﻿34:8 
  Posnjak 
  and 
  Merwin 
  — 
  Hydrated 
  Ferric 
  Oxides. 
  

  

  No 
  definitely 
  crystallized 
  synthetic 
  hydrated 
  ferric 
  

   oxide 
  has 
  np 
  to 
  the 
  present 
  been 
  prepared. 
  However, 
  

   it 
  seems 
  certain 
  that 
  only 
  two 
  distinct 
  types 
  of 
  " 
  amor- 
  

   phous' 
  ' 
  hydrated 
  ferric 
  oxide 
  exist: 
  one 
  yellow 
  and 
  the 
  

   other 
  reddish-brown. 
  The 
  yellow 
  is 
  apparently 
  essen- 
  

   tially 
  ferric 
  oxide 
  monohydrate, 
  while 
  the 
  reddish-brown 
  

   substance 
  may 
  hold 
  its 
  water 
  in 
  either 
  a 
  dissolved 
  or 
  an 
  

   adsorbed 
  condition 
  (or 
  both). 
  Thus 
  the 
  synthetic 
  and 
  

   the 
  natural 
  hydrated 
  ferric 
  oxides 
  exhibit, 
  chemically, 
  

   great 
  similarity. 
  

  

  Geophysical 
  Laboratory, 
  Carnegie 
  Institution 
  of 
  Washington, 
  

   Washington, 
  D. 
  C, 
  January, 
  1919. 
  

  

  