﻿Constituent 
  of 
  the 
  Atmosphere. 
  277 
  

  

  These 
  numbers, 
  as 
  well 
  as 
  those 
  above 
  quoted 
  for 
  " 
  atmo- 
  

   spheric 
  nitrogen," 
  are 
  subject 
  to 
  a 
  deduction 
  of 
  0*0006 
  for 
  the 
  

   shrinkage 
  of 
  the 
  globe 
  when 
  exhausted.* 
  If 
  they 
  are 
  then 
  

   multiplied 
  in 
  the 
  ratio 
  of 
  2*3108 
  : 
  1*2572, 
  they 
  will 
  express 
  the 
  

   weights 
  of 
  the 
  gas 
  in 
  grams 
  per 
  liter. 
  Thus, 
  as 
  regards 
  the 
  

   mean 
  numbers, 
  we 
  find 
  as 
  the 
  weight 
  per 
  liter 
  under 
  standard 
  

   conditions 
  of 
  chemical 
  nitrogen 
  1*2505, 
  that 
  of 
  atmospheric 
  

   nitrogen 
  being 
  1*2572. 
  

  

  It 
  is 
  of 
  interest 
  to 
  compare 
  the 
  density 
  of 
  nitrogen 
  obtained 
  

   from 
  chemical 
  compounds 
  with 
  that 
  of 
  oxygen. 
  We 
  have 
  

   X 
  2 
  : 
  2 
  = 
  2-2984 
  : 
  2*6276 
  = 
  0*87471 
  ; 
  so 
  that 
  if 
  2 
  = 
  16, 
  N 
  a 
  = 
  

   13*9951. 
  Thus, 
  when 
  the 
  comparison 
  is 
  with 
  chemical 
  nitro- 
  

   gen, 
  the 
  ratio 
  is 
  very 
  nearly 
  that 
  of 
  16 
  : 
  11 
  ; 
  but 
  if 
  " 
  atmospheric 
  

   nitrogen 
  " 
  be 
  substituted, 
  the 
  ratio 
  of 
  small 
  integers 
  is 
  widely 
  

   departed 
  from. 
  

  

  To 
  the 
  above 
  list 
  may 
  be 
  added 
  nitrogen 
  prepared 
  in 
  yet 
  

   another 
  manner, 
  whose 
  weight 
  has 
  been 
  determined 
  subse- 
  

   quently 
  to 
  the 
  isolation 
  of 
  the 
  new 
  dense 
  constituent 
  of 
  the 
  

   atmosphere. 
  In 
  this 
  case 
  nitrogen 
  was 
  actually 
  extracted 
  from 
  

   air 
  by 
  means 
  of 
  magnesium. 
  The 
  nitrogen 
  thus 
  separated 
  was 
  

   then 
  converted 
  into 
  ammonia 
  by 
  action 
  of 
  water 
  upon 
  the 
  mag- 
  

   nesium 
  nitride 
  and 
  afterwards 
  liberated 
  in 
  the 
  free 
  state 
  by 
  

   means 
  of 
  calcium 
  hypochlorite. 
  The 
  purification 
  was 
  con- 
  

   ducted 
  in 
  the 
  usual 
  way, 
  and 
  included 
  passage 
  over 
  red-hot 
  

   copper 
  and 
  copper 
  oxide. 
  The 
  following 
  was 
  the 
  result 
  : 
  

  

  Globe 
  empty, 
  Oct. 
  30, 
  Nov. 
  5 
  2*82313 
  

  

  Globe 
  full, 
  Oct. 
  31 
  0*52395 
  

  

  Weight 
  of 
  gas 
  2*29918 
  

  

  It 
  differs 
  inappreciably 
  from 
  the 
  mean 
  of 
  other 
  results, 
  viz 
  : 
  

   2*2990, 
  and 
  is 
  of 
  special 
  interest 
  as 
  relating 
  to 
  gas 
  which 
  at 
  

   one 
  stage 
  of 
  its 
  history 
  formed 
  part 
  of 
  the 
  atmosphere. 
  

  

  Another 
  detennination, 
  with 
  a 
  different 
  apparatus, 
  of 
  the 
  

   density 
  of 
  " 
  chemical 
  " 
  nitrogen 
  from 
  the 
  same 
  source, 
  magne- 
  

   sium 
  nitride, 
  which 
  had 
  been 
  prepared 
  by 
  passing 
  " 
  atmo- 
  

   spheric 
  " 
  nitrogen 
  over 
  ignited 
  magnesium, 
  may 
  here 
  be 
  

   recorded. 
  The 
  sample 
  differed 
  from 
  that 
  previously 
  men- 
  

   tioned, 
  inasmuch 
  as 
  it 
  had 
  not 
  been 
  subjected 
  to 
  treatment 
  with 
  

   red-hot 
  copper. 
  After 
  treating 
  the 
  nitride 
  with 
  water, 
  the 
  

   resulting 
  ammonia 
  was 
  distilled 
  off 
  and 
  collected 
  in 
  hydrochloric 
  

   acid 
  ; 
  the 
  solution 
  was 
  evaporated 
  byvdegrees, 
  the 
  dry 
  ammonium 
  

   chloride 
  was 
  dissolved 
  in 
  water, 
  and 
  its 
  concentrated 
  solution 
  

   added 
  to 
  a 
  freshly-prepared 
  solution 
  of 
  sodium 
  hypobromite. 
  

   The 
  nitrogen 
  was 
  collected 
  in 
  a 
  gas-holder 
  over 
  water 
  which 
  

  

  * 
  Rayleigh, 
  On 
  the 
  Densities 
  of 
  the 
  Principal 
  Gases, 
  Proc. 
  Roy. 
  Soc, 
  vol. 
  liii, 
  

   p. 
  134, 
  1893. 
  

  

  