﻿468 
  Prof. 
  0. 
  W. 
  Richardson 
  on 
  the 
  

  

  capacity 
  in 
  addition 
  to 
  that 
  of 
  the 
  electrometer, 
  at 
  about 
  

   500° 
  Pt. 
  At 
  first 
  this 
  emission 
  was 
  made 
  up 
  almost 
  entirely 
  

   of 
  heavy 
  ions. 
  As 
  the 
  heating 
  was 
  continued 
  at 
  a 
  constant 
  

   temperature 
  the 
  percentage 
  of 
  the 
  current 
  which 
  was 
  carried 
  

   by 
  heavy 
  ions 
  diminished. 
  On 
  first 
  heating 
  the 
  salt, 
  when 
  

   there 
  were 
  in 
  all 
  probability 
  practically 
  no 
  electrons 
  present 
  

   in 
  the 
  emission, 
  measurements 
  of 
  e/m 
  and 
  ra/H 
  were 
  made 
  

   by 
  the 
  balance 
  method. 
  Successive 
  measurements 
  which 
  

   occupied 
  40 
  minutes 
  gave 
  the 
  following 
  values 
  of 
  m/H 
  : 
  — 
  

   113, 
  118, 
  115, 
  118, 
  118. 
  These 
  are 
  sufficiently 
  near 
  the 
  

   iodine 
  value 
  .127 
  to 
  make 
  it 
  probable 
  that 
  the 
  heavy 
  ions 
  are 
  

   atoms 
  of 
  iodine 
  with 
  an 
  attached 
  electron. 
  

  

  After 
  the 
  salt 
  had 
  been 
  heated 
  at 
  about 
  500° 
  Pt. 
  for 
  about 
  

   two 
  hours, 
  the 
  following 
  readings 
  taken 
  successively 
  at 
  rising 
  

   temperatures 
  give 
  an 
  idea 
  of 
  the 
  magnitude 
  and 
  composition 
  

   of 
  the 
  thermionic 
  emission 
  at 
  different 
  temperatures 
  : 
  — 
  

  

  Temperature 
  | 
  ^ 
  ^ 
  ^ 
  m 
  m 
  m 
  

  

  TO 
  (fmp 
  s 
  rr 
  ) 
  ent 
  } 
  1 
  " 
  45xl0 
  ~ 
  11 
  6 
  ' 
  91 
  X10- 
  10 
  3-01X10" 
  9 
  1-13X10- 
  7 
  5'47xH)- 
  7 
  2-5x10" 
  

   cSSfl.) 
  35 
  35 
  38 
  ™ 
  8-1 
  5-2 
  

  

  In 
  these 
  experiments 
  the 
  salt 
  was 
  placed 
  all 
  over 
  the 
  strip 
  

   by 
  means 
  of 
  a 
  solution. 
  

  

  Attempts 
  were 
  made 
  to 
  measure 
  e/m 
  for 
  the 
  heavy 
  ions 
  

   present 
  in 
  the 
  large 
  current 
  at 
  606° 
  C. 
  by 
  the 
  balance 
  method, 
  

   but 
  it 
  was 
  found 
  that 
  no 
  balance 
  could 
  be 
  obtained 
  with 
  the 
  

   field 
  in 
  one 
  direction. 
  In 
  fact, 
  this 
  method 
  (and 
  also 
  the 
  

   slit 
  method) 
  of 
  measuring 
  e/m 
  for 
  the 
  heavy 
  negative 
  ions 
  

   fails 
  when 
  the 
  full 
  emission 
  contains 
  a 
  large 
  proportion 
  

   of 
  electrons. 
  I 
  have 
  made 
  a 
  number 
  of 
  experiments 
  to 
  find 
  

   out 
  precisely 
  what 
  is 
  going 
  on 
  under 
  these 
  conditions 
  without 
  

   arriving 
  at 
  any 
  satisfactory 
  conclusion. 
  They 
  seemed 
  to 
  

   show 
  pretty 
  definitely, 
  however, 
  that 
  the 
  failure 
  was 
  connected 
  

   in 
  some 
  way 
  with 
  the 
  presence 
  of 
  an 
  excess 
  of 
  electrons 
  and 
  

   not 
  to 
  the 
  magnitude 
  of 
  the 
  currents 
  or 
  the 
  presence 
  of 
  

   positive 
  ions. 
  This 
  difficulty 
  is 
  unfortunate, 
  as 
  some 
  of 
  the 
  

   salts 
  investigated 
  do 
  not 
  appear 
  to 
  emit 
  heavy 
  ions 
  sufficiently 
  

   free 
  from 
  electrons 
  for 
  e/m 
  to 
  be 
  determined 
  satisfactorily. 
  

  

  So 
  far 
  as 
  the 
  above 
  experiments 
  go 
  they 
  do 
  not 
  point 
  to 
  

   any 
  important 
  difference 
  between 
  the 
  emission 
  of 
  negative 
  

   ions 
  from 
  calcium 
  and 
  strontium 
  iodides. 
  The 
  experiments 
  

   show 
  that 
  the 
  behaviour 
  of 
  the 
  iodide 
  of 
  barium 
  is 
  also 
  quite 
  

   similar 
  to 
  that 
  of 
  calcium. 
  

  

  