﻿Foote 
  and 
  Bradley 
  — 
  Constant 
  Composition 
  of 
  Albite. 
  49 
  

  

  Neph 
  elite, 
  however, 
  lias 
  nearly 
  the 
  same 
  specific 
  gravity 
  as 
  

   albite 
  and 
  could 
  not 
  be 
  entirely 
  separated 
  from 
  the 
  latter 
  by 
  

   this 
  means. 
  The 
  material 
  obtained 
  floated 
  in 
  heavy 
  solution 
  

   of 
  sp. 
  gr. 
  2*645 
  and 
  sank 
  at 
  2'626. 
  To 
  free 
  the 
  material 
  com- 
  

   pletely 
  from 
  a 
  very 
  small 
  amount 
  of 
  nephelite, 
  it 
  was 
  boiled 
  

   three 
  times 
  with 
  dilute 
  hydrochloric 
  acid. 
  The 
  solution 
  from 
  

   the 
  first 
  treatment 
  gelatinized 
  when 
  evaporated, 
  showing 
  the 
  

   presence 
  of 
  nephelite, 
  but 
  nothing 
  further 
  was 
  extracted. 
  

   Under 
  the 
  microscope, 
  no 
  impurities 
  could 
  be 
  detected 
  in 
  the 
  

   purified 
  material. 
  

  

  The 
  nsual 
  precautions 
  were 
  observed 
  in 
  the 
  analysis. 
  Silica, 
  

   after 
  being 
  weighed, 
  was 
  tested 
  for 
  alumina 
  by 
  evaporating 
  

   with 
  sulphuric 
  and 
  hydrofluoric 
  acids, 
  and 
  alumina, 
  after 
  

   weighing, 
  was 
  dissolved 
  in 
  a 
  bisulphate 
  fusion 
  to 
  test 
  for 
  silica. 
  

   Evaporations 
  were 
  made 
  in 
  platinum. 
  Alkalies 
  were 
  deter- 
  

   mined 
  by 
  a 
  Smith 
  fusion. 
  The 
  analyses 
  by 
  Robertson, 
  Mus- 
  

   grave, 
  and 
  our 
  own 
  are 
  given 
  in 
  Table 
  I. 
  

  

  Table 
  I. 
  

  

  An 
  

  

  of 
  Albite. 
  

  

  1 
  

  

  Albite 
  

  

  associated 
  

  

  with 
  quartz 
  

  

  (Eobertson) 
  

  

  Si0 
  2 
  67*06 
  

  

  A1 
  2 
  3 
  21-72 
  

  

  CaO. 
  1-59 
  

  

  MgO 
  -03 
  

  

  Na 
  2 
  10-01 
  

  

  K 
  2 
  G 
  -39 
  

  

  h 
  2 
  o._: 
  

  

  2 
  

  

  Albite 
  

  

  associated 
  

  

  with 
  quartz 
  

  

  (Musgrave) 
  

  

  68-44 
  

   19-35 
  

  

  11-67 
  

  

  •43 
  

  

  -3- 
  

  

  Albite 
  associated 
  with 
  

   corundum 
  and 
  nephelite 
  

  

  (Bradley) 
  

   A 
  B 
  Average 
  

  

  63-82 
  63-90 
  63'86 
  

  

  23-40 
  23-24 
  23*32 
  

  

  3-77 
  3-75 
  3-76 
  

  

  9-15 
  

   •15 
  

  

  •25 
  

  

  •24 
  

  

  •17 
  

   •24 
  

  

  9-20 
  

   •16 
  

   •24 
  

  

  100-80 
  

  

  99-89 
  

  

  100*54 
  100*54 
  100'54 
  

  

  In 
  calculating 
  the 
  ratios 
  from 
  these 
  analyses, 
  it 
  is 
  necessary 
  

   to 
  make 
  allowance 
  for 
  anorthite 
  in 
  the 
  two 
  specimens 
  contain- 
  

   ing 
  lime. 
  The 
  ratios, 
  with 
  corrections, 
  are 
  given 
  in 
  Table 
  II. 
  

  

  

  

  Table 
  II. 
  

  

  

  

  

  

  Ratios 
  

  

  calculated 
  from 
  the 
  Analyses 
  

  

  of 
  Table 
  I. 
  

  

  

  

  Eatios 
  

  

  Eatios 
  Eatios 
  

  

  for 
  for 
  

  

  anorthite 
  albite 
  

  

  i 
  2 
  , 
  

  

  Eatios 
  

  

  for 
  

   albite 
  

  

  

  Eatios 
  

   for 
  

   Eatios 
  anorthite 
  

  

  Eatios 
  

  

  for 
  

   albite 
  

  

  Si0 
  2 
  . 
  

   A1 
  2 
  3 
  

   CaO. 
  

  

  ... 
  1-110 
  

   •212 
  

  

  ... 
  -028" 
  

  

  •056 
  1-054 
  

   •028 
  '184 
  

   •028 
  

  

  1-133 
  

   •189 
  

  

  

  1-057 
  -134 
  

   •228 
  -067 
  

   •067 
  -067 
  

  

  •923 
  

   •161 
  

  

  Na 
  9 
  

   K 
  2 
  

  

  I 
  . 
  -165 
  

  

  •165 
  

  

  •192 
  

  

  

  •149 
  

  

  •149 
  

  

  Am. 
  

  

  Jour. 
  Sci. 
  — 
  

   4 
  

  

  Fourth 
  Series, 
  Vo 
  

  

  l. 
  XXX^ 
  

  

  n, 
  

  

  No. 
  211.— 
  July, 
  

  

  1913. 
  

  

  