 
  even 
  ordinary 
  dry 
  wood, 
  or 
  woody 
  

   tissue, 
  which 
  swells 
  to 
  a 
  marked 
  degree 
  when 
  impregnated 
  

   with 
  water, 
  may 
  pass 
  into 
  actual 
  solution 
  if 
  the 
  temperature 
  at 
  

   which 
  the 
  water 
  acts 
  is 
  sufficiently 
  high, 
  and 
  the 
  pressure 
  

   above 
  the 
  vapor 
  tension 
  of 
  water 
  at 
  that 
  temperature.* 
  

  

  I 
  mention 
  finally 
  that 
  the 
  reduction 
  of 
  melting 
  point 
  pro- 
  

   duced 
  in 
  vulcanized 
  india 
  rubber 
  by 
  the 
  impregnating 
  reagents 
  

   may 
  perhaps 
  advantageously 
  be 
  discussed 
  in 
  accordance 
  with 
  

   Raoult's 
  law 
  ; 
  but 
  owing 
  to 
  the 
  difficulty 
  of 
  defining 
  the 
  melt- 
  

   ing 
  point 
  of 
  the 
  unimpregnated 
  rubber, 
  and 
  the 
  close 
  prox- 
  

   imity 
  of 
  the 
  melting 
  points 
  after 
  impregnation 
  with 
  different 
  

   reagents 
  (CS 
  2 
  , 
  C 
  6 
  H 
  6 
  , 
  gasolene) 
  my 
  views 
  on 
  this 
  subject 
  have 
  

   not 
  taken 
  shape. 
  It 
  is 
  known 
  that 
  in 
  general 
  that 
  the 
  melting 
  

   point 
  produced 
  by 
  a 
  dissolved 
  colloid 
  is 
  relatively 
  very 
  small, 
  

   from 
  which 
  an 
  exceedingly 
  large 
  molecular 
  weight 
  of 
  the 
  colloid 
  

   has 
  been 
  inferred. 
  The 
  above 
  results 
  show 
  that 
  in 
  the 
  converse 
  

   experiment, 
  where 
  the 
  melting 
  point 
  of 
  the 
  colloid 
  is 
  lowered 
  

   by 
  a 
  solvent, 
  the 
  effects 
  will 
  probably 
  be 
  normal 
  and 
  pronounced. 
  

  

  Nevertheless 
  I 
  doubt 
  whether 
  the 
  thin 
  rubber 
  fluids 
  obtained 
  

   are 
  true 
  solutions, 
  i. 
  e. 
  represent 
  a 
  case 
  in 
  which 
  the 
  division 
  

   of 
  the 
  solid 
  has 
  actually 
  reached 
  a 
  definite 
  molecule 
  ; 
  for 
  on 
  

  

  * 
  I 
  have 
  since 
  tested 
  this 
  surmise 
  at 
  some 
  length, 
  but 
  found 
  in 
  every 
  case 
  that 
  

   cellulose 
  is 
  decomposed 
  before 
  solution 
  in 
  water 
  takes 
  place. 
  In 
  spite 
  of 
  the 
  

   presence 
  of 
  water 
  under 
  pressure, 
  the 
  phenomenon 
  seems 
  to 
  be 
  a 
  dry 
  distillation. 
  

   1 
  may 
  here 
  refer 
  to 
  the 
  remarkably 
  close 
  analogies 
  in 
  the 
  thermal 
  behavior 
  of 
  

   rubber 
  and 
  gelatine 
  which 
  have 
  recently 
  been 
  discovered 
  by 
  Bjerken 
  (Wied. 
  Ann., 
  

   xliii, 
  p. 
  817, 
  1891). 
  The 
  author 
  lias 
  reason 
  to 
  believe 
  that 
  moist 
  gelatines 
  are 
  

   heterogeneous 
  mixtures 
  of 
  solid 
  and 
  liquid. 
  The 
  behavior 
  of 
  rubber, 
  as 
  discussed 
  

   above, 
  is 
  characterized 
  at 
  low 
  temperatures 
  by 
  a 
  tixed 
  maximum 
  of 
  absorbed 
  sol- 
  

   vent. 
  The 
  term 
  mixture 
  is 
  scarcely 
  applicable 
  at 
  once. 
  

  

  