﻿318 
  Posnjak 
  and 
  Merwin 
  — 
  Hydrated 
  Ferric 
  Oxides. 
  

  

  this 
  difference 
  can 
  be 
  calculated. 
  Table 
  II 
  shows 
  the 
  

   agreement 
  of 
  carbon 
  dioxide 
  calculated 
  in 
  this 
  way 
  with 
  

   the 
  amount 
  directly 
  determined. 
  

  

  

  

  

  Table 
  II. 
  

  

  

  

  

  % 
  ignition 
  

  

  

  

  % 
  co 
  2 
  

  

  % 
  co 
  2 
  

  

  fo.a 
  

  

  loss 
  

  

  % 
  H 
  2 
  

  

  Difference 
  13 
  

  

  calculated 
  

  

  determined 
  

  

  3 
  

  

  12-71 
  

  

  11-78 
  

  

  0-93 
  

  

  113 
  

  

  106 
  

  

  5 
  

  

  12-99 
  

  

  12-00 
  

  

  0-99 
  

  

  1-21 
  

  

  1-28 
  

  

  6 
  

  

  1308 
  

  

  12-47 
  

  

  0-61 
  

  

  0-74 
  

  

  0-70 
  

  

  7 
  

  

  13-60 
  

  

  12-80 
  

  

  0-80 
  

  

  0-98 
  

  

  0-92 
  

  

  a 
  The 
  numbers 
  refer 
  to 
  Table 
  I. 
  

  

  b 
  This 
  shows 
  that 
  the 
  determination 
  of 
  water 
  by 
  the 
  ignition 
  loss, 
  even 
  on 
  

   apparently 
  homogeneous 
  material, 
  may 
  easily 
  be 
  as 
  much 
  as 
  8% 
  too 
  high. 
  

  

  Some 
  " 
  amorphous' 
  ' 
  hydrated 
  ferric 
  oxides 
  were 
  also 
  

   analyzed. 
  The 
  term 
  " 
  amorphous' 
  ' 
  is 
  used 
  here 
  not 
  to 
  

   distinguish 
  a 
  special 
  form 
  of 
  hydrated 
  ferric 
  oxide 
  but 
  

   only 
  to 
  indicate 
  that 
  the 
  separate 
  particles 
  of 
  the 
  sub- 
  

   stance 
  were 
  of 
  such 
  fineness 
  that 
  their 
  aggregates 
  were 
  

   essentially 
  isotropic. 
  They 
  are 
  primarily 
  of 
  interest 
  in 
  

   showing 
  what 
  influence 
  the 
  structure 
  may 
  have 
  on 
  the 
  

   composition 
  of 
  the 
  mineral. 
  The 
  results 
  are 
  given 
  in 
  

   Table 
  III. 
  

  

  Table 
  III. 
  

   Analyses 
  of 
  ' 
  ' 
  amorphous 
  ' 
  ' 
  hydrated 
  ferric 
  oxide. 
  a 
  jj 
  2 
  

  

  No. 
  Locality 
  

  

  Fe 
  2 
  3 
  FeO 
  

  

  CuO 
  

  

  S0 
  3 
  

  

  Si0 
  2 
  H 
  2 
  

  

  Total 
  Fe 
  2 
  3 
  

  

  19 
  Cananea, 
  N. 
  M., 
  

  

  83-34 
  ... 
  

  

  1-23 
  

  

  1-34 
  

  

  1-73 
  13-26 
  

  

  100-90* 
  1-41 
  

  

  20 
  Shasta 
  Co., 
  Cal., 
  

  

  81-03 
  0-64 
  

  

  0-46 
  

  

  1-27 
  

  

  1-20 
  14-97 
  

  

  100-50c 
  1-64 
  

  

  21 
  Shasta 
  Co., 
  Cal., 
  

  

  76-29 
  0-25 
  

  

  0-15 
  

  

  0-35 
  

  

  5-67 
  17-41 
  

  

  100-12 
  2-02 
  

  

  22 
  Bisbee, 
  Ariz., 
  

  

  76-18 
  019 
  

  

  1-22 
  

  

  2-90 
  

  

  1-59 
  17-83 
  

  

  100-11 
  2-08 
  

  

  23 
  Shasta 
  Co., 
  Cal., 
  

  

  74-95 
  0-25 
  

  

  0-50 
  

  

  1-67 
  

  

  1-50 
  17-76 
  

  

  100-67* 
  210 
  

  

  24 
  Synthetic, 
  

  

  84-72 
  . 
  . 
  . 
  

  

  

  1-82 
  

  

  ... 
  13-91 
  

  

  100-45 
  

  

  a 
  Except 
  No. 
  24 
  they 
  are 
  gossan 
  

   connection 
  with 
  the 
  investigation 
  

   sulphide 
  ores. 
  

  

  *>With 
  trace 
  MnjA. 
  c 
  Includes 
  

  

  A1A. 
  

  

  ores 
  received 
  from 
  Prof. 
  L. 
  C. 
  Graton 
  in 
  

   of 
  the 
  secondary 
  enrichment 
  of 
  copper 
  

  

  0-93 
  MgO, 
  trace 
  Mn 
  2 
  3 
  . 
  d 
  Includes 
  404 
  

  

  Discussion 
  of 
  Analytical 
  Results. 
  

  

  In 
  the 
  last 
  column 
  of 
  Table 
  I 
  is 
  given 
  the 
  name 
  under 
  

   which 
  the 
  mineral 
  was 
  received. 
  It 
  is 
  seen 
  that 
  with 
  the 
  

   sole 
  exception 
  of 
  Nos. 
  5 
  and 
  6, 
  which 
  were 
  definite 
  crys- 
  

   tals 
  of 
  goethite, 
  the 
  compositions 
  of 
  the 
  hydrated 
  ferric 
  

   oxides 
  differ 
  considerably 
  from 
  their 
  supposed 
  formulas. 
  

  

  