﻿568 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  Without 
  giving 
  tlie 
  compositioii 
  of 
  the 
  clays 
  whicli 
  Seger 
  ex- 
  

   perimented 
  on, 
  in 
  this 
  connection 
  it 
  may 
  be 
  interesting 
  to 
  give 
  some 
  

   of 
  his 
  conclusions. 
  

  

  The 
  first 
  group 
  includes 
  the 
  porcelain 
  clays, 
  and 
  in 
  these 
  the 
  

   ferric 
  oxid 
  may 
  at 
  times 
  exceed 
  1^ 
  without, 
  influencing 
  the 
  color. 
  

   In 
  this 
  connection 
  it 
  is 
  considered 
  that 
  the 
  presence 
  of 
  a 
  large 
  

   amount 
  of 
  alumina 
  has 
  the 
  same 
  effect 
  as 
  lime, 
  in 
  destroying 
  the 
  

   red 
  color 
  of 
  the 
  iron. 
  Evidence 
  of 
  this 
  fact 
  is 
  afforded 
  by 
  Seger's 
  

   experiments 
  on 
  clays 
  included 
  in 
  the 
  second 
  group'. 
  

  

  In 
  the 
  second 
  group 
  are 
  included 
  clays 
  which 
  burn 
  white 
  at 
  low 
  

   temperatures, 
  with 
  an 
  occasional 
  pink 
  tint, 
  but 
  at 
  higher 
  tempera- 
  

   tures 
  show 
  more 
  or 
  less 
  yellowish 
  or 
  brownish 
  color, 
  but 
  never 
  a 
  red, 
  

   assuming 
  a 
  greenish 
  color 
  at 
  the 
  highest 
  temperatures 
  due 
  to 
  the 
  

   reduction 
  of 
  the 
  iron 
  to 
  a 
  ferrous 
  condition. 
  The 
  alumina 
  in 
  clays 
  

   of 
  this 
  group 
  is 
  generally 
  20^-30^ 
  and 
  even 
  more, 
  while 
  the 
  per- 
  

   centage 
  of 
  ferric 
  oxid 
  may 
  in 
  some 
  cases 
  approach 
  that 
  of 
  the 
  brick 
  

   clays, 
  but 
  it 
  generally 
  ranges 
  between 
  1^ 
  and 
  5fo. 
  It 
  is 
  an 
  interesting 
  

   fact 
  that 
  a 
  mixture 
  of 
  red 
  burning 
  clays 
  of 
  the 
  third 
  group 
  and 
  

   kaolin 
  does 
  not 
  give 
  a 
  pale 
  red 
  product 
  on 
  burning, 
  but 
  instead 
  a 
  

   yellow 
  one, 
  which 
  Seger 
  believes 
  is 
  due 
  to 
  the 
  excess 
  of 
  alumina. 
  

  

  This 
  group 
  includes 
  many 
  fire 
  clays, 
  semi-fire 
  clays, 
  stoneware 
  

   clays. 
  Five 
  exa.mples 
  are 
  given 
  by 
  Seger 
  to 
  illustrate 
  this 
  effect 
  of 
  

   the 
  alumina 
  in 
  destroying 
  the 
  red 
  color 
  of 
  the 
  ferric 
  oxid. 
  Their 
  

   color 
  when 
  burned, 
  as 
  well 
  as 
  the 
  ratio 
  of 
  ferric 
  oxid 
  to 
  alumina, 
  is 
  

   given 
  below. 
  

  

  rinlnr 
  whpn 
  hiirnpd 
  White 
  to 
  Liprht 
  Yellow 
  to 
  Yellow 
  Yellow 
  

  

  . 
  L^oior 
  wnen 
  DUrnea 
  yei. 
  white 
  yellow 
  light 
  brown 
  brown 
  J^eiiow 
  

  

  Ratio 
  of 
  ferric 
  

  

  oxid 
  to 
  alumina 
  1:13.2 
  1:7 
  1:6.4 
  1:7.2 
  1:^.3 
  

  

  The 
  exact 
  temperature 
  at 
  which 
  these 
  were 
  burned 
  is 
  not 
  stated 
  

   but 
  it 
  was 
  the 
  same 
  in 
  each 
  case. 
  

  

  This 
  group 
  somewhat 
  resembles 
  the 
  fourth 
  group 
  in 
  respect 
  to 
  the 
  

   colors 
  produced, 
  but 
  differs 
  from 
  it 
  in, 
  fusibility, 
  becoming 
  porce- 
  

   lain-like 
  at 
  high 
  temperatures, 
  and 
  not 
  green, 
  but 
  brown 
  or 
  gTay 
  in 
  

   color. 
  The 
  percentage 
  of 
  alumina, 
  it 
  will 
  be 
  seen, 
  far 
  exceeds 
  the 
  

   iron. 
  The 
  color 
  seems 
  to 
  be 
  lighter 
  the 
  greater 
  this 
  excess. 
  

  

  