﻿L 
  740 
  ] 
  

  

  LXIV. 
  The 
  Specific 
  Charge 
  of 
  the 
  Ions 
  emitted 
  by 
  Hot 
  Bodies. 
  

   By 
  0. 
  W. 
  Richardson, 
  Professor 
  of 
  Physics, 
  Princeton 
  

   University 
  *. 
  

  

  THE 
  value 
  of 
  e/m, 
  the 
  specific 
  charge 
  or 
  charge 
  per 
  unit 
  

   mass 
  of 
  the 
  negative 
  ions 
  from 
  an 
  incandescent 
  carbon 
  

   filament, 
  was 
  first 
  measured 
  by 
  J. 
  J. 
  Thomson 
  t 
  in 
  1899. 
  

   Since 
  then 
  the 
  value 
  of 
  the 
  same 
  quantity 
  for 
  the 
  negative 
  

   ions 
  emitted 
  by 
  other 
  hot 
  bodies 
  has 
  been 
  determined 
  by 
  

   a 
  number 
  of 
  different 
  investigators, 
  all 
  of 
  whom 
  have 
  

   found 
  values 
  approximating 
  to 
  10 
  7 
  electromagnetic 
  units, 
  

   indicating 
  that 
  the 
  ions 
  in 
  question 
  are 
  electrons 
  and 
  

   identical 
  for 
  all 
  substances. 
  The 
  corresponding 
  quantity 
  for 
  

   the 
  positive 
  ions 
  from 
  hot 
  bodies 
  has 
  received 
  comparatively 
  

   little 
  attention. 
  The 
  only 
  experiments 
  appear 
  to 
  be 
  some 
  by 
  

   J. 
  J. 
  Thomson 
  J, 
  on 
  an 
  iron 
  wire 
  in 
  an 
  atmosphere 
  of 
  oxygen 
  

   at 
  a 
  low 
  pressure, 
  which 
  led 
  to 
  the 
  value 
  400 
  for 
  e/m. 
  This 
  

   is 
  about 
  what 
  would 
  be 
  required 
  if 
  the 
  ions 
  were 
  atoms 
  of 
  

   iron 
  carrying 
  a 
  charge 
  equal 
  to 
  that 
  of 
  the 
  hydrogen 
  ion 
  in 
  

   electrolysis. 
  

  

  The 
  positive 
  ionization 
  produced 
  by 
  hot 
  metals 
  comprises 
  

   a 
  number 
  of 
  separate 
  phenomena 
  whose 
  mutual 
  relationships 
  

   cannot 
  be 
  said, 
  as 
  yet, 
  to 
  be 
  properly 
  understood. 
  A 
  hot 
  

   wire 
  may 
  give 
  rise 
  to 
  positive 
  ions 
  under 
  a 
  variety 
  of 
  different 
  

   circumstances. 
  The 
  most 
  important 
  of 
  these 
  conditions 
  

   which 
  have 
  been 
  investigated 
  are 
  (1) 
  newness, 
  (2) 
  previous 
  

   exposure 
  to 
  a 
  luminous 
  discharge, 
  and 
  (3) 
  the 
  presence 
  of 
  

   surrounding 
  gas. 
  A 
  fresh 
  wire, 
  however 
  carefully 
  cleaned 
  

   and 
  handled, 
  is 
  found 
  to 
  give 
  rise 
  to 
  a 
  very 
  large 
  emission 
  

   of 
  positive 
  ions 
  when 
  heated 
  for 
  the 
  first 
  time 
  in 
  a 
  good 
  

   vacuum. 
  This 
  property 
  gradually 
  disappears 
  with 
  continued 
  

   heating, 
  but 
  may 
  be 
  restored 
  to 
  a 
  certain 
  extent, 
  either 
  by 
  

   placing 
  the 
  wire 
  near 
  the 
  cathode 
  when 
  a 
  luminous 
  discharge 
  

   is 
  made 
  to 
  pass 
  in 
  the 
  tube 
  or 
  by 
  heating 
  the 
  wire 
  in 
  an 
  

   atmosphere 
  of 
  any 
  of 
  the 
  commoner 
  gases. 
  The 
  effect 
  of 
  

   the 
  luminous 
  discharge 
  is 
  of 
  a 
  temporary 
  character 
  like 
  the 
  

   property 
  of 
  freshness, 
  whereas 
  the 
  admission 
  of 
  gas 
  produces 
  

   an 
  effect 
  which 
  is 
  permanent, 
  the 
  ionization 
  at 
  any 
  given 
  

   temperature 
  being 
  a 
  definite 
  function 
  of 
  the 
  pressure 
  of 
  the 
  

   gas. 
  The 
  connexion 
  between 
  these 
  different 
  manifestations 
  

   is 
  not 
  at 
  all 
  well 
  understood, 
  so 
  that 
  it 
  is 
  difficult 
  to 
  discuss 
  

   positive 
  ionization 
  as 
  a 
  general 
  conception, 
  In 
  a 
  recent 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  

  

  t 
  Phil. 
  Mag. 
  [5] 
  vol. 
  xlviii. 
  p. 
  547. 
  

  

  X 
  Conduction 
  of 
  Electricity 
  through 
  Gases, 
  2nd 
  ed. 
  p. 
  148. 
  

  

  