﻿Constituent 
  of 
  the 
  Atmosphere. 
  295 
  

  

  Q 
  p 
  and 
  C 
  v 
  denoting 
  as 
  usual 
  the 
  specific 
  heat 
  at 
  constant 
  pres- 
  

   sure 
  and 
  at 
  constant 
  volume 
  respectively. 
  

  

  Hence 
  if, 
  as 
  for 
  mercury 
  vapor 
  and 
  for 
  argon 
  (§XIY), 
  the 
  

   ratio 
  of 
  specific 
  heats 
  Cp 
  : 
  C 
  v 
  be 
  If, 
  it 
  follows 
  that 
  K 
  = 
  H, 
  or 
  

   that 
  the 
  whole 
  kinetic 
  energy 
  of 
  the 
  gas 
  is 
  accounted 
  for 
  by 
  

   the 
  translator} 
  7 
  motion 
  of 
  its 
  molecules. 
  In 
  the 
  case 
  of 
  mer- 
  

   cury 
  the 
  absence 
  of 
  interatomic 
  energy 
  is 
  regarded 
  as 
  proof 
  of 
  

   the 
  monatomic 
  character 
  of 
  the 
  vapor, 
  and 
  the 
  conclusion 
  

   holds 
  equally 
  good 
  for 
  argon. 
  

  

  The 
  only 
  alternative 
  is 
  to 
  suppose 
  that 
  if 
  argon 
  molecules 
  

   are 
  di- 
  or 
  polyatomic, 
  the 
  atoms 
  acquire 
  no 
  relative 
  motion, 
  even 
  

   of 
  rotation, 
  a 
  .conclusion 
  exceedingly 
  improbable 
  in 
  itself 
  and 
  

   one 
  postulating 
  the 
  sphericity 
  of 
  such 
  complex 
  groups 
  of 
  

   atoms. 
  

  

  Now 
  a 
  monatomic 
  gas 
  can 
  be 
  only 
  an 
  element, 
  or 
  a 
  mixture 
  

   of 
  elements 
  ; 
  and 
  hence 
  it 
  follows 
  that 
  argon 
  is 
  not 
  of 
  a 
  com- 
  

   pound 
  nature. 
  

  

  From 
  Avogadro's 
  law, 
  the 
  density 
  of 
  a 
  gas 
  is 
  half 
  its 
  molec- 
  

   ular 
  weight 
  ; 
  and 
  as 
  the 
  density 
  of 
  argon 
  is 
  approximately 
  20, 
  

   hence 
  its 
  molecular 
  weight 
  must 
  be 
  40. 
  But 
  its 
  molecule 
  is 
  

   identical 
  with 
  its 
  atom 
  ; 
  hence 
  its 
  atomic 
  weight, 
  or, 
  if 
  it 
  be 
  a 
  

   mixture, 
  the 
  mean 
  of 
  the 
  atomic 
  weights 
  of 
  that 
  mixture, 
  

   taken 
  for 
  the 
  proportion 
  in 
  which 
  they 
  are 
  present, 
  must 
  be 
  40. 
  

  

  There 
  is 
  evidence 
  both 
  for 
  and 
  against 
  the 
  hypothesis 
  that 
  

   argon 
  is 
  a 
  mixture 
  : 
  for, 
  owing 
  to 
  Mr. 
  Crookes's 
  observations 
  of 
  

   the 
  dual 
  character 
  of 
  its 
  spectrum 
  ; 
  against, 
  because 
  of 
  Pro- 
  

   fessor 
  Olszewski's 
  statement 
  that 
  it 
  has 
  a 
  definite 
  melting 
  point, 
  

   a 
  definite 
  boiling 
  point, 
  and 
  a 
  definite 
  critical 
  temperature 
  and 
  

   pressure; 
  and 
  because 
  on 
  compressing 
  the 
  gas 
  in 
  presence 
  of 
  

   its 
  liquid, 
  pressure 
  remains 
  sensibly 
  constant 
  until 
  all 
  gas 
  has 
  

   condensed 
  to 
  liquid. 
  The 
  latter 
  experiments 
  are 
  the 
  well- 
  

   known 
  criteria 
  of 
  a 
  pure 
  substance 
  ; 
  the 
  former 
  is 
  not 
  known 
  

   with 
  certainty 
  to 
  be 
  characteristic 
  of 
  a 
  mixture. 
  The 
  conclu- 
  

   sions 
  which 
  follow 
  are, 
  however, 
  so 
  startling, 
  that 
  in 
  our 
  future 
  

   experimental 
  work 
  we 
  shall 
  endeavor 
  to 
  decide 
  the 
  question 
  by 
  

   other 
  means. 
  

  

  For 
  the 
  present, 
  however, 
  the 
  balance 
  of 
  evidence 
  seems 
  to 
  

   point 
  to 
  simplicity. 
  We 
  have 
  therefore 
  to 
  discuss 
  the 
  relations 
  

   to 
  other 
  elements 
  of 
  an 
  element 
  of 
  atomic 
  weight 
  40. 
  We 
  

   inclined 
  for 
  long 
  to 
  the 
  view 
  that 
  argon 
  was 
  possibly 
  one 
  or 
  

   more 
  than 
  one 
  of 
  the 
  elements 
  which 
  might 
  be 
  expected 
  to 
  

   follow 
  fluorine 
  in 
  the 
  periodic 
  classification 
  of 
  the 
  elements 
  — 
  

   elements 
  which 
  should 
  have 
  an 
  atomic 
  weight 
  between 
  19, 
  

   that 
  of 
  fluorine, 
  and 
  23, 
  that 
  of 
  sodium. 
  But 
  this 
  view 
  is 
  

   completely 
  put 
  out 
  of 
  court 
  by 
  the 
  discovery 
  of 
  the 
  monatomic 
  

   nature 
  of 
  its 
  molecules. 
  

  

  