﻿Gooch 
  — 
  Estimation 
  of 
  Molybdenum 
  Iodometrically. 
  237 
  

  

  Art. 
  XXIII. 
  — 
  The 
  Estimation 
  of 
  Molybdenum 
  Iodo?net- 
  

   rically 
  ; 
  by 
  F. 
  A. 
  Gooch. 
  

  

  [Contributions 
  from 
  the 
  Kent 
  Chemical 
  Laboratory 
  of 
  Yale 
  University, 
  LXIL] 
  

  

  In 
  a 
  former 
  paper 
  from 
  this 
  laboratory* 
  several 
  modes 
  of 
  

   applying 
  hydriodic 
  acid 
  to 
  the 
  reduction 
  of 
  molybdic 
  acid 
  were 
  

   studied. 
  It 
  was 
  found, 
  first, 
  that 
  the 
  digestion 
  process 
  of 
  

   Mauro 
  and 
  Danesif 
  is 
  of 
  very 
  limited 
  applicability, 
  owing 
  to 
  

   the 
  fact 
  that 
  the 
  reaction 
  of 
  reduction 
  is 
  reversible. 
  Secondly, 
  

   it 
  appeared 
  that 
  the 
  use 
  of 
  the 
  same 
  reaction 
  by 
  Friedheim 
  and 
  

   EulerJ 
  in 
  a 
  distillation 
  process, 
  so 
  arranged 
  that 
  the 
  iodine 
  set 
  

   free 
  in 
  the 
  reduction 
  might 
  be 
  caught 
  in 
  the 
  distillate 
  and 
  

   titrated 
  to 
  serve 
  as 
  the 
  measure 
  of 
  the 
  reducing 
  action, 
  was 
  not 
  

   sufficiently 
  regular 
  because 
  of 
  inattention 
  to 
  minor 
  details. 
  It 
  

   was 
  shown 
  that 
  by 
  taking 
  care 
  to 
  adjust 
  the 
  conditions 
  con- 
  

   stant 
  results 
  might 
  be 
  obtained. 
  Thirdly, 
  the 
  fact 
  was 
  devel- 
  

   oped 
  that 
  by 
  simply 
  boiling 
  the 
  solution 
  under 
  well 
  defined 
  

   conditions 
  in 
  an 
  ordinary 
  Erlenmeyer 
  flask, 
  partly 
  closed 
  by 
  a 
  

   simple 
  trap, 
  the 
  reduction 
  of 
  the 
  molybdic 
  acid 
  proceeded 
  regu- 
  

   larly, 
  and 
  that 
  the 
  addition 
  of 
  standard 
  iodine 
  to 
  the 
  solution 
  

   made 
  alkaline 
  with 
  sodium 
  bicarbonate 
  served 
  to 
  restore 
  the 
  

   original 
  condition 
  of 
  oxidation 
  of 
  the 
  molybdic 
  acid. 
  The 
  

   results 
  of 
  this 
  treatment 
  were 
  shown 
  to 
  be 
  accurate. 
  

  

  In 
  a 
  recent 
  paper§ 
  Friedheim 
  has 
  seen 
  fit 
  to 
  make 
  our 
  mod- 
  

   ifications 
  of 
  the 
  distillation 
  process 
  the 
  subject 
  of 
  attack. 
  

   Friedheim's 
  comments 
  upon 
  the 
  third 
  method 
  discussed 
  (as 
  

   well 
  as 
  upon 
  a 
  subsequent 
  application 
  of 
  the 
  process)] 
  are 
  evi- 
  

   dently 
  prompted 
  wholly 
  by 
  personal 
  opinion 
  and 
  demand 
  no 
  

   further 
  attention. 
  With 
  reference 
  to 
  Friedheim's 
  denial 
  of 
  

   the 
  necessity 
  of 
  modification 
  in 
  the 
  Friedheim 
  and 
  Euler 
  treat- 
  

   ment 
  the 
  case 
  is 
  different. 
  

  

  The 
  process 
  of 
  Friedheim 
  and 
  Euler 
  consists, 
  it 
  will 
  be 
  

   remembered, 
  in 
  treating 
  the 
  soluble 
  molybdate, 
  or 
  the 
  solution 
  

   of 
  molybdic 
  acid 
  in 
  sodium 
  hydroxide, 
  with 
  potassium 
  iodide 
  

   and 
  hydrochloric 
  acid 
  in 
  a 
  Bunsen 
  apparatus, 
  boiling 
  until 
  the 
  

   solution 
  is 
  of 
  a 
  clear 
  green 
  color, 
  collecting 
  the 
  iodine 
  distilled 
  

   in 
  potassium 
  iodide, 
  and 
  titrating 
  it 
  with 
  sodium 
  thiosulphate. 
  

   We 
  found 
  that 
  the 
  development 
  of 
  the 
  green 
  color 
  was 
  not 
  a 
  

   sufficient 
  criterion 
  of 
  the 
  exact 
  reduction 
  of 
  the 
  molybdic 
  

   acid 
  to 
  the 
  condition 
  of 
  the 
  pentoxide 
  and 
  of 
  the 
  removal 
  

   of 
  the 
  iodine 
  which 
  should 
  be 
  theoretically 
  set 
  free. 
  To 
  

   accomplish 
  that 
  end 
  we 
  found 
  it 
  safer 
  and 
  more 
  convenient 
  to 
  

  

  * 
  Gooch 
  and 
  Fairbanks, 
  this 
  Journal, 
  IV, 
  ii, 
  157, 
  1896. 
  

  

  f 
  Zeitschr. 
  fur 
  anal. 
  Chem., 
  xx, 
  507. 
  % 
  Ber. 
  d. 
  d. 
  Chem. 
  Gesell., 
  xxviii, 
  2066. 
  

   § 
  Ber. 
  d. 
  d. 
  Chem. 
  Gesell., 
  xxix, 
  2981. 
  

  

  I 
  An 
  Iodometric 
  Method 
  for 
  the 
  Determination 
  of 
  Phosphorus 
  in 
  Iron, 
  by 
  

   Charlotte 
  Fairbanks. 
  

  

  