﻿60 
  

  

  Austin— 
  Constitution 
  of 
  the 
  

  

  At 
  all 
  events, 
  the 
  treatment 
  applied 
  in 
  the 
  experiments 
  of 
  A 
  

   resulted 
  practically 
  in 
  the 
  complete 
  precipitation 
  and 
  in 
  the 
  

   production 
  of 
  a 
  precipitate 
  of 
  nearly 
  ideal 
  constitution. 
  

  

  

  

  

  Table 
  IV. 
  

  

  

  

  

  Mg 
  2 
  As 
  2 
  7 
  

  

  corresponding 
  to 
  As 
  2 
  5 
  . 
  

  

  Magnesia 
  

   mixture. 
  

  

  

  

  Taken. 
  

  

  Found. 
  

  

  Error. 
  

  

  NH 
  4 
  C1 
  

  

  

  grm. 
  

  

  grm. 
  

  

  grm. 
  A 
  cc. 
  

  

  grm. 
  

  

  (1) 
  

  

  0*7843 
  

  

  0-7830 
  

  

  0-0013 
  — 
  

  

  50 
  

  

  

  (2) 
  

  

  0-7843 
  

  

  0'7849 
  

  

  0-0006 
  — 
  

  

  50 
  

  

  

  (3) 
  

  

  0-7843 
  

  

  0-7841 
  

  

  0-0002 
  — 
  

  

  50 
  

  

  

  (*) 
  

  

  0-7843 
  

  

  0-7843 
  

  

  o-oooo— 
  

  

  50 
  

   B 
  

  

  75 
  

  

  -- 
  

  

  (5) 
  

  

  0-7843 
  

  

  0-7763 
  

  

  0-0080 
  — 
  

  

  10 
  

  

  (6) 
  

  

  0-7843 
  

  

  0-7762 
  

  

  0-0081 
  — 
  

  

  75 
  

  

  10 
  

  

  (?) 
  

  

  0-7843 
  

  

  0-7832 
  

  

  0-0011 
  — 
  

  

  100 
  

  

  10 
  

  

  (8) 
  

  

  0-7843 
  

  

  0-7838 
  

  

  0-0005 
  — 
  

  

  100 
  

  

  10 
  

  

  (8) 
  

  

  0-7843 
  

  

  0-7784 
  

  

  0-0059 
  — 
  

  

  100 
  

  

  20 
  

  

  (10) 
  

  

  0-7843 
  

  

  0-7810 
  

  

  0-0033 
  — 
  

  

  100 
  

  

  20 
  

  

  (11). 
  

  

  0-7843 
  

  

  0-7849 
  

  

  0-0006 
  + 
  

  

  150 
  

  

  60 
  

  

  (12) 
  

  

  0-7843 
  

  

  0-7846 
  

  

  0-0003 
  + 
  

  

  150 
  

  

  60 
  

  

  In 
  section 
  B 
  of 
  the 
  same 
  table 
  the 
  results 
  recorded 
  show 
  the 
  

   effect 
  of 
  increased 
  amounts 
  of 
  ammonium 
  chloride 
  on 
  the 
  

   constitution 
  of 
  the 
  ammonium 
  magnesium 
  arseniate. 
  Enough 
  

   magnesia 
  mixture 
  was 
  used 
  in 
  each 
  case 
  to 
  remove 
  the 
  arsenic 
  

   completely 
  from 
  solution. 
  The 
  precipitates 
  were 
  gathered 
  on 
  

   asbestos 
  in 
  a 
  perforated 
  platinum 
  crucible 
  and 
  treated 
  as 
  those 
  

   described 
  in 
  section 
  A 
  of 
  the 
  table. 
  It 
  is 
  evident 
  as 
  shown 
  by 
  

   (5) 
  and 
  (6) 
  of 
  the 
  table 
  that 
  ammonium 
  chloride 
  causes 
  a 
  

   replacement 
  of 
  some 
  of 
  the 
  metal 
  by 
  ammonia 
  in 
  the 
  ammo- 
  

   nium 
  magnesium 
  arseniate 
  (to 
  form, 
  possibly, 
  a 
  salt 
  of 
  the 
  con- 
  

   stitution 
  Mg(NH 
  4 
  ) 
  4 
  As0 
  4 
  ) 
  though 
  the 
  solvent 
  effect 
  of 
  the 
  

   ammonium 
  chloride 
  is 
  overcome 
  by 
  the 
  addition 
  of 
  a 
  sufficient 
  

   amount 
  of 
  magnesia 
  mixture. 
  ISTo 
  arsenic 
  appeared 
  in 
  the 
  fil- 
  

   trates, 
  and, 
  further, 
  experiments 
  (7) 
  and 
  (8) 
  show 
  that 
  increas- 
  

   ing 
  the 
  amount 
  of 
  magnesia 
  mixture 
  present 
  will 
  cause 
  the 
  

   formation 
  of 
  the 
  salt 
  of 
  ideal 
  constitution 
  even 
  in 
  presence 
  of 
  

   considerable 
  amounts 
  of 
  ammonium 
  chloride. 
  Indeed 
  this 
  is 
  

   possible 
  where 
  as 
  large 
  an 
  amount 
  as 
  sixty 
  grams 
  of 
  the 
  salt 
  is 
  

   present, 
  as 
  results 
  (11) 
  and 
  (12) 
  show. 
  Obviously, 
  ammonium 
  

   chloride 
  in 
  any 
  amount 
  above 
  what 
  is 
  required 
  for 
  the 
  magnesia 
  

   mixture 
  tends 
  to 
  dissolve 
  the 
  precipitate, 
  but 
  this 
  solvent 
  effect 
  

   may 
  be 
  neutralized 
  by 
  increasing 
  the 
  amounts 
  of 
  magnesia 
  

   mixture 
  even 
  though 
  the 
  precipitate 
  formed 
  is 
  richer 
  in 
  

   ammonia 
  than 
  the 
  ideal 
  salt. 
  

  

  