﻿Constituent 
  of 
  the 
  Atmosphere. 
  287 
  

  

  The 
  temperature 
  must 
  be 
  nearly 
  that 
  of 
  the 
  fusion 
  of 
  the 
  

   glass, 
  and 
  the 
  current 
  of 
  gas 
  must 
  be 
  carefully 
  regulated, 
  else 
  

   the 
  heat 
  developed 
  by 
  the 
  union 
  of 
  the 
  magnesium 
  with 
  nitro- 
  

   gen 
  will 
  fuse 
  the 
  tube. 
  

  

  Having 
  collected 
  the 
  residue 
  from 
  100 
  or 
  150 
  liters 
  of 
  atmos- 
  

   pheric 
  nitrogen, 
  which 
  may 
  amount 
  to 
  4 
  or 
  5 
  liters, 
  it 
  is 
  

   transferred 
  to 
  a 
  small 
  gas-holder 
  connected 
  with 
  an 
  apparatus, 
  

   whereby, 
  by 
  means 
  of 
  a 
  species 
  of 
  a 
  self-acting 
  Sprengel's 
  

   pump, 
  the 
  gas 
  is 
  caused 
  to 
  circulate 
  through 
  a 
  tube 
  half 
  tilled 
  

   with 
  copper 
  and 
  half 
  with 
  copper 
  oxide 
  ; 
  it 
  then 
  traverses 
  a 
  

   tube 
  half 
  filled 
  with 
  soda-lime 
  and 
  half 
  with 
  phosphorus 
  pent- 
  

   oxide 
  ; 
  it 
  then 
  passes 
  a 
  reservoir 
  of 
  about 
  300 
  cc 
  capacity 
  from 
  

   which, 
  by 
  raising 
  a 
  mercury 
  reservoir, 
  it 
  can 
  be 
  expelled 
  into 
  a 
  

   small 
  gas-holder. 
  Next 
  it 
  passes 
  through 
  a 
  tube 
  containing 
  

   magnesium 
  turnings 
  heated 
  to 
  bright 
  redness. 
  The 
  gas 
  is 
  thus 
  

   freed 
  from 
  any 
  possible 
  contamination 
  with 
  oxygen, 
  hydrogen, 
  

   or 
  hydrocarbons, 
  and 
  nitrogen 
  is 
  gradually 
  absorbed. 
  As 
  the 
  

   amount 
  of 
  gas 
  in 
  the 
  tubes 
  and 
  reservoir 
  diminishes 
  in 
  volume, 
  

   it 
  draws 
  supplies 
  from 
  the 
  gas-holder, 
  and, 
  finally, 
  the 
  circulat- 
  

   ing 
  system 
  is 
  full 
  of 
  argon 
  in 
  a 
  pure 
  state. 
  The 
  circulating 
  

   system 
  of 
  tubes 
  is 
  connected 
  with 
  a 
  mercury 
  pump, 
  so 
  that, 
  in 
  

   changing 
  the 
  magnesium 
  tube, 
  no 
  gas 
  may 
  be 
  lost. 
  Before 
  

   ceasing 
  to 
  heat 
  the 
  magnesium 
  tube 
  the 
  system 
  is 
  pumped 
  

   empty, 
  and 
  the 
  collected 
  gas 
  is 
  restored 
  to 
  the 
  gas-holder; 
  

   finally, 
  all 
  the 
  argon 
  is 
  transferred 
  from 
  the 
  mercury 
  reservoir 
  

   to 
  the 
  second 
  small 
  gas-holder, 
  which 
  should 
  preferably 
  be 
  

   filled 
  with 
  water 
  saturated 
  with 
  argon, 
  so 
  as 
  to 
  prevent 
  contami- 
  

   nation 
  from 
  oxygen 
  or 
  nitrogen 
  ; 
  or, 
  if 
  preferred, 
  a 
  mercury 
  

   gas-holder 
  may 
  be 
  employed. 
  The 
  complete 
  removal 
  of 
  nitro- 
  

   gen 
  from 
  argon 
  is 
  very 
  slow 
  towards 
  the 
  end, 
  but 
  circulation 
  

   for 
  a 
  couple 
  of 
  days 
  usually 
  effects 
  it. 
  

  

  The 
  principal 
  objection 
  to 
  the 
  oxygen 
  method 
  of 
  isolating 
  

   argon, 
  as 
  hitherto 
  described, 
  is 
  the 
  extreme 
  slowness 
  of 
  the 
  

   operation. 
  In 
  extending 
  the 
  scale 
  we 
  had 
  the 
  great 
  advantage 
  

   of 
  the 
  advice 
  of 
  Mr. 
  Crookes, 
  who 
  not 
  long 
  since 
  called 
  atten- 
  

   tion 
  to 
  the 
  flame 
  rising 
  from 
  platinum 
  terminals, 
  which 
  convey 
  

   a 
  high 
  tension 
  alternating 
  electric 
  discharge, 
  and 
  pointed 
  out 
  

   its 
  dependence 
  upon 
  combustion 
  of 
  the 
  nitrogen 
  and 
  oxygen 
  of 
  

   the 
  air.*" 
  The 
  plant 
  consists 
  of 
  a 
  De 
  Meritens 
  alternator, 
  actu- 
  

   ated 
  by 
  a 
  gas 
  engine, 
  and 
  the 
  currents 
  are 
  transformed 
  to 
  a 
  

   high 
  potential 
  by 
  means 
  of 
  a 
  Ruhmkorff 
  or 
  other 
  suitable 
  

   induction 
  coil. 
  The 
  highest 
  rate 
  of 
  absorption 
  of 
  the 
  mixed 
  

   gases 
  yet 
  attained 
  is 
  3 
  liters 
  per 
  hour, 
  about 
  3000 
  times 
  that 
  of 
  

   Cavendish. 
  It 
  is 
  necessary 
  to 
  keep 
  the 
  apparatus 
  cool, 
  and 
  

   from 
  this 
  and 
  other 
  causes 
  a 
  good 
  many 
  difficulties 
  have 
  been 
  

   encountered. 
  

  

  * 
  Chemical 
  Xews, 
  vol. 
  lxv, 
  p. 
  301, 
  1892. 
  

  

  