﻿Gooch 
  and 
  Kobayashi 
  —Electrolytic 
  Analysis. 
  395 
  

  

  The 
  Determination 
  of 
  Lead. 
  

  

  Lead 
  nitrate, 
  recrj^stallized 
  and 
  dried 
  at 
  200° 
  was 
  used 
  as 
  

   the 
  source 
  of 
  lead 
  to 
  be 
  deposited 
  electrolytically 
  from 
  solution 
  

   as 
  dioxide 
  upon 
  the 
  anode 
  of 
  small 
  dimensions. 
  The 
  volume 
  

   of 
  the 
  solution 
  was 
  fixed 
  at 
  100 
  em 
  3 
  and, 
  in 
  order 
  that 
  metallic 
  

   lead 
  might 
  not 
  be 
  deposited 
  on 
  the 
  cathode,* 
  this 
  was 
  generally 
  

   made 
  up 
  to 
  contain 
  30 
  cm 
  3 
  of 
  strong 
  nitric 
  acid. 
  

  

  Preliminary 
  experimentation 
  developed 
  the 
  fact 
  that 
  a 
  too 
  

   rapid 
  rotation 
  of 
  the 
  anode 
  results 
  in 
  the 
  detachment 
  of 
  large 
  

   amounts 
  of 
  the 
  anode 
  deposit 
  in 
  the 
  early 
  stage 
  of 
  action 
  — 
  

   during 
  the 
  first 
  half-hour 
  — 
  and 
  that 
  the 
  detached 
  dioxide 
  may 
  

   be 
  entirely 
  dissolved 
  in 
  the 
  electrolyte, 
  from 
  which 
  it 
  is 
  again 
  

   deposited 
  on 
  the 
  anode 
  as 
  the 
  electrolysis 
  pro- 
  

   gresses. 
  The 
  later 
  deposit 
  from 
  the 
  more 
  dilute 
  Fig. 
  4. 
  

   solution 
  adheres 
  firmly 
  to 
  the 
  anode. 
  It 
  was 
  

   found, 
  further, 
  that 
  dissolved 
  lead 
  may 
  be 
  found 
  in 
  

   the 
  electrolyte 
  so 
  long 
  as 
  any 
  appreciable 
  amount 
  

   of 
  the 
  dioxide 
  remains 
  in 
  suspension. 
  

  

  Acting 
  upon 
  the 
  hypothesis 
  that 
  nitrous 
  acid 
  

   gradually 
  and 
  continually 
  formed 
  in 
  the 
  course 
  of 
  

   action 
  is 
  the 
  active 
  agent 
  in 
  bringing 
  about 
  the 
  

   resolution 
  of 
  suspended 
  dioxide, 
  the 
  attempt 
  was 
  

   made 
  to 
  hasten 
  the 
  process 
  of 
  solution 
  by 
  adding 
  

   potassium 
  nitrite, 
  but 
  this 
  reagent 
  and 
  the 
  nitrous 
  

   acid 
  formed 
  from 
  it 
  are 
  so 
  rapidly 
  decomposed 
  

   that 
  no 
  appreciable 
  advantage 
  seems 
  to 
  be 
  gained 
  

   by 
  its 
  use. 
  When 
  the 
  suspended 
  dioxide 
  nearly 
  or 
  

   entirely 
  disappears 
  and 
  the 
  anode 
  deposit 
  has 
  

   become 
  fixed, 
  the 
  addition 
  of 
  a 
  little 
  urea 
  serves 
  to 
  

   destroy 
  the 
  nitrous 
  acid 
  in 
  solution 
  and 
  prevent 
  sol- 
  

   vent 
  action 
  of 
  the 
  electrolyte 
  upon 
  the 
  deposit 
  

   after 
  the 
  stopping 
  of 
  the 
  current. 
  

  

  Instead 
  of 
  waiting 
  until 
  the 
  detached 
  residue 
  

   has 
  been 
  dissolved 
  again, 
  it 
  is 
  possible 
  to 
  separate 
  

   the 
  clear 
  liquid 
  from 
  the 
  suspended 
  material 
  by 
  

   drawing 
  it 
  off 
  through 
  the 
  filtering 
  tube 
  and 
  again 
  

   submitting 
  it 
  to 
  electrolysis. 
  For 
  this 
  separation, 
  

   a 
  simple 
  apparatus 
  (fig. 
  4) 
  made 
  by 
  attaching 
  the 
  filtering 
  tube 
  

   to 
  a 
  separating 
  funnel 
  into 
  which 
  the 
  clear 
  liquid 
  may 
  be 
  drawn 
  

   by 
  suction 
  and 
  from 
  which 
  it 
  may 
  be 
  returned 
  to 
  the 
  elec- 
  

   trolysis 
  cell, 
  after 
  disconnecting 
  the 
  tube, 
  is 
  convenient. 
  

  

  The 
  details 
  of 
  experiments 
  upon 
  the 
  lines 
  indicated 
  are 
  given 
  

   in 
  the 
  table. 
  In 
  every 
  case, 
  at 
  the 
  end 
  of 
  the 
  electrolysis, 
  the 
  

   liquid 
  was 
  drawn 
  off 
  from 
  the 
  beaker 
  through 
  the 
  filtering 
  

   tube. 
  The 
  entire 
  apparatus 
  — 
  beaker, 
  electrodes, 
  and 
  filtering 
  

   tube 
  — 
  and 
  the 
  deposit 
  were 
  dried 
  at 
  200° 
  and 
  weighed. 
  

  

  * 
  Gooch 
  and 
  Beyer, 
  this 
  Journal, 
  xxvii, 
  59, 
  1909. 
  

  

  