﻿The 
  Adsorption 
  of 
  Hydrogen 
  hj 
  Carbon. 
  917 
  

  

  Thus 
  by 
  suitable 
  manipulation 
  a 
  sample 
  of 
  carbon 
  can 
  be 
  

   prepared 
  highly 
  charged 
  with 
  hydrogen 
  in 
  a 
  state 
  of 
  solid 
  

   solution, 
  -but 
  almost 
  destitute 
  of 
  adsorbed 
  hydrogen 
  condensed 
  

   on 
  the 
  surface. 
  This 
  is 
  clearly 
  attainable 
  (if 
  the 
  hypothesis 
  

   be 
  correct) 
  by 
  suddenly 
  exposing 
  to 
  a 
  vacuum 
  carbon 
  which 
  

   has 
  been 
  previously 
  saturated 
  by 
  long 
  contact 
  with 
  hydrogen 
  

   at 
  a 
  constant 
  temperature. 
  

  

  Such 
  carbon, 
  exposed 
  to 
  a 
  low 
  pressure 
  of 
  hydrogen 
  and 
  

   cut 
  off 
  from 
  all 
  external 
  influences, 
  took 
  up 
  hydrogen 
  at 
  first 
  

   (surface-condensation) 
  although 
  already 
  supersaturated 
  (i. 
  e. 
  

   in 
  respect 
  to 
  the 
  solid 
  solution) 
  and 
  then 
  gave 
  it 
  off 
  again 
  in 
  

   still 
  greater 
  quantity 
  until 
  final 
  equilibrium 
  was 
  established. 
  

   Tims 
  the 
  manometer 
  first 
  fell 
  and 
  then 
  rose 
  to 
  a 
  higlier 
  point 
  

   than 
  the 
  initial 
  value 
  (cf. 
  Table 
  VIII. 
  below). 
  

  

  In 
  the 
  converse 
  case 
  where 
  the 
  interior 
  was 
  free 
  from 
  

   hydrogen 
  but 
  the 
  surface 
  had 
  become 
  supersaturated 
  by 
  a 
  

   very 
  short 
  exposure 
  to 
  a 
  high 
  pressure 
  of 
  gas, 
  the 
  hydrogen 
  

   was 
  first 
  given 
  oft', 
  and 
  then 
  taken 
  up 
  again 
  by 
  diffusion 
  into 
  

   the 
  carbon. 
  Here 
  the 
  manometer 
  automatically 
  rose 
  and 
  then 
  

   steadily 
  fell 
  to 
  a 
  lower 
  value 
  than 
  previously 
  obtained 
  {cf. 
  

   Tables 
  ll. 
  to 
  VII.). 
  

  

  The 
  experimental 
  investigation 
  consisted 
  in 
  modifications 
  

   of 
  these 
  two 
  types 
  of 
  experiments 
  and 
  included 
  various 
  tests 
  

   systematically 
  applied 
  as 
  checks. 
  The 
  results 
  bear 
  out 
  the 
  

   theory 
  proposed 
  in 
  the 
  most 
  satisfactory 
  manner. 
  

  

  The 
  experiments 
  were 
  carried 
  out 
  in 
  an 
  apparatus 
  identical 
  

   with 
  that 
  which 
  Travers 
  had 
  employed 
  (see 
  Proc. 
  Roy. 
  Soc. 
  

   Ixxviii. 
  A. 
  p. 
  9 
  (1906), 
  where 
  a 
  figure 
  is 
  also 
  given). 
  The 
  

   apparatus 
  consists 
  essentially 
  of 
  a 
  bulb 
  filled 
  with 
  carbon, 
  

   connected 
  with 
  a 
  mercury 
  manometer 
  by 
  means 
  of 
  a 
  capillary 
  

   tube"^. 
  In 
  addition 
  various 
  attachments 
  allow 
  measured 
  

   quantities 
  of 
  gas 
  to 
  be 
  introduced 
  or 
  removed 
  by 
  the 
  aid 
  of 
  

   a 
  Toepler 
  pump. 
  

  

  The 
  carbon 
  was 
  practically 
  freed 
  from 
  gas 
  by 
  exposing 
  it 
  

   to 
  a 
  vacuum 
  at 
  a 
  temperature 
  of 
  M0° 
  C. 
  (boiling 
  sulphur), 
  

   but 
  to 
  obtain 
  a 
  high 
  vacuum 
  in 
  the 
  presence 
  of 
  carbon 
  

   requires 
  very 
  prolonged 
  pumping 
  indeed. 
  

  

  During 
  the 
  experiments 
  the 
  bulb 
  was 
  kept 
  at 
  the 
  experi- 
  

   mental 
  temperature 
  by 
  means 
  of 
  a 
  water-bath 
  or 
  more 
  usually 
  

   by 
  immersing 
  it 
  in 
  liquid 
  air. 
  

  

  The 
  mercury 
  manometer 
  was 
  read 
  by 
  means 
  of 
  a 
  telescope 
  

   attached 
  to 
  a 
  permanent 
  rigid 
  support. 
  The 
  eyepiece 
  was 
  

  

  * 
  A 
  small 
  plug- 
  of 
  glass-wool 
  was 
  employed 
  to 
  prevent 
  tlie 
  carbon 
  

   from 
  rising 
  into 
  the 
  capillary 
  tube, 
  in 
  place 
  of 
  the 
  asbestos 
  used 
  by 
  

   Travers. 
  

  

  Fkil. 
  Mag. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  108. 
  Dec. 
  1909. 
  3 
  Q 
  

  

  