﻿526 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  The 
  effects 
  of 
  free 
  silica 
  proper, 
  or 
  quartz, 
  and 
  sand 
  on 
  the 
  

   behavior 
  of 
  the 
  clay 
  are 
  to 
  be 
  considered 
  separately. 
  

  

  Quartz 
  serves 
  as 
  a 
  flux 
  only 
  at 
  high 
  temperatures, 
  viz, 
  2800° 
  F. 
  ; 
  

   but 
  at 
  lower 
  temperatures 
  it 
  tends 
  to 
  increase 
  the 
  refractoriness 
  of 
  

   the 
  clay, 
  and 
  this 
  property 
  is 
  governed 
  somewhat 
  by 
  th© 
  size 
  of 
  the 
  

   quartz 
  grains 
  and 
  amount 
  of 
  fluxing 
  material 
  present, 
  which 
  will 
  

   fuse 
  at 
  lower 
  temperatures. 
  

  

  In 
  connection 
  with 
  the 
  fluxing 
  action 
  of 
  silica 
  at. 
  high 
  tem- 
  

   peratures, 
  the 
  following 
  experiments 
  of 
  iBischof's^ 
  may 
  be 
  quoted. 
  

   Mixtures 
  of 
  alumina 
  and 
  silica 
  were 
  made 
  in 
  varying 
  proportions, 
  

   and 
  their 
  fusibility 
  determined. 
  The 
  fusion 
  point 
  of 
  alumina 
  alone 
  

   lies 
  above 
  cone 
  36, 
  while 
  the 
  fusion 
  point 
  of 
  silica 
  alone 
  is 
  at 
  cone 
  

   35. 
  Bischof 
  found 
  that 
  a 
  mixture 
  of 
  one 
  equivalent 
  of 
  alumina 
  and 
  

   two 
  of 
  silica 
  showed 
  the 
  greatest 
  refractoriness. 
  If 
  the 
  percentage 
  

   of 
  silica 
  increases, 
  the 
  fusibility 
  is 
  gradually 
  lowered, 
  till 
  the 
  mixture 
  

   of 
  one 
  alumina 
  to 
  17 
  silica 
  is 
  reached, 
  the 
  fusibility 
  of 
  which 
  is 
  the 
  

   same 
  as 
  cone 
  30. 
  "With 
  an 
  increase 
  of 
  the 
  silica, 
  the 
  refractoriness 
  

   of 
  the 
  mixture 
  again 
  increases 
  up 
  to 
  the 
  fusion 
  point 
  of 
  silica 
  alone. 
  

  

  Titanium 
  

  

  Titanium 
  is 
  probably 
  of 
  more 
  widespread 
  occurrence 
  in 
  clay 
  

   than 
  is 
  commonly 
  imagined. 
  The 
  apparent 
  freedom 
  of 
  the 
  

   clay 
  from 
  this 
  impurity 
  has 
  resulted 
  from 
  the 
  fact 
  that 
  in 
  

   the 
  usual 
  quantitative 
  analysis 
  it 
  is 
  ordinarily 
  overlooked. 
  Its 
  

   source 
  i^ 
  either 
  the 
  mineral 
  rutile 
  (oxid 
  of 
  titanium) 
  or 
  il- 
  

   menite 
  (the 
  titanium-bearing 
  magnetic 
  oxid 
  of 
  iron), 
  or 
  pos- 
  

   sibly 
  titanite. 
  Much 
  more 
  importance 
  has 
  at 
  times 
  been 
  at- 
  

   tached 
  to 
  its 
  presence 
  than 
  is 
  really 
  warranted, 
  and 
  some 
  chem- 
  

   ists, 
  on 
  finding 
  traces 
  of 
  it, 
  delight 
  in 
  dwelling 
  on 
  the 
  important 
  

   influence 
  which 
  it 
  may 
  exert 
  on 
  the 
  properties 
  of 
  a 
  clay. 
  While 
  it 
  

   is 
  present 
  in 
  many 
  clays, 
  the 
  percentage 
  seldom 
  exceeds 
  1.5;^ 
  to 
  2^. 
  

   The 
  analyses 
  of 
  21 
  JSTew 
  Jersey 
  clays 
  showed 
  it 
  to 
  range 
  from 
  

   1.06;^ 
  to 
  1.93^. 
  (Report 
  on 
  clays 
  of 
  N. 
  /. 
  1878. 
  p. 
  277) 
  In 
  

  

  1 
  Seger. 
  Oes. 
  Schrift. 
  p. 
  434. 
  

  

  