﻿APR. 
  19, 
  1922 
  wherry: 
  calcium 
  oxalate 
  monohydrate 
  197 
  

  

  crystallographic 
  and 
  optical 
  investigation. 
  The 
  literature 
  contains, 
  

   however, 
  contradictory 
  statements 
  as 
  to 
  its 
  optical 
  properties. 
  

   Definite 
  data 
  upon 
  these 
  properties 
  being 
  desired 
  for 
  use 
  in 
  the 
  study 
  of 
  

   this 
  compound 
  as 
  it 
  occurs 
  in 
  plant 
  tissues, 
  the 
  various 
  papers 
  have 
  

   been 
  critically 
  reviewed. 
  Crystalline 
  fragments 
  have 
  also 
  been 
  studied 
  

   by 
  the 
  immersion 
  method, 
  and 
  the 
  final 
  conclusions 
  as 
  to 
  the 
  optical- 
  

   crystallographic 
  properties 
  of 
  the 
  substance 
  are 
  here 
  presented. 
  

  

  CRYSTALLOGRAPHY 
  

  

  Calcium 
  oxalate 
  monohydrate 
  crystallizes 
  in 
  the 
  holohedral 
  class 
  

   of 
  the 
  monoclinic 
  system; 
  its 
  axial 
  ratio 
  a:b:c 
  and 
  axial 
  angle 
  /3have 
  

   been 
  determined 
  as 
  follows. 
  

  

  Authority 
  Date 
  a 
  b 
  c 
  ff 
  

  

  Miller^ 
  1840 
  .8696 
  1 
  1 
  .3695 
  72° 
  42' 
  

  

  Becke^ 
  1907 
  .8628 
  1 
  1 
  .3677 
  73 
  00 
  

  

  Ungemach^ 
  1909 
  .8620 
  1 
  1 
  .3666 
  73 
  02 
  

  

  Kolbeck, 
  Goldschmidt 
  & 
  

  

  Schroder^ 
  1918 
  .8696 
  1 
  1 
  .3695 
  72 
  42 
  

  

  The 
  elaborate 
  study 
  of 
  the 
  mineral 
  made 
  by 
  the 
  last 
  three 
  authors 
  

   appears 
  to 
  have 
  definitely 
  established 
  the 
  correctness 
  of 
  the 
  Miller 
  

   axial 
  values. 
  

  

  The 
  crystals 
  are 
  usually 
  highly 
  modified, 
  but 
  on 
  the 
  whole 
  the 
  

   base, 
  the 
  clinopinacoid 
  and 
  the 
  unit 
  prism 
  are 
  the 
  dominant 
  forms. 
  

   A 
  wide 
  variety 
  of 
  habits 
  has 
  been 
  noted. 
  See 
  figure 
  1 
  . 
  The 
  most 
  frequent 
  

   appears 
  to 
  be 
  prismatic, 
  elongated 
  on 
  axis 
  c, 
  but 
  elongation 
  in 
  the 
  direc- 
  

   tions 
  of 
  axis 
  a, 
  axis 
  6, 
  and 
  the 
  zones 
  of 
  the 
  pyramids 
  (112) 
  and 
  (121) 
  

   have 
  also 
  been 
  observed. 
  Tabular 
  habits 
  on 
  the 
  base, 
  the 
  clinopinacoid, 
  

   and 
  the 
  dome 
  (101) 
  occur 
  as 
  well. 
  Twinning 
  is 
  frequent 
  on 
  the 
  nega- 
  

   tive 
  unit 
  orthodome 
  (101). 
  At 
  all 
  of 
  its 
  seven 
  known 
  localities 
  the 
  

   mineral 
  is 
  stated 
  to 
  be 
  associated 
  with 
  some 
  carbonate 
  mineral, 
  calcite, 
  

   siderite, 
  dolomite 
  or 
  ankerite, 
  so 
  that 
  these 
  habits 
  represent 
  the 
  result 
  

   of 
  crystallization 
  in 
  an 
  alkaline 
  environment. 
  

  

  OPTICAL 
  PROPERTIES 
  

  

  The 
  values 
  of 
  the 
  refractive 
  indices 
  for 
  D 
  light, 
  a, 
  (3, 
  y, 
  and 
  optic 
  

   axial 
  angle 
  2 
  E 
  given 
  by 
  different 
  authors 
  are 
  tabulated 
  here. 
  

  

  2 
  Phil. 
  Mag. 
  (3) 
  16: 
  450. 
  1840. 
  

  

  3 
  Min. 
  petr. 
  Mitth. 
  26: 
  391. 
  1907. 
  

   * 
  Bull. 
  soc. 
  franc, 
  min. 
  32: 
  20. 
  1909. 
  

   sBeitr. 
  Krvst. 
  Min. 
  1: 
  199. 
  1918. 
  

  

  