﻿368 
  C. 
  Barus 
  — 
  Solution 
  of 
  Vulcanized 
  India 
  Hubber. 
  

  

  a 
  reciprocal 
  expression 
  of 
  the 
  affinity 
  of 
  the 
  given 
  metal 
  for 
  

   sulphur, 
  — 
  bearing 
  always 
  in 
  mind 
  that 
  the 
  stability 
  of 
  the 
  

   solid 
  metallic 
  molecule 
  also 
  enters 
  into 
  the 
  consideration. 
  The 
  

   arbitrary 
  reagent 
  CS 
  2 
  , 
  in 
  its 
  relations 
  to 
  all 
  the 
  metals 
  to 
  be 
  

   examined, 
  fulfills 
  a 
  similar 
  purpose 
  to 
  an 
  arbitrary 
  spring 
  

   balance 
  in 
  measuring 
  gravitational 
  forces. 
  § 
  21. 
  

  

  20. 
  Summary 
  of 
  the 
  results. 
  — 
  In 
  the 
  above 
  paragraphs 
  I 
  

   have 
  therefore 
  indicated 
  a 
  method 
  by 
  which 
  vulcanized 
  india 
  

   rubber 
  of 
  any 
  quality 
  or 
  character 
  whatever, 
  as 
  well 
  as 
  the 
  

   undecomposed 
  or 
  reclaimable 
  part 
  of 
  rubber 
  waste, 
  may 
  be 
  

   dissolved 
  or 
  liquified 
  in 
  a 
  reasonably 
  short 
  time 
  ;* 
  the 
  solutions 
  

   possessing 
  any 
  desirable 
  degree 
  of 
  viscosity 
  or 
  diluteness, 
  from 
  

   which 
  india 
  rubber 
  may 
  be 
  regained 
  on 
  evaporation 
  of 
  the 
  

   solvent. 
  

  

  I 
  shall 
  elsewhere 
  describe 
  divers 
  forms 
  of 
  apparatus 
  by 
  

   which 
  the 
  above 
  operations 
  may 
  be 
  carried 
  out 
  on 
  a 
  larger 
  scale. 
  

   They 
  are 
  of 
  no 
  interest 
  here 
  ; 
  but 
  I 
  mention 
  them 
  since 
  it 
  is 
  

   only 
  from 
  such 
  work 
  that 
  a 
  full 
  insight 
  into 
  the 
  quality 
  of 
  the 
  

   rubber 
  deposited 
  from 
  any 
  given 
  solution 
  may 
  be 
  obtained. 
  

   Experiments 
  made 
  in 
  bulk 
  in 
  this 
  way 
  showed 
  the 
  material 
  

   deposited 
  from 
  solution 
  to 
  be 
  considerably 
  inferior 
  to 
  the 
  orig- 
  

   inal 
  rubber, 
  both 
  as 
  regards 
  tenacity 
  and 
  elasticity. 
  Its 
  chief 
  

   value 
  in 
  the 
  physical 
  laboratory 
  will 
  therefore 
  be 
  that 
  of 
  fur- 
  

   nishing 
  an 
  air-tight 
  cement 
  or 
  an 
  acid-proof 
  varnish, 
  capable 
  

   of 
  withstanding 
  more 
  than 
  200° 
  centigrade. 
  Rubber 
  newly 
  

   deposited 
  from 
  any 
  of 
  the 
  above 
  solutions 
  presents 
  a 
  very 
  

   curious 
  case 
  of 
  slowly 
  reacting 
  elasticity. 
  If 
  a 
  thread, 
  say 
  0*1 
  

   cm. 
  thick, 
  be 
  twisted 
  and 
  then 
  let 
  go 
  on 
  a 
  frictionless 
  surface, 
  

   it 
  will 
  squirm 
  like 
  a 
  live 
  worm 
  for 
  some 
  minutes. 
  If 
  it 
  be 
  

   stretched, 
  the 
  original 
  length 
  is 
  regained 
  with 
  visible 
  slowness. 
  

  

  Throughout 
  my 
  work 
  the 
  approximate 
  constancy 
  of 
  the 
  dis- 
  

   solution 
  temperature 
  irrespective 
  of 
  the 
  solvent 
  has 
  been 
  the 
  

   marked 
  feature. 
  Thus 
  in 
  case 
  of 
  CS 
  2 
  , 
  of 
  turpentine, 
  of 
  the 
  

   vulcanization 
  of 
  dissolved 
  pure 
  india 
  rubber, 
  etc., 
  no 
  action 
  

   took 
  place 
  below 
  160°. 
  Even 
  this 
  temperature 
  is 
  higher 
  than 
  

   is 
  needful 
  for 
  vulcanization 
  effected 
  in 
  the 
  dry 
  way, 
  where 
  

   110° 
  to 
  140° 
  are 
  deemed 
  sufficient. 
  Moreover 
  the 
  solution 
  of 
  

   vulcanized 
  rubber 
  in 
  CS 
  2 
  , 
  for 
  instance, 
  takes 
  place 
  quite 
  as 
  

   easily 
  under 
  700 
  atm. 
  as 
  under, 
  say 
  20 
  atm., 
  as 
  is 
  particularly 
  

   manifest 
  from 
  the 
  fusion 
  of 
  impregnated 
  rubber, 
  and 
  in 
  special 
  

   high 
  pressure 
  experiments. 
  In 
  my 
  work 
  on 
  the 
  compressibility 
  

   of 
  liquidsf 
  I 
  showed 
  that 
  compressibility 
  is 
  essentially 
  asso- 
  

   ciated 
  with 
  the 
  extra-molecular 
  forces 
  whereas 
  the 
  molecule 
  

   remains 
  relatively 
  incompressible. 
  Temperature, 
  however, 
  has 
  

   immediate 
  access 
  to 
  the 
  molecule 
  ; 
  and 
  thus 
  it 
  follows 
  that 
  

  

  * 
  Practically 
  at 
  once, 
  if 
  the 
  material 
  is 
  not 
  too 
  bulky, 
  

   f 
  This 
  Journal, 
  xxxix, 
  p. 
  510, 
  1890. 
  

  

  