﻿212 
  

  

  M. 
  Aiistin- 
  

  

  —Double 
  Ammo7iiu7 
  

  

  

  Table 
  II. 
  

  

  ZnSOi 
  

  

  Mean 
  value 
  of 
  

  

  found 
  in 
  

  

  ZnO 
  corresponding 
  

  

  40^'"^ 
  of 
  

  

  to 
  ZnSOi 
  in 
  40«'n3 
  

  

  solution. 
  

  

  of 
  solution. 
  

  

  grm. 
  

  

  grm. 
  

  

  0-5386' 
  

  

  0-2712 
  

  

  0-5385 
  

  

  

  0-5387 
  > 
  

  

  

  0-5387 
  1 
  

  

  

  0-5390J 
  

  

  

  ZnO 
  found 
  in 
  

  

  40cm3 
  qI 
  solution 
  by 
  

  

  precipitation 
  as 
  the 
  

  

  carbonate. 
  

  

  grm. 
  

  

  0-2691 
  

   0.2685 
  

   0-2711 
  

  

  Definite 
  portions 
  of 
  the 
  solution 
  of 
  zinc 
  sulphate 
  were 
  care- 
  

   fully 
  drawn 
  from 
  a 
  burette 
  into 
  a 
  platinum 
  dish, 
  heated 
  and 
  

   treated 
  with 
  ammonium 
  phosphate 
  until 
  the 
  solution 
  turned 
  

   red 
  litmus 
  paper 
  blue. 
  The 
  whole 
  was 
  heated 
  until 
  the 
  flockj 
  

   precipitate 
  became 
  crystalline 
  and 
  fell 
  to 
  the 
  bottom 
  of 
  the 
  

   dish. 
  The 
  solution 
  after 
  standing 
  as 
  recorded 
  in 
  section 
  A 
  of 
  

   the 
  table 
  was 
  filtered 
  off 
  on 
  asbestos 
  under 
  pressure 
  in 
  a 
  per- 
  

   forated 
  platinum 
  crucible, 
  and 
  the 
  precipitate 
  was 
  washed 
  with 
  

   distilled 
  water, 
  dried, 
  ignited 
  and 
  weighed. 
  The 
  filtrate 
  in 
  

   each 
  case, 
  as 
  in 
  all 
  following 
  cases, 
  was 
  tested 
  for 
  zinc 
  with 
  

   sulphuretted 
  hydrogen. 
  The 
  results 
  recorded 
  in 
  section 
  B 
  of 
  

   the 
  table 
  were 
  obtained 
  in 
  the 
  same 
  manner 
  as 
  those 
  of 
  section 
  

   A, 
  with 
  microcosmic 
  salt 
  substituted 
  for 
  the 
  ammonium 
  salt 
  as 
  

   the 
  precipitant. 
  The 
  results 
  are 
  below 
  the 
  theory 
  for 
  the 
  

   pyrophosphate, 
  but 
  no 
  appreciable 
  amount 
  of 
  zinc 
  appeared 
  in 
  

   the 
  filtrates. 
  Neither 
  ammonium 
  phosphate 
  nor 
  ammonium 
  

   sodium 
  phosphate 
  seems 
  to 
  precipitate 
  the 
  ideal 
  ammonium 
  

   zinc 
  phosphate 
  under 
  these 
  conditions 
  ; 
  and 
  the 
  time 
  of 
  stand- 
  

   ing 
  appears 
  to 
  be 
  without 
  effect. 
  

  

  The 
  results 
  recorded 
  in 
  section 
  C 
  were 
  obtained 
  by 
  precipi- 
  

   tating 
  the 
  warm 
  solution 
  of 
  the 
  zinc 
  in 
  presence 
  of 
  large 
  

   amounts 
  of 
  ammonium 
  chloride 
  by 
  adding 
  microcosmic 
  salt 
  

   until 
  the 
  solution 
  was 
  alkaline 
  to 
  litmus. 
  From 
  these 
  results 
  

   it 
  seems 
  that 
  the 
  presence 
  of 
  ammonium 
  chloride 
  is 
  essential 
  

   for 
  the 
  conversion 
  of 
  the 
  zinc 
  phosphate 
  precipitated 
  by 
  

   hydrogen 
  sodium 
  ammonium 
  phosphate 
  to 
  the 
  ammonium 
  zinc 
  

   salt. 
  As 
  a 
  matter 
  of 
  fact 
  the 
  solutions 
  employed 
  by 
  Guyard 
  

   and 
  those 
  in 
  which 
  estimations 
  are 
  made 
  by 
  practical 
  workers 
  

   do 
  contain 
  ammonium 
  chloride 
  formed 
  in 
  previous 
  steps 
  of 
  the 
  

   analysis. 
  The 
  proportion 
  of 
  zinc 
  to 
  phosphate 
  suggested 
  by 
  

   Garrigues 
  — 
  1 
  : 
  5 
  — 
  is 
  the 
  amount 
  of 
  soluble 
  phosphate 
  neces- 
  

   sary 
  to 
  turn 
  red 
  litmus 
  blue 
  after 
  the 
  zinc 
  is 
  precipitated. 
  In 
  

   order 
  to 
  find 
  out 
  whether 
  the 
  presence 
  of 
  so 
  large 
  an 
  amount 
  

   of 
  the 
  soluble 
  phosphate 
  is 
  necessary 
  in 
  presence 
  of 
  ammonium 
  

   chloride, 
  the 
  solution 
  of 
  zinc 
  sulphate 
  was 
  precipitated 
  in 
  

   presence 
  of 
  the 
  necessary 
  amount 
  of 
  ammonium 
  chloride 
  by 
  

   the 
  microcosmic 
  salt, 
  in 
  small 
  excess 
  above 
  the 
  equivalent 
  of 
  

  

  