﻿26 
  

  

  W. 
  P. 
  White 
  — 
  Silicate 
  Specific 
  Heats. 
  

  

  pected, 
  though 
  not 
  very 
  positively, 
  the 
  evidence 
  of 
  the 
  

   forms 
  of 
  silica 
  that 
  the 
  theoretical 
  value 
  of 
  A 
  v 
  is 
  

   exceeded 
  at 
  high 
  temperatures. 
  Microcline 
  is 
  at 
  most 
  

   temperatures 
  very 
  close 
  to 
  albite; 
  its 
  differing 
  values 
  

   from 
  800° 
  to 
  1000° 
  are 
  the 
  direct 
  result 
  of 
  its 
  unsatisfac- 
  

   tory 
  value 
  at 
  1100° 
  and 
  that 
  of 
  albite 
  at 
  700°, 
  shown 
  in 
  

   Table 
  X. 
  The 
  difference 
  at 
  the 
  lower 
  temperatures 
  

   between 
  albite 
  and 
  microcline 
  and 
  the 
  other 
  silicates 
  

   seems 
  to 
  offer 
  an 
  opportunity 
  for 
  further 
  investigation. 
  

   The 
  high 
  values 
  of 
  pseudo-wollastonite 
  and 
  especially 
  

   of 
  anorthite 
  above 
  1000° 
  are 
  very 
  likely 
  due 
  to 
  latent 
  

   heat 
  from 
  a 
  slight 
  melting, 
  caused 
  by 
  a 
  very 
  slight 
  

   amount 
  of 
  impurity. 
  Such 
  effects 
  have 
  been 
  regularly 
  

   observed 
  in 
  connection 
  with 
  melting 
  point 
  determinations 
  

   on 
  silicates. 
  It 
  is 
  very 
  unlikely, 
  though, 
  that 
  such 
  an 
  

   effect 
  was 
  present 
  in 
  silica 
  itself, 
  or 
  in 
  albite 
  or 
  micro- 
  

   cline, 
  since 
  these 
  substances 
  crystallize 
  with 
  extreme 
  dif- 
  

   ficulty, 
  hence 
  whatever 
  portion 
  of 
  them 
  might 
  be 
  melted 
  

   (or 
  amorphous) 
  at 
  high 
  temperatures 
  would 
  cool 
  to 
  a 
  

   glass 
  in 
  the 
  calorimeter, 
  giving 
  out 
  no 
  latent 
  heat. 
  

   Indeed, 
  since 
  the 
  effect 
  of 
  impurities 
  on 
  melting 
  often 
  

   increases 
  as 
  the 
  square 
  of 
  the 
  temperature, 
  such 
  sub- 
  

   stances 
  are 
  peculiarly 
  adapted 
  to 
  the 
  investigation 
  of 
  the 
  

   problem 
  treated 
  in 
  this 
  section, 
  and 
  to 
  some 
  others. 
  

  

  Table 
  VIII. 
  

  

  Differences 
  Between 
  Vitreous 
  and 
  Crystalline. 
  

  

  Interval 
  specific 
  heats: 
  Glass 
  minus 
  crystal, 
  given 
  as 
  a 
  fraction 
  of 
  

  

  the 
  heat 
  of 
  the 
  crystal 
  form. 
  

  

  

  Pseudo- 
  

  

  

  Magnesium 
  -silic 
  ate 
  

  

  

  Wollastonite 
  

  

  Diopside 
  

  

  Pyroxene 
  

  

  Amphibole 
  

  

  0°-100° 
  

  

  •005* 
  

  

  •008* 
  

  

  000 
  

  

  •003 
  

  

  0°-300° 
  

  

  •016* 
  

  

  •012* 
  

  

  —003 
  

  

  •002 
  

  

  0°-500° 
  

  

  •017* 
  

  

  •008* 
  

  

  —004 
  

  

  •006 
  

  

  0°-700° 
  

  

  •043 
  

  

  •008 
  

  

  

  •009 
  

  

  

  Anorthite 
  

  

  Andesine 
  

  

  Albite 
  

  

  Microcline 
  

  

  0°-100° 
  

  

  —009 
  

  

  •004 
  

  

  (•015) 
  

  

  •026* 
  

  

  0°-300° 
  

  

  •004* 
  

  

  

  (•016) 
  

  

  •026 
  

  

  0°-500° 
  

  

  •003* 
  

  

  

  (•020) 
  

  

  •026 
  

  

  0°-700° 
  

  

  •002 
  

  

  •018 
  

  

  

  •025 
  

  

  0°-900° 
  

  

  

  •035 
  

  

  •031 
  

  

  •026 
  

  

  0°-1100° 
  

  

  

  

  

  •035 
  

  

  Preliminary 
  determination. 
  

  

  