﻿458 
  Browning 
  — 
  Yolujnetrlc 
  Estimation 
  of 
  Cerium. 
  

  

  The 
  solutions 
  used 
  were 
  prepared 
  and 
  standardized 
  as 
  fol- 
  

   lows 
  : 
  The 
  cerium 
  solutions 
  were 
  made 
  bj 
  dissolving 
  10 
  grams 
  

   of 
  pure 
  cerium 
  chloride 
  in 
  one 
  liter 
  of 
  water, 
  and 
  standardized 
  

   by 
  precipitating 
  measured 
  and 
  weighed 
  portions, 
  in 
  a 
  faintly 
  

   acid 
  solution, 
  with 
  ammonium 
  oxalate, 
  filtering, 
  washing, 
  ignit- 
  

   ing, 
  and 
  weighing 
  as 
  the 
  dioxide 
  (CeO^). 
  A 
  solution 
  of 
  potas- 
  

   sium 
  permanganate 
  was 
  prepared 
  and 
  standardized 
  by 
  titration 
  

   against 
  weighed 
  amounts 
  of 
  ammonium 
  oxalate. 
  A 
  solution 
  

   of 
  ammonium 
  oxalate 
  was 
  made 
  and 
  its 
  value 
  determined 
  by 
  

   titrating 
  measured 
  amounts 
  against 
  potassium 
  permanganate. 
  

   Definite 
  portions 
  of 
  the 
  cerium 
  solution 
  were 
  drawn 
  from 
  a 
  

   burette 
  and 
  after 
  diluting 
  with 
  water 
  from 
  100 
  to 
  200^"°' 
  a 
  

   definite 
  amount 
  of 
  ammonium 
  oxalate 
  was 
  added, 
  care 
  being 
  

   taken 
  to 
  have 
  an 
  excess 
  over 
  the 
  amount 
  necessary, 
  and 
  the 
  

   whole 
  warmed 
  to 
  insure 
  a 
  more 
  crystalline 
  precipitation.* 
  

   The 
  precipitate 
  was 
  then 
  filtered 
  off 
  on 
  paper 
  and 
  carefully 
  

   washed, 
  the 
  filtrate 
  and 
  washings 
  being 
  collected 
  in 
  a 
  liter 
  

   Erlenmeyer 
  flask 
  and 
  set 
  aside 
  for 
  future 
  use. 
  The 
  precipitate 
  

   was 
  treated 
  with 
  about 
  lO^*"'^ 
  of 
  hot 
  (1 
  — 
  4) 
  sulphuric 
  acid, 
  which, 
  

   dissolved 
  it 
  completely, 
  if 
  not 
  at 
  first, 
  by 
  running 
  it 
  through 
  

   the 
  filter 
  a 
  few 
  times, 
  and 
  the 
  solution 
  and 
  washings 
  were 
  col- 
  

   lected 
  in 
  another 
  liter 
  flask. 
  The 
  total 
  volume 
  of 
  liquid 
  was 
  

   made 
  up 
  to 
  about 
  500'°^', 
  warmed 
  to 
  about 
  70° 
  C. 
  to 
  80° 
  C. 
  

   and 
  titrated 
  with 
  potassium 
  permanganate 
  to 
  the 
  appearance 
  of 
  

   the 
  faint 
  blush 
  of 
  color 
  showing 
  the 
  complete 
  oxidation 
  of 
  the 
  

   oxalic 
  acid. 
  The 
  filtrate 
  from 
  the 
  cerium 
  oxalate 
  containing 
  

   the 
  excess 
  of 
  oxalic 
  acid 
  was 
  diluted 
  to 
  500^°"', 
  acidified 
  with 
  

   10^°"^ 
  of 
  dilute 
  (1-4) 
  sulphuric 
  acid, 
  one 
  gram 
  of 
  manganous 
  

   sulphate 
  added 
  to 
  prevent 
  the 
  interfering 
  action 
  of 
  the 
  free 
  

   hydrochloric 
  acid 
  upon 
  the 
  estimation 
  of 
  the 
  oxalic 
  acid,f 
  and 
  

   titrated 
  with 
  potassium 
  permanganate 
  after 
  the 
  same 
  manner 
  

   as 
  the 
  dissolved 
  precipitate. 
  A 
  definite 
  quantity 
  of 
  ammo- 
  

   nium 
  oxalate 
  having 
  been 
  originally 
  taken, 
  it 
  became 
  possible, 
  

   by 
  subtracting 
  from 
  it 
  the 
  amount 
  obtained, 
  to 
  derive 
  the 
  

   measure 
  of 
  the 
  oxalate 
  used 
  in 
  the 
  precipitation 
  of 
  the 
  cerium 
  

   oxalate. 
  By 
  this 
  procedure, 
  it 
  will 
  be 
  observed 
  a 
  check 
  was 
  

   made 
  upon 
  the 
  results 
  obtained 
  by 
  the 
  titration 
  of 
  the 
  precipi- 
  

   tate. 
  \\\ 
  experiments 
  (1) 
  to 
  (6) 
  tlie 
  cerium 
  oxalate 
  was 
  thrown 
  

   down 
  in 
  neutral 
  solution, 
  in 
  experiments 
  (7) 
  to 
  (10) 
  in 
  acid 
  

   solutions. 
  The 
  treatment 
  of 
  the 
  filtrate 
  in 
  experiment 
  (1) 
  was 
  

   made 
  without 
  the 
  presence 
  of 
  the 
  manganous 
  sulphate. 
  The 
  

   results 
  recorded 
  in 
  Table 
  Yll 
  seem 
  to 
  uphold 
  the 
  statement 
  of 
  

   Stolba. 
  

  

  * 
  As 
  shown 
  by 
  the 
  table, 
  tlie 
  prccipitatiou 
  was 
  sometimes 
  in 
  neutral, 
  sometimes 
  

   in 
  faintly 
  acid 
  solution. 
  

  

  f 
  Gooch 
  and 
  Peter?, 
  this 
  Journal, 
  vol. 
  vii, 
  461. 
  

  

  