﻿30 
  Prof. 
  Chattock 
  and 
  Mr. 
  Tyndall 
  on 
  Changes 
  

  

  smallest 
  percentage 
  with 
  which 
  we 
  experimented 
  was 
  

   0-00015. 
  

  

  Alongside 
  the 
  scale 
  of 
  dyne-cm. 
  -2 
  in 
  the 
  curves 
  is 
  given 
  

   the 
  scale 
  of 
  N, 
  calculated 
  as 
  already 
  explained 
  at 
  the 
  beginning 
  

   of 
  the 
  paper. 
  V 
  was 
  233 
  c.c. 
  and 
  P 
  was 
  always 
  adjusted 
  to 
  

   75 
  cm. 
  of 
  mercury. 
  

  

  Metliod 
  of 
  introducing 
  the 
  Impurities. 
  

  

  Fig. 
  2 
  is 
  a 
  diagram 
  of 
  the 
  gas 
  apparatus. 
  The 
  hydrogen 
  

   was 
  obtained 
  electrolytically 
  from 
  pure 
  sulphuric 
  acid 
  and 
  

   water; 
  after 
  which 
  it 
  was 
  dried 
  and 
  absorbed 
  by 
  palladium 
  black 
  

   at 
  Pd. 
  Gas 
  was 
  then 
  pumped 
  away 
  from 
  the 
  palladium 
  until 
  

  

  Fte. 
  2. 
  

  

  ie 
  <3iscWr 
  je 
  Vessel 
  

   To 
  bic-mlj 
  

  

  

  with 
  the 
  assistance 
  of 
  a 
  little 
  warming 
  all 
  impurity 
  might 
  be 
  

   supposed 
  to 
  have 
  been 
  swept 
  out 
  ; 
  and 
  the 
  palladium 
  vessel 
  

   was 
  connected 
  to 
  the 
  receiver 
  R 
  2 
  into 
  which 
  the 
  rest 
  of 
  the 
  

   hydrogen 
  was 
  passed 
  by 
  more 
  vigorous 
  heating. 
  E 
  x 
  con- 
  

   tained 
  P 
  2 
  5 
  . 
  

  

  The 
  impurity 
  (oxygen 
  or 
  nitrogen) 
  was 
  collected 
  in 
  the 
  

   bell-jar 
  P 
  2 
  over 
  sulphuric 
  acid 
  and 
  introduced 
  by 
  way 
  of 
  the 
  

   graduated 
  tubes 
  CiC 
  2 
  into 
  the 
  mixing 
  flask 
  M 
  (volume 
  about 
  

   1200 
  c.c). 
  

  

  The 
  discharge 
  vessels 
  having 
  been 
  filled 
  with 
  hydrogen 
  

   from 
  R 
  x 
  to 
  a 
  pressure 
  of 
  75 
  cm., 
  this 
  was 
  pumped 
  over 
  into 
  M 
  

   by 
  the 
  mercury 
  piston 
  P. 
  M 
  was 
  then 
  warmed 
  gently 
  to 
  

   ensure 
  mixing 
  and 
  the 
  gas 
  pumped 
  back 
  again 
  into 
  the 
  

   discharge 
  vessels. 
  In 
  ibis 
  way 
  we 
  were 
  sure 
  that 
  the 
  impurity 
  

   was 
  uniformly 
  distributed 
  through 
  the 
  hydrogen 
  pumped 
  over, 
  

   and 
  that 
  calculation 
  of 
  the 
  percentage 
  present 
  was 
  simply 
  a 
  

  

  