﻿Vandei 
  .V- 
  ulen 
  — 
  Two 
  So-called 
  Hallox 
  1 
  4-0' 
  

  

  the 
  hydrargillite. 
  leaving 
  the 
  kaolinite 
  unattacked. 
  For 
  this 
  

   purpose, 
  sulphuric 
  acid 
  of 
  tour 
  different 
  concentrations 
  

   employed. 
  These 
  were 
  10, 
  15, 
  20, 
  and 
  25 
  per 
  cent. 
  In 
  i 
  

  

  2 
  j 
  ram 
  of 
  the 
  finely 
  powdered 
  clay 
  w 
  _ 
  I 
  with 
  

  

  of 
  the 
  acid. 
  The 
  temperature 
  was 
  held 
  at 
  .'.." 
  I 
  

  

  and 
  the 
  digestion 
  continued 
  for 
  three 
  hoars 
  with 
  nal 
  

  

  stirring. 
  The 
  solutions 
  lined 
  was 
  filtered. 
  Alumina 
  and 
  

  

  silica 
  were 
  precipitated 
  with 
  ammonium 
  hydroxide 
  from 
  the 
  

   hot 
  solution, 
  collected 
  on 
  a 
  filter, 
  dried, 
  ignited 
  in 
  a 
  platinum 
  

   crucible, 
  and 
  weighed. 
  The 
  contents 
  of 
  the 
  crucible 
  were 
  

   treated 
  with 
  a 
  few 
  drops 
  of 
  sulphuric 
  acid, 
  and 
  fumed 
  down 
  

   with 
  a 
  little 
  hydrofluoric 
  acid, 
  ignited, 
  and 
  again 
  weighed. 
  

   The 
  final 
  residue 
  was 
  considered 
  to 
  be 
  alumina 
  and 
  the 
  loss 
  in 
  

   weight 
  due 
  to 
  the 
  hydrofluoric 
  acid 
  treatment, 
  silica. 
  The 
  

   results 
  of 
  these 
  experiments 
  are 
  given 
  below. 
  

  

  Chattooga 
  clay 
  Alabama 
  clay 
  

  

  Coii 
  c 
  . 
  of 
  acid 
  . 
  %\_ 
  3iOj 
  £ 
  A 
  : 
  . 
  

  

  10$ 
  3-50 
  2'1 
  2'65 
  1*05 
  

  

  15 
  '40 
  2'21 
  8-10 
  1-45 
  

  

  20 
  10-55 
  3 
  20 
  4-5 
  2'2 
  

  

  . 
  25 
  10 
  2-00 
  4-55 
  1*45 
  

  

  Even 
  at 
  the 
  relatively 
  low 
  temperature 
  employed, 
  some 
  

   decomposition 
  of 
  the 
  hydrous 
  aluminium 
  st 
  have 
  

  

  taken 
  place. 
  The 
  results 
  do 
  no* 
  any 
  regularity, 
  and 
  no 
  

  

  specific 
  conclusions 
  can 
  be 
  drawn 
  from 
  them, 
  except 
  perhaps, 
  

   that 
  the 
  use 
  of 
  dilute 
  sulphuric 
  acid 
  for 
  the 
  rational 
  ana"; 
  

   of 
  clays 
  is 
  of 
  doubtful 
  value. 
  

  

  Brown 
  and 
  Montgomery,* 
  and 
  other-, 
  have 
  shown 
  that 
  kao- 
  

   lin 
  when 
  dehydrated 
  loses 
  but 
  Htl 
  ter 
  at 
  300 
  ( 
  .. 
  and 
  1 
  

   most 
  of 
  its 
  chemically 
  combined 
  water 
  between 
  450" 
  and 
  5 
  I 
  

   It 
  appeared 
  interesting 
  to 
  study 
  the 
  dehydration 
  of 
  these 
  c 
  

   in 
  an 
  analogous 
  manner. 
  Approximately 
  0*5 
  graj 
  

   the 
  finely 
  powdered 
  clays 
  were 
  weighed 
  out 
  in 
  platinum 
  crucibles 
  

   and 
  heated 
  side 
  by 
  side. 
  In 
  each 
  case 
  the 
  heating 
  w 
  tinned 
  

   until 
  the 
  lo 
  weight 
  on 
  reheating 
  for 
  fifteen 
  minir 
  .me 
  

  

  - 
  than 
  0*2 
  _ 
  This 
  was 
  found 
  to 
  he 
  the 
  nearest 
  approach 
  

   to 
  equilibrium 
  that 
  could 
  be 
  reached 
  in 
  a 
  rea-onable 
  time. 
  

  

  2 
  C. 
  the 
  crucibles 
  were 
  heated 
  in 
  an 
  air 
  oven, 
  but 
  for 
  

   higher 
  temperatures 
  a 
  small 
  gas-muffle 
  furnace 
  was 
  employed, 
  

   the 
  temperature 
  being 
  measured 
  with 
  a 
  thermo-electric 
  pyr- 
  

   ometer. 
  The 
  probable 
  error 
  in 
  temperature 
  readings 
  ess 
  

   than 
  5° 
  C. 
  Weighings 
  were 
  made 
  at 
  interval- 
  C. 
  

   until 
  all 
  the 
  water 
  had 
  been 
  removed. 
  Curves 
  were 
  plotted 
  

   {fig. 
  1) 
  using 
  per 
  cent 
  of 
  water 
  lost 
  as 
  abscissae, 
  and 
  tempera- 
  

   ture 
  as 
  ordi 
  nates. 
  

  

  *Tr. 
  Am. 
  Cer. 
  Soc 
  x: 
  

  

  