﻿Separation 
  of 
  Antimony 
  from 
  Arsenic. 
  311 
  

  

  excepting 
  those 
  of 
  Table 
  III, 
  starch 
  gave 
  no 
  test 
  for 
  free 
  

   iodine 
  in 
  the 
  diluted 
  liquid, 
  though 
  it 
  must 
  not 
  be 
  overlooked 
  

   that 
  the 
  presence 
  of 
  a 
  considerable 
  amount 
  of 
  hydrochloric 
  

   acid 
  tends 
  to 
  impair 
  the 
  delicacy 
  of 
  the 
  test. 
  If, 
  on 
  the 
  other 
  

   hand, 
  the 
  color 
  is 
  not 
  due 
  altogether 
  to 
  free 
  iodine 
  it 
  is 
  difficult 
  

   to 
  account 
  for 
  its 
  development 
  unless 
  it 
  is 
  caused 
  by 
  the 
  for- 
  

   mation 
  of 
  antimonious 
  iodide 
  as 
  the 
  solution 
  of 
  strong 
  hydro- 
  

   chloric 
  containing 
  also 
  hydriodic 
  acid 
  cools. 
  On 
  the 
  whole, 
  

   we 
  are 
  inclined 
  to 
  attribute 
  at 
  least 
  a 
  part 
  of 
  the 
  apparent 
  

   deficiency 
  to 
  the 
  presence, 
  at 
  the 
  time 
  of 
  neutralization, 
  of 
  a 
  

   small 
  amount 
  of 
  iodine 
  chloride, 
  which, 
  in 
  accordance 
  with 
  

   what 
  is 
  known 
  of 
  its 
  modes 
  of 
  formation, 
  might 
  be 
  formed 
  by 
  

   the 
  oxidizing 
  effect 
  of 
  the 
  antimonic 
  and 
  arsenic 
  oxides 
  upon 
  

   the 
  mixed 
  acids. 
  At 
  all 
  events, 
  it 
  is 
  evident 
  that 
  if 
  iodine 
  

   chloride 
  were 
  present 
  we 
  should 
  expect 
  to 
  note 
  the 
  phenomena 
  

   which 
  we 
  do 
  see 
  ; 
  it 
  would 
  give, 
  in 
  small 
  quantity, 
  little 
  or 
  no 
  

   color 
  to 
  the 
  liquid, 
  would 
  not 
  show 
  the 
  starch 
  reaction 
  for 
  free 
  

   iodine 
  in 
  the 
  acid 
  solution, 
  and 
  would 
  be 
  destroyed 
  with 
  the 
  

   formation 
  hydrochloric 
  and 
  hydriodic 
  acids 
  by 
  the 
  addition 
  of 
  

   sulphurous 
  acid 
  to 
  the 
  still 
  acid 
  liquid, 
  leaving 
  the 
  antimony 
  

   unchanged 
  and 
  determinable 
  iodometrically 
  in 
  alkaline 
  solution 
  

   after 
  the 
  exact 
  oxidation 
  of 
  the 
  excess 
  of 
  sulphurous 
  acid 
  by 
  

   iodine 
  in 
  acid 
  solution 
  ; 
  on 
  the 
  other 
  hand, 
  it 
  would 
  act 
  in 
  alka- 
  

   line 
  solution 
  like 
  the 
  free 
  halogens 
  and 
  tend 
  to 
  diminish 
  the 
  

   antimony 
  indicated 
  by 
  titration. 
  Whatever 
  the 
  real 
  cause 
  or 
  

   causes 
  of 
  the 
  deficiency 
  may 
  be, 
  it 
  appears 
  in 
  the 
  results 
  of 
  

   Table 
  III 
  that 
  the 
  treatment 
  with 
  sulphurous 
  acid 
  affects 
  the 
  

   indications 
  favorably. 
  The 
  mean 
  error 
  of 
  three 
  closely 
  agree- 
  

   ing 
  determinations 
  is 
  0*0006 
  grm. 
  — 
  and 
  this 
  is 
  plainly 
  within 
  

   the 
  limits 
  of 
  allowable 
  variation 
  in 
  iodometric 
  work 
  with 
  

   decinormal 
  solutions. 
  

  

  It 
  appears, 
  therefore, 
  that 
  hydriodic 
  acid 
  may 
  be 
  made 
  to 
  

   serve 
  satisfactorily 
  as 
  a 
  substitute 
  for 
  the 
  ferrous 
  chloride 
  of 
  

   Fischer's 
  original 
  method, 
  or 
  for 
  the 
  ferrous 
  sulphate 
  of 
  the 
  

   modification 
  of 
  Classen 
  and 
  Ludwig, 
  the 
  determination 
  of 
  the 
  

   residual 
  antimony 
  being 
  perfectly 
  practicable. 
  The 
  method 
  of 
  

   proceeding 
  which 
  we 
  advocate 
  is 
  briefly 
  summarized 
  in 
  the 
  

   following 
  statement 
  : 
  To 
  the 
  solution 
  of 
  the 
  oxides 
  of 
  arsenic 
  

   and 
  antimony, 
  taken 
  in 
  amounts 
  not 
  exceeding 
  0'5 
  grm. 
  of 
  

   each, 
  potassium 
  iodide 
  is 
  to 
  be 
  added 
  in 
  a 
  little 
  more 
  than 
  the 
  

   equivalent 
  quantity, 
  and 
  enough 
  strong 
  hydrochloric 
  acid 
  to 
  

   raise 
  the 
  entire 
  volume 
  of 
  the 
  solution 
  to 
  100 
  cm. 
  3 
  Hydro- 
  

   chloric 
  acid 
  gas 
  is 
  passed 
  into 
  the 
  liquid 
  to 
  saturation 
  as 
  well 
  as 
  

   during 
  the 
  distillation 
  to 
  follow, 
  and 
  the 
  distillation 
  is 
  carried 
  

   on 
  until 
  the 
  volume 
  of 
  the 
  liquid 
  decreases 
  to 
  50 
  cm. 
  3 
  or 
  a 
  

   little 
  less. 
  The 
  liquid 
  is 
  cooled 
  rapidly, 
  treated 
  first 
  with 
  an 
  

   excess 
  of 
  sulphurous 
  acid 
  and 
  then 
  with 
  iodine 
  to 
  the 
  exact 
  

  

  