﻿72 
  Browning 
  and 
  Minnig 
  — 
  Preparation 
  of 
  Telluric 
  Acid. 
  

  

  Art. 
  X. 
  — 
  A 
  Note 
  on 
  the 
  Preparation 
  of 
  Telluric 
  Acid 
  

   and 
  a 
  Test 
  for 
  Associated 
  Tellurous 
  Acid 
  ; 
  by 
  Philip 
  E. 
  

   Browning 
  and 
  H. 
  D. 
  Minnig. 
  

  

  [Contributions 
  from 
  the 
  Kent 
  Chemical 
  Laboratory 
  of 
  Yale 
  Univ. 
  — 
  ccxlvi.] 
  

  

  Of 
  the 
  various 
  methods 
  suggested 
  for 
  the 
  preparation 
  of 
  

   telluric 
  acid, 
  two 
  only 
  seem 
  to 
  be 
  in 
  general 
  use 
  : 
  first 
  the 
  oxi- 
  

   dation 
  of 
  tellurous 
  acid 
  by 
  chromic 
  acid,* 
  and 
  the 
  precipita- 
  

   tion 
  of 
  the 
  telluric 
  acid 
  by 
  nitric 
  acid 
  after 
  the 
  concentration 
  

   of 
  the 
  solution 
  ; 
  and 
  second, 
  the 
  oxidation 
  of 
  an 
  alkali 
  tellurite 
  

   by 
  hydrogenf 
  dioxide, 
  followed 
  by 
  the 
  precipitation 
  of 
  the 
  

   tellnric 
  acid 
  by 
  nitric 
  acid. 
  While 
  both 
  of 
  these 
  methods 
  give 
  

   quite 
  satisfactory 
  yields, 
  the 
  difficulty 
  of 
  washing 
  out 
  the 
  

   chromium 
  salt;): 
  in 
  the 
  first 
  method, 
  and 
  of 
  removing 
  the 
  alkali 
  

   salt 
  in 
  the 
  second 
  method 
  is 
  apparent. 
  Eerzelius 
  formed 
  tellu- 
  

   rates 
  by 
  passing 
  chlorine 
  into 
  an 
  alkaline 
  solution 
  of 
  a 
  tellurite, 
  

   but 
  here 
  also 
  the 
  precipitation 
  of 
  the 
  telluric 
  acid 
  would 
  have 
  

   the 
  same 
  disadvantage 
  in 
  the 
  inclusion 
  of 
  alkali 
  salts. 
  

  

  The 
  work 
  to 
  be 
  described 
  was 
  undertaken 
  to 
  study 
  the 
  effect 
  

   of 
  free 
  chlorine 
  upon 
  elementary 
  tellurium 
  suspended 
  in 
  water. 
  

   The 
  element 
  in 
  the 
  form 
  of 
  an 
  amorphous 
  powder 
  weighing 
  

   several 
  grams 
  was 
  suspended 
  in 
  water 
  and 
  subjected 
  to 
  the 
  

   action 
  of 
  a 
  current 
  of 
  washed 
  chlorine 
  gas. 
  After 
  about 
  an 
  

   hour 
  the 
  tellurium 
  had 
  dissolved, 
  and 
  a 
  portion 
  of 
  the 
  solution, 
  

   made 
  alkaline 
  and 
  then 
  acidified 
  with 
  acetic 
  acid, 
  remained 
  

   clear, 
  showing 
  the 
  complete 
  oxidation 
  to 
  telluric 
  acid. 
  

  

  It 
  was 
  found 
  by 
  experimentation 
  with 
  solutions 
  of 
  tellurates 
  

   and 
  tellurites 
  that 
  this 
  method 
  of 
  testing 
  would 
  detect 
  a 
  milli- 
  

   gram 
  of 
  tellurous 
  acid 
  in 
  the 
  presence 
  of 
  between 
  one 
  and 
  two 
  

   hundred 
  milligrams 
  of 
  telluric 
  acid, 
  in 
  a 
  volume 
  of 
  5 
  cm3 
  . 
  

  

  When 
  the 
  solution 
  was 
  thoroughly 
  saturated 
  with 
  chlorine 
  

   and 
  the 
  complete 
  oxidation 
  was 
  shown 
  by 
  this 
  method 
  of 
  test- 
  

   ing, 
  the 
  solution 
  was 
  evaporated 
  to 
  small 
  volume, 
  tested 
  to 
  be 
  

   sure 
  that 
  no 
  reduction 
  had 
  taken 
  place, 
  and 
  again 
  treated 
  with 
  

   chlorine 
  if 
  necessary. 
  The 
  concentrated 
  solution 
  was 
  then 
  

   treated 
  with 
  acetone 
  or 
  ethyl 
  alcohol 
  to 
  the 
  complete 
  precipita- 
  

   tion 
  of 
  a 
  beautifully 
  crystalline 
  product 
  of 
  satisfactory 
  yield. 
  

   This 
  product 
  was 
  washed 
  with 
  acetone 
  or 
  alcohol 
  until 
  the 
  

   washings 
  gave 
  no 
  test 
  with 
  silver 
  nitrate 
  for 
  hydrochloric 
  acid. 
  

  

  The 
  telluric 
  acid 
  obtained 
  was 
  readily 
  soluble 
  in 
  water 
  ; 
  

   moreover, 
  the 
  solution 
  gave 
  no 
  indication 
  of 
  the 
  presence 
  of 
  

   tellurous 
  acid 
  on 
  treatment 
  with 
  an 
  alkali 
  hydroxide 
  and 
  acetic 
  

   acid, 
  and 
  was 
  not 
  reduced 
  by 
  stannous 
  chloride 
  except 
  on 
  

   warming. 
  

  

  * 
  Staudenmaier, 
  Zs. 
  anorg. 
  Chem. 
  x, 
  189 
  ; 
  Gutbier, 
  xxix, 
  22. 
  

   f 
  Gutbier, 
  Zs. 
  anorg. 
  Chem., 
  xl, 
  260. 
  

   JKothner, 
  A., 
  cccxix, 
  39. 
  

  

  