﻿Gooch 
  and 
  Morley 
  — 
  Determinafion 
  of 
  Gold. 
  265 
  

  

  Table 
  II 
  (continued). 
  

   B 
  

  

  

  Gold 
  chloride 
  

  

  

  = 
  0-0871 
  to 
  1 
  liter. 
  

  

  

  

  Sodium 
  thiosulphate, 
  nearly 
  =0-17012 
  " 
  " 
  

  

  7»j 
  1000 
  

  

  

  

  Iodine 
  

  

  1, 
  nearly 
  

  

  1000 
  

  

  = 
  0-13697 
  

  

  

  

  AuCls 
  

  

  KI 
  

  

  XasSsOs 
  

  

  Gold 
  

  

  Gold 
  

  

  

  

  taken. 
  

  

  taken. 
  

  

  used. 
  

  

  taken. 
  

  

  found. 
  

  

  Error. 
  

  

  

  cm3. 
  

  

  grm. 
  

  

  cm^. 
  

  

  grm. 
  

  

  grm. 
  

  

  grm. 
  

  

  (21) 
  

  

  10 
  

  

  0-01 
  

  

  8-39 
  

  

  0-000871 
  

  

  0-000890 
  

  

  + 
  0-000019 
  

  

  (22) 
  

  

  9 
  

  

  0-01 
  

  

  7-45 
  

  

  0-000784 
  

  

  0-000790 
  

  

  + 
  0000006 
  

  

  (23) 
  

  

  8 
  

  

  0-01 
  

  

  6-30 
  

  

  0-000697 
  

  

  0-000668 
  

  

  -0-000029 
  

  

  (•24) 
  

  

  7 
  

  

  0-008 
  

  

  5-50 
  

  

  0-000610 
  

  

  0-0005S3 
  

  

  — 
  0-000027 
  

  

  (25) 
  

  

  6 
  

  

  0-008 
  

  

  5-12 
  

  

  0-000523 
  

  

  0-000543 
  

  

  + 
  0-000020 
  

  

  (26) 
  

  

  5 
  

  

  005 
  

  

  4-23 
  

  

  0-000435 
  

  

  0-000449 
  

  

  + 
  0-000014 
  

  

  (27) 
  

  

  4 
  

  

  005 
  

  

  3-38 
  

  

  0-000348 
  

  

  0-000358 
  

  

  + 
  0-000010 
  

  

  (28) 
  

  

  3 
  

  

  0-003 
  

  

  255 
  

  

  0-000261 
  

  

  0-000270 
  

  

  + 
  0-000009 
  

  

  (29) 
  

  

  2 
  

  

  0-003 
  

  

  1-71 
  

  

  0-000174 
  

  

  0-000181 
  

  

  + 
  0-000007 
  

  

  (30) 
  

  

  1 
  

  

  0-003 
  

  

  0-90 
  

  

  0-0000?7 
  

  

  0-000095 
  

  

  + 
  0-000008 
  

  

  These 
  results 
  run 
  on 
  the 
  whole 
  as 
  regularly 
  as 
  could 
  be 
  

   expected, 
  and 
  the 
  use 
  of 
  the 
  dilute 
  standard 
  solutions 
  is 
  

   obviously 
  of 
  advantage. 
  

  

  In 
  the 
  practical 
  application 
  of 
  any 
  such 
  process 
  for 
  the 
  

   determination 
  of 
  gold, 
  the 
  elementary 
  form 
  of 
  that 
  metal 
  is 
  

   the 
  natural 
  starting 
  point. 
  To 
  get 
  the 
  metal 
  into 
  solution 
  

   with 
  chlorine 
  water 
  or 
  mixed 
  hydrochloric 
  and 
  nitric 
  acids 
  is 
  

   an 
  easy 
  matter, 
  but 
  the 
  removal 
  of 
  the 
  excess 
  of 
  the 
  oxidizer 
  

   by 
  evaporation 
  without 
  reducing 
  some 
  auric 
  chloride 
  to 
  the 
  

   aurous 
  form 
  is 
  difficult. 
  We 
  have 
  found, 
  however, 
  that 
  the 
  

   free 
  chlorine 
  may 
  be 
  removed 
  from 
  a 
  solution 
  of 
  auric 
  chloride, 
  

   without 
  reducing 
  the 
  auric 
  salt, 
  by 
  treatment 
  of 
  the 
  solution 
  

   with 
  ammonia 
  in 
  excess, 
  boiling 
  gently, 
  acidifying 
  with 
  hydro- 
  

   chloric 
  acid 
  and 
  heating 
  if 
  necessary 
  to 
  redissolve 
  the 
  precipi- 
  

   tate 
  by 
  ammonia, 
  again 
  treating 
  with 
  ammonia 
  and 
  heating, 
  

   and 
  once 
  more 
  acidifying. 
  On 
  the 
  second 
  addition 
  of 
  ammo- 
  

   nia 
  no 
  precipitation 
  usually 
  takes 
  place 
  with 
  the 
  amounts 
  of 
  

   gold 
  which 
  we 
  have 
  thus 
  handled, 
  perhaps 
  because 
  enough 
  

   ammonium 
  chloride 
  has 
  been 
  found 
  to 
  hold 
  it 
  up. 
  

  

  The 
  following 
  table 
  contains 
  determinations 
  made 
  with 
  such 
  

   a 
  solution 
  of 
  pure 
  gold 
  leaf 
  — 
  tested 
  gravimetrically 
  as 
  to 
  

   purity.^ 
  

  

  Obviously, 
  this 
  method, 
  which 
  rests 
  upon 
  the 
  hypothesis 
  that 
  

   sodium 
  thiosulphate 
  acts 
  in 
  the 
  normal 
  manner 
  only 
  upon 
  the 
  

   iodine 
  set 
  free 
  by 
  the 
  interaction 
  of 
  gold 
  chloride 
  and 
  potassium 
  

   iodide, 
  offers 
  trustworthy 
  means 
  for 
  the 
  determination 
  of 
  small 
  

   amounts 
  of 
  gold. 
  

  

  