﻿Positive 
  Ions 
  emitted 
  from 
  various 
  Hot 
  Bodies. 
  659 
  

  

  Tantalum. 
  

  

  Tantalum 
  was 
  investigated 
  under 
  varying 
  conditions. 
  At 
  

   first 
  the 
  thermionic 
  current 
  was 
  measured 
  from 
  a 
  filament 
  of 
  

   circular 
  section 
  0*05 
  mm. 
  diameter. 
  This 
  filament 
  was 
  taken 
  

   from 
  an 
  incandescent 
  lamp. 
  The 
  logarithm 
  of 
  the 
  current 
  

   when 
  plotted 
  against 
  the 
  potential 
  was 
  approximately 
  a 
  

   straight 
  line 
  which 
  led 
  to 
  the 
  value 
  R 
  = 
  9'6 
  X 
  10^ 
  for 
  the 
  

   gas 
  constant. 
  The 
  mean 
  kinetic 
  energy 
  was 
  therefore 
  

   apparently 
  larger 
  than 
  the 
  predicted 
  value. 
  

  

  A 
  second 
  filament 
  was 
  rolled 
  into 
  a 
  strip 
  with 
  a 
  thickness 
  

   of 
  0*01 
  mm. 
  and 
  a 
  width 
  of 
  0*04 
  mm. 
  This 
  strip 
  was 
  bent 
  

  

  over 
  a 
  form 
  with 
  square 
  edges, 
  so 
  that 
  it 
  had 
  the 
  form 
  I 
  1. 
  

  

  The 
  lower 
  disk 
  surrounded 
  the 
  upper 
  surface, 
  leaving 
  an 
  

   area 
  of 
  about 
  0*2 
  mm.^ 
  free 
  to 
  emit 
  ions 
  to 
  the 
  upper 
  plate. 
  

   There 
  was 
  a 
  fall 
  of 
  potential 
  over 
  this 
  surface 
  of 
  probably 
  0*03 
  

   volt. 
  The 
  heating 
  current 
  was 
  of 
  the 
  order 
  of 
  005 
  ampere. 
  

   The 
  results 
  are 
  shown 
  in 
  the 
  accompanying 
  table. 
  The 
  

   curve 
  3 
  (fig. 
  4) 
  is 
  for 
  the 
  absolute 
  temperature 
  1050 
  degrees 
  

   and 
  curve 
  4 
  is 
  for 
  the 
  temperature 
  1273 
  degrees 
  absolute. 
  

  

  Tantalum. 
  

  

  

  

  

  

  

  

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  a 
  

  

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  ^'- 
  

  

  ns 
  

  

  ;: 
  

  

  2. 
  

  

  s 
  

  

  

  -. 
  

  

  c 
  

  

  j; 
  

  

  c3 
  

  

  S 
  

  

  

  

  

  

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  „ 
  

  

  11 
  

  

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  fl' 
  

  

  o 
  

  

  -^ 
  

  

  Oapaci 
  

   micro 
  

  

  1 
  

  

  

  1— 
  1 
  *^ 
  

  

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  £ 
  S 
  

  

  2 
  o 
  

  

  1 
  

  

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  T" 
  

  

  6-6 
  

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  198x10"^* 
  

   138 
  „ 
  

  

  0-014 
  

   0037 
  

  

  

  

  

  

  0-1 
  

  

  4-7 
  

  

  71 
  „ 
  

  

  0-11 
  

  

  

  

  

  

  0^2 
  

  

  2-9 
  

  

  14-5 
  „ 
  

  

  0-205 
  

  

  

  

  

  

  0-3 
  

  

  1^13 
  

  

  0-6 
  „ 
  

  

  0-30 
  

  

  

  

  

  

  0^4 
  

  

  0-61 
  

  

  1-7 
  „ 
  

  

  0-40 
  

  

  30x103 
  

  

  001 
  

  

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  220x10"^^ 
  

  

  001 
  

  

  

  

  

  

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  21 
  

  

  105 
  „ 
  

  

  0-104 
  

  

  

  

  

  

  6-2 
  

  

  103 
  „ 
  

  

  0-113 
  

  

  

  

  

  

  02 
  

  

  2-55 
  

  

  42 
  „ 
  

  

  0-21 
  

  

  

  

  

  

  03 
  

  

  2-3 
  

  

  19 
  „ 
  

  

  0-31 
  

  

  

  

  

  

  0-4 
  

  

  •80 
  

  

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  , 
  

  

  0-40 
  

  

  

  

  

  

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  •40 
  

  

  3 
  

  

  0-50 
  

  

  3-6x103 
  

  

  