﻿JUNE 
  19, 
  1922 
  WHERRY 
  AND 
  hann: 
  calcium 
  fumarate 
  and 
  maleate 
  295 
  

  

  refraction 
  weaker. 
  It 
  appears 
  under 
  the 
  microscope 
  in 
  rods 
  or 
  frag- 
  

   ments, 
  with 
  the 
  indices: 
  a 
  = 
  1.495, 
  /3 
  = 
  1.580, 
  y 
  = 
  1.640, 
  all 
  

   ±0.003, 
  making 
  the 
  double 
  refraction 
  0.145. 
  The 
  axial 
  angle 
  2V 
  is 
  

   calculated 
  to 
  be 
  77°36', 
  and 
  2E 
  164°; 
  this 
  is 
  too 
  great 
  an 
  angle 
  to 
  

   be 
  determined 
  by 
  the 
  immersion 
  method. 
  The 
  orientation 
  is 
  A'= 
  c, 
  

   Y 
  = 
  a, 
  and 
  Z 
  = 
  b, 
  so, 
  as 
  in 
  the 
  case 
  of 
  the 
  fumarate, 
  the 
  longer 
  crystal 
  

   axes 
  do 
  not 
  correspond 
  to 
  the 
  lesser 
  refractive 
  indices. 
  The 
  mean 
  

   n 
  = 
  1.571 
  gives, 
  on 
  the 
  same 
  basis 
  as 
  before, 
  the 
  refractivity 
  30.8. 
  

  

  DISCUSSION 
  OF 
  THE 
  REFRACTIVITY 
  DATA 
  

  

  The 
  refractivities 
  of 
  the 
  elements 
  other 
  than 
  calcium 
  used 
  are 
  those 
  

   of 
  Eisenlohr:^ 
  C 
  = 
  2.4, 
  0= 
  = 
  2.2, 
  —0— 
  = 
  1.5, 
  and 
  H 
  = 
  1.1. 
  

   In 
  calcium 
  formate 
  two 
  entirely 
  separate 
  acid 
  radicles 
  are 
  present, 
  

   so 
  the 
  difference 
  between 
  the 
  total 
  refractivity 
  and 
  that 
  calculated 
  

   for 
  the 
  elements 
  of 
  the 
  radicle 
  may 
  be 
  regarded 
  as 
  the 
  normal 
  value 
  for 
  

   calcium. 
  It 
  is 
  4.9. 
  

  

  In 
  calcium 
  oxide 
  X-ray 
  study 
  has 
  shown 
  the 
  atoms 
  to 
  be 
  arranged 
  

   as 
  shown, 
  with 
  directions 
  of 
  attraction 
  (electrostatic) 
  also 
  perpendicu- 
  

   lar 
  to 
  the 
  paper. 
  This 
  represents 
  but 
  little 
  strain, 
  and 
  the 
  additional 
  

   refractivity 
  due 
  to 
  the 
  structure 
  is 
  slight. 
  In 
  the 
  oxalate 
  the 
  calcium 
  

   unites 
  the 
  two 
  ends 
  of 
  the 
  radicle 
  into 
  a 
  ring, 
  and 
  as 
  would 
  be 
  expected 
  

   this 
  produces 
  a 
  slightly 
  higher 
  extra 
  refractivity. 
  

  

  In 
  calcium 
  maleate 
  a 
  double 
  bond 
  is 
  present, 
  which 
  according 
  to 
  

   Eisenlohr 
  produces 
  in 
  any 
  case 
  an 
  extra 
  refractivity 
  of 
  1.0; 
  but 
  in 
  

   addition 
  the 
  calcium 
  unites 
  two 
  ends 
  of 
  the 
  radicle. 
  The 
  ring 
  pro- 
  

   duced 
  in 
  this 
  case 
  is 
  much 
  larger 
  than 
  that 
  of 
  the 
  oxalate, 
  and 
  the 
  

   double 
  bond 
  forms 
  part 
  of 
  the 
  ring, 
  so 
  that 
  an 
  additional 
  strain 
  must 
  

   be 
  represented 
  ; 
  and 
  this 
  is 
  seen 
  to 
  produce 
  an 
  excess 
  of 
  refractivity 
  

   of 
  2.0. 
  

  

  The 
  most 
  complex 
  of 
  all 
  of 
  the 
  compounds 
  considered 
  is 
  calcium 
  

   fumarate, 
  which 
  not 
  only 
  has 
  the 
  calcium 
  uniting 
  the 
  ends 
  of 
  the 
  radi- 
  

   cle 
  into 
  a 
  ring, 
  but 
  also, 
  because 
  the 
  position 
  of 
  the 
  substituting 
  

   groups 
  with 
  respect 
  to 
  the 
  double 
  bond, 
  has 
  an 
  irregular 
  ring. 
  Still 
  

   more 
  excess 
  refractivity 
  than 
  in 
  the 
  maleate 
  would 
  be 
  expected, 
  and 
  

   as 
  a 
  matter 
  of 
  fact 
  the 
  calculation 
  gives 
  2.3. 
  

  

  SUMMARY 
  

  

  The 
  preparation 
  and 
  crystallographic-optical 
  properties 
  of 
  calcium 
  

   fumarate 
  and 
  maleate 
  are 
  described. 
  Both 
  are 
  orthorhombic, 
  but 
  

   they 
  show 
  no 
  definite 
  space 
  relationships. 
  From 
  a 
  calculation 
  of 
  the 
  

  

  ^ 
  Spektrochemie 
  Organischer 
  Verbindungen, 
  p. 
  48. 
  1912. 
  

  

  