﻿454 
  Prof. 
  0. 
  W. 
  Richardson 
  on 
  the 
  

  

  1. 
  Positive 
  Ions. 
  

  

  The 
  papers 
  already 
  cited 
  have 
  shown 
  that 
  the 
  salts 
  of 
  

   the 
  alkali 
  and 
  alkaline 
  earth 
  metals 
  emitted 
  in 
  appreciable 
  

   quantity 
  only 
  univalent 
  ions 
  of 
  the 
  type 
  Li 
  + 
  Na 
  + 
  K 
  + 
  Hb 
  + 
  

   Cs 
  + 
  Oa 
  + 
  Sr 
  + 
  and 
  Ba 
  + 
  . 
  In 
  the 
  case 
  of 
  the 
  haloid 
  salts 
  of 
  

   zinc 
  there 
  were 
  indications 
  of 
  the 
  presence 
  of 
  divalent 
  as 
  well 
  

   as 
  monovalent 
  ions, 
  the 
  proportion 
  of 
  the 
  former 
  apparently 
  

   increasing 
  with 
  the 
  atomic 
  weight 
  of 
  the 
  haloid 
  constituent. 
  

   In 
  order 
  to 
  obtain 
  further 
  information 
  about 
  this 
  question 
  

   new 
  experiments 
  have 
  been 
  made 
  with 
  the 
  iodides 
  of 
  zinc 
  

   and 
  cadmium. 
  

  

  Zinc 
  Iodide. 
  Znl 
  2 
  . 
  

  

  In 
  the 
  experiments 
  with 
  this 
  substance 
  the 
  distance 
  z 
  

   between 
  the 
  strip 
  and 
  the 
  plates 
  was 
  l 
  - 
  256 
  cm., 
  the 
  mag- 
  

   netic 
  field 
  H 
  was 
  2820 
  E.M. 
  units, 
  the 
  electrostatic 
  potential 
  

   difference 
  V 
  = 
  204xl0 
  8 
  E.M. 
  units, 
  and 
  the 
  displacement 
  

   2oc 
  of 
  the 
  maximum, 
  produced 
  by 
  reversing 
  the 
  magnetic 
  

   field, 
  is 
  given, 
  for 
  a 
  series 
  of 
  measurements, 
  in 
  the 
  following 
  

   table. 
  Throughout 
  this 
  paper 
  the 
  unit 
  in 
  which 
  x 
  is 
  ex- 
  

   pressed 
  is 
  0*0635 
  cm. 
  

  

  Date 
  Nov. 
  6. 
  8. 
  9. 
  10. 
  11. 
  15. 
  16. 
  

  

  Number 
  ... 
  1 
  2 
  3 
  4 
  5 
  6 
  7 
  

  

  2x 
  8-6 
  8 
  10-5 
  10-5 
  10-1 
  8"3 
  7"8 
  

  

  e/m 
  337 
  290 
  515 
  515 
  476 
  320 
  282 
  

  

  m/K 
  28-8 
  333 
  18'7 
  18-7 
  20-2 
  304 
  34'2 
  

  

  In 
  No. 
  6 
  and 
  No. 
  7 
  V 
  = 
  203 
  and 
  202 
  volts 
  respectively 
  

   instead 
  of 
  204. 
  

  

  The 
  above 
  data 
  were 
  all 
  obtained 
  by 
  the 
  slit 
  method. 
  

   Experiments 
  1—5 
  were 
  made 
  with 
  one 
  specimen 
  of 
  salt 
  and 
  

   experiments 
  6 
  and 
  7 
  with 
  another. 
  Nos. 
  3, 
  4 
  and 
  5, 
  which 
  

   show 
  much 
  higher 
  values 
  of 
  e\m 
  than 
  the 
  others, 
  were 
  made 
  

   with 
  the 
  salt 
  after 
  it 
  had 
  been 
  heated 
  for 
  a 
  considerable 
  

   time. 
  The 
  mean 
  of 
  the 
  values 
  of 
  the 
  electric 
  atomic 
  weight 
  

   given 
  by 
  the 
  freshly 
  heated 
  salt 
  is 
  31/6. 
  The 
  value 
  for 
  Zn 
  ++ 
  

   would 
  be 
  32'7. 
  The 
  mean 
  of 
  the 
  values 
  from 
  the 
  old 
  salt 
  is 
  

   19*2 
  and 
  suggests 
  the 
  presence 
  of 
  sodium 
  as 
  an 
  impurity, 
  al- 
  

   though 
  it 
  is 
  rather 
  low. 
  There 
  was 
  no 
  indication 
  in 
  these 
  

   experiments 
  of 
  the 
  presence 
  of 
  potassium, 
  which 
  is 
  the 
  most 
  

   common 
  adventitious 
  source 
  of 
  this 
  kind 
  of 
  ionization. 
  Un- 
  

   less 
  the 
  rather 
  copious 
  ionization 
  from 
  freshly 
  heated 
  zinc 
  

   iodide 
  all 
  arises 
  from 
  contamination 
  by 
  impurities, 
  which 
  

   seems 
  unlikely, 
  the 
  above 
  results 
  show 
  quite 
  clearly 
  that 
  

   practically 
  all 
  the 
  ions 
  are 
  Zn 
  + 
  + 
  and 
  not 
  Zn 
  + 
  . 
  

  

  