﻿L. 
  C. 
  Jones 
  — 
  lodometric 
  Method 
  for 
  Esthnation^ 
  etc. 
  127 
  

  

  Aet. 
  XIII. 
  — 
  An 
  lodometric 
  Method 
  for 
  the 
  Estimation 
  of 
  

   Boric 
  Acid; 
  by 
  Louis 
  Cleveland 
  Jones. 
  

  

  [Contributions 
  from 
  the 
  Kent 
  Chemical 
  Laboratory 
  of 
  Yale 
  College 
  — 
  LXXXV.] 
  

  

  In 
  a 
  recent 
  article,"^ 
  I 
  have 
  described 
  a 
  process 
  for 
  the 
  alka- 
  

   limetric 
  estimation 
  of 
  boric 
  acid, 
  depending 
  upon 
  the 
  forma- 
  

   tion 
  of 
  a 
  strongly 
  acidic 
  compound 
  when 
  boric 
  acid 
  and 
  a 
  

   polyatomic 
  alcohol 
  are 
  placed 
  together 
  in 
  solution. 
  The 
  

   method 
  in 
  brief 
  consists 
  in 
  destroying 
  the 
  free 
  mineral 
  acid 
  in 
  

   a 
  solution 
  containing 
  boric 
  acid, 
  by 
  means 
  of 
  a 
  mixture 
  of 
  

   potassium 
  iodide 
  and 
  iodate, 
  bleaching 
  the 
  liberated 
  iodine 
  by 
  

   sodium 
  thiosulphate, 
  adding 
  the 
  indicator 
  phenol 
  phthalein 
  

   and 
  sufficient 
  standard 
  solution 
  of 
  caustic 
  soda 
  to 
  give 
  a 
  faint 
  

   alkaline 
  coloration, 
  bleaching 
  by 
  a 
  small 
  amount 
  of 
  mannite 
  

   and 
  adding 
  caustic 
  soda 
  again 
  to 
  alkalinity, 
  and 
  thus 
  alternat- 
  

   ing 
  with 
  mannite 
  and 
  alkali 
  until 
  the 
  alkaline 
  coloration 
  pro- 
  

   duced 
  is 
  permanent. 
  The 
  amount 
  of 
  sodium 
  hydroxide 
  used 
  

   represents 
  the 
  amount 
  of 
  acidity 
  developed 
  by 
  the 
  influence 
  

   of 
  the 
  mannite 
  upon 
  the 
  boric 
  acid 
  present, 
  according 
  to 
  the 
  

   hypotheses 
  that 
  the 
  molecule 
  B^Og 
  acts 
  as 
  two 
  molecules 
  of 
  a 
  

   univalent 
  acid, 
  HO 
  . 
  BO. 
  

  

  On 
  making 
  further 
  study 
  of 
  this 
  reaction, 
  I 
  have 
  found 
  that 
  

   the 
  acid 
  developed 
  by 
  the 
  combination 
  of 
  boric 
  acid 
  and 
  man- 
  

   nite 
  is, 
  under 
  certain 
  definite 
  conditions, 
  sufficiently 
  strong 
  to 
  

   liberate, 
  quantitatively, 
  from 
  a 
  mixture 
  of 
  potassium 
  iodide 
  

   and 
  iodate, 
  the 
  amount 
  of 
  iodine 
  required 
  on 
  the 
  supposition 
  

   that 
  each 
  molecule 
  of 
  metaboric 
  acid 
  (HO 
  . 
  BO) 
  acts 
  in 
  a 
  man- 
  

   ner 
  similar 
  to 
  a 
  univalent 
  mineral 
  acid 
  under 
  the 
  same 
  condi- 
  

   tions. 
  (5KI-fKIO,-l-6HOBO 
  = 
  3I,-f-6KOBO-h3H,0.) 
  Ob- 
  

   viously, 
  this 
  reaction 
  depends 
  upon 
  the 
  behavior 
  of 
  the 
  acidic 
  

   boromannite 
  compound 
  as 
  a 
  strong 
  acid, 
  stronger 
  than 
  acetic, 
  

   tartaric, 
  or 
  citric 
  acid 
  ; 
  for 
  these 
  acids 
  have 
  been 
  found 
  by 
  

   Furryf 
  to 
  be 
  incapable 
  of 
  liberating 
  iodine 
  regularly 
  from 
  a 
  

   mixture 
  of 
  iodide 
  and 
  iodate. 
  Conditions 
  which 
  tend 
  to 
  in- 
  

   crease 
  the 
  acidic 
  activity 
  of 
  this 
  compound 
  are 
  concentrated 
  

   solutions 
  and 
  moderately 
  low 
  temperatures. 
  ;}: 
  

  

  Glycerine 
  acts 
  in 
  general 
  as 
  mannite 
  to 
  produce 
  acidic 
  com- 
  

   pounds 
  with 
  boric 
  acid 
  ; 
  and 
  in 
  a 
  preliminary 
  way, 
  the 
  relative 
  

   acidity 
  of 
  the 
  products 
  formed 
  by 
  these 
  two 
  polyatomic 
  alco- 
  

   hols 
  with 
  boric 
  acid 
  may 
  be 
  indicated 
  by 
  the 
  results 
  of 
  two 
  

   experiments 
  in 
  which 
  the 
  iodine 
  liberated 
  from 
  a 
  mixture 
  of 
  

  

  * 
  This 
  Journal, 
  vii, 
  147. 
  f 
  Am. 
  Chem. 
  Jour., 
  vi, 
  341. 
  

  

  X 
  Magnanini 
  Glaz. 
  Chim 
  , 
  xx, 
  428, 
  xxi, 
  134, 
  and 
  Lambert, 
  Compt. 
  Rend., 
  cviii, 
  

   1016, 
  1017. 
  

  

  