﻿138 
  D. 
  A. 
  Kreider 
  — 
  Detection 
  and 
  Separation^ 
  etc. 
  

  

  results 
  were 
  in 
  no 
  respects 
  different 
  from 
  those 
  obtained 
  when 
  

   an 
  equal 
  quantity 
  of 
  both 
  crystals 
  were 
  taken 
  at 
  the 
  start. 
  

   The 
  same 
  was 
  done 
  with 
  laevo 
  crystals 
  and 
  with 
  a 
  number 
  of 
  

   independent 
  lots. 
  In 
  one 
  case, 
  starting 
  with 
  pure 
  Igevo 
  crystals, 
  

   a 
  crop 
  having 
  eighty 
  per 
  cent 
  of 
  dextro 
  crystals 
  was 
  obtained 
  and 
  

   upon 
  recrystallization 
  gave 
  an 
  excess 
  of 
  Isevo. 
  To 
  record 
  the 
  

   results 
  in 
  detail, 
  is 
  hardly 
  worth 
  the 
  space. 
  It 
  may 
  simply 
  be 
  

   said, 
  that 
  there 
  is 
  no 
  connection 
  whatever 
  with 
  the 
  'optical 
  

   activity 
  of 
  the 
  original 
  crystals 
  and 
  that 
  of 
  the 
  new 
  crop. 
  

   This 
  will 
  of 
  course 
  be 
  true 
  only 
  when 
  the 
  crystals 
  are 
  thoroughly 
  

   dissolved 
  or 
  the 
  solution 
  filtered 
  before 
  recrystallization 
  , 
  since 
  

   any 
  nucleus 
  left 
  in 
  it 
  would 
  affect 
  the 
  result, 
  as 
  the 
  following 
  

   experiments 
  prove. 
  

  

  In 
  the 
  second 
  case, 
  as 
  has 
  previously 
  been 
  pointed 
  out, 
  when 
  

   a 
  crystal 
  of 
  one 
  kind 
  is 
  placed 
  in 
  a 
  saturated 
  solution, 
  the 
  

   resultant 
  optical 
  activity 
  of 
  the 
  crop 
  of 
  crystals 
  is 
  always 
  the 
  

   same 
  as 
  that 
  of 
  the 
  crystal 
  inserted 
  ; 
  the 
  percentage, 
  however, 
  

   seems 
  to 
  depend 
  upon 
  the 
  rate 
  of 
  precipitation. 
  This 
  seems 
  

   to 
  point 
  to 
  the 
  influence 
  of 
  the 
  first 
  crystal 
  formed, 
  as 
  the 
  cause 
  

   of 
  the 
  excess 
  of 
  one 
  or 
  the 
  other 
  kind 
  in 
  the 
  crop. 
  To 
  further 
  

   investigate 
  this, 
  I 
  have 
  grown 
  crystals 
  by 
  carefully 
  observing 
  

   the 
  optical 
  properties 
  of 
  the 
  first 
  one 
  formed. 
  The 
  apparatus 
  

   illustrated 
  in 
  fig. 
  1 
  is 
  admirably 
  adapted 
  to 
  this 
  purpose, 
  since 
  

   it 
  permits 
  of 
  the 
  observations 
  without 
  the 
  slightest 
  disturbance 
  

   of 
  the 
  crystallizing 
  solution. 
  Owing 
  to 
  the 
  irregularity 
  in 
  the 
  

   rate 
  of 
  formation 
  of 
  the 
  crystals 
  under 
  varying 
  conditions 
  of 
  

   temperature 
  and 
  humidity, 
  a 
  series 
  of 
  such 
  results 
  is 
  tedious 
  

   and 
  difficult 
  ; 
  demanding 
  the 
  continual 
  presence 
  of 
  the 
  observer, 
  

   in 
  order 
  that 
  the 
  determination 
  should 
  be 
  made 
  at 
  the 
  moment 
  

   of 
  the 
  appearance 
  of 
  the 
  first 
  crystal. 
  For 
  example, 
  one 
  

   experiment 
  which 
  was 
  started 
  at 
  noon 
  by 
  filtering 
  a 
  portion 
  of 
  

   a 
  saturated 
  solution 
  — 
  in 
  this 
  case 
  one 
  which 
  had 
  stood 
  over 
  an 
  

   excess 
  of 
  crystals 
  for 
  several 
  weeks 
  and 
  had 
  been 
  well 
  shaken 
  

   several 
  times 
  daily 
  — 
  had 
  formed 
  no 
  crystals 
  by 
  9 
  o'clock 
  of 
  the 
  

   next 
  day 
  ; 
  though 
  by 
  10.30, 
  nine 
  fair-sized 
  crystals 
  had 
  

   developed. 
  In 
  other 
  cases 
  they 
  appeared 
  during 
  the 
  same 
  

   afternoon 
  or 
  night. 
  Moreover, 
  any 
  particles 
  of 
  dust 
  settling 
  

   on 
  the 
  solution 
  form 
  nuclei, 
  about 
  which 
  clusters 
  of 
  crys- 
  

   tals 
  are 
  apt 
  to 
  develop 
  and 
  in 
  such 
  cases 
  grow 
  more 
  rapidly 
  

   than 
  those 
  under 
  the 
  liquid, 
  though 
  the 
  latter 
  may 
  have 
  been 
  

   first 
  to 
  appear. 
  The 
  conclusion 
  of 
  many 
  experiments 
  was 
  pre- 
  

   vented 
  in 
  this 
  way., 
  as 
  well 
  as 
  by 
  the 
  simultaneous 
  appearance 
  

   of 
  a 
  number 
  of 
  crystals. 
  However, 
  by 
  taking 
  precautions 
  

   against 
  dust 
  and 
  by 
  securing 
  approximate 
  uniformity 
  of 
  tem- 
  

   perature, 
  etc., 
  a 
  number 
  of 
  experiments 
  were 
  successfully 
  con- 
  

   cluded 
  : 
  and 
  in 
  every 
  single 
  case 
  where 
  the 
  first 
  crystal 
  formed 
  

   developed 
  appreciably 
  before 
  others 
  appeared, 
  the 
  resultant 
  

   activity 
  of 
  the 
  crop 
  was 
  invariably 
  that 
  of 
  the 
  first 
  crystal. 
  

  

  Sloane 
  Physical 
  Laboratory. 
  

  

  Yale 
  University, 
  July 
  1, 
  1899. 
  

  

  