﻿W. 
  P. 
  White 
  — 
  Silicate 
  Specific 
  Heats. 
  41 
  

  

  of 
  inversion, 
  53 
  nevertheless 
  most 
  of 
  the 
  real 
  change 
  occur- 
  

   ring 
  occurs 
  elsewhere. 
  Benedicks 
  54 
  has 
  said 
  that 
  a 
  part 
  

   of 
  the 
  transformation 
  may 
  take 
  place 
  below 
  the 
  transi- 
  

   tion 
  temperature 
  ; 
  which 
  also 
  may 
  be 
  expressed 
  by 
  saying 
  

   that 
  a 
  small 
  quantity 
  of 
  the 
  other 
  form 
  is 
  produced 
  and 
  

   then 
  dissolves 
  in 
  the 
  first. 
  But, 
  he 
  adds, 
  "no 
  real 
  suppo- 
  

   sition 
  is 
  hereby 
  made. 
  ' 
  ' 
  

  

  Dr. 
  R. 
  B. 
  Sosman 
  has 
  called 
  to 
  my 
  attention 
  that 
  a 
  

   specific 
  heat 
  curve 
  shaped 
  like 
  that 
  of 
  quartz 
  below 
  575° 
  

   is 
  found 
  below 
  the 
  A 
  2 
  change 
  of 
  iron. 
  This 
  change 
  in 
  

   iron 
  is 
  also 
  accompanied 
  by 
  an 
  unusual 
  expansion, 
  as 
  in 
  

   quartz. 
  Xow 
  the 
  iron 
  change 
  is 
  known 
  to 
  be 
  connected 
  

   with 
  magnetic 
  phenomena, 
  and 
  the 
  accompanying 
  ther- 
  

   mal 
  phenomena 
  are, 
  consistently 
  with 
  magnetic 
  theory, 
  

   explained 
  as 
  the 
  result 
  of 
  the 
  mechanical 
  work 
  done 
  in 
  

   destroying 
  the 
  magnetic 
  arrangement. 
  55 
  It 
  seems 
  plausi- 
  

   ble 
  that 
  this 
  type 
  of 
  curve 
  is 
  one 
  characterizing 
  the 
  fading 
  

   out 
  of 
  an 
  attractive 
  force. 
  

  

  If 
  the 
  difference 
  in 
  total 
  heat 
  between 
  quartz 
  and 
  silica 
  

   glass 
  from 
  0° 
  to 
  700° 
  is 
  supposed 
  to 
  be 
  due 
  simply 
  to 
  the 
  

   total 
  thermal 
  effect 
  involved 
  in 
  the 
  protracted 
  inversion, 
  

   that 
  effect 
  is 
  given 
  as 
  7-8 
  calories 
  per 
  gram, 
  nearly 
  as 
  

   much 
  as 
  the 
  10 
  cal. 
  of 
  the 
  wollastonite-pseudo-wollas- 
  

   tonite 
  inversion, 
  and 
  similarly 
  the 
  inversion 
  heat 
  a-/? 
  

   cristobalite 
  above 
  0° 
  is 
  about 
  6 
  cal. 
  Some 
  values 
  of 
  the 
  

   quartz 
  inversion 
  heat 
  at 
  the 
  inversion 
  point, 
  575°, 
  which 
  

   I 
  formerly 
  gave, 
  are 
  evidently 
  meaningless. 
  

  

  Conclusions: 
  5. 
  Effect 
  of 
  Chemical 
  Composition. 
  

  

  The 
  differences 
  in 
  specific 
  heat 
  just 
  noticed 
  between 
  

   different 
  crystalline 
  forms 
  of 
  the 
  same 
  substance 
  show 
  

   that 
  specific 
  heat 
  differences 
  between 
  substances 
  of 
  unlike 
  

   composition 
  need 
  to 
  be 
  interpreted 
  with 
  caution. 
  The 
  

   substances 
  may 
  not 
  be 
  in 
  comparable 
  states. 
  It 
  seems 
  

   desirable, 
  however, 
  to 
  show 
  more 
  definitely 
  what 
  are 
  the 
  

   differences 
  in 
  mean 
  atomic 
  heat 
  between 
  different 
  sub- 
  

   stances 
  occurring 
  in 
  the 
  present 
  work; 
  this 
  is 
  done 
  in 
  

   Table 
  X 
  by 
  comparing 
  the 
  various 
  substances 
  with 
  an 
  

   arbitrary 
  standard. 
  This 
  standard 
  is 
  very 
  near 
  the 
  

   mean 
  of 
  all 
  those 
  in 
  Table 
  X, 
  and 
  is 
  exactly 
  the 
  mean 
  of 
  

   diopside 
  and 
  albite, 
  except 
  at 
  700°, 
  where 
  a 
  comparison 
  

  

  63 
  Carl 
  Benedicks, 
  On 
  Allotropy 
  in 
  general 
  and 
  that 
  of 
  Iron 
  in 
  particular, 
  

   Jour. 
  Iron 
  and 
  Steel 
  Inst., 
  86, 
  No. 
  II, 
  243, 
  1912. 
  

   84 
  Op. 
  cit., 
  p. 
  244. 
  

   55 
  P. 
  N. 
  Beck, 
  quoted 
  p. 
  355, 
  in 
  A. 
  Dumas, 
  op. 
  cit. 
  

  

  