﻿JUNE 
  19, 
  1922 
  WHERRY 
  AND 
  HANN: 
  CALCIUM 
  FUMARATE 
  AND 
  MALEATE 
  291 
  

  

  with 
  a 
  small 
  axial 
  angle, 
  but 
  extreme 
  double 
  refraction. 
  It 
  has 
  the 
  form 
  

   of 
  rectangular 
  plates 
  and 
  irregular 
  angular 
  fragments, 
  with 
  refractive 
  

   indices 
  of 
  a 
  = 
  1.413, 
  = 
  1.602 
  and 
  y 
  = 
  1.611, 
  all 
  ±0.003. 
  

   The 
  double 
  refraction 
  is 
  thus 
  0.198, 
  and 
  2V 
  calcd. 
  = 
  22°24', 
  2E 
  

   calcd. 
  = 
  36°16', 
  2E 
  obs. 
  = 
  37° 
  ± 
  1°. 
  The 
  optical 
  orientation, 
  

   however, 
  is 
  not 
  what 
  might 
  have 
  been 
  expected 
  from 
  the 
  peritetragonal 
  

   crystal 
  form 
  ; 
  for 
  X 
  = 
  a, 
  Y 
  = 
  b 
  and 
  Z 
  = 
  c, 
  so 
  that 
  perpendicular 
  to 
  

   the 
  pinacoid 
  it 
  is 
  not 
  the 
  acute 
  but 
  the 
  obtuse 
  bisectrix 
  which 
  is 
  visible. 
  

   The 
  mean 
  refractive 
  index 
  n 
  = 
  1.539, 
  from 
  which 
  the 
  refractivity 
  

   may 
  be 
  derived, 
  using 
  the 
  formula 
  M 
  = 
  VX 
  {n- 
  — 
  l)/(w- 
  + 
  2) 
  {V 
  

   being 
  molecular 
  volume, 
  already 
  determined). 
  This 
  gives 
  M 
  = 
  34.8, 
  

   the 
  significance 
  of 
  which 
  value 
  is 
  discussed 
  after 
  the 
  data 
  for 
  calcium 
  

   maleate 
  are 
  given, 
  

  

  CAI.CIUM 
  MALEATE, 
  Ca(C4H204) 
  . 
  H2O 
  

  

  Preparation. 
  — 
  A 
  number 
  of 
  unsuccessful 
  attempts 
  were 
  made 
  to 
  

   prepare 
  this 
  salt 
  in 
  a 
  form 
  suitable 
  for 
  crystallographic 
  measurement, 
  

   but 
  the 
  crystals 
  were 
  in 
  general 
  too 
  minute 
  to 
  handle. 
  After 
  experi- 
  

   menting 
  to 
  determine 
  the 
  best 
  strengths 
  of 
  the 
  solution 
  to 
  employ, 
  the 
  

   following 
  plan 
  was 
  adopted, 
  the 
  acid 
  used 
  coming 
  from 
  the 
  same 
  

   source 
  as 
  the 
  fumarate: 
  Dissolve 
  5 
  grams 
  of 
  maleic 
  acid 
  in 
  50 
  cc. 
  of 
  

   H2O, 
  heat 
  to 
  boiling, 
  neutralize 
  with 
  30% 
  KOH 
  solution, 
  and 
  slightly 
  

   acidify 
  with 
  additional 
  acid. 
  To 
  the 
  boiling 
  solution 
  add 
  an 
  equal 
  

   volume 
  of 
  boiling 
  10% 
  CaCl2 
  solution, 
  and 
  continue 
  boiling 
  until 
  the 
  

   slight 
  bumping 
  which 
  often 
  precedes 
  precipitation 
  is 
  noticed. 
  Filter 
  

   rapidly 
  into 
  a 
  vessel 
  kept 
  at 
  about 
  80°, 
  by 
  immersion 
  in 
  a 
  large 
  water 
  

   bath, 
  cover 
  closely 
  and 
  allow 
  the 
  bath 
  to 
  cool. 
  When 
  cooling 
  is 
  rapid, 
  

   rosette 
  groups 
  of 
  needle-like 
  crystals 
  form; 
  when 
  it 
  is 
  gradual, 
  a 
  con- 
  

   tinuous 
  crust, 
  which 
  ultimately 
  develops 
  into 
  interlacing 
  needles, 
  de- 
  

   posits. 
  After 
  some 
  days 
  the 
  vessel 
  is 
  placed 
  on 
  ice 
  for 
  a 
  time 
  and 
  the 
  

   crystals 
  are 
  removed 
  and 
  dried. 
  

  

  Composition 
  .■ 
  — 
  ^On 
  ignition 
  the 
  salt 
  was 
  found 
  to 
  yield 
  a 
  residue 
  of 
  CaO 
  

   equivalent 
  to 
  32.38%, 
  showing 
  the 
  presence 
  of 
  one 
  molecule 
  of 
  water 
  

   of 
  crystallization 
  (theory 
  32.6%). 
  

  

  Crystallography 
  . 
  — 
  The 
  crystals 
  obtained 
  are 
  not 
  altogether 
  satis- 
  

   factory, 
  for 
  although 
  the 
  prism 
  faces 
  are 
  fairly 
  well 
  developed 
  and 
  do 
  

   not 
  give 
  excessive 
  variation 
  in 
  angles, 
  the 
  terminations 
  seem 
  always 
  to 
  

   be 
  dull 
  or 
  rounded. 
  However, 
  by 
  measuring 
  ten 
  crystals 
  and 
  taking 
  

   the 
  average 
  values 
  of 
  the 
  angles 
  a 
  fairly 
  close 
  approximation 
  to 
  the 
  

   probable 
  values 
  could 
  be 
  obtained. 
  It 
  is 
  noteworthy 
  that 
  the 
  more 
  

  

  