﻿Effects 
  at 
  the 
  Cathode 
  in 
  Vacuum 
  Tubes. 
  421 
  

  

  There 
  appears 
  no 
  good 
  reason 
  why 
  the 
  values 
  in 
  air 
  should 
  

   be 
  above 
  the 
  value 
  1*0, 
  yet 
  they 
  are 
  invariably 
  so. 
  The 
  

   column 
  B 
  (Table 
  IV.) 
  gives 
  the 
  ratio 
  

  

  cathode 
  fall 
  oxygen 
  

  

  cathode 
  fall 
  air 
  

   and 
  apparently 
  both 
  in 
  air 
  and 
  impure 
  nitrogen 
  the 
  bom- 
  

   barding 
  ions 
  have 
  passed 
  through 
  the 
  oxygen 
  cathode 
  fall. 
  

  

  § 
  9. 
  As 
  mentioned 
  in 
  § 
  6, 
  the 
  evolution 
  of 
  gas 
  from 
  the 
  

   electrodes 
  is 
  a 
  source 
  of 
  much 
  impurity 
  in 
  the 
  gases 
  used. 
  

   The 
  effect 
  of 
  prolonged 
  running 
  of 
  the 
  tube 
  was 
  tried 
  with 
  

   lead 
  and 
  nickel 
  cathodes 
  in 
  nitrogen. 
  The 
  following 
  table 
  

   gives 
  the 
  results: 
  — 
  

  

  Table 
  VI. 
  

   Nickel 
  in 
  nitrogen. 
  

  

  Exp. 
  

  

  a/8. 
  

  

  Notes. 
  

  

  1 
  

  

  1-59 
  

  

  N 
  dry 
  and 
  fresh. 
  Tube 
  run 
  only 
  a 
  short 
  time. 
  

  

  2 
  

  

  134 
  

  

  Same 
  gas 
  used. 
  Gas 
  evolved. 
  

  

  3 
  

  

  1-25 
  

  

  Same 
  gas 
  used. 
  Gas 
  evolved. 
  

  

  4 
  

  

  1-35 
  

  

  Same 
  gas 
  used. 
  Gas 
  evolved. 
  

  

  5 
  

  

  1-25 
  

  

  Current 
  run 
  3 
  hours 
  before 
  taking 
  a 
  reading.' 
  

  

  6 
  

  

  1-59 
  

  

  Fresh, 
  dry 
  N 
  let 
  in. 
  

  

  Table 
  VII. 
  

   Lead 
  in 
  nitrogen. 
  

  

  Exp. 
  

  

  a/p. 
  

  

  Notes. 
  

  

  1 
  

  

  1-48 
  

  

  Fresh 
  dry 
  nitrogen. 
  

  

  2 
  

  

  1-28 
  

  

  Gas 
  absorbed. 
  

  

  3 
  

  

  116 
  

  

  Fresh 
  nitrogen. 
  Gas 
  evolved. 
  

  

  4 
  ...... 
  

  

  110 
  

  

  Nascent 
  sodium 
  used. 
  Gas 
  absorbed. 
  

  

  5 
  

  

  1-08 
  

  

  Nascent 
  sodium 
  used. 
  Gas 
  absorbed. 
  

  

  8 
  

  

  0-98 
  

  

  Nascent 
  sodium 
  used. 
  Gas 
  absorbed. 
  

  

  7 
  

  

  1-32 
  

  

  Fresh 
  N 
  admitted, 
  Gas 
  evolved. 
  

  

  8 
  

  

  1-08 
  

  

  Nascent 
  sodium 
  used. 
  Gas 
  absorbed. 
  

  

  