﻿116 
  JV. 
  L. 
  Bowen 
  — 
  Sodium- 
  Potassium 
  Nejjhelites. 
  

  

  indices 
  are 
  7 
  = 
  1-514 
  =b 
  *002, 
  a 
  = 
  1*509 
  =b 
  '002. 
  It 
  is 
  biaxial, 
  

   with 
  negative 
  optical 
  character 
  and 
  2V 
  =±= 
  12°-15°. 
  The 
  

   density 
  is 
  2-513 
  at 
  21°. 
  

  

  Glass 
  of 
  composition 
  NaAlSi0 
  4 
  has 
  a 
  refractive 
  index 
  

   1-510 
  d= 
  -002, 
  

  

  KAlSiO^ 
  — 
  The 
  preparation 
  of 
  the 
  pure 
  potash 
  compound 
  

   is 
  not 
  so 
  readily 
  accomplished. 
  The 
  same 
  precautions 
  of 
  sin- 
  

   tering 
  at 
  a 
  low 
  temperature 
  before 
  raising 
  above 
  the 
  melting 
  

   point 
  are 
  not 
  adequate 
  in 
  this 
  case 
  to 
  prevent 
  volatilization 
  of 
  

   the 
  alkali, 
  partly 
  because 
  the 
  potash 
  is 
  much 
  more 
  volatile 
  than 
  

   soda 
  and 
  partly 
  because 
  of 
  the 
  high 
  melting-temperature 
  of 
  the 
  

   potash 
  compound. 
  In 
  raising 
  the 
  charge 
  to 
  this 
  temperature 
  

   which 
  is 
  somewhat 
  above 
  the 
  melting-point 
  of 
  platinum, 
  con- 
  

   siderable 
  potash 
  is 
  lost. 
  The 
  pure 
  compound 
  cannot, 
  then, 
  be 
  

   prepared 
  in 
  the 
  dry 
  way 
  simply 
  by 
  mixing 
  the 
  components 
  

   and 
  melting 
  them, 
  though 
  its 
  preparation 
  by 
  this 
  method 
  has 
  

   been 
  claimed. 
  Especially 
  should 
  one 
  not 
  attempt 
  to 
  prepare 
  

   it 
  by 
  fusion 
  in 
  a 
  platinum 
  crucible, 
  for 
  the 
  crucible 
  melts 
  and 
  

   runs 
  away 
  when 
  the 
  sintered 
  charge 
  is 
  still 
  intact. 
  In 
  a 
  poorly 
  

   mixed 
  charge 
  melting 
  can 
  be 
  obtained 
  at 
  comparatively 
  low 
  

   temperatures, 
  silica 
  and 
  potash 
  fluxing 
  together 
  and 
  leaving 
  

   much 
  alumina 
  undissolved, 
  but 
  this 
  is 
  not 
  melting 
  of 
  kalio- 
  

   philite. 
  Nevertheless 
  one 
  can 
  obtain 
  a 
  product 
  with 
  only 
  a 
  

   moderate 
  deficiency 
  in 
  potash 
  by 
  sintering 
  at 
  a 
  low 
  tempera- 
  

   ture 
  as 
  described 
  and 
  then 
  rapidly 
  raising 
  to 
  the 
  melting 
  

   temperature 
  in 
  an 
  iridium 
  furnace. 
  The 
  glass 
  so 
  obtained 
  is 
  

   apparently 
  not 
  very 
  different 
  in 
  viscosity 
  from 
  the 
  nephelite 
  

   glass 
  and 
  crystallizes 
  about 
  as 
  readily 
  when 
  not 
  too 
  rapidly 
  

   cooled. 
  In 
  this 
  way 
  one 
  obtains 
  crystals 
  which 
  correspond 
  in 
  

   properties 
  with 
  the 
  natural 
  mineral 
  kaliophilite, 
  always, 
  how- 
  

   ever, 
  with 
  a 
  little 
  foreign 
  material 
  since 
  the 
  composition 
  does 
  

   not 
  lie 
  exactly 
  at 
  the 
  compound 
  KAlSi0 
  4 
  . 
  

  

  The 
  artificial 
  kaliophilite 
  so 
  obtained 
  is 
  hexagonal 
  and 
  nega- 
  

   tive, 
  a) 
  = 
  1-532 
  ± 
  -002, 
  e 
  = 
  1*527 
  ± 
  002. 
  The 
  prism 
  and 
  base 
  

   are 
  predominant 
  with 
  only 
  an 
  occasional 
  truncation 
  of 
  the 
  

   edge 
  by 
  a 
  pyramidal 
  face. 
  One 
  sees, 
  then, 
  the 
  hexagonal 
  

   basal 
  sections 
  and 
  quadratic 
  prismatic 
  sections 
  precisely 
  as 
  in 
  

   nephelite. 
  

  

  With 
  the 
  aid 
  of 
  potassium 
  tungstate 
  as 
  a 
  flux 
  good 
  crystals 
  

   of 
  kaliophilite 
  were 
  prepared 
  at 
  about 
  1300°. 
  The 
  largest 
  of 
  

   these 
  were 
  somewhat 
  contaminated 
  with 
  the 
  flux 
  and 
  showed 
  

   higher 
  indices 
  of 
  refraction 
  than 
  those 
  given 
  above, 
  but 
  the 
  

   smallest 
  crystals 
  were 
  found 
  to 
  agree 
  exactly 
  in 
  all 
  their 
  

   properties. 
  

  

  Small 
  crystals 
  of 
  kaliophilite 
  were 
  prepared 
  hydrothermally 
  

   by 
  Morey 
  in 
  this 
  laboratory. 
  Kahlbaum's 
  potassium 
  aluminate 
  

   and 
  potassium 
  silicate 
  were 
  used. 
  These 
  were 
  placed 
  with 
  

  

  