﻿604 
  Gooeh, 
  etc. 
  — 
  Dehydration 
  and 
  Recovery 
  of 
  Silica. 
  

  

  amount 
  of 
  silica 
  recovered 
  in 
  the 
  second 
  treatment. 
  In 
  the 
  

   experiments 
  in 
  which 
  acetic 
  anhydride 
  (B.P. 
  137°) 
  was 
  used 
  to 
  

   moisten 
  the 
  residue 
  (after 
  thorough 
  desiccation 
  on 
  the 
  steam 
  

   bath) 
  and 
  then 
  partially 
  removed 
  by 
  boiling, 
  the 
  average 
  

   deficiency 
  in 
  silica 
  after 
  the 
  first 
  treatment 
  amounted 
  to 
  0*0061 
  

   grm., 
  and 
  the 
  amount 
  recovered 
  in 
  the 
  second 
  treatment 
  to 
  

   0*0051 
  grm. 
  Obviously, 
  the 
  insolubility 
  of 
  the 
  silica, 
  after 
  the 
  

   process 
  of 
  desiccation, 
  extraction, 
  and 
  filtration 
  depends 
  very 
  

   largely 
  upon 
  the 
  thoroughness 
  of 
  the 
  drying 
  ; 
  and, 
  while 
  the 
  

   drying 
  at 
  110° 
  or 
  at 
  137° 
  (in 
  acetic 
  anhydride) 
  greatly 
  dimin- 
  

   ishes 
  the 
  solubility 
  of 
  the 
  silica 
  as 
  compared 
  with 
  that 
  of 
  the 
  

   substance 
  when 
  simply 
  dried 
  on 
  the 
  steam 
  bath, 
  the 
  treatment 
  

   with 
  acetic 
  anhydride 
  offers 
  no 
  advantage 
  over 
  the 
  process 
  of 
  

   drying 
  in 
  the 
  air 
  bath 
  at 
  110°, 
  at 
  least, 
  when 
  the 
  contami- 
  

   nating 
  substance 
  is 
  sodium 
  chloride. 
  

  

  The 
  slight 
  variations 
  in 
  the 
  weights 
  obtained 
  when 
  residues 
  

   which 
  had 
  been 
  ignited 
  with 
  the 
  Bunsen 
  burner 
  were 
  submit- 
  

   ted 
  to 
  the 
  temperature 
  of 
  the 
  blast 
  lamp 
  appear 
  to 
  be 
  due 
  to 
  the 
  

   presence 
  of 
  sodium 
  chloride 
  which 
  by 
  strong 
  ignition 
  is 
  either 
  

   transformed 
  to 
  sodium 
  silicate 
  or 
  is 
  partially 
  volatilized. 
  

  

  