﻿214 
  M. 
  Austin 
  — 
  Double 
  Ammonium 
  Phosphates. 
  

  

  In 
  section 
  E 
  of 
  the 
  table 
  are 
  recorded 
  results 
  where 
  the 
  pre- 
  

   cipitation 
  was 
  made 
  in 
  presence 
  of 
  an 
  excess 
  of 
  the 
  precipitant 
  

   either 
  alone 
  or 
  in 
  presence 
  of 
  ammonium 
  chloride, 
  the 
  solu- 
  

   tion 
  being 
  made 
  faintly 
  acid 
  to 
  litmus 
  with 
  acetic 
  acid, 
  accord- 
  

   ing 
  to 
  the 
  manner 
  in 
  which 
  Langmuir 
  recommends 
  to 
  conduct 
  

   the 
  precipitation. 
  All 
  the 
  results 
  by 
  the 
  method 
  are 
  low. 
  

   The 
  condition 
  of 
  the 
  ammonium 
  zinc 
  phosphate 
  most 
  nearly 
  

   approximating 
  to 
  the 
  ideal 
  is 
  obtained 
  as 
  shown 
  in 
  (9) 
  to 
  (14) 
  

   by 
  precipitating 
  in 
  presence 
  of 
  ammonium 
  chloride 
  in 
  large 
  

   amount. 
  Microcosmic 
  salt 
  is 
  added 
  until 
  the 
  solution 
  contain- 
  

   ing 
  the 
  ammonium 
  salt 
  is 
  alkaline 
  and 
  the 
  whole 
  is 
  heated 
  until 
  

   the 
  mass 
  subsides 
  in 
  crystalline 
  condition. 
  The 
  amount 
  of 
  

   ammonium 
  chloride 
  should 
  be 
  twenty 
  grams 
  if 
  the 
  filtration 
  is 
  

   to 
  be 
  made 
  as 
  soon 
  as 
  the 
  solution 
  cools. 
  One-half 
  the 
  amount 
  

   will 
  do 
  if 
  the 
  liquid 
  stands 
  a 
  number 
  of 
  hours. 
  Larger 
  

   amounts 
  tend 
  to 
  give 
  a 
  salt 
  too 
  rich 
  in 
  ammonia. 
  The 
  time 
  of 
  

   standing 
  seems 
  to 
  be 
  a 
  less 
  important 
  factor 
  than 
  either 
  the 
  

   excess 
  of 
  microcosmic 
  salt 
  or 
  ammonium 
  chloride. 
  

  

  The 
  Amtiionium 
  Cadmium 
  Phosphate. 
  

  

  According 
  to 
  S. 
  Drewsen"^ 
  the 
  cadmium 
  ammonium 
  phos- 
  

   phate 
  is 
  precipitated 
  by 
  allowing 
  a 
  solution 
  of 
  cadmium 
  sul- 
  

   phate 
  to 
  stand 
  twenty-four 
  hours 
  with 
  ammonium 
  phosphate. 
  

   It 
  is 
  very 
  soluble 
  both 
  in 
  acids 
  and 
  alkalies, 
  No 
  further 
  prep- 
  

   aration 
  of 
  this 
  seems 
  to 
  have 
  been 
  recorded. 
  For 
  the 
  work 
  on 
  

   this 
  salt 
  to 
  be 
  given 
  below, 
  made 
  with 
  reference 
  to 
  determining 
  

   the 
  constitution 
  of 
  the 
  salt 
  by 
  hydrogen 
  sodium 
  ammonium 
  

   phosphate, 
  the 
  effect 
  of 
  ammonium 
  chloride 
  in 
  the 
  precipita- 
  

   tion, 
  and 
  the 
  value 
  of 
  the 
  salt 
  for 
  quantitative 
  work, 
  the 
  solu- 
  

   tion 
  of 
  cadmium 
  chloride 
  employed 
  was 
  prepared 
  as 
  follows 
  : 
  

   A 
  solution 
  of 
  cadmium 
  sulphate 
  acidulated 
  with 
  hydrochloric 
  

   acid 
  was 
  precipitated 
  with 
  sulphuretted 
  hydrogen, 
  filtered 
  and 
  

   washed, 
  and 
  the 
  precipitated 
  sulphide 
  was 
  dissolved 
  in 
  hydro- 
  

   chloric 
  acid 
  and 
  filtered 
  from 
  possible 
  traces 
  of 
  copper 
  and 
  

   lead. 
  The 
  solution 
  of 
  the 
  sulphide 
  in 
  hydrochloric 
  acid 
  was 
  

   boiled 
  until 
  all, 
  the 
  sulphuretted 
  hydrogen 
  was 
  expelled, 
  and 
  

   filtered 
  on 
  asbestos 
  in 
  a 
  perforated 
  crucible 
  of 
  platinum 
  under 
  

   pressure. 
  The 
  cadmium 
  in 
  the 
  filtrate 
  precipitated 
  with 
  ammo- 
  

   nium 
  carbonate 
  in 
  excess 
  was 
  washed 
  free 
  from 
  chloride, 
  dis- 
  

   solved 
  in 
  hydrochloric 
  acid 
  and 
  diluted 
  to 
  definite 
  volume. 
  It 
  

   was 
  standardized 
  as 
  oxidef 
  after 
  precipitating 
  with 
  sodium 
  car- 
  

   bonate 
  with 
  the 
  necessary 
  precautions. 
  

  

  The 
  standard 
  solution 
  of 
  cadmium 
  chloride 
  was 
  drawn 
  care- 
  

   fully 
  from 
  a 
  burette 
  into 
  a 
  platinum 
  dish, 
  and, 
  while 
  hot, 
  was 
  

   precipitated 
  by 
  adding 
  hydrogen 
  sodium 
  ammonium 
  phosphate 
  

  

  *GmeliD-Kraut, 
  Q>^^ 
  Aiifiage, 
  iii, 
  74. 
  

   •}■ 
  Browning, 
  this 
  Journal, 
  xlvi, 
  280. 
  

  

  