﻿Posnjak 
  and 
  Merwin 
  — 
  Hydrated 
  Ferric 
  Oxides. 
  341 
  

  

  preparations 
  are 
  similar 
  to 
  the 
  natural 
  " 
  amorphous 
  ' 
  ' 
  

   hydrated 
  ferric 
  oxides, 
  which 
  were 
  found 
  to 
  be 
  from 
  a 
  

   chemical 
  standpoint 
  essentially 
  a 
  monohydrate 
  of 
  ferric 
  

   oxide, 
  and 
  in 
  all 
  probability 
  the 
  two 
  are 
  identical. 
  The 
  

   synthetic 
  yellow 
  preparations 
  present 
  then 
  the 
  same 
  pos- 
  

   sibilities 
  in 
  respect 
  to 
  their 
  nature 
  as 
  those 
  discussed 
  in 
  

   connection 
  with 
  the 
  natural 
  ' 
  ' 
  amorphous 
  ' 
  ' 
  hydrated 
  fer- 
  

   ric 
  oxides, 
  i. 
  e., 
  they 
  ultimately 
  may 
  be 
  found 
  to 
  be 
  either 
  

   goethite 
  or 
  lepidocrocite 
  or 
  isotropic 
  ferric 
  oxide 
  mono- 
  

   hydrate. 
  

  

  As 
  to 
  the 
  synthetic 
  red 
  substance 
  van 
  Bemmelen 
  52 
  

   proved 
  by 
  careful 
  dehydration 
  experiments 
  that 
  it 
  was 
  

   not 
  a 
  hydrate 
  of 
  ferric 
  oxide, 
  and 
  concluded 
  that 
  the 
  

   water 
  it 
  held 
  was 
  adsorbed. 
  The 
  latter 
  may 
  be 
  true 
  but 
  

   it 
  is 
  also 
  possible 
  that 
  these 
  red 
  substances 
  are 
  partly 
  a 
  

   solid 
  solution 
  of 
  ferric 
  oxide 
  and 
  ferric 
  oxide 
  monohy- 
  

   drate, 
  analogous 
  to 
  turgite. 
  53 
  Due 
  to 
  the 
  extreme 
  fine- 
  

   ness 
  of 
  such 
  preparations 
  they 
  undoubtedly 
  adsorb 
  a 
  con- 
  

   siderable 
  amount 
  of 
  water 
  ; 
  some 
  of 
  the 
  water, 
  however, 
  

   may 
  be 
  accounted 
  for 
  by 
  the 
  solid 
  solution 
  mentioned. 
  

   To 
  determine 
  whether 
  water 
  is 
  held 
  only 
  in 
  one 
  or 
  both 
  

   the 
  ways 
  just 
  indicated 
  is 
  very 
  difficult, 
  owing 
  to 
  the 
  char- 
  

   acter 
  of 
  the 
  material, 
  and 
  is 
  certainly 
  impossible 
  by 
  

   dehydration 
  experiments 
  alone. 
  Both 
  possibilities 
  must 
  

   therefore 
  be 
  considered. 
  

  

  Since 
  only 
  "amorphous" 
  substances 
  have 
  been 
  pre- 
  

   pared 
  artificially 
  no 
  strict 
  comparison 
  of 
  these 
  prepara- 
  

   tions 
  with 
  the 
  natural 
  crystallized 
  hydrated 
  ferric 
  oxides 
  

   can 
  be 
  made. 
  However, 
  as 
  the 
  result 
  of 
  the 
  present 
  

   investigation, 
  a 
  certain 
  analogy 
  in 
  their 
  chemical 
  compo- 
  

   sition 
  can 
  readily 
  be 
  seen: 
  in 
  both 
  cases 
  ferric 
  oxide 
  

   monohydrate 
  is 
  probably 
  the 
  only 
  definite 
  compound 
  and 
  

   it 
  is 
  likely 
  that 
  in 
  both 
  cases 
  solid 
  solutions 
  of 
  this 
  com- 
  

   pound 
  and 
  ferric 
  oxide 
  exist. 
  

  

  Description 
  of 
  Specimens. 
  

  

  GOETHITE. 
  

  

  Goethite, 
  Negaunee, 
  Michigan. 
  (N. 
  M. 
  84970).— 
  The 
  

   ends 
  of 
  two 
  prismatic 
  crystals 
  were 
  measured 
  goniomet- 
  

  

  52 
  Zs. 
  anorg. 
  Chem., 
  20, 
  185, 
  1899. 
  

  

  53 
  Kecently 
  H. 
  W. 
  Foote 
  and 
  B. 
  Saxton 
  (J. 
  Amer. 
  Chem. 
  Soc, 
  38, 
  588, 
  

   1916; 
  39, 
  1103, 
  1917) 
  attempted 
  to 
  determine 
  the 
  condition 
  in 
  which 
  water 
  

   exists 
  in 
  precipitated 
  hydrated 
  ferric 
  oxide 
  by 
  observing 
  volume 
  changes 
  

   on 
  freezing 
  such 
  preparations. 
  They 
  came 
  to 
  the 
  conclusion 
  that 
  it 
  must 
  

   be 
  essentially 
  a 
  case 
  of 
  solid 
  solutions. 
  

  

  