﻿W. 
  P. 
  White 
  — 
  Silicate 
  Specific 
  Heats. 
  27 
  

  

  Conclusions: 
  3. 
  Comparison 
  of 
  Glass 
  and 
  Crystal. 
  

  

  One 
  important 
  characteristic 
  of 
  silica 
  compounds 
  is 
  the 
  

   comparative 
  ease 
  with 
  which 
  they 
  may 
  be 
  obtained 
  as 
  

   glasses. 
  In 
  the 
  present 
  case 
  every 
  crystalline 
  substance 
  

   examined 
  was 
  also 
  examined 
  in 
  the 
  form 
  of 
  glass, 
  and 
  in 
  

   all 
  but 
  two 
  instances 
  the 
  same 
  sample 
  was 
  used, 
  first 
  in 
  

   one 
  state 
  and 
  then 
  in 
  the 
  other. 
  The 
  differences 
  of 
  glass 
  

   and 
  crystal, 
  evident 
  from 
  Table 
  IV, 
  are 
  brought 
  together 
  

   in 
  Table 
  VIII. 
  These 
  results, 
  it 
  should 
  be 
  noted, 
  are 
  for 
  

   the 
  interval 
  specific 
  heats. 
  

  

  Three 
  facts 
  appear 
  from 
  Table 
  VIII: 
  (1) 
  The 
  

   specific 
  heat 
  of 
  the 
  glass 
  is 
  usually 
  little 
  if 
  any 
  greater 
  

   than 
  that 
  of 
  the 
  crystal; 
  (2) 
  the 
  exceptions 
  to 
  this 
  rule 
  

   occur 
  in 
  the 
  glasses 
  containing 
  sodium 
  or 
  potassium, 
  and 
  

   may 
  be 
  connected 
  with 
  the 
  fact 
  that 
  sodium 
  and 
  potas- 
  

   sium 
  tend 
  to 
  impart 
  exceptionally 
  high 
  expansion 
  coeffi- 
  

   cients 
  to 
  glasses 
  in 
  which 
  they 
  occur; 
  (3) 
  several 
  of 
  the 
  

   glasses 
  show 
  a 
  decided 
  increase 
  in 
  specific 
  heat 
  at 
  some 
  

   fairly 
  elevated 
  temperature. 
  No 
  explanation 
  has 
  been 
  

   established 
  for 
  any 
  of 
  these 
  facts. 
  It 
  seems 
  probable 
  

   that 
  the 
  increase 
  in 
  specific 
  heat 
  would 
  have 
  appeared 
  in 
  

   other 
  glasses 
  if 
  they 
  had 
  been 
  carried 
  higher. 
  It 
  may 
  be 
  

   a 
  phenomenon 
  of 
  considerable 
  importance, 
  but 
  for 
  its 
  

   complete 
  investigation 
  a 
  knowledge 
  of 
  the 
  expansion 
  and 
  

   perhaps 
  of 
  other 
  properties 
  of 
  the 
  glasses 
  is 
  desirable. 
  

  

  Anorthite 
  at 
  0°-100° 
  furnishes 
  a 
  well-marked 
  case 
  of 
  a 
  

   glass 
  of 
  less 
  specific 
  heat 
  than 
  the 
  crystals, 
  which 
  

   appeared 
  so 
  anomalous 
  30 
  as 
  to 
  be 
  somewhat 
  doubtful. 
  

   Hence 
  the 
  glass 
  was 
  repeated 
  very 
  carefully 
  with 
  a 
  dif- 
  

   ferent 
  heater. 
  The 
  repetition 
  (3d 
  to 
  6th 
  results 
  in 
  Table 
  

   IV) 
  confirms 
  the 
  difference 
  first 
  observed. 
  The 
  crystal 
  

   results 
  were 
  not 
  repeated, 
  since 
  they 
  were 
  more 
  trust- 
  

   worthy, 
  and 
  there 
  was 
  no 
  probability 
  of 
  a 
  large 
  positive 
  

   error. 
  Table 
  X 
  also 
  indicates 
  that 
  these 
  results 
  were 
  

   not 
  unduly 
  high. 
  

  

  Conclusions: 
  4. 
  Inversions 
  and 
  Specific 
  Heat. 
  

  

  These 
  determinations 
  cover 
  five 
  cases 
  of 
  inversion, 
  or 
  

   transformation 
  in 
  the 
  solid 
  state, 
  belonging 
  to 
  at 
  least 
  

   three 
  different 
  types. 
  

  

  30 
  The 
  anomaly 
  in 
  the 
  ease 
  of 
  silica 
  glass 
  is 
  more 
  apparent 
  than 
  real, 
  as 
  

   appears 
  above 
  600°. 
  Below 
  550° 
  for 
  quartz, 
  and 
  probably 
  at 
  100° 
  for 
  

   cristobalite, 
  the 
  specific 
  heat 
  of 
  the 
  crystal 
  is 
  increased 
  by 
  the 
  approaching 
  

   inversion, 
  as 
  explained 
  below. 
  

  

  