﻿Ford 
  and 
  Bradley 
  — 
  Pyroxmangite. 
  173 
  

  

  oxygen 
  gas. 
  It 
  gives 
  manganese 
  reactions 
  with 
  the 
  fluxes. 
  It 
  

   is 
  readilv 
  soluble 
  in 
  hydrochloric 
  acid, 
  giving 
  off 
  chlorine 
  gas. 
  

  

  The 
  method 
  of 
  analysis 
  was 
  as 
  follows. 
  The 
  mineral 
  was 
  

   crushed 
  and 
  then 
  dissolved 
  in 
  hydrochloric 
  acid, 
  the 
  weight 
  of 
  

   the 
  insoluble 
  residue 
  being 
  deducted 
  from 
  that 
  of 
  the 
  original 
  

   portion. 
  The 
  sesqnioxides 
  were 
  separated 
  by 
  the 
  basic 
  acetate 
  

   precipitation 
  and 
  determined 
  as 
  usual. 
  The 
  manganese 
  was 
  

   determined 
  as 
  outlined 
  above 
  in 
  the 
  case 
  of 
  pyroxmangite. 
  

   The 
  available 
  oxygen 
  in 
  the 
  manganese 
  oxide 
  was 
  determined 
  

   by 
  means 
  of 
  the 
  oxalic 
  acid 
  method. 
  The 
  iron 
  was 
  proved 
  to 
  

   be 
  all 
  ferric 
  in 
  valence. 
  The 
  water 
  was 
  determined 
  by 
  the 
  

   Pentield 
  direct 
  method. 
  

  

  The 
  results 
  of 
  the 
  analyses 
  by 
  Bradley 
  follow 
  : 
  

  

  I 
  

  

  MnO 
  31-71 
  

  

  O 
  6-50 
  

  

  Fe 
  o 
  0„ 
  43-67 
  

  

  A1 
  2 
  3 
  ... 
  2-43 
  

  

  H/0° 
  . 
  15-57 
  

  

  II 
  

  

  Average 
  

  

  31-96 
  

  

  31-84 
  

  

  6-56 
  

  

  6-53 
  

  

  44-24 
  

  

  43*95 
  

  

  1-49 
  

  

  1-96 
  

  

  15 
  "5 
  5 
  

  

  15-56 
  

  

  99-92 
  99-76 
  99'84 
  

  

  The 
  ratio 
  of 
  the 
  manganous 
  oxide 
  to 
  the 
  available 
  oxygen 
  is 
  

   as 
  0-448 
  : 
  0*408 
  or 
  as 
  lTO'910. 
  This 
  indicates 
  that 
  the 
  oxide 
  

   of 
  manganese 
  present 
  must 
  be 
  almost 
  wholly 
  the 
  dioxide, 
  

   Mn0 
  2 
  . 
  In 
  the 
  calculations 
  to 
  follow 
  it 
  has 
  been 
  assumed 
  that 
  

   the 
  sum 
  of 
  the 
  percentages 
  of 
  manganous 
  oxide 
  and 
  available 
  

   oxygen 
  represent 
  the 
  percentage 
  of 
  manganese 
  dioxide 
  present. 
  

   Considered 
  in 
  this 
  way 
  the 
  analysis 
  becomes 
  as 
  follows 
  : 
  

  

  

  

  

  

  

  

  

  Theoretical 
  

  

  

  Average 
  

  

  Eatios 
  

  

  

  

  

  

  Composition 
  

  

  MnO 
  a 
  -__ 
  

  

  -. 
  38*36 
  

  

  0-441 
  

  

  or 
  

  

  1-48 
  

  

  or 
  

  

  3-00 
  

  

  37-88 
  

  

  Fe 
  a 
  3 
  - 
  

  

  Al 
  a 
  3 
  — 
  

  

  . 
  . 
  43-95 
  I 
  

   1-96 
  j 
  

  

  0-298 
  

  

  

  1-00 
  

  

  

  2-00 
  

  

  46-44 
  

  

  H,0 
  ... 
  

  

  15-57 
  

  

  0-865 
  

  

  

  2-90 
  

  

  

  6-00 
  

  

  15*68 
  

  

  99-83 
  100-00 
  

  

  From 
  the 
  ratios 
  given 
  above 
  is 
  derived 
  the 
  following 
  for- 
  

   mula, 
  which 
  closely 
  expresses 
  the 
  composition 
  of 
  the 
  mineral, 
  

   3MnO 
  a 
  . 
  2Fe 
  2 
  O 
  a 
  . 
  611,0. 
  The 
  theoretical 
  percentage 
  composition 
  

   corresponding 
  to 
  this 
  formula 
  is 
  given 
  in 
  the 
  last 
  column 
  

   above 
  and 
  agrees 
  closely 
  with 
  the 
  results 
  of 
  the 
  analysis. 
  

  

  Although 
  many 
  oxides 
  of 
  manganese 
  have 
  been 
  described, 
  

   no 
  one 
  of 
  them 
  agrees 
  with 
  this 
  mineral 
  in 
  its 
  composition. 
  

   Two 
  new 
  oxides 
  of 
  manganese 
  from 
  India, 
  vredenburgite, 
  

  

  