﻿124: 
  J\ 
  T 
  . 
  L. 
  Bovien 
  — 
  Sodium-Potassium 
  N'ephelites. 
  

  

  perature 
  of 
  beginning 
  of 
  melting 
  may 
  be 
  very 
  great 
  if 
  the 
  

   impurity 
  has 
  a 
  low 
  melting 
  pointy 
  whence 
  the 
  small 
  amounts 
  

   of 
  glass 
  found 
  in 
  these 
  mixtures 
  at 
  moderate 
  temperatures. 
  

   The 
  effect 
  on 
  the 
  temperature 
  of 
  completion 
  of 
  melting, 
  the 
  

   so-called 
  melting 
  point, 
  is, 
  however, 
  a 
  more 
  or 
  less 
  direct 
  func- 
  

   tion 
  of 
  the 
  amount 
  of 
  imparity. 
  Since 
  the 
  deviation 
  from 
  true 
  

   composition 
  is 
  small 
  the 
  position 
  of 
  the 
  curve 
  as 
  far 
  as 
  it 
  has 
  

   been 
  determined 
  is 
  believed 
  to 
  be 
  substantially 
  correct. 
  

  

  The 
  equilibrium 
  diagram 
  is 
  of 
  a 
  peculiar 
  type, 
  though 
  

   among 
  those 
  deduced 
  by 
  Roozeboom 
  as 
  possible 
  in 
  a 
  system 
  

   involving 
  solid 
  solution 
  and 
  inversion." 
  Between 
  the 
  potash 
  

   compound 
  and 
  carnegieite 
  there 
  is 
  a 
  eutectic, 
  but 
  with 
  nephe- 
  

   lite 
  a 
  complete 
  series 
  of 
  solid 
  solutions 
  is 
  formed. 
  As 
  was 
  

   noted 
  formerly, 
  solid 
  solution 
  cannot 
  be 
  definitely 
  proved 
  by 
  

   optical 
  means 
  but 
  such 
  is 
  the 
  only 
  possible 
  interpretation 
  of 
  the 
  

   thermal 
  results. 
  There 
  is 
  a 
  continuous 
  rise 
  in 
  the 
  inversion 
  

   temperature 
  of 
  nephelite 
  as 
  far 
  as 
  35 
  per 
  cent 
  KAlSi0 
  4 
  amount- 
  

   ing 
  in 
  all 
  to 
  more 
  than 
  150°. 
  Such 
  a 
  change 
  of 
  inversion 
  temper- 
  

   ature 
  can 
  be 
  accomplished 
  only 
  through 
  solid 
  solution. 
  At 
  35 
  

   per 
  cent 
  KAlSi0 
  4 
  the 
  inversion 
  curve 
  gives 
  place 
  to 
  a 
  melting 
  

   curve 
  which 
  shows 
  a 
  continuous 
  rise 
  in 
  temperature 
  of 
  begin- 
  

   ning 
  of 
  melting. 
  If 
  the 
  possibility 
  is 
  entertained 
  that 
  an 
  

   hiatus 
  may 
  exist 
  in 
  the 
  series 
  in 
  those 
  mixtures 
  close 
  to 
  kalio- 
  

   philite 
  whose 
  beginning 
  of 
  melting 
  cannot 
  be 
  accurately 
  fixed, 
  

   then 
  it 
  may 
  be 
  pointed 
  out 
  that 
  there 
  should 
  be 
  a 
  correspond- 
  

   ing 
  break 
  in 
  the 
  liquidus. 
  There 
  is, 
  however, 
  no 
  break 
  in 
  the 
  

   liquidus 
  at 
  least 
  up 
  to 
  about 
  1580°. 
  In 
  the 
  neighborhood 
  of 
  

   this 
  latter 
  temperature 
  there 
  probably 
  is 
  a 
  break, 
  but 
  this 
  is 
  

   occasioned 
  not 
  by 
  the 
  appearance 
  of 
  kaliophilite 
  as 
  a 
  separate 
  

   phase 
  but 
  by 
  the 
  appearance 
  of 
  the 
  orthorhombic 
  form 
  of 
  

   KAlSiO.. 
  Solid 
  solution 
  as 
  far 
  as 
  about 
  70 
  per 
  cent 
  KAlSi0 
  4 
  

   is 
  established, 
  therefore, 
  beyond 
  all 
  question, 
  while 
  none 
  of 
  

   the 
  evidence 
  furnishes 
  any 
  reason 
  for 
  doubting 
  complete 
  solid 
  

   solution. 
  

  

  It 
  may 
  seem 
  at 
  first 
  thought 
  that 
  the 
  evidence 
  of 
  the 
  natural 
  

   minerals 
  is 
  against 
  complete 
  solid 
  solution. 
  We 
  have, 
  for 
  

   example, 
  nephelite 
  with 
  upwards 
  of 
  32 
  per 
  cent 
  KAlSi0 
  4 
  in 
  

   solid 
  solution 
  but 
  none 
  with 
  a 
  greater 
  amount. 
  Then 
  at 
  the 
  

   other 
  end 
  we 
  have 
  a 
  maximum 
  of 
  10 
  per 
  cent 
  of 
  NaAlSi0 
  4 
  in 
  

   kaliophilite. 
  The 
  interval 
  is 
  unbridged 
  among 
  known 
  natural 
  

   minerals, 
  but 
  this 
  does 
  not 
  mean 
  that 
  no 
  such 
  minerals 
  are 
  

   possible. 
  Nephelites 
  which 
  contain, 
  say 
  20 
  to 
  30 
  per 
  cent 
  

   KAlSi0 
  4 
  , 
  are 
  never 
  found 
  in 
  contact 
  with 
  kaliophilite 
  in 
  such 
  

   a 
  manner 
  as 
  to 
  indicate 
  approximately 
  simultaneous 
  formation. 
  

   Only 
  such 
  an 
  association 
  would 
  prove 
  that 
  the 
  nephelite 
  was 
  

   incapable 
  of 
  taking 
  up 
  more 
  KAlSi0 
  4 
  . 
  For 
  these 
  reasons 
  we 
  

  

  *Zs. 
  phys. 
  Chem., 
  xxx, 
  p. 
  426, 
  1899. 
  

  

  

  