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  Radioactivity 
  of 
  Potassium 
  and 
  other 
  Alkali 
  Metals, 
  

  

  these 
  active 
  products 
  were 
  present 
  in 
  the 
  salt, 
  and 
  that 
  the 
  

   source 
  of 
  its 
  activity 
  must 
  be 
  sought 
  for 
  elsewhere. 
  

  

  The 
  only 
  remaining 
  known 
  active 
  product 
  whose 
  presence 
  

   in 
  the 
  salt 
  could 
  account 
  for 
  its 
  activity 
  appeared 
  to 
  be 
  

   uranium 
  X, 
  and 
  although 
  it 
  was 
  not 
  clear 
  how 
  such 
  a 
  pro- 
  

   duct 
  could 
  become 
  mixed 
  with 
  the 
  salts 
  of 
  potassium, 
  attempts 
  

   were 
  made 
  to 
  separate 
  it 
  out 
  by 
  recrystallization, 
  by 
  preci- 
  

   pitation 
  with 
  ammonium 
  carbonate, 
  and 
  also 
  by 
  treating 
  

   solutions 
  of 
  the 
  salts 
  with 
  ether 
  after 
  the 
  manner 
  of 
  Meyer 
  

   and 
  Schweidler*. 
  By 
  none 
  of 
  these 
  processes, 
  however, 
  

   was 
  it 
  found 
  possible 
  to 
  effect 
  to 
  a 
  measurable 
  degree 
  the 
  

   separation 
  of 
  any 
  active 
  product. 
  

  

  Attempts 
  were 
  also 
  made 
  with 
  some 
  of 
  the 
  salts 
  to 
  separate 
  

   out 
  by 
  electrolysis 
  active 
  impurities 
  which 
  might 
  be 
  present, 
  

   but 
  it 
  was 
  again 
  found 
  impossible 
  to 
  bring 
  about 
  any 
  separation 
  

   of 
  the 
  active 
  constituents 
  in 
  this 
  way. 
  

  

  XI. 
  Summary 
  of 
  Results. 
  

  

  1. 
  It 
  has 
  been 
  shown 
  that 
  the 
  activity 
  of 
  uniform 
  layers 
  

  

  of 
  active 
  potassium 
  salts 
  was 
  directly 
  proportional 
  to 
  

   the 
  area 
  of 
  the 
  salt 
  exposed. 
  

  

  2. 
  With 
  uniform 
  layers 
  of 
  a 
  number 
  of 
  potassium 
  salts 
  

  

  the 
  activity 
  was 
  found 
  to 
  increase 
  with 
  the 
  thickness 
  

   of 
  the 
  layer, 
  and 
  maximum 
  activities 
  were 
  obtained 
  

   with 
  all 
  the 
  salts 
  examined 
  with 
  layers 
  of 
  the 
  salts 
  

   from 
  2 
  to 
  3 
  mm. 
  in 
  thickness. 
  

  

  3. 
  Wide 
  variations 
  were 
  found 
  in 
  the 
  activities 
  of 
  different 
  

  

  potassium 
  salts, 
  and 
  of 
  potassium 
  salts 
  of 
  the 
  same 
  

   composition 
  obtained 
  from 
  different 
  sources, 
  and 
  ordi- 
  

   narily 
  sold 
  as 
  chemical]}* 
  pure. 
  In 
  particular, 
  dif- 
  

   ferent 
  samples 
  of 
  potassium 
  cyanide 
  were 
  found 
  to 
  

   vary 
  widely 
  in 
  their 
  potassium 
  content, 
  but 
  the 
  acti- 
  

   vities 
  of 
  the 
  different 
  samples 
  were 
  found 
  to 
  be 
  

   approximately 
  proportional 
  to 
  the 
  amount 
  of 
  potassium 
  

   present. 
  

  

  4. 
  The 
  rays 
  from 
  the 
  potassium 
  salts, 
  which 
  were 
  found 
  to 
  

  

  be 
  heterogeneous 
  and 
  to 
  possess 
  considerable 
  pene- 
  

   trating 
  power, 
  exhibited 
  characteristics 
  similar 
  to 
  those 
  

   of 
  the 
  radiation 
  emitted 
  by 
  uranium 
  X. 
  The 
  pene- 
  

   trating 
  power 
  of 
  the 
  latter, 
  however, 
  is 
  somewhat 
  

   greater 
  than 
  that 
  possessed 
  by 
  the 
  potassium 
  rays. 
  

  

  5. 
  Experiments 
  have 
  been 
  described 
  which 
  go 
  to 
  show 
  

  

  that 
  the 
  activity 
  of 
  potassium 
  salts 
  is 
  not 
  due 
  to 
  the 
  

   excitation 
  of 
  a 
  secondary 
  radiation 
  in 
  the 
  salts 
  by 
  the 
  

  

  * 
  Meyer 
  and 
  Schweidler, 
  Wien. 
  Ber. 
  113. 
  July 
  1904. 
  

  

  