﻿Oxides 
  and 
  Sulphides 
  of 
  Iron, 
  etc. 
  59 
  

  

  The 
  ignition 
  was 
  by 
  means 
  of 
  an 
  iron 
  wire 
  heated 
  by 
  electric- 
  

   ity. 
  Most 
  of 
  the 
  product 
  of 
  a 
  combustion 
  was 
  in 
  one 
  button 
  

   which 
  contained 
  a 
  few 
  cavities 
  indicating 
  dissociation 
  of 
  ferric 
  

   oxide. 
  The 
  contents 
  of 
  the 
  bomb 
  were 
  collected 
  and 
  weighed. 
  

   Then 
  it 
  was 
  washed 
  and 
  the 
  few 
  decigrams 
  of 
  dust 
  collected 
  

   were 
  ignited 
  and 
  weighed. 
  The 
  experiments 
  were 
  as 
  follows 
  : 
  

  

  12 
  3 
  

  

  Iron 
  8-105 
  8*499 
  8*609 
  grams 
  

  

  Product 
  11-202 
  11*676 
  11*757 
  

  

  Oxygen 
  combined 
  3*097 
  3*177 
  1-148 
  

  

  Heat 
  effect 
  12685 
  13167 
  13067 
  c 
  

  

  " 
  " 
  of 
  1 
  grm. 
  

  

  of 
  oxygen 
  4096 
  4144 
  4150 
  c 
  

  

  The 
  average 
  is 
  4125 
  c 
  . 
  While 
  the 
  product 
  of 
  a 
  combustion 
  is 
  

   a 
  mixture 
  of 
  iron 
  and 
  oxides 
  it 
  is 
  mostly 
  ferrous 
  ferric 
  oxide 
  as 
  

   shown 
  later. 
  Moreover, 
  the 
  heat 
  effect 
  of 
  an 
  atom 
  of 
  oxygen 
  

   in 
  the 
  different 
  iron 
  oxides 
  is 
  nearly 
  the 
  same. 
  Hence 
  the 
  

   error 
  is 
  insignificant 
  in 
  the 
  value 
  derived 
  for 
  3Fe-f-40, 
  which 
  

   is 
  4125 
  C 
  X64 
  = 
  264,000 
  c 
  at 
  constant 
  volume 
  and 
  265,200 
  c 
  at 
  

   constant 
  pressure. 
  

  

  The 
  products 
  of 
  the 
  experiments 
  were 
  united, 
  pulverized 
  and 
  

   sifted. 
  About 
  0*2 
  gram 
  of 
  iron 
  was 
  picked 
  out 
  and 
  a 
  small 
  

   portion 
  of 
  the 
  substance 
  remaining 
  on 
  the 
  sieve 
  contained 
  

   metallic 
  iron. 
  The 
  powder 
  appeared 
  to 
  be 
  free 
  from 
  metal, 
  

   as 
  it 
  gave 
  no 
  gas 
  when 
  dissolved 
  in 
  hydrochloric 
  acid. 
  The 
  

   iron 
  in 
  the 
  powder, 
  determined 
  as 
  ferric 
  oxide, 
  was 
  found 
  to 
  

   be 
  72*14 
  and 
  72*07, 
  mean 
  72*1 
  per 
  cent 
  ; 
  oxygen 
  by 
  difference 
  

   27*9 
  per 
  cent. 
  The 
  corresponding 
  formula 
  is 
  Fe 
  3 
  O 
  4 
  . 
  05 
  . 
  

  

  Magnetite. 
  — 
  Magnetite 
  from 
  a 
  large 
  crystal, 
  excluding 
  0*27 
  

   per 
  cent 
  of 
  silica, 
  was 
  found 
  to 
  have 
  the 
  following 
  composition 
  : 
  

  

  Calculated 
  

   I 
  II 
  Mean 
  for 
  Fe 
  3 
  4 
  

  

  Iron 
  72*74 
  [72*65] 
  72*7 
  72-36$ 
  

  

  Oxygen 
  [27'36] 
  27*35 
  27*3 
  27*64$ 
  

  

  The 
  iron 
  in 
  I 
  was 
  determined 
  as 
  ferric 
  oxide, 
  and 
  the 
  oxygen 
  

   in 
  II 
  by 
  loss 
  on 
  heating 
  2*6481 
  grams 
  of 
  the 
  substance 
  in 
  

   hydrogen. 
  The 
  mineral 
  contained 
  no 
  aluminum, 
  manganese, 
  

   calcium 
  or 
  magnesium. 
  The 
  composition 
  is 
  expressed 
  by 
  the 
  

   formula 
  Fe 
  3 
  3 
  . 
  94 
  . 
  

  

  The 
  calorimetric 
  fusions 
  were 
  treated 
  with 
  water, 
  and 
  dilute 
  

   nitric 
  acid 
  was 
  added 
  to 
  dissolve 
  the 
  ferric 
  hydroxide 
  formed 
  

   and 
  the 
  magnetite 
  left 
  was 
  collected 
  and 
  weighed. 
  The 
  follow- 
  

   ing 
  are 
  the 
  results 
  obtained 
  with 
  magnetite 
  and 
  the 
  magnetic 
  

   oxide 
  described 
  above 
  : 
  

  

  