﻿D. 
  A. 
  Kr 
  eider 
  — 
  Detection 
  and 
  Separation^ 
  etc. 
  ■ 
  133 
  

  

  Aet. 
  XIY. 
  — 
  A 
  Method 
  for 
  the 
  Detection 
  and 
  Separation 
  

   of 
  Dextro- 
  and 
  Lcevo-rotating 
  Crystals, 
  with 
  Some 
  Obser- 
  

   vations 
  upon 
  the 
  Growth 
  and 
  Properties 
  of 
  Crystals 
  of 
  

   Sodium 
  Chlorate 
  ; 
  by 
  D. 
  Albeet 
  Keeidee. 
  

  

  Two 
  properties 
  of 
  optically 
  active 
  crystals 
  are 
  available 
  for 
  

   their 
  detection 
  and 
  separation. 
  First, 
  the 
  sense 
  of 
  the 
  optical 
  

   activity 
  itself, 
  and 
  second, 
  the 
  hemihedral 
  structure 
  which, 
  in 
  

   many 
  cases 
  at 
  least, 
  differentiates 
  the 
  enantiomorphic 
  forms. 
  

   While 
  it 
  is 
  possible, 
  in 
  some 
  cases, 
  as 
  in 
  the 
  separation 
  of 
  the 
  

   dextro 
  and 
  Isevo 
  tartaric 
  acids 
  by 
  the 
  crystallization 
  of 
  the 
  

   sodium-ammonium 
  racemate, 
  according 
  to 
  the 
  method 
  of 
  

   Pasteur, 
  to 
  pick 
  out 
  the 
  two 
  sets 
  of 
  crystals 
  by 
  taking 
  advan- 
  

   tage 
  of 
  their 
  hemihedral 
  structure, 
  this 
  is 
  rarely 
  if 
  ever 
  the 
  

   case 
  with 
  crystals 
  of 
  sodium 
  chlorate, 
  which 
  in 
  many 
  respects 
  is 
  

   the 
  most 
  desirable 
  substance 
  to 
  employ 
  in 
  certain 
  investigations 
  

   upon 
  optical 
  activity. 
  

  

  In 
  these 
  crystals 
  it 
  is 
  only 
  rarely 
  that 
  the 
  hemihedral 
  pyra- 
  

   midal 
  face 
  which 
  distinguishes 
  the 
  dextro 
  from 
  the 
  l^evo 
  form, 
  

   is 
  sufficiently 
  well 
  developed 
  to 
  enable 
  one 
  to 
  distinguish 
  thus 
  

   between 
  them. 
  Indeed 
  in 
  not 
  a 
  single 
  set 
  of 
  the 
  many 
  crops 
  

   of 
  crystals 
  which 
  the 
  writer 
  has 
  grown 
  has 
  there 
  been 
  any 
  

   considerable 
  number 
  of 
  crystals 
  showing 
  even 
  traces 
  of 
  this 
  

   face. 
  The 
  crystals 
  commonly 
  grow 
  in 
  rectangular 
  forms; 
  

   these 
  vary 
  greatly 
  in 
  shape, 
  some 
  being 
  cubical, 
  but 
  almost 
  

   without 
  exception 
  they 
  are 
  flattened 
  and 
  very 
  generally 
  elon- 
  

   gated, 
  with 
  the 
  hemihedral 
  faces 
  rarely 
  showing. 
  

  

  Dependence 
  must, 
  therefore, 
  be 
  placed 
  upon 
  their 
  optical 
  

   properties, 
  and 
  this 
  involves 
  the 
  use 
  of 
  the 
  polarimeter 
  or 
  

   polarization-microscope, 
  both 
  of 
  which 
  are 
  expensive 
  and 
  unsat- 
  

   isfactory 
  for 
  this 
  purpose, 
  inasmuch 
  as 
  only 
  one 
  crystal 
  at 
  a 
  

   time 
  can 
  be 
  examined 
  and 
  even 
  then 
  for 
  a 
  decisive 
  test 
  must 
  

   be 
  of 
  considerable 
  size. 
  

  

  In 
  the 
  course 
  of 
  an 
  extended 
  investigation 
  upon 
  related 
  sub- 
  

   jects 
  which 
  involved 
  the 
  separation 
  of 
  the 
  two 
  kinds 
  of 
  crys- 
  

   tals, 
  some 
  of 
  the 
  results 
  of 
  which 
  have 
  been 
  published 
  in 
  a 
  

   recent 
  communication 
  from 
  this 
  laboratory,"^ 
  I 
  have 
  been 
  

   impressed 
  with 
  the 
  inconvenience 
  and 
  tedium 
  of 
  the 
  methods 
  

   usually 
  employed. 
  My 
  efforts 
  to 
  devise 
  some 
  means 
  of 
  effect- 
  

   ing 
  the 
  separation, 
  which 
  would 
  be 
  more 
  expeditious 
  and 
  at 
  the 
  

   same 
  time 
  sufficiently 
  delicate, 
  have 
  resulted 
  in 
  a 
  very 
  simple 
  

   arrangement 
  of 
  apparatus 
  the 
  parts 
  of 
  which 
  may 
  be 
  found 
  

   in 
  any 
  laboratory 
  and 
  which 
  makes 
  it 
  possible 
  to 
  examine 
  a 
  

   whole 
  crop 
  of 
  crystals 
  in 
  a 
  glance 
  or 
  to 
  separate 
  them 
  with 
  

   ease. 
  Moreover, 
  it 
  permits 
  of 
  the 
  examination 
  or 
  determina- 
  

  

  *This 
  Journal, 
  vol. 
  vi, 
  p. 
  416, 
  1898. 
  

  

  