﻿26 
  Norton 
  — 
  Estimation 
  of 
  Iron 
  in 
  the 
  Ferric 
  State. 
  

  

  the 
  moderately 
  acid 
  solution 
  of 
  ferric 
  chloride 
  in 
  the 
  presence 
  

   of 
  a 
  cupric 
  salt 
  with 
  a 
  few 
  drops 
  of 
  sodinm 
  salicylate 
  and 
  

   then 
  reduced 
  with 
  sodium 
  thiosulphate 
  previously 
  standardized 
  

   upon 
  a 
  known 
  quantity 
  of 
  iron 
  by 
  the 
  same 
  process 
  and 
  esti- 
  

   mated 
  the 
  excess 
  by 
  potassium 
  dicliromate. 
  Bruel^ 
  modified 
  

   this 
  process 
  by 
  operating 
  without 
  the 
  copper 
  solution, 
  reiving 
  

   merely 
  on 
  the 
  discharge 
  of 
  the 
  violet 
  color 
  in 
  a 
  boiling 
  sohi- 
  

   tion 
  by 
  sodium 
  thiosulphate 
  standardized 
  on 
  a 
  ferric 
  solution 
  

   of 
  known 
  strength. 
  

  

  Although 
  considerable 
  work 
  has 
  been 
  done 
  on 
  the 
  reaction 
  

   between 
  ferric 
  iron 
  and 
  sodium 
  thiosulphate, 
  no 
  process 
  depend- 
  

   ing 
  upon 
  this 
  reaction 
  has 
  obtained 
  acceptance. 
  In 
  view, 
  

   therefore, 
  of 
  previous 
  work 
  on 
  the 
  action 
  of 
  hydrochloric 
  acid 
  

   upon 
  sodium 
  thiosulphatef 
  and 
  with 
  the 
  idea 
  that 
  a 
  careful 
  con- 
  

   trol 
  of 
  the 
  dilution 
  and 
  quantity 
  of 
  acid 
  present 
  might 
  greatly 
  

   better 
  the 
  accuracy 
  of 
  the 
  method, 
  it 
  has 
  seemed 
  to 
  me 
  to 
  be 
  

   desirable 
  to 
  study 
  this 
  process 
  again 
  in 
  detail. 
  

  

  The 
  ferric 
  oxide 
  employed 
  in 
  the 
  experiments 
  was 
  prepared 
  

   with 
  great 
  care 
  by 
  the 
  ignition 
  of 
  ferrous 
  oxalate 
  obtained 
  by 
  

   acting 
  with 
  oxalic 
  acid 
  on 
  pure 
  ammonium 
  ferrous 
  sulphate. 
  

   To 
  ascertain, 
  however, 
  if 
  this 
  oxide 
  contained 
  any 
  impurity, 
  

   about 
  0'5 
  of 
  a 
  grm. 
  was 
  put 
  into 
  a 
  porcelain 
  boat 
  and 
  submitted 
  

   to 
  the 
  action 
  of 
  a 
  current 
  of 
  hydrochloric 
  acid 
  gas 
  and 
  chlorine 
  

   at 
  a 
  temperature 
  of 
  about 
  280° 
  C. 
  (according 
  to 
  a 
  process 
  

   recently 
  described 
  from 
  this 
  laboratory:}:) 
  until 
  all 
  the 
  ferric 
  

   salt 
  is 
  volatilized 
  in 
  the 
  form 
  of 
  ferric 
  chloride. 
  A 
  residue 
  of 
  

   O'OOIO 
  grm. 
  for 
  every 
  0-5 
  of 
  a 
  grm. 
  of 
  the 
  oxide 
  was 
  found, 
  

   and 
  this 
  correction, 
  small 
  for 
  the 
  amounts 
  generally 
  used, 
  has 
  

   been 
  applied 
  in 
  the 
  following 
  determinations. 
  The 
  sodium 
  

  

  n 
  

   thiosulphate 
  used 
  was 
  taken 
  in 
  nearly 
  — 
  solution 
  and 
  was 
  stand- 
  

   ardized 
  against 
  an 
  approximately 
  decinormal 
  solution 
  of 
  

   iodine 
  which 
  had 
  been 
  determined 
  by 
  comparison 
  Vv^ith 
  deci- 
  

   normal 
  arsenious 
  acid 
  made 
  from 
  carefully 
  resublimed 
  arsenious 
  

   oxide. 
  

  

  In 
  those 
  experiments 
  which 
  deal 
  with 
  amounts 
  of 
  ferric 
  

   oxide 
  not 
  exceeding 
  0*2 
  of 
  a 
  grm., 
  measured 
  portions 
  of 
  a 
  solu- 
  

   tion 
  of 
  ferric 
  chloride 
  made 
  of 
  known 
  strength 
  by 
  dissolving 
  

   about 
  2 
  grms. 
  of 
  the 
  pure 
  carefully 
  weighed 
  ferric 
  oxide 
  in 
  

   20^^'"' 
  of 
  strong 
  hydrochloric 
  acid 
  and 
  diluting 
  to 
  onejiter, 
  were 
  

   drawn 
  from 
  a" 
  burette. 
  In 
  the 
  case 
  of 
  the 
  larger 
  quantities 
  of 
  

   ferric 
  oxide 
  the 
  salt 
  was 
  weighed 
  out, 
  dissolved 
  in 
  hydrochloric 
  

   acid 
  and 
  brought 
  to 
  the 
  required 
  dilution. 
  The 
  ferric 
  chloride, 
  

   either 
  drawn 
  "from 
  the 
  burette 
  or 
  prepared 
  directly 
  from 
  the 
  

   weighed 
  oxide, 
  was 
  diluted 
  with 
  water, 
  a 
  drop 
  of 
  potassium 
  

  

  * 
  Conipt. 
  Rendus, 
  xcvii, 
  954. 
  f 
  This 
  Joiirnal, 
  vol. 
  vii, 
  287. 
  

  

  \ 
  Gooch 
  and 
  Havens, 
  this 
  Journal, 
  

  

  