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  Electrons 
  from 
  Tungsten 
  at 
  High 
  Temperatures, 
  349 
  

  

  case, 
  will 
  be 
  considered 
  instead 
  in 
  the 
  following 
  experiment 
  

   for 
  which 
  the 
  other 
  data 
  are 
  lacking. 
  

  

  A 
  filament 
  3 
  cm. 
  long 
  gave 
  0*099 
  amp. 
  electronic 
  emission 
  

   continuously 
  for 
  2'h 
  hours. 
  The 
  resistance 
  when 
  hot 
  rose 
  

   from 
  4773 
  to 
  4787 
  in 
  arbitrary 
  units. 
  The 
  number 
  of 
  atoms 
  

   of 
  tungsten 
  lost 
  by 
  the 
  filament 
  in 
  this 
  time 
  was 
  = 
  5*66 
  X 
  10 
  1; 
  " 
  

   whilst 
  the 
  number 
  of 
  electrons 
  emitted 
  = 
  5'57xl0 
  21 
  . 
  The 
  

   number 
  of 
  electrons 
  emitted 
  per 
  atom 
  of 
  tungsten 
  lost 
  was 
  

   9'84 
  x 
  10°. 
  The 
  mass 
  o£ 
  the 
  electrons 
  emitted 
  in 
  this 
  expe- 
  

   riment 
  was 
  thus 
  very 
  close 
  to 
  three 
  times 
  the 
  mass 
  of 
  the 
  

   tungsten 
  lost 
  by 
  the 
  filament. 
  

  

  This 
  tube 
  gave 
  0*1 
  amp. 
  electronic 
  emission 
  on 
  the 
  average 
  

   for 
  6 
  hours 
  altogether. 
  By 
  that 
  time 
  the 
  mass 
  of 
  the 
  electrons 
  

   emitted 
  was 
  approximately 
  2 
  per 
  cent, 
  of 
  the 
  mass 
  of 
  the 
  

   tungsten 
  filament. 
  The 
  tube 
  came 
  to 
  an 
  end 
  owing 
  to 
  an 
  

   accident: 
  the 
  filament 
  gradually 
  became 
  deformed 
  until 
  it 
  

   touched 
  the 
  copper 
  electrode 
  and 
  broke. 
  The 
  hardness 
  of 
  

   the 
  tube 
  was 
  then 
  tested 
  with 
  an 
  induction-coil 
  and 
  the 
  

   equivalent 
  spark-gap 
  was 
  found 
  to 
  be 
  3*3 
  cm. 
  The 
  discharge 
  

   through 
  the 
  tube 
  gave 
  a 
  bright 
  green 
  fluorescence 
  on 
  the 
  

   glass 
  around 
  the 
  negative 
  wire, 
  but 
  there 
  was 
  no 
  indication 
  

   of 
  a 
  glow 
  or 
  the 
  faint 
  purple 
  haze 
  which 
  is 
  obtained 
  when 
  

   traces 
  of 
  gas 
  are 
  present 
  in 
  tubes 
  of 
  this 
  kind. 
  There 
  is 
  

   thus 
  no 
  appreciable 
  accumulation 
  of 
  gas 
  even 
  when 
  the 
  

   filaments 
  are 
  allowed 
  to 
  emit 
  a 
  large 
  thermionic 
  current 
  

   continuously 
  for 
  a 
  long 
  time. 
  

  

  Another 
  tube 
  with 
  a 
  wire 
  2*7 
  cm. 
  long 
  giving 
  0'050 
  amp. 
  

   lost 
  1*19 
  x 
  10 
  17 
  atoms 
  of 
  tungsten 
  in 
  12 
  hours 
  as 
  measured 
  by 
  

   the 
  change 
  in 
  the 
  cold 
  resistance. 
  The 
  number 
  of 
  electrons 
  

   emitted 
  for 
  each 
  atom 
  of 
  tungsten 
  lost 
  was 
  thus 
  l'13x 
  10' 
  5 
  ,. 
  

   and 
  the 
  mass 
  of 
  the 
  emitted 
  electrons 
  about 
  one 
  third 
  of 
  the 
  

   mass 
  of 
  the 
  tungsten 
  lost. 
  This 
  tube 
  ran 
  altogether 
  for 
  

   about 
  23 
  hours 
  giving 
  various 
  currents, 
  and 
  finally 
  gave 
  out 
  

   owing 
  to 
  the 
  local 
  loss 
  of 
  material 
  near 
  one 
  end 
  caused 
  by 
  

   the 
  sputtering 
  or 
  evaporation. 
  Local 
  over-heating 
  is 
  very 
  

   apt 
  to 
  occur 
  in 
  these 
  experiments 
  as 
  the 
  thermionic 
  leakage 
  

   causes 
  the 
  heating 
  current 
  in 
  the 
  wire 
  to 
  be 
  bigger 
  at 
  one 
  

   end 
  than 
  the 
  other. 
  The 
  mass 
  of 
  all 
  the 
  electrons 
  emitted 
  

   by 
  this 
  filament 
  was 
  equal 
  to 
  4 
  per 
  cent, 
  of 
  its 
  total 
  mass. 
  

   Under 
  a 
  low-power 
  microscope 
  the 
  filament 
  did 
  not 
  appear 
  to 
  

   be 
  much 
  changed 
  except 
  in 
  the 
  region 
  where 
  it 
  had 
  burnt 
  

   out, 
  where 
  it 
  was 
  much 
  thinner 
  than 
  elsewhere. 
  

  

  There 
  is 
  no 
  known 
  reason 
  for 
  believing 
  that 
  the 
  loss 
  of 
  

   tungsten 
  is 
  due 
  to 
  anything 
  more 
  profound 
  than 
  evaporation. 
  

   But, 
  in 
  any 
  event, 
  the 
  fact 
  that 
  the 
  mass 
  of 
  the 
  emitted 
  

  

  