﻿884 
  Mr. 
  E. 
  Parr 
  Metcalfe 
  on 
  

  

  Propane. 
  — 
  Prepared 
  by 
  the 
  action 
  o£ 
  nascent 
  hydrogen 
  

   (from 
  zinc 
  and 
  hydrochloric 
  acid) 
  on 
  isopropyl 
  iodide. 
  The 
  

   propane 
  mixed 
  with 
  hydrogen 
  and 
  a 
  little 
  air 
  was 
  passed 
  in 
  

   succession 
  through 
  alcoholic 
  potash 
  and 
  strong 
  sulphuric 
  

   acid, 
  and 
  was 
  collected 
  over 
  water. 
  It 
  was 
  then 
  drawn 
  

   slowly 
  from 
  the 
  reservoir 
  through 
  concentrated 
  sulphuric 
  

   acid 
  and 
  over 
  P2O5 
  into 
  a 
  previously 
  evacuated 
  fractionating 
  

   bulb 
  immersed 
  in 
  liquid 
  air. 
  Here 
  the 
  propane, 
  with 
  im- 
  

   purities 
  of 
  higher 
  boiling-point, 
  was 
  retained 
  — 
  the 
  hydrogen 
  

   and 
  air 
  being 
  removed 
  through 
  the 
  pump. 
  Only 
  the 
  middle 
  

   fractions 
  of 
  the 
  propane 
  were 
  used. 
  

  

  Butane. 
  — 
  Prepared 
  by 
  the 
  electrolysis 
  of 
  a 
  solution 
  of 
  

   sodium 
  propionate, 
  the 
  CO2 
  being 
  removed 
  from 
  the 
  resulting 
  

   mixed 
  gases 
  by 
  passing 
  through 
  KOH. 
  The 
  gas 
  was 
  care- 
  

   fully 
  dried 
  and 
  then 
  fractionated, 
  the 
  middle 
  fractions 
  only 
  

   being 
  used. 
  

  

  Pentane. 
  — 
  The 
  '' 
  total 
  ionization 
  '' 
  in 
  this 
  gas 
  has 
  been 
  

   measured 
  by 
  Laby"^. 
  From 
  his 
  results 
  the 
  number 
  4'83 
  is 
  

   deduced 
  as 
  the 
  molecular 
  ionization 
  of 
  pentane. 
  

  

  Helium. 
  — 
  Prepared 
  by 
  the 
  writer 
  by 
  heating 
  finely 
  ground 
  

   thorianite 
  in 
  vacuo 
  in 
  a 
  specially 
  made 
  silica 
  tube. 
  The 
  gas 
  

   was 
  purified 
  in 
  the 
  usual 
  way 
  by 
  passing 
  through 
  a 
  liquid 
  

   air-cooled 
  charcoal 
  tube. 
  The 
  only 
  lines 
  foreign 
  to 
  helium 
  

   observed 
  in 
  the 
  spectrum 
  of 
  the 
  purified 
  gas 
  were 
  those 
  of 
  

   mercury, 
  which 
  were 
  so 
  faint 
  as 
  only 
  to 
  be 
  visible 
  with 
  a 
  

   wide 
  spectroscope 
  slit. 
  

  

  Ionization 
  by 
  collision 
  has 
  been 
  shown 
  f 
  to 
  be 
  much 
  greater 
  

   in 
  helium 
  than 
  in 
  other 
  gases 
  under 
  the 
  same 
  conditions. 
  

   This 
  is 
  amply 
  confirmed, 
  qualitatively, 
  by 
  the 
  writer's 
  ex- 
  

   periments. 
  Some 
  little 
  difficulty 
  was 
  experienced 
  at 
  first 
  in 
  

   determining 
  whether 
  the 
  voltage 
  used 
  was 
  sufficiently 
  great 
  

   to 
  produce 
  " 
  saturation 
  " 
  without 
  complicating 
  matters 
  by 
  

   setting 
  up 
  ionizing 
  collisions. 
  By 
  suitably 
  adjusting 
  the 
  

   pressure 
  satisfactory 
  results 
  were 
  at 
  length 
  obtained. 
  

  

  It 
  is 
  interesting 
  to 
  note 
  that 
  the 
  molecular 
  a-ionization 
  of 
  

   helium 
  is 
  less 
  than 
  that 
  of 
  hydrogen, 
  and 
  is 
  thus 
  the 
  low^est 
  

   yet 
  measured. 
  

  

  In 
  view 
  of 
  the 
  peculiar 
  behaviour 
  of 
  helium, 
  it 
  is 
  thought 
  

   that 
  a 
  record 
  of 
  the 
  actual 
  measurements 
  may 
  be 
  of 
  interest. 
  

   A 
  table 
  is 
  accordingly 
  appended 
  giving 
  them 
  in 
  the 
  order 
  in 
  

   which 
  they 
  were 
  taken, 
  and 
  the 
  results 
  are 
  shown 
  graphically 
  

   in 
  fig. 
  2 
  (PI. 
  XXIX.). 
  

  

  * 
  Labv, 
  loc. 
  cit. 
  

  

  t 
  See"E. 
  W. 
  B. 
  Gill 
  and 
  F. 
  B. 
  Pidduck, 
  Phil. 
  Mag. 
  August 
  1908, 
  

   p. 
  286. 
  

  

  