﻿Adsorption 
  of 
  Hydrogen 
  hy 
  Carbon. 
  931 
  

  

  total 
  solubility 
  at 
  19 
  mm. 
  was 
  4*0 
  c.c. 
  (corr.). 
  The 
  differ- 
  

   ence 
  between 
  the 
  two 
  numbers 
  (which 
  in 
  these 
  particular 
  

   experiments 
  were 
  merely 
  semiquantitative) 
  indicates 
  the 
  

   excess 
  of 
  solubility 
  o£ 
  hydrooen 
  in 
  carbon 
  at 
  the 
  tempera- 
  

   ture 
  of 
  liquid 
  air 
  (at 
  19 
  mm.), 
  over 
  its 
  solubility 
  at 
  room 
  

   temperature 
  (under 
  1200 
  mm. 
  pressure). 
  

  

  It 
  follows 
  that 
  the 
  solubility 
  of 
  hydrogen 
  in 
  carbon 
  at 
  room 
  

   temperature 
  is 
  nothing 
  like 
  as 
  great 
  as 
  that 
  at 
  the 
  temperature 
  

   of 
  liquid 
  air, 
  even 
  though 
  the 
  gas 
  pressure 
  be 
  60-fold 
  greater 
  in 
  

   the 
  former 
  case. 
  Of 
  course 
  the 
  pressure 
  difference 
  may 
  be 
  

   allowed 
  for 
  on 
  the 
  assumption 
  that 
  the 
  solubiUty 
  at 
  room 
  

   temperature 
  also 
  varies 
  as 
  the 
  square 
  root 
  of 
  the 
  pressure, 
  

   and 
  the 
  two 
  solubilities 
  may 
  then 
  be 
  compared 
  directly. 
  

   Here 
  we 
  get 
  the 
  result 
  that 
  the 
  solubility 
  is 
  at 
  least 
  a 
  

   hundredfold 
  greater 
  at 
  the 
  temperature 
  of 
  liquid 
  air. 
  For 
  

   accurate 
  work 
  a 
  thermostat 
  of 
  fixed 
  and 
  constant 
  tempera- 
  

   ture 
  (e. 
  g. 
  liquid 
  oxygen) 
  would 
  be 
  required, 
  and 
  compara- 
  

   tive 
  experiments 
  would 
  have 
  to 
  be 
  carried 
  out 
  under 
  strictly 
  

   comparable 
  conditions. 
  

  

  Probably 
  the 
  most 
  accurate 
  method 
  of 
  all, 
  which 
  was 
  not 
  

   investigated, 
  would 
  consist 
  in 
  exposing 
  the 
  carbon 
  at 
  room 
  

   temperature 
  to 
  greater 
  and 
  greater 
  f)ressures 
  of 
  hydrogen, 
  

   until 
  on 
  plunging 
  the 
  carbon 
  bulb 
  into 
  into 
  liquid 
  air, 
  the 
  

   pressure 
  becomes 
  quite 
  constant 
  within 
  say 
  fifteen 
  minutes 
  

   (time 
  for 
  the 
  carbon 
  to 
  assume 
  the 
  temperature 
  of 
  the 
  liquid 
  

   air). 
  It 
  is 
  easily 
  seen 
  that 
  this 
  phenomenon 
  will 
  only 
  be 
  

   observed 
  when 
  the 
  actual 
  amount 
  of 
  dissolved 
  hydrogen 
  at 
  

   room 
  temperature 
  under 
  very 
  high 
  pressure 
  is 
  the 
  same 
  as 
  

   it 
  is 
  at 
  very 
  low 
  temperature 
  and 
  pressure. 
  Thus, 
  the 
  relation- 
  

   ship 
  between 
  solubility 
  and 
  pressure 
  at 
  ordinary 
  temperature 
  

   might 
  be 
  studied. 
  

  

  It 
  is 
  interesting 
  to 
  note 
  that 
  this 
  method 
  measures 
  directly 
  

   the 
  difference 
  in 
  the 
  amount 
  of 
  surface 
  condensation 
  at 
  the 
  

   two 
  temperatures. 
  This 
  follows 
  from 
  the 
  fact 
  that 
  owing 
  to 
  

   the 
  conditions 
  of 
  the 
  experiment, 
  the 
  solid 
  solution 
  is 
  constant 
  

   in 
  amount. 
  

  

  Sorption 
  at 
  Boom 
  Temperature. 
  

  

  The 
  diffusion 
  of 
  hydrogen 
  into 
  carbon 
  is 
  not 
  quite 
  instan- 
  

   taneous 
  even 
  at 
  ordinary 
  temperatures, 
  as 
  shown 
  by 
  the 
  

   following 
  experiment 
  (among 
  others): 
  — 
  

  

  