﻿856 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  9 
  Corundiini 
  

   10 
  Diamond 
  

  

  If 
  the 
  hardness 
  of 
  the 
  brick 
  is 
  such 
  that 
  it 
  can 
  be 
  scratched 
  by 
  

   quartz 
  but 
  not 
  by 
  orthoclasCj 
  its 
  hardness 
  is 
  no. 
  7 
  of 
  the 
  scale. 
  

   Vitrified 
  products 
  should 
  show 
  a 
  hardness 
  of 
  6-7. 
  

  

  Determination 
  of 
  deleterious 
  impurities 
  

  

  The 
  stone 
  or 
  brick 
  is 
  to 
  be 
  subjected 
  to 
  a 
  damp 
  atmosphere 
  for 
  

   a 
  period 
  of 
  time. 
  If 
  it 
  contains 
  any 
  lumps 
  of 
  carbonate 
  of 
  lime 
  

   or 
  pieces 
  of 
  pyrite, 
  these 
  will 
  soon 
  show 
  themselves 
  by 
  causing 
  

   the 
  brick 
  to 
  flake 
  off. 
  The 
  moist 
  atmosphere 
  can 
  be 
  produced 
  by 
  

   placing 
  the 
  brick 
  under 
  a 
  bell 
  glass 
  containing 
  a 
  bowl 
  of 
  water. 
  

   The 
  method 
  suggested 
  by 
  an 
  international 
  committee 
  appointed 
  

   to 
  decide 
  on 
  a 
  standard 
  test, 
  was 
  that 
  a 
  portion 
  of 
  the 
  brick 
  should 
  

   be 
  put 
  in 
  a 
  Papin 
  digester 
  containing 
  vapor 
  under 
  one 
  fourth 
  

   atmospheric 
  pressure 
  for 
  three 
  hours. 
  

  

  It 
  is 
  advisable 
  in 
  all 
  cases 
  to 
  subject 
  the 
  raw 
  material 
  to 
  an 
  

   examination 
  to 
  see 
  if 
  any 
  harmful 
  impurities 
  are 
  present. 
  

  

  Determination 
  of 
  soluble 
  salts 
  

  

  These 
  are 
  determined 
  by 
  breaking 
  off 
  chips 
  of 
  the 
  brick 
  and 
  

   grinding 
  these 
  to 
  100 
  mesh 
  fineness. 
  25 
  grams 
  of 
  this 
  powder 
  

   are 
  boiled 
  for 
  one 
  hour 
  in 
  250 
  cc 
  of 
  water. 
  The 
  water 
  is 
  then 
  

   filtered, 
  and 
  from 
  this 
  filtrate 
  by 
  evaporation 
  the 
  amount 
  of 
  dis- 
  

   solved 
  salts 
  is 
  determined. 
  Salts 
  of 
  vanadium 
  show 
  themselves 
  

   by 
  the 
  presence 
  of 
  a 
  green 
  tint 
  on 
  the 
  surface 
  of 
  the 
  wet 
  brick 
  

   after 
  it 
  has 
  been 
  set 
  aside 
  in 
  a 
  place 
  protected 
  from 
  dust. 
  

  

  Resistance 
  to 
  weathering 
  

  

  One 
  method 
  of 
  testing 
  this 
  is 
  to 
  subject 
  the 
  bricks, 
  which 
  have 
  

   been 
  immersed 
  in 
  water, 
  to 
  a 
  freezing 
  temperature, 
  which 
  can 
  

   be 
  easily 
  done 
  by 
  covering 
  them 
  with 
  a 
  mixture 
  of 
  ice 
  and 
  

   salt. 
  The 
  frozen 
  bricks 
  are 
  then 
  subjected 
  to 
  water 
  having 
  ^a 
  

   temperature 
  of 
  20° 
  C. 
  This 
  process 
  of 
  freezing 
  and 
  thawing 
  is 
  

   repeated 
  20 
  or 
  25 
  times. 
  The 
  particles 
  which 
  break 
  off 
  in 
  the 
  

  

  