﻿Constituent 
  of 
  the 
  Atmosphere. 
  279 
  

  

  II. 
  Reasons 
  for 
  suspecting 
  a 
  hitherto 
  Undiscovered 
  Constituent 
  

  

  in 
  Air. 
  

  

  When 
  the 
  discrepancy 
  of 
  weights 
  was 
  first 
  encountered, 
  

   attempts 
  were 
  naturally 
  made 
  to 
  explain 
  it 
  by 
  contamination 
  

   with 
  known 
  impurities. 
  Of 
  these 
  the 
  most 
  likely 
  appeared 
  to 
  

   be 
  hydrogen, 
  present 
  in 
  the 
  lighter 
  gas 
  in 
  spite 
  of 
  the 
  passage 
  

   over 
  red-hot 
  cupric 
  oxide. 
  But 
  inasmuch 
  as 
  the 
  intentional 
  

   introduction 
  of 
  hydrogen 
  into 
  the 
  heavier 
  gas, 
  afterwards 
  

   treated 
  in 
  the 
  same 
  way 
  with 
  cupric 
  oxide, 
  had 
  no 
  effect 
  upon 
  

   its 
  weight, 
  this 
  explanation 
  had 
  to 
  be 
  abandoned, 
  and 
  finally 
  it 
  

   became 
  clear 
  that 
  the 
  difference 
  could 
  not 
  be 
  accounted 
  for 
  by 
  

   the 
  presence 
  of 
  any 
  known 
  impurity. 
  At 
  this 
  stage 
  it 
  seemed 
  

   not 
  improbable 
  that 
  the 
  lightness 
  of 
  the 
  gas 
  extracted 
  from 
  

   chemical 
  compounds 
  was 
  to 
  be 
  explained 
  by 
  partial 
  dissociation 
  

   of 
  nitrogen 
  molecules 
  N 
  2 
  into 
  detached 
  atoms. 
  In 
  order 
  to 
  

   test 
  this 
  suggestion 
  both 
  kinds 
  of 
  gas 
  were 
  submitted 
  to 
  the 
  

   action 
  of 
  the 
  silent 
  electric 
  discharge, 
  with 
  the 
  result 
  that 
  both 
  

   retained 
  their 
  weights 
  unaltered. 
  This 
  was 
  discouraging, 
  and 
  

   a 
  further 
  experiment 
  pointed 
  still 
  more 
  markedly 
  in 
  the 
  nega- 
  

   tive 
  direction. 
  The 
  chemical 
  behavior 
  of 
  nitrogen 
  is 
  such 
  as 
  

   to 
  suggest 
  that 
  dissociated 
  atoms 
  would 
  possess 
  a 
  high 
  degree 
  

   of 
  activity, 
  and 
  that 
  even 
  though 
  they 
  might 
  be 
  formed 
  in 
  the 
  

   first 
  instance 
  their 
  life 
  would 
  probably 
  be 
  short. 
  On 
  standing 
  

   they 
  might 
  be 
  expected 
  to 
  disappear, 
  in 
  partial 
  analogy 
  with 
  

   the 
  known 
  behavior 
  of 
  ozone. 
  With 
  this 
  idea 
  in 
  view, 
  a 
  sam- 
  

   ple 
  of 
  chemically 
  prepared 
  nitrogen 
  was 
  stored 
  for 
  eight 
  

   months. 
  But 
  at 
  the 
  end 
  of 
  this 
  time 
  the 
  density 
  showed 
  no 
  

   sign 
  of 
  increase, 
  remaining 
  exactly 
  as 
  at 
  first.* 
  

  

  Kegarding 
  it 
  as 
  established 
  that 
  one 
  or 
  other 
  of 
  the 
  gases 
  

   must 
  be 
  a 
  mixture, 
  containing, 
  as 
  the 
  case 
  might 
  be, 
  an 
  ingre- 
  

   dient 
  much 
  heavier 
  or 
  much 
  lighter 
  than 
  ordinary 
  nitrogen, 
  we 
  

   had 
  to 
  consider 
  the 
  relative 
  probabilities 
  of 
  the 
  various 
  possible 
  

   interpretations. 
  Except 
  upon 
  the 
  already 
  discredited 
  hypoth- 
  

   esis 
  of 
  dissociation, 
  it 
  was 
  difficult 
  to 
  see 
  how 
  the 
  gas 
  of 
  chem- 
  

   ical 
  origin 
  could 
  be 
  a 
  mixture. 
  To 
  suppose 
  this 
  would 
  be 
  to 
  

   admit 
  two 
  kinds 
  of 
  nitric 
  acid, 
  hardly 
  reconcilable 
  with 
  the 
  

   work 
  of 
  Stas 
  and 
  others 
  upon 
  the 
  atomic 
  weight 
  of 
  that 
  sub- 
  

   stance. 
  The 
  simplest 
  explanation 
  in 
  many 
  respects 
  was 
  to 
  

   admit 
  the 
  existence 
  of 
  a 
  second 
  ingredient 
  in 
  air 
  from 
  which 
  

   oxygen, 
  moisture, 
  and 
  carbonic 
  anhydride 
  had 
  already 
  been 
  

   removed. 
  The 
  proportional 
  amount 
  required 
  was 
  not 
  great. 
  

   If 
  the 
  density 
  of 
  the 
  supposed 
  gas 
  were 
  double 
  that 
  of 
  nitro- 
  

   gen 
  \ 
  per 
  cent 
  only 
  by 
  volume 
  would 
  be 
  needed; 
  or 
  if 
  the 
  

   density 
  were 
  but 
  half 
  as 
  much 
  again 
  as 
  that 
  of 
  nitrogen, 
  then 
  

   1 
  per 
  cent 
  would 
  still 
  suffice. 
  But 
  in 
  accepting 
  this 
  explana- 
  

  

  * 
  Proc. 
  Roy. 
  Soc, 
  vol. 
  lv, 
  p. 
  344, 
  1894. 
  

  

  ■*' 
  

  

  