﻿346 
  Prof. 
  0. 
  W. 
  Richardson 
  on 
  the 
  Emission 
  of 
  

  

  theory 
  of 
  metallic 
  conductors*, 
  contact 
  potential 
  f, 
  and 
  

   photoelectric 
  action 
  J. 
  

  

  It 
  has 
  long 
  been 
  known 
  that 
  ions 
  are 
  emitted 
  in 
  a 
  number 
  

   of 
  cases 
  in 
  which 
  solids 
  react 
  chemically 
  with 
  gases. 
  The' 
  

   recent 
  experiments 
  of 
  Haber 
  and 
  Just§ 
  indicate 
  that 
  the 
  

   alkali 
  metals 
  liberate 
  electrons 
  when 
  they 
  are 
  attacked 
  by 
  

   certain 
  gases. 
  It 
  seems 
  likely, 
  from 
  various 
  considerations 
  || 
  ,. 
  

   that 
  effects 
  of 
  this 
  nature 
  would 
  account 
  for 
  most 
  of 
  the 
  

   emission 
  from 
  heated 
  sodium 
  which 
  was 
  measured 
  by 
  the 
  

   writer 
  If. 
  In 
  consequence 
  of 
  this 
  conclusion, 
  together 
  with 
  

   the 
  results 
  of 
  a 
  number 
  of 
  experiments 
  which 
  are 
  at 
  first 
  

   sight 
  in 
  conflict 
  with 
  the 
  theory 
  referred 
  to 
  at 
  the 
  beginning 
  

   of 
  this 
  paper**, 
  the 
  view 
  appears 
  to 
  have 
  become 
  rather 
  pre- 
  

   valent 
  that 
  the 
  emission 
  of 
  electrons 
  from 
  hot 
  bodies 
  is 
  

   invariably 
  a 
  secondary 
  effect, 
  arising 
  in 
  some 
  way 
  from 
  

   traces 
  of 
  chemical 
  action. 
  That 
  this 
  view 
  is 
  a 
  mistaken 
  one 
  

   is, 
  I 
  think, 
  conclusively 
  shown 
  by 
  the 
  following 
  experiments, 
  

   which 
  I 
  have 
  made 
  with 
  tungsten 
  filaments. 
  

  

  The 
  tests 
  to 
  be 
  described 
  were 
  made 
  with 
  experimental' 
  

   tungsten 
  lamps 
  carrying 
  a 
  vertical 
  filament 
  of 
  ductile 
  tungsten- 
  

   which 
  passed 
  axially 
  down 
  a 
  concentric 
  cylindrical 
  electrode 
  

   of 
  copper 
  gauze 
  or 
  foil. 
  The 
  tungsten 
  filaments 
  were 
  welded 
  

   electrically 
  in 
  a 
  hydrogen 
  atmosphere 
  to 
  stout 
  metal 
  leads.. 
  

   These 
  in 
  turn 
  were 
  silver 
  soldered 
  to 
  platinum 
  wires 
  sealed 
  

   into 
  the 
  glass 
  container. 
  The 
  lead 
  to 
  the 
  copper 
  electrode 
  

   was 
  sealed 
  into 
  the 
  glass 
  in 
  the 
  same 
  way. 
  The 
  lamps 
  were 
  

   exhausted 
  with 
  a 
  Gaede 
  pump 
  for 
  several 
  hours, 
  during 
  which 
  

   time 
  they 
  were 
  maintained 
  at 
  a 
  temperature 
  of 
  550-570° 
  C 
  

   by 
  means 
  of 
  a 
  vacuum 
  furnace. 
  The 
  exhaustion 
  was 
  then 
  

   completed 
  by 
  means 
  of 
  liquid 
  air 
  and 
  charcoal, 
  the 
  tungsten 
  

   filament 
  meanwhile 
  being 
  glowed 
  out 
  by 
  means 
  of 
  an 
  electric 
  

   current 
  at 
  over 
  2200° 
  C. 
  Most 
  of 
  the 
  tests 
  were 
  made 
  after 
  

   the 
  furnace 
  had 
  been 
  opened 
  up 
  and 
  the 
  walls 
  of 
  the 
  lamps 
  

   allowed 
  to 
  cool 
  off. 
  The 
  walls 
  were 
  always 
  considerably 
  above 
  

   the 
  temperature 
  of 
  the 
  room 
  on 
  account 
  of 
  the 
  heat 
  radiated 
  

   by 
  the 
  glowing 
  filament. 
  

  

  The 
  processes 
  described 
  are 
  extremely 
  well 
  adapted 
  for 
  

  

  * 
  Richardson, 
  Phil. 
  Mag. 
  vol. 
  xxiii. 
  p. 
  594 
  (1912), 
  vol. 
  xxiv. 
  p. 
  737 
  

   (1912). 
  

  

  t 
  Richardson, 
  Phil. 
  Mag. 
  vol. 
  xxiii. 
  p. 
  263 
  (1912>. 
  

  

  X 
  Richardson, 
  Phil. 
  Mag. 
  vol. 
  xxiv. 
  p. 
  570 
  (1912) 
  ; 
  Richardson 
  and 
  

   Compton, 
  Phil. 
  Mag. 
  vol. 
  xxiv. 
  p. 
  575 
  (1912). 
  

  

  § 
  Ann. 
  der 
  Phys. 
  vol. 
  xxx. 
  p. 
  411 
  (1909), 
  vol. 
  xxxvi. 
  p. 
  308 
  (1911). 
  

  

  || 
  Cf. 
  Fredenhagen, 
  Verh. 
  der 
  Deutsck. 
  Phijsik. 
  Ges. 
  14 
  Jahrg. 
  p. 
  384 
  

   (1912) 
  ; 
  Richardson, 
  Phil. 
  Mag. 
  vol. 
  xxiv. 
  p. 
  737 
  (1912). 
  

  

  H 
  Phil. 
  Trans. 
  A. 
  vol. 
  cci. 
  p. 
  497 
  (1903). 
  

  

  ** 
  Cf. 
  Pring 
  and 
  Parker, 
  Phil. 
  Mag. 
  vol. 
  xxiii. 
  p. 
  192 
  (1912). 
  

  

  