﻿CLAYS 
  OF 
  ]N'£W 
  YOEK 
  535 
  

  

  little 
  of 
  it, 
  and 
  partly 
  because 
  it 
  wa5 
  thought 
  to 
  be 
  like 
  kaolinite 
  in 
  

   its 
  behavior. 
  Where 
  the 
  mica 
  percentage 
  is 
  very 
  low, 
  say 
  1^ 
  or 
  2^ 
  

   and 
  is 
  in 
  a 
  very 
  finely 
  divided 
  condition, 
  it 
  can 
  be 
  neglected, 
  but 
  

   Tvhere 
  it 
  reaches 
  5^ 
  or 
  more 
  it 
  does 
  not 
  seem 
  proper 
  to 
  class 
  it 
  as 
  

   clay 
  substance, 
  for 
  the 
  reason 
  that 
  mica 
  tends 
  to 
  decrease 
  the 
  plas- 
  

   ticity, 
  which 
  effect 
  is 
  greater 
  the 
  coarser 
  the 
  mica. 
  It 
  does 
  resem- 
  

   ble 
  kaolinite 
  in 
  refractoriness. 
  In 
  many 
  of 
  our 
  washed 
  kaolins 
  

   now 
  on 
  the 
  market 
  there 
  is 
  vei'v 
  little 
  mica, 
  but 
  some 
  contain 
  

   8^10^, 
  which 
  does 
  not 
  always 
  yield 
  to 
  sulfuric 
  acid 
  treatment. 
  

  

  If 
  now 
  a 
  kaolin 
  containing 
  clay 
  substance, 
  quartz 
  and 
  feldspar 
  

   be 
  treated 
  first 
  with 
  sulfuric 
  acid, 
  the 
  kaolinite 
  is 
  decomposed 
  into 
  

   sulfate 
  of 
  alumina 
  and 
  hydrous 
  silica. 
  The 
  former 
  is 
  soluble 
  in 
  

   water, 
  the 
  latter 
  is 
  removed 
  by 
  subsequent 
  treatment 
  with 
  caustic 
  

   soda, 
  and 
  we 
  have 
  the 
  insoluble 
  residue 
  consisting 
  of 
  quartz 
  and 
  

   feldspar. 
  In 
  this 
  residue 
  the 
  alumina 
  is 
  determined, 
  and 
  from 
  this 
  

   the 
  amount 
  of 
  feldspar 
  is 
  calculated, 
  viz 
  : 
  

  

  102 
  : 
  556 
  : 
  : 
  a 
  : 
  X 
  

  

  molec. 
  \rt 
  molec. 
  vrt 
  "weight 
  of 
  

   alumina 
  orthoclase 
  alumina 
  

  

  This 
  is 
  subtracted 
  from 
  the 
  insoluble 
  residue, 
  and 
  the 
  differ- 
  

   ence 
  is 
  the 
  quartz. 
  

  

  There 
  is 
  still 
  another 
  way 
  of 
  conducting 
  a 
  rational 
  analysis, 
  

   which 
  is 
  chiefly 
  applicable 
  when 
  the 
  clay 
  contains 
  other 
  minerals 
  

   beside 
  the 
  kaolinite, 
  feldspar 
  and 
  quartz, 
  such 
  as 
  carbonate 
  of 
  

   lime 
  and 
  magnesia, 
  and 
  appreciable 
  amounts 
  of 
  ferric 
  oxid 
  and 
  

   such 
  mica 
  as 
  is 
  attacked 
  by 
  sulfuric 
  acid. 
  This 
  second 
  method 
  is 
  

   Seger's 
  method 
  as 
  elaborated 
  by 
  Langenbeck, 
  and 
  may 
  be 
  illus- 
  

   trated 
  by 
  the 
  following 
  example, 
  a 
  fire 
  clay 
  from 
  Ohio. 
  

  

  