﻿122 
  N. 
  L. 
  Bow 
  en 
  — 
  Sodium- 
  Potassium 
  Nephelites. 
  

  

  Eatectic 
  temperature 
  and 
  composition. 
  

  

  Composition 
  Initial 
  Temper- 
  

  

  Ne 
  Kp 
  condition 
  ature 
  Time 
  Kesult 
  

  

  80 
  20 
  crystalline 
  1402 
  1 
  hr. 
  nephelite 
  and 
  carnegieite 
  

  

  " 
  " 
  " 
  1406 
  " 
  carnegieite 
  and 
  glass 
  

  

  75 
  25 
  " 
  1402 
  " 
  nephelite 
  and 
  carnegieite 
  

  

  " 
  " 
  " 
  1406 
  " 
  carnegieite 
  and 
  glass 
  

  

  72*5 
  27'5 
  " 
  1402 
  fi 
  nephelite 
  and 
  carnegieite 
  

  

  " 
  " 
  " 
  1406 
  " 
  glass 
  only 
  

  

  70 
  30 
  " 
  1402 
  " 
  nephelite 
  and 
  carnegieite 
  

  

  " 
  " 
  " 
  14()6 
  " 
  nephelite 
  and 
  glass 
  

  

  65 
  35 
  " 
  1402 
  " 
  nephelite 
  only 
  

  

  " 
  1406 
  " 
  glass 
  and 
  nephelite 
  

  

  a 
  a 
  

  

  Beginning 
  of 
  melting 
  of 
  mix-crystals. 
  

  

  50 
  50 
  crystalline 
  1435 
  1/2 
  hr. 
  crystals 
  and 
  glass 
  stringers 
  

  

  " 
  " 
  " 
  1445 
  " 
  marked 
  increase 
  of 
  glass 
  

  

  40 
  60 
  " 
  1480 
  " 
  crystals 
  and 
  glass 
  stringers 
  

  

  " 
  " 
  " 
  1490 
  " 
  marked 
  increase 
  of 
  glass 
  

  

  30 
  70 
  " 
  1540 
  " 
  crystals 
  and 
  glass 
  stringers 
  

  

  " 
  1550 
  " 
  marked 
  increase 
  of 
  glass 
  

  

  a 
  a 
  

  

  Completion 
  of 
  melting 
  of 
  mix- 
  crystals. 
  

  

  70 
  30 
  crystalline 
  1420 
  1/2 
  hr. 
  glass 
  and 
  crystals 
  

  

  " 
  " 
  "■ 
  1424 
  " 
  glass 
  only 
  

  

  60 
  40 
  " 
  1463 
  " 
  glass 
  and 
  crystals 
  

  

  " 
  " 
  " 
  1467 
  " 
  glass 
  only 
  

  

  50 
  50 
  " 
  1520 
  " 
  glass 
  and 
  crystals 
  

  

  " 
  " 
  " 
  1524 
  " 
  glass 
  only 
  

  

  40 
  60 
  " 
  1570 
  " 
  glass 
  and 
  crystals 
  

  

  " 
  " 
  u 
  1574 
  " 
  glass 
  only 
  

  

  70 
  " 
  1629 
  " 
  glass 
  and 
  crystals 
  

  

  " 
  1633 
  " 
  glass 
  only 
  

  

  o 
  

  

  Discussion 
  of 
  JResults. 
  

  

  The 
  mixtures 
  containing 
  50 
  per 
  cent 
  or 
  more 
  of 
  KAlSi0 
  4 
  

   always 
  show 
  a 
  little 
  glass 
  even 
  when 
  quenched 
  from 
  tempera- 
  

   tures 
  below 
  the 
  eutectic. 
  This 
  behavior 
  is 
  the 
  result 
  of 
  the 
  

   deviation 
  from 
  true 
  composition 
  to 
  which 
  reference 
  has 
  already 
  

   been 
  made. 
  Concerning 
  the 
  method 
  of 
  determining 
  the 
  tem- 
  

   perature 
  of 
  beginning 
  of 
  melting 
  in 
  such 
  material 
  a 
  word 
  of 
  

   explanation 
  is, 
  perhaps, 
  necessary. 
  The 
  glass 
  formed 
  at 
  mod- 
  

   erate 
  temperatures 
  occurs 
  throughout 
  the 
  crystalline 
  grains 
  as 
  

   shreds 
  which 
  are 
  revealed 
  only 
  after 
  close 
  scrutiny 
  under 
  the 
  

   microscope. 
  These 
  shreds 
  do 
  not 
  increase 
  very 
  materially 
  in 
  

   amount 
  as 
  the 
  temperature 
  is 
  raised 
  and 
  appear, 
  moreover, 
  to 
  

   be 
  of 
  a 
  highly 
  viscous, 
  presumably 
  siliceous, 
  glass 
  which 
  occa- 
  

  

  