﻿of 
  Pressure 
  which 
  accompany 
  Point 
  Discharge. 
  

  

  43 
  

  

  P 
  is 
  the 
  percentage 
  o£ 
  air 
  in 
  the 
  hydrogen, 
  P' 
  that 
  of 
  

   oxygen 
  in 
  the 
  air, 
  calculated 
  as 
  in 
  Tables 
  3 
  and 
  4. 
  If 
  we 
  

   neglect 
  the 
  third 
  positive 
  determination 
  for 
  which 
  the 
  value 
  

   of 
  P 
  is 
  somewhat 
  doubtful, 
  the 
  mean 
  of 
  the 
  values 
  of 
  P 
  / 
  

   comes 
  to 
  20 
  ; 
  this 
  is 
  satisfactorily 
  close 
  to 
  the 
  true 
  value 
  21. 
  

   Altogether 
  it 
  seems 
  safe 
  to 
  conclude 
  that 
  when 
  small 
  quantities 
  

   of 
  oxygen 
  and 
  nitrogen 
  are 
  mixed 
  with 
  hydrogen 
  at 
  atmo- 
  

   spheric 
  pressure, 
  it 
  is 
  the 
  oxygen 
  only 
  with 
  which 
  the 
  

   hydrogen 
  combines. 
  

  

  Table 
  5 
  ends 
  at 
  0*05 
  per 
  cent, 
  of 
  air. 
  It 
  is, 
  however, 
  

   probable 
  that 
  up 
  to 
  14 
  per 
  cent, 
  the 
  oxygen 
  alone 
  is 
  active 
  ; 
  

   at 
  any 
  rate 
  when 
  the 
  nitrogen 
  is 
  not 
  present 
  in 
  enormous 
  

   excess. 
  

  

  In 
  Table 
  6 
  are 
  given 
  the 
  contractions 
  observed 
  in 
  air 
  at 
  

   four 
  higher 
  percentages 
  with 
  the 
  cleaned 
  point 
  ; 
  and 
  in 
  

   parallel 
  columns 
  the 
  contractions 
  in 
  oxygen 
  at 
  percentages 
  

   one-fifth 
  of 
  each 
  of 
  these 
  four, 
  taken 
  from 
  the 
  first 
  set 
  of 
  

   observations 
  on 
  oxygen 
  ; 
  i. 
  e. 
  before 
  the 
  point 
  became 
  dirty. 
  

  

  

  

  Table 
  6. 
  

  

  

  

  1 
  

  

  Percentage 
  

   of 
  Air 
  in 
  

   Hydrogen. 
  

  

  4- 
  Discharge. 
  

  

  I 
  

   Air. 
  2 
  . 
  

  

  — 
  Discharge. 
  

  

  Percentage 
  

  

  of 
  Oxygen 
  in 
  

  

  Hydrogen. 
  

  

  Air. 
  

  

  O, 
  

  

  0-19 
  

  

  0-60 
  0-59 
  

  

  3-43 
  

  

  3-48 
  

  

  0038 
  

  

  0-32 
  

  

  0-64 
  

  

  0-61 
  

  

  2 
  90 
  

  

  305 
  ■ 
  

  

  0064 
  

  

  3-7 
  

  

  0-97 
  

  

  083 
  

  

  2-09 
  

  

  T84 
  

  

  0-74 
  

  

  14-2 
  

  

  1-08 
  0-97 
  

  

  1-45 
  

  

  1-66 
  

  

  2-84 
  

  

  The 
  agreement 
  is 
  sufficiently 
  close 
  to 
  render 
  it 
  probable 
  

   that 
  we 
  are 
  still 
  dealing 
  mainly 
  with 
  the 
  oxygen 
  in 
  the 
  air. 
  

  

  The 
  position 
  of 
  the 
  peak 
  on 
  the 
  other 
  hand 
  is 
  no 
  longer 
  a 
  

   guide, 
  as 
  its 
  shape 
  has 
  changed 
  since 
  heating 
  the 
  point. 
  

   The 
  effect 
  on 
  it 
  of 
  the 
  condition 
  of 
  the 
  point 
  is 
  very 
  interesting, 
  

   and 
  Ave 
  have 
  plotted 
  in 
  Curves 
  VIII. 
  the 
  shapes 
  of 
  the 
  

   various 
  peaks 
  we 
  have 
  obtained, 
  with 
  the 
  percentages 
  of 
  

   oxygen 
  corresponding, 
  to 
  illustrate 
  this. 
  

  

  The 
  highest 
  and 
  sharpest 
  peak 
  is 
  that 
  taken 
  in 
  air 
  directly 
  

   after 
  heating 
  the 
  point 
  and 
  when 
  the 
  latter 
  was 
  therefore 
  at 
  

   its 
  cleanest 
  ; 
  then 
  comes 
  that 
  for 
  the 
  first 
  oxygen 
  set, 
  lower 
  

   at 
  the 
  peak 
  itself, 
  but 
  coinciding 
  beyond 
  about 
  0'0l 
  per 
  

   cent. 
  ; 
  and 
  below 
  that 
  again 
  the 
  first 
  air 
  and 
  the 
  second 
  

   oxygen 
  sets 
  taken 
  with 
  the 
  point 
  quite 
  dirty. 
  Each 
  of 
  these 
  

  

  