﻿682 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  to 
  moisture. 
  This 
  is 
  generally 
  due 
  to 
  the 
  formation 
  of 
  salts 
  during- 
  

   burning, 
  and 
  they 
  are 
  specially 
  annoying 
  on 
  account 
  of 
  their 
  tardy 
  

   appearance. 
  The 
  salts 
  formed 
  during 
  drying 
  do 
  not 
  necessarily 
  

   arise 
  simply 
  from 
  the 
  combination 
  of 
  sulfur 
  in 
  the 
  fire 
  gases 
  with 
  

   bases 
  in 
  the 
  clay, 
  but 
  may 
  also 
  be 
  due 
  to 
  iron 
  pyrite 
  which, 
  during 
  

   burning, 
  aids 
  in 
  the 
  formation 
  of 
  white 
  washing 
  sulfates 
  in 
  the 
  in- 
  

   terior 
  of 
  the 
  bricks. 
  The 
  formation 
  of 
  white 
  washing 
  sulfates 
  dur- 
  

   ing 
  burning 
  is 
  described 
  by 
  Gerlach 
  as 
  follows: 
  ^^A 
  part 
  of 
  the 
  

   sulfur 
  in 
  the 
  iron 
  pyrite 
  is 
  loosely 
  combined 
  with 
  the 
  iron, 
  and 
  

   oxidation 
  of 
  tthis 
  part 
  begins 
  at 
  approximately 
  650° 
  F., 
  whereas 
  

   the 
  other 
  parts 
  bum 
  at 
  ordinary 
  heat. 
  The 
  products 
  of 
  disintegra- 
  

   tion 
  are 
  oxid 
  of 
  iron, 
  and 
  sulfurous 
  acid 
  gas. 
  This 
  chemical 
  re- 
  

   action 
  is 
  expressed 
  as 
  follows: 
  1) 
  FeSg 
  -f- 
  '^02= 
  FeS 
  + 
  SO2, 
  and 
  

   ii) 
  iiFeS+TO^FcgOs 
  2SO2. 
  The 
  sulfurous 
  acid 
  gas 
  SO2 
  when 
  

   heated 
  in 
  contact 
  with 
  solid 
  porous 
  bodies 
  is 
  oxidized 
  by 
  the 
  super- 
  

   fluous 
  oxygen 
  of 
  the 
  air 
  of 
  combustion 
  to 
  sulfuric 
  acid, 
  or 
  converts 
  

   existing 
  oxids 
  into 
  sulfuric 
  salts. 
  It 
  was 
  for 
  a 
  long 
  time 
  erroneously 
  

   believed 
  that 
  the 
  presence 
  of 
  water 
  or 
  watery 
  vapor 
  was 
  necessary 
  

   for 
  the 
  formation 
  of 
  sulfates." 
  Gerlach's 
  conclusion 
  is 
  that 
  it 
  fol- 
  

   lows 
  that 
  white 
  washing 
  sulfates 
  are 
  formed 
  in 
  large 
  quantities 
  only 
  

   when 
  sulfurous 
  acids 
  and 
  carbonate 
  of 
  lime 
  or 
  other 
  carbonates 
  

   occur 
  together 
  in 
  chemical 
  action. 
  Sulfurous 
  acid 
  has 
  no 
  injurious- 
  

   effect 
  on 
  clay 
  containing 
  no 
  carbonates 
  of 
  lime, 
  magnesia, 
  or 
  alka- 
  

   lis; 
  such 
  clays 
  accordingly 
  can 
  be 
  burned 
  with 
  sulfurous 
  coal 
  with- 
  

   out 
  any 
  fear 
  of 
  white 
  washing 
  sulfates, 
  while 
  clay 
  containing; 
  

   carbonate 
  of 
  lime 
  requires 
  a 
  fuel 
  free 
  from 
  sulfur. 
  

  

  Gerlach 
  sums 
  up 
  the 
  causes 
  of 
  efflorescences 
  as 
  follows. 
  

  

  White 
  efflorescence 
  

  

  Source 
  1 
  The 
  green 
  clay 
  

  

  a 
  Caused 
  by 
  the 
  presence 
  of 
  sulfates 
  in 
  the 
  clay 
  

   h 
  Caused 
  by 
  the 
  formation 
  of 
  sulfates 
  during 
  the 
  storage 
  of 
  the 
  

   clay 
  

  

  