﻿Adsorption 
  of 
  Hydrogen 
  hy 
  Carbon, 
  923 
  

  

  at 
  the 
  lowest 
  pressure 
  67*70 
  c.c. 
  (corr.); 
  that 
  is 
  a 
  difference 
  

   of 
  0*73 
  c.c, 
  or 
  just 
  over 
  1 
  per 
  cent. 
  

  

  But 
  attention 
  must 
  be 
  drawn 
  to 
  the 
  one 
  feature 
  of 
  great 
  

   significance, 
  viz. 
  that 
  the 
  higher 
  pressure 
  at 
  5^ 
  minutes 
  

   was 
  even 
  less 
  than 
  corresponded 
  to 
  the 
  gas 
  condensed 
  on 
  the 
  

   surface 
  of 
  the 
  carbon, 
  and 
  jet 
  after 
  a 
  dozen 
  hours 
  had 
  

   elapsed 
  a 
  much 
  lower 
  pressure 
  was 
  attained, 
  a 
  pressure 
  

   which 
  then 
  actually 
  did 
  correspond 
  to 
  the 
  condensed 
  gas 
  in 
  

   equilibrium 
  with 
  it. 
  Thus 
  a 
  considerable 
  body 
  of 
  hydrogen 
  

   has 
  been 
  transferred 
  from 
  the 
  surface 
  to 
  the 
  interior 
  of 
  the 
  

   carbon. 
  

  

  The 
  extent 
  of 
  this 
  transfer 
  can 
  be 
  at 
  least 
  approximately 
  

   calculated. 
  The 
  calculation 
  may 
  be 
  based 
  upon 
  the 
  assump- 
  

   tion 
  that 
  at 
  the 
  beginning 
  all 
  the 
  gas 
  is 
  on 
  the 
  surface, 
  and 
  

   that 
  only 
  after 
  many 
  hours 
  does 
  the 
  interior 
  solid 
  solution 
  

   reach 
  its 
  normal 
  concentration. 
  

  

  The 
  pressure 
  at 
  5^ 
  minutes 
  (e. 
  g. 
  Table 
  VII.) 
  is 
  certainly 
  

   too 
  low 
  to 
  correspond 
  to 
  the 
  surface 
  condensation 
  alone 
  

   (although 
  it 
  must 
  be 
  taken 
  for 
  the 
  calculation), 
  for 
  there 
  is 
  

   considerable 
  opportunity 
  for 
  diffusion 
  to 
  take 
  place, 
  even 
  

   under 
  the 
  best 
  circumstances. 
  The 
  approach 
  to 
  the 
  value 
  it 
  

   would 
  have 
  were 
  all 
  the 
  gas 
  condensed 
  in 
  the 
  surface 
  and 
  

   none 
  in 
  the 
  interior, 
  is 
  clearly 
  greater 
  the 
  sooner 
  the 
  pressure 
  

   reading 
  is 
  taken 
  after 
  the 
  removal 
  of 
  the 
  gas, 
  and 
  the 
  less 
  

   amount 
  removed 
  from 
  the 
  apparatus 
  and 
  the 
  shorter 
  the 
  

   initial 
  exposure 
  of 
  the 
  carbon 
  to 
  the 
  gas 
  at 
  high 
  pressure. 
  

  

  The 
  minimum 
  pressure 
  observed 
  later 
  on 
  in 
  the 
  experiment 
  

   requires 
  two 
  corrections. 
  In 
  the 
  first 
  place 
  the 
  value 
  is 
  

   higher 
  than 
  it 
  would 
  have 
  been 
  had 
  no 
  new 
  gas 
  passed 
  into 
  

   the 
  carbon 
  out 
  of 
  the 
  bulb 
  and 
  manometer. 
  This 
  can 
  be 
  

   allowed 
  for 
  by 
  using 
  the 
  equilibrium 
  formula 
  found 
  by 
  

   Travers 
  *, 
  \^p 
  = 
  kx^ 
  where 
  p 
  is 
  the 
  pressure, 
  and 
  ka 
  constant, 
  

   and 
  X 
  the 
  percentage 
  of 
  hydrogen 
  sorbed 
  by 
  the 
  carbon. 
  In 
  

   the 
  second 
  place 
  the 
  liquid 
  air 
  of 
  the 
  thermostat 
  has 
  been 
  

   evaporating, 
  its 
  composition 
  varying, 
  and 
  consequently 
  the 
  

   temperature 
  slowly 
  rising; 
  a 
  correction 
  for 
  this 
  was 
  made 
  by 
  

   blank 
  experiments. 
  

  

  If 
  the 
  calculation 
  be 
  carried 
  out 
  for 
  the 
  experiment 
  re- 
  

   corded 
  in 
  Table 
  VII. 
  an 
  observed 
  minimum 
  pressure 
  of 
  

   19*0 
  mm, 
  is 
  found. 
  The 
  temperature 
  correction 
  leaves 
  ap- 
  

   proximately 
  17*9 
  mm. 
  The 
  total 
  amount 
  of 
  sorbed 
  gas 
  is 
  

   67*70 
  c.c. 
  (corr.), 
  of 
  which 
  0*73 
  c.c. 
  passed 
  into 
  the 
  carbon 
  

   from 
  the 
  bulb 
  and 
  manometer 
  spaces 
  while 
  the 
  diffusion 
  was 
  

   taking 
  place. 
  Hence 
  the 
  true 
  minimum 
  pressure 
  should 
  

  

  * 
  Travers, 
  loc, 
  cit. 
  

  

  