﻿CLAYS 
  OF 
  IfEW 
  TOEK 
  533 
  

  

  salts 
  driven 
  out 
  by 
  heat. 
  The 
  residue 
  is 
  dissolved 
  in 
  water, 
  filtered 
  

   into 
  a 
  weighed 
  platinum 
  dish, 
  evaporated, 
  dried 
  and 
  weighed 
  as 
  Ka 
  

   CI 
  + 
  K 
  CI. 
  If 
  the 
  last 
  addition 
  of 
  ammonium 
  carbonate 
  failed 
  to 
  

   produce 
  a 
  precipitate, 
  the 
  transfer 
  to 
  another 
  dish 
  may 
  be 
  dispensed 
  

   with 
  and 
  the 
  ammonia 
  salts 
  driven 
  off 
  at 
  once. 
  

  

  Rational 
  analysis 
  

  

  It 
  is 
  a 
  common 
  custom 
  of 
  the 
  manufacturers 
  of 
  porcelain, 
  white 
  

   earthenware, 
  fire 
  brick, 
  and 
  other 
  refractory 
  goods 
  — 
  in 
  fact 
  of 
  all 
  

   products 
  made 
  from 
  high 
  grades 
  of 
  clay 
  — 
  to 
  use 
  the 
  rational 
  

   analysis 
  as 
  a 
  guide 
  in 
  making 
  up 
  their 
  mixtures 
  and 
  keeping 
  them 
  

   constant. 
  The 
  advantage 
  of 
  this 
  analytical 
  method 
  is 
  that 
  it 
  re- 
  

   solves 
  the 
  clay 
  into 
  its 
  mineral 
  components, 
  and 
  enables 
  us 
  thereby 
  

   to 
  get 
  an 
  insight 
  into 
  the 
  physical 
  character 
  of 
  the 
  material 
  used, 
  

   which 
  is 
  frequently 
  a 
  matter 
  of 
  far 
  gTeater 
  importance 
  than 
  its 
  

   chemical 
  composition. 
  

  

  The 
  ordinaiy 
  quantitative 
  or 
  ultimate 
  chemical 
  analysis 
  regards 
  

   the 
  clay 
  as 
  a 
  mixture 
  of 
  oxids 
  of 
  the 
  elements, 
  though 
  they 
  may 
  be 
  

   present 
  in 
  entirely 
  different 
  combinations, 
  such 
  as 
  silicates, 
  carbon- 
  

   ates 
  or 
  hydrates, 
  sulfates, 
  etc. 
  This 
  condition 
  of 
  combination 
  is 
  

   of 
  importance, 
  for 
  it 
  may 
  make 
  a 
  vast 
  difference 
  whether 
  a 
  material 
  

   is 
  present 
  as 
  a 
  silicate 
  or 
  a 
  carbonate. 
  Silica 
  if 
  present 
  as 
  quartz 
  

   will 
  decrease 
  the 
  shrinkage 
  and 
  up 
  to 
  certain 
  temperatures 
  increase 
  

   the 
  refractoriness, 
  but 
  if 
  present 
  in 
  the 
  clay 
  as 
  a 
  component 
  of 
  feld- 
  

   spar 
  it 
  serves 
  the 
  purpose 
  of 
  a 
  flux 
  and 
  somewhat 
  increases 
  the 
  

   plasticity. 
  ^ 
  

  

  It 
  is 
  not 
  intended, 
  though, 
  that 
  the 
  rational 
  analysis 
  should 
  en- 
  

   tirely 
  supplant 
  the 
  ultimate, 
  for 
  this 
  is 
  not 
  possible, 
  as 
  each 
  serves 
  

   its 
  own 
  purpose. 
  The 
  ultimate 
  analysis 
  may 
  be 
  used 
  to 
  supply 
  in- 
  

   formation 
  on 
  the 
  following 
  points: 
  

  

  1 
  The 
  purity 
  of 
  the 
  clay, 
  showing 
  the 
  proportions 
  of 
  silica, 
  

   alumina, 
  combined 
  water, 
  and 
  fluxing 
  impurities. 
  

  

  2 
  The 
  refractoriness 
  of 
  the 
  clay, 
  for, 
  other 
  things 
  being 
  equal, 
  

   the 
  greater 
  the 
  total 
  sum 
  of 
  fluxing 
  impurities 
  the 
  more 
  fusible 
  the 
  

   clay. 
  

  

  