﻿122 
  Gooch 
  and 
  Peters 
  — 
  Determination 
  of 
  Telliirous 
  

  

  Art. 
  Xir. 
  — 
  T/ie 
  Determination 
  of 
  Telhorous 
  Acid 
  in 
  j9r^5- 
  

   ence 
  of 
  Haloid 
  Salts 
  ; 
  bj 
  F. 
  A. 
  Gooch 
  and 
  C. 
  A. 
  Peters. 
  

  

  [Contributions 
  from 
  the 
  Kent 
  Chemical 
  Laboratory 
  of 
  Yale 
  University 
  — 
  LXXXIV.] 
  

  

  The 
  estimation 
  of 
  tellurons 
  acid 
  by 
  oxidation 
  with 
  excess 
  of 
  

   potassium 
  permanganate 
  (either 
  in 
  acid 
  or 
  alkaline 
  solution), 
  

   destruction 
  of 
  the 
  higher 
  oxides 
  of 
  manganese 
  or 
  the 
  manga- 
  

   nate 
  by 
  standard 
  oxalic 
  acid 
  in 
  presence 
  of 
  sulphuric 
  acid, 
  and 
  

   titration 
  of 
  the 
  residual 
  oxalic 
  acid 
  by 
  more 
  permanganate, 
  has 
  

   been 
  shown 
  by 
  Brauner^ 
  to 
  be 
  feasible. 
  The 
  tendency 
  of 
  the 
  

   permanganate 
  to 
  throw 
  off 
  too 
  much 
  oxygen 
  when 
  the 
  oxida- 
  

   tion 
  is 
  made 
  in 
  solutions 
  strongly 
  acidified 
  with 
  sulphuric 
  acid 
  

   (as 
  must 
  be 
  the 
  case 
  if 
  the 
  teliurous 
  oxide 
  is 
  to 
  be 
  held 
  perma- 
  

   nently 
  in 
  solution 
  by 
  sulphuric 
  acid) 
  necessitates 
  the 
  application 
  

   of 
  a 
  considerable 
  correction.! 
  Fortunately, 
  however, 
  as 
  has 
  

   been 
  shown 
  in 
  a 
  former 
  paper 
  from 
  this 
  laboratory,^ 
  when 
  

   the 
  teliurous 
  oxide 
  is 
  dissolved 
  originally 
  in 
  an 
  alkaline 
  hydrox- 
  

   ide 
  and 
  the 
  solution 
  made 
  acid 
  only 
  to 
  a 
  limited 
  degree 
  with 
  

   sulphuric 
  acid 
  either 
  before 
  or 
  after 
  oxidation 
  by 
  the 
  perman- 
  

   ganate, 
  no 
  correction 
  appears 
  to 
  be 
  necessary. 
  Thus, 
  when 
  an 
  

   excess 
  of 
  permanganate 
  is 
  added 
  to 
  the 
  alkaline 
  solution, 
  

   followed 
  by 
  an 
  excess 
  of 
  oxalic 
  acid 
  and 
  sulphuric 
  acid 
  to 
  an 
  

   amount 
  not 
  exceeding 
  5^°^^ 
  of 
  the 
  [1 
  : 
  1] 
  mixture 
  with 
  water, 
  

   the 
  titration 
  of 
  the 
  residual 
  oxalic 
  acid 
  by 
  more 
  permanganate 
  

   (after 
  heating 
  to 
  80° 
  C.) 
  leads 
  to 
  results 
  which 
  give 
  no 
  indi- 
  

   cation 
  of 
  over-decomposition 
  of 
  the 
  permanganate 
  ; 
  so 
  also, 
  

   when 
  the 
  process 
  is 
  similarly 
  conducted 
  excepting 
  that 
  before 
  

   addition 
  of 
  the 
  permanganate 
  the 
  original 
  alkaline 
  solution 
  is 
  

   acidified 
  with 
  sulphuric 
  acid 
  [1 
  : 
  1] 
  to 
  an 
  amount 
  1^""' 
  in 
  excess 
  

   of 
  that 
  necessary 
  to 
  re-dissolve 
  the 
  first 
  precipitate, 
  the 
  results 
  

   are 
  theoretically 
  accurate, 
  and 
  in 
  close 
  agreement 
  with 
  those 
  

   obtained 
  by 
  the 
  former 
  procedure. 
  

  

  In 
  the 
  presence 
  of 
  free 
  hydrochloric 
  acid 
  the 
  action 
  of 
  the 
  

   permanganate 
  upon 
  teliurous 
  acid 
  has 
  been 
  shown 
  by 
  Brauner§ 
  

   to 
  be 
  irregular 
  and 
  excessive, 
  and 
  the 
  irregularity 
  cannot 
  be 
  

   corrected 
  (as 
  in 
  the 
  titration 
  of 
  ferrous 
  salts 
  in 
  presence 
  of 
  

   hydrochloric 
  acid) 
  by 
  the 
  addition 
  of 
  a 
  manganous 
  salt 
  accord- 
  

   ing 
  to 
  the 
  well-known 
  procedure 
  of 
  Kessler|! 
  and 
  Zimmer- 
  

   inann.^f 
  So 
  far 
  as 
  appears, 
  however, 
  there 
  should 
  be 
  nothing 
  

   to 
  prevent 
  the 
  accurate 
  determination 
  of 
  tellurium 
  in 
  teliurous 
  

   compounds 
  in 
  the 
  presence 
  of 
  chlorides 
  by 
  the 
  permanganate 
  

   process 
  providing 
  the 
  first 
  oxidation 
  is 
  made 
  in 
  alkaline 
  solu- 
  

   tion, 
  and 
  the 
  second 
  oxidation 
  carried 
  out 
  with 
  such 
  precautions 
  

  

  * 
  Jour. 
  Chem. 
  Soc. 
  1891, 
  p. 
  2.S8. 
  + 
  Loc. 
  cit., 
  p. 
  249. 
  

  

  i 
  Gooch 
  and 
  Dauner: 
  this 
  Journal, 
  xliv, 
  301. 
  i^ 
  Loc. 
  cit., 
  p. 
  241. 
  

   I 
  Ann. 
  der 
  Phys., 
  cxviii, 
  48; 
  cxix, 
  225, 
  226. 
  ^Ann. 
  der 
  Chem., 
  ccxiii, 
  302. 
  

  

  