﻿GoocK 
  etc. 
  — 
  Dehydration 
  and 
  Recovery 
  of 
  Silica. 
  599 
  

  

  which 
  must 
  either 
  be 
  volatilized 
  or 
  made 
  to 
  enter 
  into 
  stable 
  

   chemical 
  relation 
  with 
  the 
  silica. 
  From 
  the 
  results 
  of 
  certain 
  

   experiments 
  to 
  be 
  detailed 
  it 
  will 
  appear 
  that, 
  while 
  prolonged 
  

   ignition 
  with 
  the 
  Bunsen 
  burner 
  or 
  with 
  the 
  blast 
  lamp 
  may 
  

   sometimes 
  be 
  necessary 
  to 
  secure 
  constant 
  weights 
  of 
  silica 
  

   separated 
  from 
  an 
  alkali 
  silicate 
  by 
  the 
  action 
  of 
  hydrochloric 
  

   acid, 
  when 
  the 
  difficulty 
  of 
  securing 
  constant 
  weights 
  appears 
  

   it 
  is 
  to 
  be 
  attributed 
  to 
  the 
  inclusion 
  of 
  foreign 
  material 
  more 
  

   or 
  less 
  volatile 
  and 
  changeable 
  at 
  high 
  heat, 
  and 
  not 
  to 
  the 
  

   obstinate 
  retention 
  of 
  water 
  by 
  the 
  silica. 
  

  

  The 
  original 
  material 
  taken 
  for 
  our 
  experiments 
  was 
  a 
  com- 
  

   mercial 
  "analyzed" 
  hydrous 
  silicic 
  acid 
  containing 
  approxi- 
  

   mately 
  from 
  45 
  to 
  50 
  per 
  cent 
  of 
  anhydrous 
  silica 
  according 
  to 
  

   the 
  degree 
  of 
  exposure. 
  When 
  digested 
  with 
  boiling 
  water 
  

   this 
  material 
  yielded 
  traces 
  of 
  a 
  soluble 
  chloride 
  and 
  soluble 
  

   sulphate. 
  After 
  the 
  ignition 
  of 
  portions* 
  of 
  the 
  original 
  sub- 
  

   stance 
  — 
  from 
  0'5 
  grm. 
  to 
  5 
  grms. 
  — 
  for 
  fifteen 
  minutes 
  over 
  a 
  

   large 
  Bunsen 
  burner, 
  traces 
  of 
  chloride 
  or 
  sulphate 
  could 
  be 
  

   still 
  detected 
  in 
  the 
  silica. 
  When 
  similar 
  portions 
  of 
  the 
  

   original 
  substance 
  were 
  ignited 
  over 
  the 
  burner 
  for 
  forty-five 
  

   minutes 
  or 
  over 
  the 
  blast 
  lamp 
  for 
  half 
  an 
  hour 
  neither 
  chlo- 
  

   ride 
  nor 
  sulphate 
  was 
  found 
  in 
  the 
  aqueous 
  extraction 
  of 
  the 
  

   residue, 
  but 
  treatment 
  with 
  sulphuric 
  acid 
  left 
  a 
  residue 
  which 
  

   amounted 
  in 
  the 
  average 
  to 
  0"24 
  per 
  cent 
  of 
  the 
  original 
  sub- 
  

   stance. 
  The 
  barium 
  sulphate 
  preci 
  pi 
  table 
  by 
  barium 
  chloride 
  

   from 
  the 
  solution 
  of 
  this 
  residue 
  proved 
  to 
  be 
  nearly 
  equiva- 
  

   lent 
  to 
  the 
  entire 
  residue 
  counted 
  as 
  sodium 
  sulphate. 
  Inas- 
  

   much 
  as 
  neither 
  chloride 
  nor 
  sulphate 
  could 
  be 
  found 
  in 
  this 
  

   strongly 
  ignited 
  silica, 
  it 
  may 
  be 
  presumed 
  that 
  sodium 
  oxide, 
  

   remaining 
  in 
  combination 
  with 
  the 
  silica, 
  constituted, 
  at 
  least 
  

   after 
  the 
  strong 
  ignition, 
  the 
  impurity 
  which 
  after 
  the 
  treat- 
  

   ment 
  with 
  the 
  acids 
  appeared 
  in 
  the 
  form 
  of 
  sodium 
  sulphate. 
  

   Upon 
  this 
  presumption, 
  the 
  silica 
  used 
  was 
  99*92 
  per 
  cent 
  pure 
  

   after 
  the 
  strong 
  ignition. 
  The 
  record 
  of 
  experiments 
  in 
  which 
  

   portions 
  of 
  the 
  hydrous 
  silica 
  were 
  heated 
  during 
  successive 
  

   half-hour 
  periods, 
  with 
  the 
  Bunsen 
  burner 
  and 
  with 
  the 
  blast 
  

   lamp, 
  is 
  given 
  in 
  the 
  following 
  table. 
  These 
  results 
  show 
  

   plainly 
  that 
  the 
  silica 
  used 
  may 
  be 
  brought 
  to 
  a 
  practically 
  

   constant 
  weight 
  in 
  half-hour 
  ignitions 
  with 
  a 
  good-sized 
  Bunsen 
  

   burner. 
  

  

  The 
  next 
  experiments 
  show 
  the 
  effects 
  of 
  treating 
  similarly 
  

   the 
  product 
  obtained 
  by 
  fusion 
  of 
  the 
  ignited 
  silica 
  with 
  sodium 
  

   carbonate, 
  treatment 
  with 
  hydrochloric 
  acid, 
  evaporation, 
  

   extraction 
  with 
  very 
  dilute 
  hydrochloric 
  acid, 
  and 
  careful 
  

   washing. 
  In 
  series 
  A 
  of 
  these 
  experiments 
  the 
  drying 
  was 
  

   effected 
  at 
  110° 
  in 
  the 
  air 
  bath. 
  In 
  series 
  B 
  the 
  residue 
  

   obtained 
  by 
  evaporation 
  to 
  apparent 
  dryness 
  on 
  the 
  steam 
  bath 
  

  

  