﻿180 
  

  

  Allen 
  and 
  Lombard 
  — 
  Determination 
  of 
  

  

  The 
  current 
  in 
  each 
  of 
  the 
  six 
  furnace 
  coils 
  is 
  separately 
  con- 
  

   trolled 
  by 
  a 
  sliding 
  resistance. 
  Ours 
  possessed 
  a 
  resistance 
  of 
  

   about 
  30 
  ohms 
  and 
  a 
  carrying 
  capacity 
  of 
  5 
  amperes. 
  With 
  

   this 
  arrangement 
  the 
  currents 
  could 
  be 
  regulated 
  to 
  about 
  *01 
  

   ampere. 
  The 
  coils 
  were 
  used 
  either 
  in 
  55 
  volt 
  or 
  110 
  volt 
  cir- 
  

   cuit 
  according 
  to 
  the 
  desired 
  temperature. 
  An 
  important 
  

  

  Fig 
  3. 
  

  

  

  

  

  

  /J 
  

  

  I 
  \ 
  

  

  

  

  

  JKg 
  

  

  

  

  *T 
  Vm 
  

  

  

  MMb 
  

  

  

  

  

  

  

  |^H|^fHEf& 
  

  

  

  

  

  

  

  

  «t 
  

  

  1 
  

  

  Hkv" 
  x 
  i 
  

  

  ■ 
  -■-,- 
  ■ 
  : 
  ■ 
  . 
  4 
  >' 
  

  

  

  

  

  Fig. 
  3. 
  Apparatus 
  used 
  in 
  the 
  determination 
  of 
  the 
  dissociation 
  pressures 
  

   of 
  sulphides. 
  

  

  detail 
  of 
  the 
  furnace 
  construction, 
  which 
  should 
  be 
  mentioned, 
  

   is 
  a 
  pair 
  of 
  asbestos 
  plugs, 
  A, 
  B, 
  fig. 
  2, 
  which 
  afford 
  the 
  neces- 
  

   sary 
  thermal 
  insulation 
  between 
  the 
  two 
  furnaces. 
  These 
  plugs 
  

   fit 
  the 
  alundum 
  tubes 
  which 
  form 
  the 
  working 
  spaces 
  of 
  the 
  

   furnaces. 
  They 
  are 
  about 
  2*5 
  cm 
  thick. 
  Each 
  plug 
  is 
  pierced 
  

   in 
  the 
  center 
  with 
  a 
  hole 
  which 
  admits 
  the 
  stem 
  of 
  the 
  glass 
  

   apparatus 
  (fig. 
  1) 
  easily, 
  and 
  each 
  is 
  split 
  into 
  halves 
  so 
  that 
  it 
  

  

  