﻿598 
  Gooch, 
  etc. 
  — 
  Dehydration 
  and 
  Recovery 
  of 
  Silica. 
  

  

  Art. 
  LII. 
  — 
  The 
  Dehydration 
  and 
  Recovery 
  of 
  Silica 
  in 
  

   Analysis 
  ; 
  by 
  F. 
  A. 
  Gooch, 
  F. 
  C. 
  Keckert 
  and 
  S. 
  B. 
  

  

  KlTZIRIAN. 
  

  

  [Contributions 
  from 
  the 
  Kent 
  Chemical 
  Laboratory 
  of 
  Yale 
  University 
  — 
  ccliij 
  

  

  The 
  Dehydration 
  of 
  Silica. 
  

  

  The 
  question 
  as 
  to 
  the 
  temperature 
  which 
  must 
  be 
  applied, 
  

   and 
  of 
  the 
  duration 
  of 
  the 
  ignition 
  necessary 
  to 
  bring 
  silica 
  to 
  

   a 
  constant 
  weight 
  in 
  the 
  analysis 
  of 
  silicates, 
  has 
  been 
  the 
  sub- 
  

   ject 
  of 
  much 
  investigation 
  and 
  discussion. 
  The 
  opinion 
  is 
  

   general* 
  that 
  in 
  order 
  to 
  obtain 
  the 
  correct 
  weight 
  of 
  anhydrous 
  

   silica 
  derived 
  by 
  precipitation 
  in 
  the 
  usual 
  course 
  of 
  analysis, 
  

   and 
  ignition, 
  the 
  temperature 
  employed 
  must 
  be 
  that 
  of 
  the 
  

   blast 
  lamp. 
  Lunge 
  and 
  Milbergf 
  have 
  shown, 
  however, 
  that 
  

   silica 
  obtained 
  by 
  hydrolyzing 
  silicon 
  fluoride 
  sustains 
  after 
  

   ignition 
  in 
  the 
  full 
  flame 
  of 
  a 
  good 
  Bunsen 
  burner 
  no 
  further 
  

   appreciable 
  loss 
  upon 
  application 
  of 
  the 
  blast 
  heat, 
  and 
  these 
  

   results 
  have 
  been 
  confirmed 
  by 
  Lohof 
  qy\ 
  in 
  Lunge's 
  laboratory, 
  

   and 
  by 
  Hillebrand, 
  for 
  silica 
  thus 
  derived 
  from 
  silicon 
  fluoride. 
  

   On 
  the 
  other 
  hand, 
  Hillebrand 
  found 
  in 
  the 
  case 
  of 
  silica 
  

   derived 
  by 
  fusing 
  quartz 
  with 
  sodium 
  carbonate, 
  treating 
  the 
  

   product 
  with 
  hydrochloric 
  acid, 
  and 
  evaporating 
  three 
  times, 
  

   with 
  intermediate 
  extractions 
  and 
  nitrations, 
  that 
  constant 
  

   weights 
  were 
  obtainable 
  only 
  by 
  blasting, 
  and 
  that 
  blasting 
  

   for 
  half 
  an 
  hour 
  (as 
  is 
  generally 
  recommended) 
  is 
  often 
  insuf- 
  

   ficient 
  to 
  secure 
  constancy 
  of 
  weight. 
  Quartz 
  powder 
  was 
  

   used 
  as 
  the 
  source 
  of 
  the 
  silica 
  in 
  Hillebrand's 
  experiments, 
  

   and 
  this 
  was 
  found 
  to 
  be 
  99"88 
  per 
  cent 
  pure, 
  by 
  careful 
  treat- 
  

   ment 
  with 
  sulphuric 
  and 
  hydrofluoric 
  acids. 
  

  

  It 
  has 
  been 
  shown 
  recently 
  in 
  certain 
  experiments 
  by 
  B. 
  H. 
  

   Walker 
  and 
  J. 
  B. 
  Wilson§ 
  that 
  silica 
  precipitated 
  by 
  acid 
  may 
  

   be 
  brought 
  to 
  a 
  constant 
  weight 
  by 
  prolonged 
  ignition 
  over 
  

   the 
  Bunsen 
  burner, 
  thus 
  avoiding 
  the 
  danger 
  of 
  loss 
  which 
  

   may 
  occur 
  when 
  platinum 
  is 
  submitted 
  to 
  prolonged 
  ignition 
  

   with 
  the 
  blast 
  lamp. 
  Three 
  hours 
  is 
  the 
  minimum 
  period 
  

   mentioned 
  as 
  requisite. 
  It 
  is 
  to 
  be 
  noted, 
  however, 
  that 
  in 
  

   these 
  experiments 
  no 
  test 
  was 
  made 
  for 
  impurity 
  in 
  the 
  residue 
  

   after 
  ignition, 
  and 
  that, 
  as 
  will 
  appear 
  from 
  the 
  work 
  to 
  be 
  

   described, 
  the 
  main 
  source 
  of 
  trouble 
  in 
  bringing 
  precipitated 
  

   silica 
  to 
  a 
  constant 
  weight 
  does 
  not 
  lie 
  in 
  the 
  process 
  of 
  dehy- 
  

   dration 
  in 
  ignition, 
  but 
  is 
  due 
  to 
  the 
  presence 
  of 
  an 
  impurity 
  

  

  * 
  Hillebrand, 
  Jour. 
  Amer. 
  Chem. 
  Soc, 
  xxiv, 
  371 
  ; 
  Treadwell, 
  Quant. 
  Anal, 
  

   trans. 
  Hall, 
  3d 
  ed., 
  p. 
  486. 
  

  

  fZeit. 
  angew. 
  Chem., 
  1897, 
  425. 
  

  

  X 
  Cf. 
  Hillebrand, 
  loc. 
  cit. 
  

  

  §U. 
  S. 
  Geol. 
  Survey, 
  Circular 
  No. 
  101, 
  August 
  16, 
  1912. 
  

  

  