﻿certain 
  Micas, 
  Yermiculites 
  and 
  Chlorites. 
  

  

  245 
  

  

  callj 
  by 
  Mr. 
  Lindgren, 
  who 
  found 
  in 
  the 
  hallite 
  some 
  spear- 
  

   shaped, 
  rhombic, 
  or 
  more 
  rarely 
  hexagonal 
  inclusions 
  of 
  a 
  dark 
  

   brown 
  mineral, 
  not 
  further 
  identified. 
  His 
  optical 
  notes 
  will 
  

   be 
  published 
  in 
  an 
  official 
  bulletin, 
  later. 
  Analyses 
  as 
  fol- 
  

   lows, 
  with 
  itemized 
  water 
  determinations 
  : 
  

  

  Hallite. 
  

  

  SiO 
  a 
  35-54 
  

  

  Ti0 
  2 
  undet. 
  

  

  A1 
  2 
  3 
  9-74 
  

  

  Fe 
  2 
  O 
  s 
  9-07 
  

  

  Cr 
  2 
  8 
  __.. 
  

  

  FeO 
  0-28 
  

  

  MnO 
  0-25 
  

  

  NiO 
  0-16 
  

  

  MgO. 
  30-05 
  

  

  BaO 
  

  

  H 
  2 
  0, 
  105°. 
  _. 
  2-64 
  

  

  " 
  250°-300° 
  1-23 
  

  

  " 
  red 
  beat 
  10*91 
  

  

  B. 
  

  

  Lenni 
  1. 
  

  

  c. 
  

  

  Lenni 
  2. 
  

  

  D. 
  

  

  Lenni 
  3. 
  

  

  36-72 
  

  

  35-09 
  

  

  34-90 
  

  

  0-18 
  

  

  0-58 
  

  

  o-io 
  

  

  10-06 
  

  

  12-05 
  

  

  10-60 
  

  

  5-37 
  

  

  667 
  

  

  8-57 
  

  

  0-26 
  

  

  0-46 
  

  

  0-23 
  

  

  0-12 
  

  

  0-11 
  

  

  0-22 
  

  

  0-31 
  

  

  0-27 
  

  

  0-17 
  

  

  0-20 
  

  

  0-20 
  

  

  019 
  

  

  29-40 
  

  

  27-62 
  

  

  28-21 
  

  

  

  

  trace 
  

  

  

  

  6-40 
  

  

  5-70 
  

  

  4-99 
  

  

  2-68 
  

  

  1-98 
  

  

  1-60 
  

  

  8-69 
  

  

  9-22 
  

  

  9-88 
  

  

  100-39 
  

  

  99-95 
  

  

  99-66 
  

  

  6-92 
  

  

  5-84 
  

  

  5-21 
  

  

  B. 
  

  

  c. 
  

  

  D. 
  

  

  •614 
  

  

  •591 
  

  

  •583 
  

  

  •134 
  

  

  •163 
  

  

  •159 
  

  

  •744 
  

  

  •698 
  

  

  •712 
  

  

  •483 
  

  

  •512 
  

  

  •549 
  

  

  •504 
  

  

  •427 
  r 
  

  

  •366 
  

  

  99-87 
  

   Loss 
  over 
  H 
  a 
  S0 
  4 
  undet. 
  

  

  In 
  these 
  analyses 
  we 
  at 
  once 
  see 
  that 
  the 
  combined 
  water 
  is 
  

   mostly 
  in 
  excess 
  of 
  the 
  crystalline 
  water, 
  and 
  that 
  the 
  formulae 
  

   deduced 
  must 
  be 
  correspondingly 
  modified. 
  The 
  molecular 
  

   ratios 
  are 
  as 
  follows 
  : 
  

  

  A. 
  

  

  Si0 
  2 
  -592 
  

  

  R 
  2 
  3 
  -152 
  

  

  RO 
  -760 
  

  

  H 
  2 
  0, 
  fixed 
  -606 
  

  

  Aq. 
  -215 
  

  

  In 
  order 
  to 
  learn 
  something 
  as 
  to 
  the 
  distribution 
  of 
  the 
  

   hydroxyl 
  indicated 
  by 
  these 
  ratios, 
  resort 
  was 
  had 
  to 
  the 
  process 
  

   of 
  heating 
  in 
  dry, 
  gaseous, 
  hydrochloric 
  acid, 
  as 
  described 
  in 
  

   our 
  former 
  paper. 
  From 
  this 
  test, 
  however, 
  the 
  brown 
  Lenni 
  

   vermiculite 
  was 
  omitted, 
  as 
  being 
  intermediate 
  in 
  its 
  character 
  

   between 
  the 
  white 
  and 
  the 
  green. 
  Each 
  experiment 
  was 
  made 
  

   at 
  the 
  temperature 
  383 
  -412 
  . 
  

  

  A. 
  B. 
  D. 
  

  

  Hours 
  heated 
  16£ 
  16 
  17 
  

  

  R 
  2 
  3 
  removed 
  3-42 
  1'08 
  1-56 
  

  

  MgO 
  " 
  _ 
  8-09 
  6-30 
  6-57 
  

  

  Molec. 
  ratio 
  MgOH 
  -202 
  -158 
  -164 
  

  

  Here 
  it 
  is 
  assumed, 
  on 
  the 
  grounds 
  of 
  our 
  former 
  work, 
  that 
  

   the 
  magnesia 
  rendered 
  soluble 
  by 
  gaseous 
  HC1 
  is 
  present 
  as 
  

  

  