﻿36 
  W. 
  P. 
  White 
  — 
  Silicate 
  Specific 
  Heats. 
  

  

  in 
  the 
  inversion. 
  Such 
  demonstration 
  is 
  very 
  difficult 
  in 
  

   view 
  of 
  the 
  general 
  sluggishness 
  and 
  irregularity 
  of 
  inver- 
  

   sion 
  in 
  solids. 
  Smits 
  appears 
  to 
  be 
  the 
  only 
  one 
  who 
  has 
  

   made 
  a 
  serious 
  attempt 
  to 
  provide 
  it. 
  The 
  principal 
  

   things 
  he 
  adduces 
  seem 
  to 
  be 
  the 
  following: 
  (1) 
  The 
  

   specific 
  heats 
  of 
  solids 
  usually 
  change 
  prior 
  to 
  melting^ 
  

   thus 
  indicating 
  a 
  change 
  in 
  chemical 
  composition 
  in 
  the 
  

   solid, 
  connected 
  with 
  the 
  change 
  of 
  state, 
  which 
  is 
  here 
  

   a 
  melting, 
  not 
  an 
  inversion. 
  This 
  instance, 
  however, 
  

   appears 
  to 
  be 
  the 
  result 
  of 
  a 
  misapprehension. 
  Smits 
  

   quotes 
  Wigand 
  44 
  as 
  saying 
  that 
  substances, 
  especially 
  

   metals, 
  show 
  an 
  increase 
  in 
  specific 
  heat 
  just 
  below 
  melt- 
  

   ings. 
  But 
  Wigand 
  expressly 
  states 
  that 
  this 
  effect 
  may 
  

   be 
  attributed 
  merely 
  to 
  premature 
  melting 
  caused 
  by 
  

   impurity. 
  This 
  explanation, 
  also 
  offered 
  by 
  other 
  

   writers, 
  receives 
  the 
  strongest 
  confirmation 
  by 
  the 
  recent 
  

   work 
  of 
  Dickinson 
  and 
  Osborne 
  45 
  on 
  ice, 
  which 
  shows 
  that 
  

   adequate 
  attention 
  to 
  purity 
  banishes 
  all 
  perceptible 
  

   effect 
  of 
  this 
  character, 
  even 
  in 
  that 
  case 
  where 
  its 
  inde- 
  

   pendence 
  of 
  impurity 
  had 
  been 
  supposed 
  to 
  be, 
  perhaps, 
  

   most 
  fully 
  established. 
  (2) 
  Smits 
  also 
  adduces 
  the 
  fact 
  

   that 
  inversions 
  commonly 
  come 
  lower 
  on 
  rapid 
  cooling 
  

   or 
  higher 
  on 
  rapid 
  heating 
  as 
  a 
  confirmation 
  of 
  the 
  

   theory. 
  It 
  is 
  so 
  to 
  this 
  extent, 
  that 
  the 
  theory 
  is 
  capable 
  

   of 
  giving 
  an 
  explanation 
  of 
  the 
  fact. 
  Fig. 
  4 
  was 
  orig- 
  

   inally 
  given 
  by 
  Smits 
  to 
  show 
  this. 
  The 
  rapidly 
  cooled 
  

   material 
  does 
  not 
  have 
  time 
  to 
  reach 
  the 
  chemical 
  equi- 
  

   librium, 
  and 
  therefore 
  reaches 
  the 
  solubility 
  line 
  at 
  W 
  t 
  ; 
  

   the 
  inverting 
  crystal 
  has 
  the 
  composition 
  ~W 
  t 
  instead 
  of 
  

   "W. 
  Unfortunately, 
  mere 
  sluggishness 
  of 
  transformation 
  

   will 
  also 
  account 
  for 
  the 
  only 
  observed 
  difference, 
  which 
  

   is 
  the 
  change 
  in 
  transformation 
  temperature. 
  If 
  we 
  

   could 
  make 
  the 
  inversion 
  come 
  higher 
  by 
  rapid 
  cooling 
  

   the 
  argument 
  for 
  the 
  theory 
  would 
  be 
  far 
  stronger; 
  

   hence 
  the 
  main 
  interest 
  centers 
  around 
  those 
  cases 
  where 
  

   such 
  a 
  phenomenon 
  is 
  in 
  question. 
  There 
  appear 
  to 
  be 
  

   two 
  such 
  which 
  are 
  specially 
  pertinent, 
  but 
  the 
  case 
  of 
  the 
  

   melting 
  of 
  sulphur 
  may 
  profitably 
  be 
  included 
  also, 
  since 
  

   although 
  this 
  melting 
  comes 
  higher 
  with 
  rapid 
  heating, 
  

  

  44 
  A. 
  Wigand, 
  Neure 
  TJntersuchungen 
  iiber 
  spezifische 
  Warmen, 
  Jahrbuch 
  

   der 
  Radioaktiviat 
  und 
  Elektronik, 
  10-75, 
  1913. 
  

  

  48 
  H. 
  C. 
  Dickinson 
  and 
  N. 
  S. 
  Osborne, 
  The 
  specific 
  heat 
  and 
  heat 
  of 
  fusion 
  

   of 
  ice, 
  Am. 
  Soc. 
  Refrig. 
  Engineers, 
  1, 
  32, 
  1915; 
  J. 
  Wash. 
  Acad. 
  Sci., 
  5, 
  

   338, 
  1915; 
  Bull. 
  Bur. 
  Standards, 
  12, 
  49, 
  1915. 
  

  

  