﻿130 
  L. 
  C. 
  Jones 
  — 
  An 
  lodomefric 
  Method 
  for 
  the 
  

  

  vigorously 
  the 
  small 
  amount 
  of 
  uncombined 
  carbon 
  dioxide 
  

   remaining 
  has 
  almost 
  an 
  inappreciable 
  effect 
  upon 
  the 
  results. 
  

   The 
  length 
  of 
  time 
  required 
  for 
  the 
  liberation 
  of 
  the 
  theoret- 
  

   ical 
  amount 
  of 
  iodine 
  in 
  a 
  solution 
  of 
  the 
  volume 
  suggested 
  

   above, 
  is 
  20 
  to 
  45 
  minutes, 
  and 
  at 
  the 
  end 
  of 
  45 
  minutes 
  stand- 
  

   ing 
  in 
  a 
  solution 
  saturated 
  with 
  mannite 
  the 
  reaction 
  may 
  be 
  

   considered 
  complete. 
  During 
  this 
  period, 
  however, 
  it 
  is 
  well 
  

   to 
  keep 
  the 
  solution 
  cool 
  — 
  at 
  zero 
  will 
  do 
  no 
  harm 
  — 
  and 
  

   shake 
  occasionally 
  to 
  insure 
  thorough 
  mixture. 
  The 
  free 
  

   iodine 
  would 
  tend 
  to 
  escape 
  upon 
  standing 
  unless 
  kept 
  in 
  a 
  

   closed 
  flask, 
  but 
  it 
  is 
  more 
  convenient, 
  immediately 
  after 
  the 
  

   addition 
  of 
  mannite, 
  to 
  treat 
  with 
  an 
  excess 
  of 
  the 
  standard 
  

   solution 
  of 
  thiosulphate— 
  8 
  or 
  10^""' 
  more 
  than 
  the 
  amount 
  

   required 
  to 
  bleach 
  the 
  iodine 
  liberated, 
  and 
  at 
  the 
  expiration 
  

  

  of 
  40 
  to 
  60 
  minutes 
  titrate 
  back 
  with 
  — 
  iodine. 
  The 
  strentjth 
  

  

  of 
  the 
  thiosulphate 
  solution 
  found 
  most 
  convenient 
  is 
  — 
  , 
  while 
  

  

  the 
  use 
  of 
  iodine 
  of 
  one-half 
  this 
  strength 
  (— 
  ) 
  enables 
  the 
  

  

  ength 
  g) 
  

  

  error 
  of 
  reading 
  to 
  be 
  correspondingly 
  diminished. 
  In 
  solu- 
  

   tions 
  of 
  the 
  volume 
  recommended 
  the 
  addition 
  of 
  starch 
  to 
  

   give 
  the 
  indication 
  with 
  iodine 
  is 
  unnecessary 
  and 
  even 
  detri- 
  

   mental, 
  since 
  a 
  single 
  drop 
  of 
  one-twentieth 
  normal 
  iodine 
  in 
  

   excess 
  is 
  sufficient 
  to 
  give 
  a 
  strong 
  lemon 
  coloration, 
  while 
  in 
  

   the 
  presence 
  of 
  starch 
  an 
  indefinite 
  dirty 
  red 
  first 
  appears 
  and 
  

   remains 
  until 
  the 
  blue 
  is 
  brought 
  out 
  by 
  the 
  further 
  addition 
  

   of 
  iodine. 
  

  

  With 
  these 
  observations 
  in 
  mind, 
  a 
  series 
  of 
  experiments 
  was 
  

   made 
  in 
  which 
  the 
  standard 
  solution 
  of 
  boric 
  acid 
  was 
  drawn 
  

   into 
  an 
  Erlenmeyer 
  flask, 
  containing 
  a 
  small 
  amount 
  of 
  free 
  

   hydrochloric 
  acid 
  and 
  made 
  up 
  to 
  a 
  definite 
  volume. 
  To 
  

   bring 
  the 
  conditions 
  to 
  those 
  of 
  an 
  actual 
  analysis 
  about 
  1 
  grm. 
  

   of 
  crystalline 
  calcium 
  chloride 
  in 
  solution 
  was 
  also 
  added. 
  

   Potassium 
  iodate 
  (5-10^™^ 
  of 
  a 
  5 
  per 
  cent 
  solution) 
  and 
  iodide 
  

   (3-5*^™^ 
  of 
  a 
  40 
  per 
  cent 
  solution) 
  were 
  added, 
  and 
  the 
  iodine 
  

   liberated 
  by 
  the 
  hydrochloric 
  acid, 
  barely 
  bleached 
  and 
  again 
  

   brought 
  to 
  coloration 
  by 
  iodine. 
  Mannite 
  was 
  added 
  to 
  satu- 
  

   rate 
  the 
  solution, 
  an 
  excess 
  of 
  standard 
  thiosulphate 
  put 
  in, 
  and 
  

   the 
  solution 
  set 
  aside 
  for 
  various 
  periods 
  of 
  time, 
  at 
  the 
  end 
  of 
  

   which 
  the 
  excess 
  of 
  thiosulphate 
  was 
  titrated 
  by 
  iodine 
  and 
  

   the 
  amount 
  of 
  unrecovered 
  thiosulphate 
  taken 
  as 
  a 
  measure 
  of 
  

   the 
  boric 
  acid 
  present. 
  

  

  The 
  thiosulphate 
  used 
  w^as 
  O'lOS 
  normal 
  and 
  the 
  iodine 
  

   0*0996 
  normal. 
  The 
  solution 
  of 
  boric 
  acid 
  contained 
  T'733 
  

   grm. 
  per 
  liter. 
  

  

  