﻿Austin 
  — 
  Ammonium 
  Magnesium 
  Arseniate. 
  55 
  

  

  Art. 
  VII. 
  — 
  The 
  Constitution 
  of 
  the 
  Ammonium 
  Magnesium 
  

   Arseniate 
  of 
  Analysis 
  ; 
  by 
  Martha 
  Austin. 
  

  

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

  

  The 
  striking 
  analogy 
  between 
  the 
  phosphates 
  and 
  the 
  arse- 
  

   nates 
  led 
  Levol* 
  to 
  undertake 
  the 
  separation 
  of 
  an 
  ammonium 
  

   arseniate 
  corresponding 
  to 
  the 
  ammonium 
  magnesium 
  phos- 
  

   phate, 
  the 
  composition 
  of 
  which 
  Berzelius 
  had 
  given. 
  Levol 
  

   states 
  that 
  ammonium 
  magnesium 
  arseniate 
  of 
  the 
  composition 
  

   NH 
  4 
  MgAsO 
  4 
  .10H 
  2 
  O 
  is 
  obtained 
  by 
  adding 
  a 
  solution 
  of 
  a 
  

   double 
  ammonium 
  magnesium 
  salt 
  to 
  arsenic 
  acid, 
  and 
  that 
  it 
  

   is 
  a 
  salt 
  possessing 
  about 
  the 
  same 
  degree 
  of 
  solubility 
  in 
  water, 
  

   in 
  ammoniacal 
  water, 
  and 
  in 
  ammoniacal 
  water 
  containing 
  mag- 
  

   nesium 
  salt, 
  as 
  the 
  corresponding 
  phosphate. 
  Further, 
  he 
  

   found 
  that 
  by 
  heating 
  this 
  salt 
  to 
  red 
  heat 
  after 
  carefully 
  dry- 
  

   ing, 
  magnesium 
  pyroarseniate 
  was 
  given, 
  from 
  which 
  arsenic 
  

   can 
  be 
  estimated 
  readily. 
  

  

  Wachf 
  and 
  H. 
  Rose:); 
  obtained 
  the 
  ammonium 
  magnesium 
  

   arseniate 
  containing 
  six 
  molecules 
  of 
  water 
  of 
  crystallization 
  

   by 
  precipitating 
  arsenic 
  acid 
  with 
  magnesia 
  mixture 
  and 
  then 
  

   adding 
  an 
  excess 
  of 
  ammonia, 
  and 
  by 
  drying 
  at 
  100° 
  C. 
  were 
  

   able 
  to 
  estimate 
  the 
  arsenic 
  present 
  as 
  the 
  ammonio-magnesium 
  

   arseniate 
  containing 
  one-half 
  molecule 
  of 
  water. 
  This 
  method 
  

   seemed 
  to 
  offer 
  an 
  advantage 
  over 
  the 
  method 
  of 
  estimation 
  as 
  

   the 
  ]3yroarseniate, 
  for 
  results 
  obtained 
  below 
  the 
  theoretical 
  

   amount 
  of 
  arsenic 
  present 
  gave 
  rise 
  to 
  the 
  suspicion 
  that 
  dur- 
  

   ing 
  ignition 
  arsenic 
  was 
  reduced 
  by 
  the 
  ammonia 
  driven 
  off. 
  

   Rose 
  attempted 
  in 
  another 
  way 
  to 
  avoid 
  this 
  loss 
  by 
  igniting 
  in 
  

   a 
  current 
  of 
  oxygen 
  ; 
  and 
  later 
  Reichelf 
  ignited 
  the 
  residue 
  

   after 
  carefully 
  saturating 
  it 
  with 
  ammonium 
  nitrate 
  and 
  nitric 
  

   acid, 
  and 
  drying 
  at 
  100° 
  C. 
  Rammelsbergg 
  believed 
  that 
  it 
  

   was 
  safer 
  to 
  ignite 
  after 
  drying 
  at 
  120° 
  C. 
  because 
  drying 
  at 
  

   100-110° 
  C. 
  caused 
  a 
  loss 
  of 
  ammonia 
  before 
  ignition. 
  Kaiser 
  1 
  ! 
  

   dried 
  the 
  residue 
  in 
  a 
  current 
  of 
  air. 
  

  

  A 
  second 
  source 
  of 
  error 
  discussed 
  by 
  H. 
  Rose,** 
  Fresenius 
  

   and 
  others 
  is 
  due 
  to 
  the 
  solubility 
  of 
  the 
  ammonium 
  mag- 
  

   nesium 
  arseniate 
  in 
  w 
  r 
  ater, 
  in 
  ammoniacal 
  water, 
  and 
  ammonia- 
  

   cal 
  water 
  containing 
  magnesium 
  salts. 
  Woodft 
  attempted 
  to 
  

   avoid 
  this 
  by 
  precipitating 
  the 
  ammonio-magnesium 
  arseniate 
  

   with 
  an 
  alcoholic 
  magnesia 
  mixture, 
  and 
  by 
  washing 
  the 
  pre- 
  

   cipitate 
  with 
  an 
  alcoholic 
  solution, 
  by 
  weighing 
  the 
  residue 
  

  

  * 
  Ann. 
  de 
  Chim. 
  et 
  de 
  Phys., 
  Ill, 
  xvii, 
  501, 
  1846. 
  

  

  f 
  Schweigger, 
  Jo 
  urn. 
  f. 
  Oh. 
  u. 
  Phys., 
  lix. 
  297. 
  % 
  Ann. 
  d. 
  Phys 
  , 
  lxxvi, 
  20. 
  

  

  P 
  Ber. 
  d. 
  d. 
  Chem. 
  Gesell., 
  xiv, 
  27*9. 
  || 
  Ber. 
  d. 
  d. 
  Chem 
  Gesell 
  , 
  vii. 
  5 
  44. 
  

  

  •" 
  Zeitschr. 
  f. 
  Anal. 
  Chem., 
  xiv, 
  250. 
  ** 
  Zeitschr. 
  L 
  Anal. 
  Chem., 
  iii, 
  206. 
  

  

  ft 
  This 
  Journal, 
  III, 
  vi, 
  368. 
  

  

  