﻿Gases 
  of 
  the 
  Helium 
  Group 
  in 
  Minerals. 
  675 
  

  

  fergusonite, 
  which 
  gives 
  off 
  about 
  1 
  c.c. 
  o£ 
  hehum 
  per 
  gram 
  

   on 
  heating, 
  and 
  is 
  more 
  easily 
  obtained 
  than 
  cleveite. 
  

  

  The 
  apparatus 
  used 
  (fig. 
  2) 
  was 
  exhausted 
  whilst 
  the 
  

   charcoal 
  bulb 
  was 
  continuously 
  kept 
  hot 
  to 
  expel 
  all 
  traces 
  

   of 
  air. 
  It 
  was 
  then 
  rinsed 
  out 
  with 
  oxygen 
  supplied 
  by 
  a 
  

   side 
  tube 
  containing 
  potassium 
  permanganate, 
  and 
  again 
  

   exhausted. 
  The 
  hard 
  glass 
  tube 
  containing 
  the 
  mineral 
  

   (about 
  140 
  grams) 
  was 
  heated 
  in 
  an 
  ordinary 
  combustion- 
  

   furnace, 
  and 
  the 
  gases 
  conducted 
  over 
  suitable 
  absorbents 
  and 
  

  

  Fig. 
  2. 
  

  

  QlZ 
  

  

  vJ 
  

  

  a. 
  

  

  Hard 
  glass 
  tube 
  containing 
  140 
  grams 
  of 
  fergusonite. 
  

   h. 
  Hot 
  copper 
  oxide 
  for 
  absorbing 
  hydrogen. 
  

  

  c. 
  Bulb 
  for 
  receiving 
  condensed 
  moisture 
  and 
  drainings 
  from 
  d. 
  

  

  d. 
  Potassium 
  hydroxide 
  to 
  absorb 
  carbon 
  dioxide. 
  

  

  e. 
  Side 
  tube 
  for 
  producing 
  oxygen. 
  

  

  /. 
  Phosphoric 
  oxide 
  to 
  absorb 
  last 
  traces 
  of 
  water 
  yapour. 
  

  

  (/. 
  Bulb 
  containing 
  charcoal 
  for 
  absorbing 
  gases 
  at 
  low 
  temperatures. 
  

  

  finally 
  passed 
  through 
  charcoal 
  cooled 
  by 
  liquid 
  air. 
  This 
  

   absorbed 
  all 
  but 
  the 
  helium 
  which 
  was 
  pumped 
  away. 
  When 
  

   no 
  more 
  helium 
  could 
  be 
  obtained, 
  the 
  heating 
  was 
  stopped 
  

   and 
  the 
  charcoal 
  heated 
  to 
  expel 
  the 
  absorbed 
  gases, 
  which 
  

   were 
  collected 
  through 
  the 
  pump. 
  The 
  nitrogen 
  was 
  

   removed 
  by 
  sparking 
  with 
  excess 
  o£ 
  oxygen 
  over 
  hydrated 
  

   potassium 
  hydroxide 
  for 
  about 
  hal£-an-hoar. 
  The 
  excess 
  of 
  

   oxygen 
  was 
  removed 
  by 
  melted 
  phosphorus 
  and 
  the 
  residue 
  

   introduced 
  into 
  the 
  apparatus 
  shown 
  in 
  fig. 
  3 
  (p. 
  G76), 
  where 
  

   the 
  last 
  traces 
  of 
  all 
  gases, 
  except 
  the 
  inert 
  gases, 
  were 
  removed 
  

   by 
  means 
  of 
  the 
  sodium-potassium 
  electrodes. 
  Spectro- 
  

   scopic 
  examination 
  showed 
  the 
  presence 
  of 
  helium 
  and 
  argon 
  

   in 
  the 
  tube. 
  Before 
  the 
  presence 
  of 
  krypton 
  could 
  be 
  investi- 
  

   gated 
  with 
  certainty, 
  the 
  helium 
  had 
  to 
  be 
  removed. 
  This 
  

   was 
  done 
  by 
  absorbing 
  the 
  argon, 
  and 
  heavier 
  gases 
  if 
  present, 
  

   with 
  charcoal 
  cooled 
  by 
  liquid 
  air 
  and 
  pumping 
  away 
  the 
  

   helium. 
  After 
  closing 
  the 
  pumji 
  and 
  warming 
  up 
  the 
  

  

  