﻿CLAYS 
  OF 
  ]S^EW 
  YOEK 
  511 
  

  

  Chemical 
  properties 
  

  

  The 
  cliemical 
  composition, 
  and 
  indirectly 
  tlierefore 
  the 
  minera- 
  

   logic 
  composition, 
  may 
  influence 
  the 
  fusibility 
  of 
  a 
  clay, 
  its 
  color 
  

   in 
  burning, 
  shrinkage, 
  and 
  perhaps 
  plasticity. 
  

  

  The 
  compounds 
  which 
  may 
  be 
  found 
  in 
  clay 
  are 
  silica, 
  alumina, 
  

   iron 
  oxid, 
  lime, 
  magnesia, 
  potash, 
  soda, 
  titanic 
  acid, 
  sulfuric 
  acid, 
  

   manganese 
  oxid, 
  phosphoric 
  acid 
  and 
  organic 
  matter. 
  Compounds 
  

   of 
  chromium-^ 
  and 
  vanadium^ 
  may 
  also 
  be 
  present 
  in 
  small 
  amounts, 
  

   and 
  even 
  lithium 
  (N. 
  W. 
  Lord. 
  J. 
  A. 
  I. 
  M. 
  E. 
  12:505) 
  and 
  

   cerium, 
  yttrium 
  and 
  beryllium 
  oxids 
  {Jour. 
  pr. 
  chem. 
  33: 
  132) 
  

   have 
  been 
  recorded. 
  Phosphoric 
  acid 
  is 
  also 
  known.^ 
  'Not 
  

   all 
  of 
  these 
  are 
  present 
  in 
  every 
  clay, 
  but 
  most 
  of 
  them 
  are. 
  

   Pure 
  clay 
  would 
  contain 
  silica, 
  alumina 
  and 
  combined 
  water. 
  The 
  

   purest 
  clays 
  known 
  contain 
  traces 
  of 
  iron 
  oxid, 
  lime 
  and 
  alkalies. 
  

  

  All 
  of 
  the 
  constituents 
  of 
  clay 
  except 
  alumina, 
  organic 
  matter, 
  

   and 
  water, 
  may 
  exert 
  a 
  fluxing 
  action 
  on 
  the 
  clay 
  when 
  burned, 
  

   the 
  intensity 
  of 
  this 
  action 
  depending 
  on 
  the 
  amount 
  of 
  fluxing 
  

   material 
  and 
  the 
  temperature. 
  Consequently 
  the 
  impurities 
  of 
  

   clay 
  are 
  often 
  divided 
  into 
  fluxing 
  and 
  non-fluxing. 
  

  

  Fluxing 
  impurities 
  

  

  Pure 
  clay, 
  theoretically 
  composed 
  altogether 
  of 
  the 
  mineral 
  

   kaolinite, 
  is 
  very 
  refractory. 
  This 
  mineral 
  contains 
  two 
  molecules 
  

   of 
  silica 
  and 
  one 
  molecule 
  of 
  alumina. 
  A 
  higher 
  percentage 
  of 
  

   silica 
  tends, 
  up 
  to 
  a 
  certain 
  point, 
  to 
  increase 
  the 
  fusibility 
  provided 
  

   it 
  is 
  in 
  a 
  finely 
  divided 
  condition. 
  If 
  the 
  silica 
  percentage 
  how- 
  

   ever 
  gets 
  above 
  a 
  certain 
  point, 
  the 
  refractoriness 
  of 
  the 
  clay 
  in- 
  

   creases 
  with 
  the 
  increase 
  in 
  silica 
  up 
  to 
  the 
  point 
  at 
  which 
  the 
  

   mass 
  contains 
  nothing 
  but 
  silica. 
  This 
  has 
  been 
  demonstrated 
  

   by 
  the 
  experiments 
  of 
  Seger. 
  {Tlionindustrie 
  zeitung, 
  1893. 
  

   no. 
  17) 
  

  

  Other 
  substances 
  act 
  as 
  far 
  more 
  powerful 
  fluxes 
  than 
  the 
  silica, 
  

   and 
  these 
  fluxes 
  include 
  not 
  only 
  elements 
  but 
  also 
  definite 
  chemical 
  

  

  ' 
  Some 
  Brazilian 
  clays. 
  

  

  3 
  See 
  p. 
  509. 
  

  

  3 
  Some 
  pleistocene 
  clays 
  near 
  Baltimore, 
  Md., 
  contain 
  much 
  vivianite. 
  

  

  