﻿460 
  Browning 
  and 
  Hutchins 
  — 
  Estimation 
  of 
  Thallium. 
  

  

  Art. 
  LIII. 
  — 
  On 
  the 
  Estimation 
  of 
  Thallium 
  as 
  the 
  Chro- 
  

   mate; 
  by 
  Philip 
  E.Browning 
  and 
  George 
  P. 
  Hutchins. 
  

  

  [CoutributioDS 
  from 
  the 
  Kent 
  Chemical 
  Laboratory 
  of 
  Tale 
  University 
  — 
  XCI.] 
  

  

  Crookes 
  has 
  sliown^ 
  that 
  tlie 
  chromate 
  precipitated 
  by 
  the 
  

   addition 
  of 
  potassium 
  diehromate 
  to 
  an 
  alkaline 
  solution 
  of 
  a 
  

   thallous 
  salt 
  has 
  the 
  constitution 
  of 
  a 
  neutral 
  salt 
  and 
  is 
  very 
  

   insoluble 
  in 
  water 
  — 
  100 
  parts 
  of 
  water 
  at 
  100° 
  C. 
  dissolving 
  

   about 
  0*2 
  parts 
  and 
  at 
  60° 
  C. 
  about 
  0*03 
  parts. 
  He 
  has 
  also 
  

   made 
  use 
  Of 
  this 
  reactionf 
  to 
  effect 
  a 
  rough 
  separation 
  of 
  thal- 
  

   lium 
  from 
  cadmium. 
  

  

  The 
  object 
  of 
  this 
  paper 
  is 
  to 
  describe 
  some 
  work 
  directed 
  

   toward 
  a 
  study 
  of 
  the 
  application 
  of 
  this 
  reaction 
  to 
  the 
  gravi- 
  

   metric 
  estimation 
  of 
  thallium 
  and 
  the 
  best 
  conditions 
  under 
  

   which 
  to 
  effect 
  the 
  precipitation. 
  For 
  the 
  work 
  a 
  solution 
  of 
  

   thallous 
  nitrate 
  was 
  made 
  by 
  dissolving 
  10 
  grms. 
  in 
  water 
  

   making 
  up 
  to 
  a 
  liter. 
  The 
  standard 
  was 
  determined 
  by 
  taking 
  

   measured 
  and 
  weighed 
  portions 
  from 
  a 
  burette, 
  precipitating 
  

   with 
  a 
  slight 
  excess 
  of 
  potassium 
  iodide, 
  agitating 
  to 
  bring- 
  

   about 
  a 
  good 
  separation 
  of 
  the 
  thallous 
  iodide, 
  and 
  allowing 
  to 
  

   stand 
  until 
  the 
  supernatant 
  liquid 
  was 
  clear. 
  The 
  iodide 
  was 
  

   then 
  filtered 
  off 
  upon 
  an 
  asbestos 
  felt 
  contained 
  in 
  a 
  perforated 
  

   platinum 
  crucible, 
  the 
  whole 
  having 
  been 
  previously 
  ignited 
  

   and 
  weighed, 
  washed 
  with 
  a 
  mixture 
  of 
  alcohol 
  and 
  water, 
  

   dried 
  over 
  a 
  low 
  flame 
  and 
  weighed 
  to 
  a 
  constant 
  weight. 
  The 
  

   filtrate, 
  which 
  together 
  with 
  the 
  washings 
  seldom 
  amounted 
  to 
  

   more 
  than 
  50^""", 
  was 
  evaporated 
  to 
  dryness 
  on 
  a 
  water 
  bath, 
  a 
  

   few 
  drops 
  of 
  water 
  added 
  and 
  thus 
  the 
  small 
  amount 
  of 
  thal- 
  

   lous 
  iodide 
  which 
  had 
  been 
  dissolved 
  recovered. 
  This 
  small 
  

   insoluble 
  residue, 
  which 
  seldom 
  amounted 
  to 
  one 
  milligram 
  in 
  

   weight, 
  was 
  filtered 
  off, 
  washed 
  and 
  weighed 
  as 
  previously 
  

   described. 
  Baubigny:}: 
  has 
  shown 
  this 
  method 
  to 
  give 
  very 
  

   satisfactory 
  results, 
  and 
  the 
  uniformity 
  of 
  our 
  determinations 
  

   certainly 
  confirms 
  his 
  statements. 
  

  

  For 
  convenience 
  in 
  the 
  calculations 
  of 
  results 
  to 
  be 
  described 
  

   later, 
  a 
  solution 
  of 
  potassium 
  diehromate 
  of 
  definite 
  strength 
  

   was 
  made. 
  Portions 
  of 
  the 
  thallium 
  solution 
  were 
  drawn 
  

   from 
  a 
  burette 
  into 
  test 
  tubes 
  of 
  about 
  100"^' 
  capacity 
  and 
  

   weighed 
  as 
  a 
  check 
  on 
  the 
  burette 
  reading. 
  The 
  solution 
  was 
  

   heated 
  to 
  about 
  70° 
  C. 
  to 
  80° 
  C. 
  and 
  a 
  few 
  drops 
  of 
  ammonia 
  

   or 
  potassium 
  carbonate 
  solution 
  added 
  to 
  distinct 
  alkalinity. 
  

   A 
  definite 
  amount 
  of 
  the 
  potassium 
  diehromate 
  in 
  solution 
  was 
  

   delivered 
  from 
  a 
  burette, 
  care 
  being 
  taken 
  to 
  have 
  an 
  excess, 
  

  

  * 
  Chem. 
  News, 
  viii, 
  255. 
  f 
  Chem. 
  News, 
  vii, 
  145. 
  

  

  :j: 
  Chem. 
  News, 
  Ixiv, 
  239. 
  

  

  