﻿of 
  Mercury 
  as 
  Mercurous 
  Oxalate. 
  405 
  

  

  was 
  doubled 
  and 
  the 
  results 
  are 
  accurate. 
  In 
  EE 
  the 
  amount 
  

   of 
  mercuric 
  salt 
  was 
  also 
  doubled 
  and 
  the 
  results 
  are 
  still 
  

   fairly 
  accurate 
  ; 
  but 
  when 
  a 
  large 
  excess 
  of 
  ammonium 
  oxalate 
  

   is 
  present 
  as 
  in 
  experiments 
  F, 
  even 
  with 
  the 
  smaller 
  amount 
  

   of 
  mercuric 
  salt, 
  the 
  results 
  are 
  high. 
  At 
  a 
  dilution 
  of 
  

   200 
  cm3 
  the 
  results 
  are 
  normal 
  as 
  seen 
  in 
  experiments 
  G 
  ; 
  but 
  

   the 
  introduction 
  of 
  more 
  mercuric 
  salt, 
  as 
  in 
  experiments 
  H, 
  

   causes 
  a 
  plus 
  error. 
  

  

  Using 
  5 
  cra3 
  of 
  nitric 
  acid, 
  the 
  larger 
  amount 
  of 
  mercuric 
  salt, 
  

   together 
  with 
  a 
  large 
  excess 
  of 
  ammonium 
  oxalate, 
  as 
  recorded 
  

   in 
  experiments 
  K, 
  the 
  error 
  is 
  raised 
  a 
  trifle 
  ; 
  but 
  with 
  a 
  smaller 
  

   amount 
  of 
  mercurous 
  salt 
  as 
  in 
  experiment 
  I 
  the 
  result 
  is 
  normal. 
  

  

  In 
  precipitating 
  mercurous 
  salts 
  by 
  ammonium 
  oxalate 
  (— 
  ) 
  

  

  it 
  is 
  an 
  easy 
  matter 
  to 
  keep 
  the 
  excess 
  of 
  the 
  precipitant 
  within 
  

   the 
  limits 
  of 
  1 
  or 
  2 
  cm3 
  , 
  because 
  the 
  mercurous 
  oxalate, 
  when 
  

   properly 
  stirred, 
  settled 
  very 
  rapidly. 
  

  

  The 
  Gravimetric 
  Estimation. 
  

   All 
  the 
  conditions 
  described 
  above 
  in 
  the 
  volumetric 
  estima- 
  

   tion 
  of 
  mercurous 
  oxalate, 
  for 
  the 
  separation 
  of 
  mercurous 
  

   from 
  mercuric 
  salts, 
  may 
  be 
  applied 
  to 
  the 
  gravimetric 
  estima- 
  

   tion 
  of 
  mercurous 
  oxalate. 
  The 
  precipitate 
  is 
  collected 
  on 
  a 
  

   weighed 
  asbestos 
  filter, 
  washed 
  two 
  or 
  three 
  times 
  with 
  cold 
  

   water 
  and 
  dried 
  over 
  sulphuric 
  acid 
  to 
  a 
  constant 
  weight. 
  

   Amounts 
  of 
  mercurous 
  oxalate 
  equivalent 
  to 
  0-1217 
  and 
  0*2211: 
  

   gms. 
  of 
  metallic 
  mercury 
  dried 
  to 
  a 
  constant 
  weight 
  over 
  sul- 
  

   phuric 
  acid 
  in 
  about 
  15 
  hours; 
  a 
  larger 
  amount 
  equivalent 
  to 
  

   - 
  3 
  gm. 
  of 
  metallic 
  mercury, 
  required 
  about 
  2 
  days 
  to 
  dry 
  to 
  a 
  

   constant 
  weight. 
  Sonchay 
  and 
  Lenssen* 
  state 
  that 
  mercurous 
  

   oxalate 
  breaks 
  up 
  at 
  100° 
  ; 
  consequently 
  this 
  temperature 
  can- 
  

   not 
  be 
  used 
  for 
  drying. 
  For 
  example, 
  a 
  precipitate 
  containing 
  

   0-1122 
  gms. 
  mercury 
  as 
  the 
  oxalate 
  which 
  when 
  brought 
  to 
  a 
  

   constant 
  weight 
  at 
  the 
  ordinary 
  temperature 
  over 
  sulphuric 
  acid 
  

   weighed 
  0'1371 
  gms., 
  and 
  was 
  heated 
  and 
  weighed 
  as 
  follows 
  : 
  

  

  After 
  1 
  hours 
  at 
  110°, 
  weight 
  = 
  0-1338 
  gms. 
  

   '< 
  2 
  a 
  « 
  c< 
  0-132S 
  " 
  

  

  " 
  7 
  " 
  " 
  " 
  0-1302 
  " 
  

  

  The 
  result 
  shows 
  a 
  loss 
  of 
  0'0069 
  gms. 
  for 
  16 
  hours 
  heating, 
  

   and 
  agrees 
  with 
  the 
  statement 
  of 
  Sonchay 
  and 
  Lenssen. 
  

  

  The 
  following 
  experiments 
  give 
  the 
  results 
  of 
  the 
  gravi- 
  

   metric 
  work, 
  in 
  which 
  the 
  drying 
  was 
  effected, 
  by 
  exposure 
  for 
  

   15 
  hours 
  or 
  less, 
  at 
  ordinary 
  temperatures, 
  over 
  sulphuric 
  acid. 
  

   The 
  larger 
  amounts 
  of 
  nitric 
  acid 
  present 
  in 
  the 
  separations 
  

   cause 
  the 
  precipitate 
  to 
  be 
  more 
  granular 
  and 
  aid 
  in 
  the 
  filter- 
  

   ing 
  process. 
  

  

  * 
  Add., 
  ciii, 
  308. 
  

  

  