﻿Energy 
  of 
  Negative 
  Electrons 
  emitted 
  by 
  Hot 
  Bodies. 
  369 
  

   If 
  we 
  use 
  logarithms 
  to 
  the 
  base 
  10 
  formula 
  (11) 
  becomes 
  

  

  log^-log 
  lo 
  ; 
  = 
  '432g-0-V. 
  

  

  As 
  i 
  w 
  v, 
  e, 
  0, 
  and 
  R 
  are 
  constant 
  in 
  any 
  one 
  experiment, 
  the 
  

   curve 
  obtained 
  by 
  plotting 
  log 
  10 
  i 
  against 
  V 
  should 
  be 
  a 
  

   straight 
  line. 
  The 
  accuracy 
  with 
  which 
  the 
  linear 
  relation 
  

   was 
  fulfilled 
  is 
  shown 
  by 
  the 
  diagram. 
  From 
  the 
  slope 
  of 
  

  

  this 
  line 
  the 
  value 
  of 
  the 
  coefficient 
  — 
  ^ 
  could 
  be 
  deduced. 
  

  

  Substituting 
  the 
  known 
  value 
  of 
  ve, 
  the 
  quantity 
  of 
  electricity 
  

   required 
  to 
  liberate 
  half 
  a 
  cubic 
  centimetre 
  of 
  hydrogen 
  at 
  

   0° 
  C. 
  and 
  760 
  mms. 
  by 
  electrolysis, 
  and 
  the 
  value 
  of 
  #, 
  the 
  

   absolute 
  temperature, 
  found 
  experimentally, 
  a 
  value 
  of 
  R 
  the 
  

   gas 
  constant 
  could 
  be 
  determined 
  by 
  these 
  experiments 
  and 
  

   compared 
  with 
  the 
  well-known 
  value 
  of 
  this 
  constant. 
  This 
  

   particular 
  experiment 
  gave 
  for 
  R 
  the 
  value 
  4*1 
  x 
  10 
  3 
  C.G.s. 
  

   units 
  compared 
  with 
  the 
  standard 
  value 
  3*7 
  x 
  10 
  5 
  . 
  The 
  

   agreement 
  is 
  fairly 
  good 
  when 
  all 
  the 
  difficulties 
  of 
  the 
  

   investigation 
  are 
  taken 
  into 
  account. 
  

  

  A 
  large 
  number 
  of 
  experiments 
  were 
  made 
  with 
  platinum 
  

   under 
  varied 
  conditions, 
  and 
  this 
  linear 
  relation 
  was 
  always 
  

   verified 
  provided 
  the 
  general 
  method 
  of 
  treatment 
  of 
  the 
  

   platinum 
  which 
  has 
  been 
  described 
  was 
  adhered 
  to. 
  In 
  most 
  

   of 
  the 
  experiments 
  the 
  surrounding 
  gas 
  was 
  air 
  at 
  a 
  low 
  

   pressure 
  ; 
  but 
  the 
  effect 
  of 
  replacing 
  the 
  air 
  by 
  hydrogen 
  at 
  

   a 
  similar 
  pressure 
  was 
  examined. 
  In 
  another 
  set 
  of 
  expe- 
  

   riments 
  the 
  platinum 
  was 
  covered 
  with 
  calcium 
  oxide 
  by 
  

   heating 
  a 
  drop 
  of 
  calcium 
  nitrate 
  solution 
  placed 
  on 
  it. 
  In 
  

   both 
  these 
  cases 
  it 
  was 
  noticed 
  that 
  for 
  some 
  time 
  after 
  the 
  

   change 
  in 
  the 
  conditions 
  had 
  been 
  made 
  the 
  above 
  law 
  con- 
  

   necting 
  the 
  current 
  with 
  the 
  potential-difference 
  was 
  obeyed 
  

   just 
  as 
  with 
  platinum 
  alone 
  surrounded 
  by 
  air. 
  It 
  was 
  also 
  

   noticed 
  that 
  on 
  first 
  heating 
  the 
  strip 
  after 
  letting 
  in 
  hydrogen 
  

   or 
  after 
  coating 
  it 
  with 
  lime, 
  the 
  value 
  of 
  the 
  current 
  at 
  any 
  

   given 
  temperature 
  was 
  practically 
  unchanged 
  from 
  that 
  which 
  

   had 
  obtained 
  for 
  pure 
  platinum 
  at 
  the 
  same 
  temperature 
  in 
  

   air. 
  The 
  subsequent 
  increase 
  in 
  the 
  emission 
  of 
  ions, 
  whether 
  

   caused 
  by 
  hydrogen 
  or 
  by 
  lime, 
  appeared 
  to 
  take 
  some 
  time 
  to 
  

   establish 
  itself, 
  and 
  as 
  soon 
  as 
  a 
  marked 
  increase 
  in 
  the 
  initial 
  

   absolute 
  value 
  of 
  the 
  current 
  occurred, 
  it 
  was 
  found 
  that 
  

   the 
  law 
  was 
  no 
  longer 
  obeyed. 
  Thus 
  the 
  character 
  of 
  the 
  

   phenomena 
  appears 
  to 
  change 
  when 
  the 
  metal 
  is 
  heated 
  for 
  a 
  

   long 
  time 
  either 
  in 
  a 
  hydrogen 
  vacuum 
  or 
  when 
  coated 
  with 
  

   lime. 
  The 
  results 
  which 
  we 
  obtained 
  after 
  heating 
  for 
  some 
  

   time 
  in 
  hydrogen 
  were 
  too 
  irregular 
  to 
  draw 
  very 
  definite 
  

  

  Phil 
  Mag. 
  S. 
  6. 
  Vol. 
  16. 
  No. 
  93. 
  Sept. 
  1908. 
  2 
  C 
  

  

  