﻿254 
  

  

  Mr. 
  Gr. 
  B. 
  Bryan 
  on 
  the 
  Determination 
  of 
  

  

  separated 
  from 
  it 
  by 
  three 
  small 
  pieces 
  of 
  glass, 
  all 
  of 
  the 
  

   same 
  thickness, 
  which 
  was 
  carefully 
  measured. 
  These 
  plates 
  

   formed 
  the 
  electrodes, 
  and 
  as 
  the 
  glass 
  vessel 
  was 
  of 
  very 
  

   little 
  greater 
  diameter 
  than 
  the 
  plates, 
  the 
  specific 
  resistance 
  

   of 
  the 
  liquid 
  was 
  calculated 
  from 
  the 
  formula, 
  Sp. 
  H. 
  = 
  ra/d 
  f 
  

   where 
  a 
  is 
  the 
  area 
  of 
  the 
  plates, 
  d 
  the 
  thickness 
  of 
  the 
  layer, 
  

   and 
  r 
  its 
  resistance. 
  Two 
  pairs 
  of 
  plates 
  were 
  used 
  ; 
  one 
  pair 
  

   of 
  brass, 
  gilded 
  and 
  polished, 
  and 
  the 
  other 
  pair 
  of 
  zinc, 
  

   carefully 
  amalgamated. 
  The 
  diameter 
  of 
  the 
  gilded 
  plates 
  

   was 
  6'6 
  cm. 
  ; 
  that 
  of 
  the 
  zinc 
  plates 
  was 
  slightly 
  less. 
  

  

  To 
  measure 
  the 
  resistance 
  between 
  the 
  electrodes 
  they 
  were 
  

   connected 
  in 
  series 
  with 
  a 
  standard 
  resistance 
  and 
  a 
  battery 
  of 
  

   constant 
  E.M.F. 
  The 
  potentials 
  at 
  the 
  terminals 
  of 
  the 
  

   electrodes 
  and 
  the 
  standard 
  resistance 
  were 
  compared 
  by 
  

   means 
  of 
  an 
  electrometer, 
  and 
  the 
  unknown 
  resistance 
  thus 
  

   determined. 
  Readings 
  were 
  taken 
  at 
  a 
  given 
  time, 
  T, 
  after 
  

   starting 
  the 
  current. 
  

  

  Roller 
  tested 
  a 
  large 
  number 
  of 
  substances, 
  including 
  

   turpentine, 
  benzol, 
  toluol, 
  xylol, 
  and 
  CS 
  2 
  , 
  with 
  which 
  the 
  

   gilded 
  electrodes 
  were 
  used. 
  The 
  following 
  is 
  a 
  specimen 
  of 
  

   the 
  results 
  obtained 
  : 
  — 
  

  

  Turpentine, 
  

   E.M.F. 
  = 
  1 
  Daniell 
  Cell. 
  Temp. 
  = 
  24° 
  C. 
  

  

  d. 
  

  

  Specific 
  Resistance 
  in 
  C.G.S. 
  

  

  T 
  = 
  li 
  minutes. 
  

  

  T 
  very 
  great. 
  

  

  0*15 
  mm. 
  

   1-135 
  „ 
  

   7-49 
  „ 
  

  

  228 
  . 
  10 
  19 
  

   20-5 
  . 
  10 
  19 
  

   2-37 
  . 
  10 
  19 
  

  

  273. 
  10 
  39 
  

   176 
  . 
  10 
  19 
  

   158. 
  10 
  19 
  

  

  Water, 
  alcohol, 
  and 
  ether 
  were 
  also 
  tested, 
  and 
  the 
  following 
  

   figures 
  obtained 
  : 
  — 
  

  

  Water. 
  

  

  E.M.F. 
  

  

  = 
  1 
  Daniell 
  Cell. 
  

  

  Temp. 
  = 
  24° 
  C. 
  

  

  

  I. 
  

  

  

  II. 
  

  

  d. 
  

  

  T 
  = 
  l 
  minute. 
  

  

  T 
  = 
  2 
  minutes. 
  

  

  Sp. 
  Resistance. 
  

  

  Sp. 
  Resistance. 
  

  

  i 
  

  

  1*135 
  mm 
  

  

  109 
  . 
  10 
  12 
  

  

  136 
  . 
  10 
  12 
  

  

  3-015 
  „ 
  

  

  80 
  

  

  74 
  

  

  7-49 
  „ 
  

  

  58 
  

  

  

  51 
  

  

  