﻿through 
  the 
  Gases 
  HCl, 
  HBr, 
  and 
  HI. 
  

  

  467 
  

  

  by 
  sealing 
  the 
  tube 
  i 
  and 
  evacuating. 
  Then 
  the 
  acid 
  ^\'as 
  

   introduced 
  into 
  the 
  bulb 
  j. 
  The 
  gas 
  given 
  off 
  by 
  the 
  

   liquid 
  had 
  to 
  pass 
  through 
  the 
  tube 
  Jc 
  containing 
  a 
  number 
  

   of 
  layers 
  o£ 
  glass 
  wool 
  and 
  phosphorus 
  pentoxide, 
  and 
  

   finally 
  a 
  plug 
  o£ 
  phosphorus. 
  Thus 
  water-vapour 
  and 
  

   traces 
  o£ 
  bromine 
  and 
  iodine 
  vapours 
  were 
  removed 
  from 
  

   the 
  gas. 
  

  

  The 
  discharge-tube 
  was 
  similar 
  in 
  form 
  to 
  that 
  used 
  by 
  

   Matthies, 
  the 
  chief 
  difference 
  being 
  that 
  the 
  electrodes 
  con- 
  

   sisted 
  of 
  elliptical-shaped 
  platinum 
  plates 
  fixed 
  to 
  platinum 
  

   rods 
  (fig. 
  3), 
  while 
  he 
  used 
  thick 
  platinum 
  rods. 
  The 
  dis- 
  

   tribution 
  of 
  potential 
  was 
  measured 
  with 
  fixed 
  explorers 
  of 
  

   platinum 
  surrounded 
  with 
  narrow 
  glass 
  tubes. 
  The 
  tube 
  

   had 
  the 
  followino^ 
  dimensions 
  : 
  — 
  

  

  i 
  

  

  Diam. 
  of 
  

   the 
  tube. 
  

  

  Area 
  of 
  

  

  the 
  

   Cathode 
  

   surface. 
  

  

  Distance 
  bet^veen 
  electrodes 
  and 
  

   Area 
  of 
  explorers. 
  

   Anode 
  

  

  surface. 
  

  

  A— 
  1. 
  A— 
  2. 
  

  

  A-3. 
  

  

  A— 
  4. 
  

  

  A-5. 
  

  

  A— 
  K. 
  

  

  3-3 
  cm. 
  

  

  3-2 
  cm.-^ 
  

  

  mm. 
  mm. 
  

   1-3 
  cm.- 
  3-1 
  2o-3 
  

  

  mm. 
  

   46-1 
  

  

  mm. 
  

   67-5 
  

  

  mm. 
  

   87-2 
  

  

  mm. 
  

   91-6 
  

  

  The 
  potential 
  for 
  producing 
  the 
  discharge 
  was 
  taken 
  

   from 
  a 
  number 
  of 
  storage-cells, 
  the 
  potential 
  of 
  which 
  was 
  

   measured 
  before 
  and 
  after 
  each 
  series 
  of 
  measurements. 
  

  

  The 
  arrangement 
  for 
  current 
  and 
  P.D. 
  measurements 
  is 
  

   shown 
  in 
  fig. 
  3. 
  The 
  P.D.''s 
  were 
  measured 
  with 
  a 
  quadrant 
  

   electrometer 
  (Dolezalek 
  type). 
  This 
  instrument 
  being 
  too 
  

   sensitive 
  for 
  the 
  purpose, 
  the 
  following 
  way 
  of 
  measuring 
  

   was 
  used 
  : 
  — 
  The 
  anode 
  and 
  the 
  positive 
  end 
  of 
  the 
  battery 
  

   being 
  connected 
  through 
  a 
  very 
  small 
  resistance 
  had 
  the 
  

   same 
  potential. 
  To 
  measure 
  the 
  P.D., 
  say 
  between 
  the 
  

   anode 
  and 
  the 
  explorer 
  (4), 
  the 
  latter 
  is 
  put 
  in 
  connexion 
  

   with 
  the 
  terminal 
  leading 
  to 
  the 
  electrometer 
  and 
  the 
  other 
  

   electrometer 
  terminal 
  is 
  connected 
  to 
  the 
  wire 
  (d) 
  coming 
  

   from 
  the 
  battery. 
  By 
  taking 
  out 
  a 
  suitable 
  voltage 
  from 
  

   the 
  battery 
  the 
  P.D. 
  (A 
  — 
  4) 
  can 
  be 
  so 
  balanced 
  that 
  the 
  

   electrometer 
  gives 
  a 
  suitable 
  deflexion. 
  

  

  AVires 
  from 
  the 
  electrodes 
  and 
  explorers 
  were 
  connected 
  to 
  

   a 
  set 
  of 
  mercury 
  cups 
  cut 
  in 
  a 
  piece 
  of 
  paraffin 
  wax 
  and 
  placed 
  

   on 
  the 
  periphery 
  of 
  a 
  circle, 
  so 
  that 
  by 
  the 
  key 
  b 
  they 
  can 
  easily 
  

   be 
  put 
  in 
  connexion 
  with 
  the 
  electrometer. 
  

  

  