﻿Ions 
  in 
  Gases 
  under 
  Different 
  Pressures. 
  297 
  

  

  Although 
  it 
  has 
  not 
  been 
  practicable 
  to 
  take 
  observations 
  

   beyond 
  these 
  limits, 
  yet 
  we 
  think 
  the 
  same 
  law 
  would, 
  in 
  all 
  

   probability, 
  hold 
  true 
  at 
  other 
  pressures 
  as 
  well. 
  

  

  The 
  Relation 
  of 
  a. 
  to 
  Pressure. 
  

  

  The 
  next 
  question 
  to 
  be 
  considered 
  is 
  the 
  relation 
  which 
  

   the 
  value 
  of 
  the 
  quantity 
  a, 
  at 
  any 
  given 
  pressure, 
  bears 
  to 
  

   that 
  at 
  any 
  other 
  pressure 
  : 
  in 
  other 
  words, 
  to 
  decide 
  whether 
  

   the 
  coefficient 
  of 
  recombination 
  is 
  a 
  constant 
  for 
  all 
  pressures, 
  

   or 
  whether 
  it 
  varies 
  when 
  the 
  pressure 
  varies. 
  

  

  In 
  order 
  to 
  get 
  over 
  the 
  difficulty 
  of 
  any 
  variation 
  in 
  the 
  

   intensity 
  of 
  the 
  radiation 
  which 
  might 
  occur 
  in 
  the 
  course 
  

   of 
  taking 
  observations 
  at 
  different 
  pressures, 
  the 
  following 
  

   method 
  was 
  adopted 
  : 
  — 
  

  

  Selecting 
  two 
  given 
  pressures 
  at 
  a 
  time, 
  sets 
  of 
  observa- 
  

   tions 
  were 
  taken 
  alternately 
  for 
  the 
  two 
  pressures, 
  and 
  then 
  

   taking 
  the 
  mean 
  value 
  of 
  the 
  observations 
  for 
  one 
  pressure, 
  I 
  

   compared 
  them 
  with 
  the 
  mean 
  for 
  the 
  other. 
  By 
  this 
  means 
  

   it 
  was 
  possible 
  to 
  compare 
  the 
  value 
  of 
  a 
  at 
  various 
  pressures 
  

   with 
  that 
  at 
  atmospheric 
  pressure. 
  

  

  Suppose 
  «! 
  is 
  the 
  value 
  of 
  the 
  coefficient 
  for 
  air 
  at 
  atmo- 
  

   spheric 
  pressure, 
  and 
  a 
  2 
  that 
  any 
  other 
  given 
  pressure, 
  then 
  

  

  a 
  i 
  = 
  Kjp 
  and 
  a 
  2 
  = 
  K^p, 
  

  

  where 
  Q 
  l5 
  N 
  x 
  , 
  and 
  Q 
  2 
  , 
  N 
  2 
  are 
  the 
  corresponding 
  values 
  of 
  Q 
  

   and 
  N 
  ; 
  

  

  . 
  t 
  «i 
  = 
  Qi 
  N/ 
  

  

  a 
  2 
  Q2 
  ' 
  ~^1 
  2 
  ' 
  

  

  By 
  comparing 
  the 
  values 
  of 
  a, 
  by 
  this 
  formula, 
  it 
  was 
  found 
  

   that 
  the 
  coefficient 
  is 
  not 
  only 
  a 
  constant 
  for 
  any 
  one 
  given 
  

   pressure, 
  but 
  has 
  the 
  same 
  value 
  at 
  different 
  pressures. 
  In 
  

   other 
  words, 
  the 
  coefficient 
  of 
  recombination 
  is 
  independent 
  

   of 
  the 
  pressure. 
  The 
  value 
  of 
  a, 
  at 
  several 
  pressures, 
  as 
  com- 
  

   pared 
  with 
  the 
  value 
  at 
  atmospheric 
  pressure, 
  is 
  given 
  in 
  

   Table 
  II. 
  (p. 
  298). 
  

  

  In 
  the 
  table, 
  a 
  x 
  is 
  the 
  value 
  of 
  a 
  at 
  atmospheric 
  pressure, 
  

   while 
  a 
  2 
  is 
  the 
  value 
  at 
  the 
  other 
  pressure 
  compared 
  with 
  it. 
  

  

  The 
  numbers 
  given 
  in 
  the 
  last 
  column 
  of 
  Table 
  II. 
  do 
  not 
  

   show 
  an 
  absolute 
  constancy 
  in 
  the 
  value 
  of 
  a. 
  at 
  the 
  different 
  

   pressure?, 
  but 
  the 
  difference 
  from 
  unity, 
  in 
  each 
  case, 
  is 
  well 
  

   within 
  the 
  limits 
  of 
  experimental 
  error, 
  considering 
  the 
  various 
  

   sources 
  of 
  error 
  which 
  may 
  come 
  into 
  the 
  results. 
  Since 
  1ST 
  

   is 
  squared, 
  any 
  small 
  error 
  which 
  might 
  occur 
  would 
  be 
  

   intensified 
  by 
  squaring. 
  

  

  