﻿CLAYS 
  OF 
  ^s'EW 
  YOEK 
  

  

  5G7 
  

  

  The 
  physical 
  condition 
  of 
  the 
  iron 
  in 
  the 
  claj 
  may 
  also 
  exert 
  a 
  

   marked 
  influence. 
  If 
  the 
  iron 
  be 
  distributed 
  evenly 
  through 
  the 
  

   clay 
  in 
  a 
  finely 
  divided 
  condition 
  or 
  as 
  a 
  film 
  around 
  the 
  clay 
  gi-ains, 
  

   the 
  coloration 
  produced 
  will 
  be 
  more 
  even 
  than 
  if 
  it 
  were 
  scattered 
  

   through 
  the 
  clay 
  as 
  isolated 
  grains. 
  The 
  percentage 
  of 
  iron 
  oxid 
  

   shown 
  by 
  analysis 
  might 
  in 
  either 
  case 
  be 
  the 
  same, 
  but 
  the 
  effect 
  

   produced 
  in 
  burning 
  would 
  be 
  an 
  even 
  color 
  in 
  the 
  former 
  case, 
  and 
  

   a 
  speckled 
  appearance 
  in 
  the 
  latter. 
  

  

  Ferrous 
  oxid 
  may 
  form 
  in 
  burning, 
  under 
  several 
  conditions; 
  it 
  

   may 
  be 
  due 
  to 
  the 
  presence 
  of 
  organic 
  matter, 
  or 
  to 
  reducing 
  action 
  

   of 
  the 
  fire, 
  or 
  it 
  may 
  have 
  existed 
  in 
  the 
  unbumed 
  clay. 
  It 
  is 
  not 
  

   as 
  strong 
  a 
  coloring 
  agent 
  as 
  the 
  ferric 
  oxid. 
  Alone 
  it 
  produces 
  a 
  

   green 
  color 
  in 
  burning, 
  but 
  variable 
  mixtures 
  of 
  ferrous 
  and 
  ferric 
  

   oxids 
  are 
  capable 
  of 
  producing 
  a 
  variety 
  of 
  shades. 
  (See 
  ^' 
  Division 
  

   on 
  iron 
  ") 
  

  

  Manganese 
  oxid 
  in 
  general 
  produces 
  darker 
  colors 
  than 
  iron. 
  

  

  Other 
  . 
  coloring 
  substances 
  might 
  be 
  present 
  in 
  clays 
  in 
  small 
  

   amounts. 
  Cobalt 
  oxid 
  might 
  produce 
  a 
  blue 
  color, 
  and 
  chromium 
  

   a 
  green 
  color. 
  

  

  Both 
  cobalt 
  and 
  chromium 
  are 
  sometimes 
  added 
  to 
  white 
  or 
  light 
  

   burning 
  clays 
  to 
  color 
  them 
  artificially, 
  6^ 
  of 
  the 
  former 
  producing 
  a 
  

   bright 
  blue, 
  and 
  ^^-1^ 
  of 
  the 
  latter 
  giving 
  a 
  green. 
  A 
  black 
  color 
  

   can 
  be 
  produced 
  by 
  adding 
  a 
  mixture 
  of 
  6^ 
  iron 
  oxid, 
  and 
  6^ 
  manga- 
  

   nese 
  superoxid. 
  

  

  Seger 
  ^ 
  classifies 
  clays 
  according 
  to 
  the 
  color 
  assumed 
  in 
  burning 
  

   as 
  follows 
  : 
  

  

  1 
  Aluminous 
  clays, 
  poor 
  in 
  iron, 
  which 
  bum 
  white 
  or 
  very 
  

   slightly 
  yellowish 
  

  

  2 
  Aluminous, 
  moderately 
  ferruginous 
  clays, 
  whose 
  color 
  when 
  

   burned 
  is 
  pale 
  yellow 
  to 
  light 
  brown 
  

  

  3 
  Aluminous, 
  ferruginous 
  clays, 
  such 
  as 
  brick 
  clays, 
  whose 
  color 
  

   when 
  burned 
  is 
  brick 
  red 
  . 
  

  

  4 
  Nonaluminous 
  clays, 
  rich 
  in 
  iron 
  and 
  lime, 
  whose 
  color 
  when 
  

   burned 
  is 
  yellow 
  

  

  1 
  Seger. 
  Ges. 
  Schrift. 
  p. 
  85. 
  

  

  