﻿708 
  

  

  Prof. 
  Rutherford 
  and 
  Mr. 
  Nuttall 
  

  

  on 
  

  

  Methane. 
  This 
  was 
  prepared 
  by 
  acting 
  on 
  aluminium 
  car- 
  

   bide 
  with 
  water 
  and 
  passing 
  through 
  cuprous 
  sulphate 
  

   to 
  remove 
  the 
  acetylene. 
  The 
  resulting 
  impure 
  

   methane 
  was 
  condensed 
  by 
  liquid 
  air, 
  and 
  pure 
  

   methane 
  obtained 
  by 
  fractional 
  distillation. 
  

  

  Carbon 
  dioxide 
  was 
  obtained 
  from 
  a 
  cylinder 
  of 
  compressed 
  

   gas, 
  which 
  on 
  analysis 
  was 
  found 
  to 
  be 
  of 
  99*7 
  per 
  cent, 
  

   purity. 
  

  

  Sulphuretted 
  hydrogen 
  was 
  prepared 
  by 
  action 
  of 
  sulphuric 
  

   acid 
  on 
  calcium 
  sulphide. 
  It 
  was 
  analysed 
  and 
  found 
  

   to 
  be 
  of 
  99*8 
  per 
  cent, 
  purity. 
  

  

  From 
  the 
  results 
  obtained 
  in 
  these 
  experiments, 
  the 
  re- 
  

   lative 
  atomic 
  coefficients 
  of 
  scattering 
  were 
  deduced 
  for 
  

   hydrogen, 
  helium, 
  carbon, 
  air, 
  oxygen, 
  and 
  sulphur. 
  In 
  the 
  

   case 
  of 
  complex 
  molecules, 
  it 
  was 
  assumed 
  that 
  the 
  scattering 
  

   coefficient 
  of 
  the 
  molecule 
  was 
  the 
  sum 
  of 
  the 
  values 
  for 
  

   each 
  of 
  its 
  individual 
  components. 
  For 
  example, 
  the 
  co- 
  

   efficient 
  for 
  carbon 
  was 
  deduced 
  from 
  the 
  value 
  of 
  methane 
  

   (CH 
  4 
  ) 
  by 
  subtracting 
  from 
  the 
  observed 
  value 
  the 
  scattering 
  

   coefficient 
  due 
  to 
  four 
  atoms 
  of 
  hydrogen. 
  In 
  a 
  similar 
  way, 
  

   the 
  value 
  for 
  oxygen 
  was 
  deduced 
  from 
  C0 
  2 
  and 
  sulphur 
  

   from 
  H 
  2 
  S. 
  A 
  correction 
  was 
  required 
  in 
  each 
  case 
  to 
  allow 
  

   for 
  the 
  variation 
  of 
  scattering 
  with 
  velocity 
  of 
  the 
  a 
  particle. 
  

   The 
  reduction 
  in 
  velocity 
  of 
  the 
  a 
  particle 
  in 
  passing 
  through 
  

   a 
  sufficient 
  pressure 
  of 
  gas 
  to 
  scatter 
  half 
  the 
  a 
  particles 
  was 
  

   deduced 
  from 
  the 
  loss 
  of 
  range 
  of 
  the 
  a 
  particle 
  in 
  the 
  gas, 
  

   using 
  the 
  relation 
  between 
  velocity 
  and 
  range 
  found 
  bv 
  

   Geiger. 
  In 
  making 
  this 
  correction 
  it 
  was 
  assumed, 
  as 
  will 
  

  

  Table 
  III. 
  

  

  Gas. 
  

  

  Corrected 
  pressure 
  

   to 
  scatter 
  half 
  of 
  

   incident 
  radiation. 
  

  

  Eelative 
  

   scattering 
  

   coefficient. 
  

  

  Atomic 
  

   weight. 
  

  

  Remarks. 
  

  

  Air 
  

  

  5-32 
  cm. 
  

  

  1332 
  „ 
  

  

  3-64 
  „ 
  

  

  5-00 
  „ 
  

  

  3-36 
  „ 
  

  

  46-3 
  „ 
  

  

  26-2 
  „ 
  

  

  100 
  

  

  •40 
  

  

  1-064 
  

  

  1-61 
  

   •0353 
  

   •064 
  

  

  14-4 
  

   12-0 
  

  

  15-99 
  

   32-0 
  

   1-0 
  

   3-99 
  

  

  Diatomic. 
  

   Monatomic. 
  

  

  Diatomic. 
  

   Monatomic. 
  

   Diatomic. 
  

   Monatomic. 
  

  

  Carbon 
  (from 
  CH 
  4 
  ). 
  

  

  Carbon 
  dioxide 
  

  

  Oxvsren 
  

  

  Sulphur 
  

  

  Hydrogen* 
  

  

  Helium* 
  

  

  

  * 
  In 
  the 
  cases 
  of 
  hydrogen 
  and 
  helium 
  the 
  pressures 
  given 
  are 
  those 
  

   required 
  to 
  cut 
  down 
  the 
  incident 
  radiation 
  to 
  80 
  per 
  cent, 
  of 
  its 
  initial 
  value, 
  

   and 
  they 
  are 
  compared 
  with 
  the 
  pressure 
  of 
  air 
  required 
  to 
  scatter 
  to 
  the 
  same 
  

   extent, 
  viz. 
  1*68 
  cm. 
  of 
  mercury. 
  

  

  