﻿Electric 
  Discharge 
  throiigli 
  Gases 
  HCl, 
  HBr, 
  S^' 
  HI. 
  465 
  

  

  by 
  (19). 
  It 
  will 
  be 
  seen 
  that 
  the 
  agreement 
  between 
  the 
  

   observed 
  and 
  calculated 
  frequencies 
  is 
  very 
  satisfactory. 
  

  

  I 
  should 
  like 
  to 
  take 
  this 
  opportunity 
  of 
  making 
  a 
  slight 
  

   correction 
  in 
  my 
  paper 
  '' 
  On 
  the 
  Lateral 
  Vibration 
  of 
  Bars 
  

   subjected 
  to 
  Forces 
  in 
  the 
  Direction 
  of 
  their 
  Axes." 
  On 
  

   page 
  23G 
  of 
  the 
  Philosophical 
  Magazine 
  for 
  September 
  1906, 
  

   and 
  on 
  page 
  227 
  of 
  the 
  Proceedings 
  of 
  the 
  Physical 
  Society, 
  

   vol. 
  XX., 
  instead 
  of 
  tanh</) 
  I 
  have 
  used 
  its 
  reciprocal. 
  Tlip 
  

   error 
  makes 
  very 
  little 
  difference 
  to 
  the 
  final 
  equation, 
  the 
  

   correct 
  expression 
  being 
  

  

  -•^^= 
  500-56^. 
  +12-91 
  ^,,-'16 
  

  

  i/i 
  pcol"^ 
  " 
  pwP 
  occFJ- 
  

  

  Armstrong 
  Colleg-e. 
  

   January 
  1908. 
  

  

  Lir. 
  0)1 
  tJie 
  Electric 
  Discharge 
  through 
  the 
  Gases 
  HCl, 
  

   HBr, 
  and 
  HI. 
  By 
  L. 
  Yegard, 
  Universitets 
  stipendiat 
  

   of 
  Christiania 
  University 
  *. 
  

  

  [Plate 
  XIV.] 
  

  

  § 
  1. 
  "FX 
  some 
  recent 
  experiments 
  made 
  by 
  Matthies 
  f 
  on 
  the 
  

   X 
  discharge 
  through 
  the 
  vapours 
  of 
  HgCl. 
  HgBr, 
  

   Hgl, 
  as 
  well 
  as 
  through 
  the 
  elements 
  CU, 
  Brg, 
  and 
  I, 
  some 
  

   very 
  striking 
  results 
  are 
  found 
  regarding 
  the 
  potential 
  

   gradient 
  in 
  the 
  positive 
  cohmm. 
  When 
  compared 
  for 
  equal 
  

   currents 
  and 
  pressures 
  the 
  gradients 
  are 
  found 
  to 
  be 
  greatest 
  

   for 
  Br 
  and 
  smallest 
  in 
  the 
  case 
  of 
  I. 
  This 
  remarkable 
  result 
  

   led 
  me, 
  at 
  the 
  suggestion 
  of 
  Sir 
  J. 
  J. 
  Thomson, 
  to 
  undertake 
  

   an 
  investigation 
  of 
  the 
  distribution 
  of 
  potential 
  in 
  the 
  gases 
  

   HOI, 
  HBr, 
  and 
  HI. 
  

  

  As 
  the 
  properties 
  of 
  discharge 
  depend 
  on 
  the 
  form 
  and 
  

   size 
  of 
  the 
  tube, 
  it 
  is 
  difficult 
  to 
  reduce 
  the 
  numbers 
  to 
  

   universal 
  units. 
  In 
  order 
  therefore 
  to 
  compare 
  our 
  results 
  

   with 
  those 
  found 
  for 
  other 
  gases, 
  measurements 
  have 
  been 
  

   made 
  with 
  the 
  same 
  tube 
  for 
  oxygen. 
  

  

  Apparatus 
  and 
  Mode 
  of 
  Procedure. 
  

  

  § 
  2. 
  Fig. 
  1 
  gives 
  the 
  general 
  arrangement 
  of 
  the 
  tube- 
  

   system. 
  The 
  air 
  could 
  be 
  pumped 
  out 
  with 
  a 
  mercury- 
  

   pump 
  and 
  the 
  vacuum 
  tested 
  with 
  a 
  McLeod 
  gauge. 
  The 
  

   chemically 
  active 
  gases 
  were 
  removed 
  by 
  blowing 
  a 
  current 
  

  

  * 
  Communicated 
  by 
  Sir 
  J. 
  J. 
  Thomson. 
  

  

  t 
  W. 
  ZNlatthies, 
  A/m. 
  d. 
  Fhys. 
  xvii. 
  p. 
  67o 
  (1905) 
  ; 
  id., 
  ibid, 
  xviii. 
  

   p. 
  473 
  (1905). 
  

  

  