﻿482 
  Electric 
  Uiscliarge 
  through. 
  Gases 
  HCl, 
  HBr, 
  Sf 
  HI. 
  

  

  ions 
  that 
  would 
  meet 
  the 
  walls 
  or 
  anode 
  with 
  the 
  velocity 
  

   necessary 
  for 
  absorption. 
  This 
  is 
  also 
  in 
  ag-reement 
  with 
  the 
  

   experiment 
  that 
  silvering 
  o£ 
  the 
  inner 
  surface 
  had 
  no 
  effect 
  

   on 
  absorption. 
  And 
  if 
  the 
  absorption 
  was 
  brought 
  about 
  

   quite 
  as 
  much 
  by 
  negative 
  as 
  by 
  positive 
  ions, 
  it 
  would 
  be 
  

   difficult 
  to 
  understand 
  why 
  the 
  potential 
  fall 
  between 
  the 
  

   electrodes 
  had 
  to 
  be 
  concentrated 
  near 
  the 
  cathode 
  in 
  order 
  

   to 
  produce 
  absorption. 
  

  

  This 
  hypothesis, 
  that 
  the 
  absorption 
  is 
  caused 
  by 
  the 
  posi- 
  

   tive 
  ions 
  being 
  shot 
  into 
  the 
  cathode, 
  also 
  explains 
  the 
  rapid 
  

   increase 
  of 
  absorption 
  when 
  the 
  cathode 
  fall 
  exceeds 
  a 
  certain 
  

   value, 
  for 
  it 
  only 
  means 
  that 
  a 
  certain 
  velocity 
  is 
  required 
  

   for 
  ions 
  to 
  be 
  shot 
  into 
  solid 
  matter. 
  

  

  It 
  is 
  worth 
  noticing 
  that 
  it 
  is 
  in 
  the 
  state 
  of 
  the 
  rapid 
  

   absorption 
  that 
  the 
  most 
  rapid 
  disintegration 
  of 
  the 
  cathode 
  

   takes 
  place, 
  which 
  suggests, 
  what 
  from 
  our 
  view 
  seems 
  quite 
  

   natural, 
  that 
  these 
  two 
  phenomena 
  are 
  closely 
  connected. 
  

  

  Summary 
  of 
  Results. 
  

  

  (1) 
  The 
  general 
  character 
  of 
  the 
  discharge 
  through 
  HCl, 
  

   HBr, 
  and 
  HI 
  is 
  the 
  same 
  as 
  for 
  elementary 
  gases. 
  

  

  (2) 
  In 
  HCl 
  and 
  HBr 
  the 
  discharge 
  could 
  be 
  kept 
  constant 
  

   and 
  with 
  a 
  uniform 
  structure 
  within 
  wide 
  current 
  intervals 
  ; 
  

   the 
  conditions 
  were 
  "reversible." 
  For 
  HI 
  a 
  constant 
  dis- 
  

   charge 
  could 
  only 
  be 
  got 
  for 
  very 
  small 
  currents. 
  

  

  (3) 
  Within 
  the 
  interval 
  of 
  reversibility 
  the 
  decomposition 
  

   is 
  too 
  small 
  to 
  effect 
  the 
  discharge. 
  

  

  (4) 
  The 
  characteristic 
  curve 
  depends 
  on 
  the 
  " 
  history 
  " 
  of 
  

   the 
  tube, 
  and 
  a 
  change 
  in 
  structure 
  caused 
  by 
  current 
  is 
  

   always 
  accompanied 
  by 
  a 
  fall 
  in 
  the 
  P.G. 
  in 
  the 
  positive 
  

   column 
  . 
  

  

  (5) 
  Under 
  comparable 
  conditions 
  the 
  potential 
  gradients 
  

   in 
  HCl, 
  HBr, 
  HI 
  follow 
  the 
  order 
  of 
  the 
  molecular 
  weights. 
  

  

  (6) 
  The 
  variations 
  of 
  P.G. 
  with 
  current 
  for 
  HCl 
  and 
  HBr 
  

   follow 
  Herz's 
  law 
  except 
  for 
  very 
  small 
  currents. 
  

  

  (7) 
  The 
  normal 
  cathode 
  fall 
  is 
  found 
  for 
  HCl 
  and 
  HBr 
  ; 
  

   the 
  smallest 
  pressure 
  that 
  can 
  give 
  a 
  normal 
  cathode 
  fall 
  is 
  

   the 
  same 
  for 
  O2, 
  HCl, 
  and 
  HBr. 
  

  

  (8) 
  The 
  anode 
  fall 
  in 
  the 
  interval 
  of 
  observation 
  is 
  found 
  

   to 
  be 
  expressible 
  by 
  either 
  of 
  the 
  two 
  functions 
  : 
  

  

  A 
  = 
  A^^ 
  + 
  ttip 
  +p(a2 
  — 
  hpy-"'^, 
  

  

  A 
  = 
  Ao+T 
  T 
  • 
  

  

  8 
  /^(«i-h«2<?-'^'i) 
  

  

  