﻿918 
  Dr. 
  J. 
  W. 
  McBain 
  on 
  the 
  Alechanism 
  of 
  the 
  

  

  fitted 
  with 
  a 
  micrometer 
  adjustment 
  by 
  Hilger, 
  on 
  which 
  

   110 
  divisions 
  corresponded 
  to 
  one 
  millimetre. 
  In 
  the 
  

   following 
  tables 
  these 
  results, 
  in 
  micrometer 
  scale-divisions, 
  

   are 
  given 
  as 
  hundredths 
  o£ 
  a 
  millimetre 
  as 
  this 
  does 
  not 
  affect 
  

   the 
  qualitative 
  aspect 
  of 
  the 
  experiments. 
  

  

  The 
  gas 
  was 
  measured 
  by 
  means 
  o£ 
  a 
  constant 
  pressure 
  gas 
  

   burette 
  surrounded 
  by 
  a 
  water-jacket. 
  The 
  hydrogen, 
  pre- 
  

   pared 
  b}^ 
  action 
  of 
  hydrochloric 
  acid 
  on 
  zinc, 
  was 
  dried 
  by 
  

   phosphorus 
  pentoxide 
  and 
  collected 
  in 
  tubes 
  over 
  mercury. 
  

  

  Carbon 
  was 
  prepared 
  in 
  large 
  quantity 
  by 
  heating 
  in 
  a 
  

   mufEe 
  the 
  white 
  tissues 
  of 
  the 
  fruit 
  of 
  the 
  coconut 
  to 
  a 
  tem- 
  

   perature 
  just 
  below 
  redness 
  for 
  several 
  hours, 
  until 
  no 
  more 
  

   fumes 
  were 
  evolved. 
  The 
  temperature 
  was 
  then 
  allowed 
  to 
  

   rise 
  to 
  dull 
  red 
  heat 
  for 
  about 
  thirty 
  seconds, 
  but 
  without 
  

   causing 
  more 
  vapour 
  to 
  be 
  given 
  off. 
  Only 
  the 
  carbon 
  taken 
  

   from 
  the 
  interior 
  of 
  the 
  mass 
  was 
  employed 
  *. 
  It 
  was 
  dried 
  

   at 
  160° 
  C. 
  before 
  weighing. 
  

  

  In 
  the 
  calculation 
  of 
  the 
  results 
  no 
  allowances 
  were 
  made 
  

   for 
  change 
  in 
  the 
  volume 
  of 
  the 
  bulb 
  or 
  of 
  the 
  carbon, 
  nor 
  

   for 
  the 
  deviation 
  of 
  hydrogen 
  from 
  the 
  gas 
  laws. 
  This, 
  

   however, 
  does 
  not 
  affect 
  the 
  present 
  investigation 
  which 
  is 
  

   mainly 
  concerned 
  with 
  relative 
  and 
  not 
  absolute 
  measure- 
  

   ments. 
  

  

  An 
  idea 
  of 
  the 
  quality 
  of 
  the 
  carbon 
  employed 
  may 
  i}e 
  

   obtained 
  from 
  the 
  amount 
  of 
  gas 
  sorbed 
  by 
  it 
  in 
  actual 
  

   experiment. 
  Thus 
  in 
  one 
  case, 
  the 
  weight 
  of 
  carbon 
  was 
  

   2*65 
  g., 
  the 
  amount 
  of 
  hydrogen 
  in 
  the 
  apparatus 
  was 
  63*15 
  c.c. 
  

   (corr.), 
  under 
  a 
  pressure 
  of 
  10*0 
  mm. 
  Since 
  the 
  volume 
  of 
  

   the 
  dead 
  space 
  in 
  the 
  connexions 
  and 
  capillary 
  tubing- 
  

   amounted 
  to 
  1'79 
  c.c. 
  and 
  that 
  of 
  the 
  bulb 
  immersed 
  in 
  liquid 
  

   air 
  to 
  18*44 
  c.c, 
  the 
  amount 
  of 
  unsorbed 
  gas 
  was 
  0*82 
  c.c. 
  

   (corr.). 
  Hence 
  2*65 
  g. 
  of 
  carbon 
  used 
  in 
  the 
  experiment 
  had 
  

   sorbed 
  62*33 
  c.c. 
  (corr.) 
  of 
  hydrogen, 
  or 
  5'607 
  mg., 
  that 
  is 
  

   0*21 
  per 
  cent, 
  by 
  weight. 
  This 
  value 
  is 
  over 
  three 
  times 
  as 
  

   great 
  as 
  that 
  obtained 
  by 
  Travers, 
  whose 
  specimen 
  of 
  carbon 
  

   sorbed 
  at 
  a 
  slightly 
  higher 
  pressure 
  an 
  amount 
  equal 
  to 
  

   0*065 
  per 
  cent, 
  at 
  12 
  mm. 
  

  

  Tune 
  required 
  for 
  Saturation. 
  

  

  The 
  time 
  required 
  for 
  complete 
  equilibrium 
  betv/een 
  carbon 
  

   and 
  hydrogen 
  at 
  any 
  definite 
  pressure 
  could 
  not 
  be 
  accurately 
  

   measured 
  at 
  low 
  temperatures, 
  because 
  the 
  temperature 
  of 
  

  

  * 
  Davis, 
  loe. 
  cit. 
  pp. 
  1678 
  and 
  1682, 
  used 
  some 
  of 
  this 
  carbon 
  iu 
  his 
  

   experiments. 
  It 
  will 
  be 
  noted 
  that 
  my 
  results 
  show 
  that 
  it 
  is 
  highly 
  

   sorbent 
  towards 
  hydrogen 
  while 
  Davis's 
  measurements 
  showed 
  that 
  it 
  

   sorbed 
  relatively 
  very 
  little 
  iodine 
  from 
  solution. 
  

  

  