﻿Ions 
  from 
  Hot 
  Salts. 
  469 
  

  

  Barium 
  Iodide. 
  Bal 
  2 
  . 
  

  

  Measurements 
  of 
  m/H 
  on 
  first 
  heating 
  at 
  525° 
  Pt. 
  gave 
  

   the 
  following 
  successive 
  values 
  o£ 
  ??i/H, 
  viz. 
  : 
  — 
  103, 
  108, 
  

   105, 
  113, 
  116. 
  These 
  are 
  rather 
  low 
  but 
  may 
  probably 
  be 
  

   taken 
  to 
  indicate 
  I_, 
  (127). 
  Experiments 
  made 
  after 
  the 
  

   salt 
  had 
  been 
  heated 
  some 
  time 
  failed 
  on 
  account 
  of 
  the 
  

   presence 
  of 
  too 
  many 
  electrons. 
  

  

  Cadmium 
  Iodide. 
  Cdl 
  2 
  . 
  

  

  A 
  number 
  of 
  experiments 
  were 
  made 
  to 
  determine 
  e/m 
  

   for 
  the 
  negative 
  ions 
  emitted 
  by 
  this 
  substance, 
  but 
  the 
  

   success 
  attained 
  was 
  rather 
  limited. 
  When 
  the 
  salt 
  was 
  

   heated 
  initially 
  a 
  transient 
  negative 
  emission 
  was 
  observed, 
  

   but 
  it 
  did 
  not 
  last 
  long 
  enough 
  to 
  enable 
  e/m 
  to 
  be 
  measured. 
  

   This 
  seemed 
  rather 
  surprising 
  in 
  view 
  of 
  the 
  results 
  obtained 
  

   by 
  Sheard 
  * 
  with 
  this 
  substance, 
  but 
  it 
  is 
  to 
  be 
  remembered 
  

   that 
  his 
  experiments 
  were 
  carried 
  out 
  at 
  much 
  higher 
  

   pressures. 
  At 
  the 
  low 
  pressure 
  at 
  which 
  the 
  present 
  experi- 
  

   ments 
  were 
  attempted 
  (0*001 
  mm.) 
  the 
  salt 
  would 
  probably 
  

   volatilize 
  before 
  the 
  ionization 
  occurred. 
  This 
  behaviour 
  of 
  

   the 
  negative 
  ionization 
  supports 
  the 
  view 
  of 
  the 
  nature 
  of 
  the 
  

   positive 
  ionization 
  from 
  this 
  substance 
  which 
  was 
  expressed 
  

   on 
  p. 
  456. 
  In 
  the 
  present 
  case 
  experiments 
  were 
  tried 
  with 
  

   a 
  millimetre 
  or 
  so 
  of 
  air 
  present 
  in 
  the 
  apparatus, 
  and 
  much 
  

   larger 
  negative 
  emissions 
  were 
  obtained, 
  but 
  the 
  pressure 
  was 
  

   then 
  too 
  high 
  for 
  e/m 
  to 
  be 
  measured. 
  

  

  Under 
  these 
  circumstances 
  I 
  have 
  had 
  to 
  be 
  content 
  with 
  

   making 
  qualitative 
  experiments 
  on 
  the 
  emission 
  from 
  the 
  

   salt 
  at 
  about 
  1 
  mm. 
  pressure. 
  At 
  1*3 
  mm. 
  I 
  found 
  that 
  

   when 
  the 
  salt 
  was 
  first 
  heated, 
  about 
  16 
  per 
  cent, 
  of 
  the 
  

   emission 
  was 
  not 
  stopped 
  by 
  the 
  magnetic 
  field, 
  and 
  that 
  

   this 
  proportion 
  fell 
  to 
  10 
  per 
  cent, 
  in 
  about 
  half 
  an 
  hour. 
  

   At 
  a 
  higher 
  temperature, 
  after 
  further 
  heating, 
  the 
  pro- 
  

   portion 
  which 
  was 
  not 
  stopped 
  had 
  fallen 
  to 
  3*2 
  per 
  cent. 
  

   Although 
  the 
  conditions 
  are 
  rather 
  complicated 
  at 
  this 
  

   pressure 
  it 
  seems 
  a 
  fair 
  inference 
  that 
  both 
  heavy 
  ions 
  and 
  

   electrons 
  are 
  given 
  off 
  by 
  the 
  salt, 
  and 
  that 
  the 
  proportion 
  

   of 
  the 
  current 
  which 
  is 
  carried 
  by 
  electrons 
  is 
  greater 
  at 
  

   higher 
  temperatures 
  and 
  increases 
  with 
  continued 
  heating 
  as 
  

   with 
  the 
  other 
  iodides 
  which 
  have 
  been 
  examined. 
  

  

  Ferric 
  Chloride. 
  FeCl 
  3 
  . 
  

   This 
  substance 
  gave 
  a 
  transient 
  negative 
  emission 
  which 
  

   was 
  too 
  small 
  to 
  make 
  measurements 
  with. 
  

  

  * 
  Phil. 
  Mag. 
  vol. 
  xxv. 
  p. 
  370 
  (1913). 
  

  

  