METHODS  FOR  DISCRIMINATING  CINCHONA  ALKALOIDS.  241 
ON  THE  ORDINARY  METHODS  FOR  DISCRIMINATING  THE 
CINCHONA  ALKALOIDS. 
By  W.  Bird  Hekapath,  M.  D.  Lond.,  F.  R.  S.  E. 
In  consequence  of  the  gradually  increasing  scarcity  of  the 
cortex  cinchonce  calysayoe,  and  its  chief  product,  quinine,  many 
other  barks  have  been  introduced  into  commerce,  which  furnish 
alkaloids,  having  a  strong  general  resemblance  in  the  physical 
characters  of  those  preparations  of  them  more  commonly  em- 
ployed in  medicine,  but  differing  widely  in  medicinal  properties 
and  commercial  values. 
In  order  to  prevent  fraudulent  adulterations,  it  has  long  been 
highly  desirable  to  have  some  ready  methods  of  detecting  ad- 
mixtures of  these  alkaloids  and  their  salts.  The  author  having 
discovered  several  optical  salts  of  these  vegetable  alkaloids,  pro- 
poses to  make  their  well-marked  optical  characters  the  means  of 
such  detection,  and  in  a  subsequent  paper  has  fully  developed 
his  views  upon  this  ready  method  of  analysis ;  whilst  in  the  pre- 
sent he  has  passed  under  review  the  various  existing  tests  for 
the  different  cinchona  alkaloids,  and  the  results  of  his  investi- 
gations may  be  enumerated  under  the  following  conclusions  : — 
The  following  different  methods  for  detecting  the  various  cin- 
chona alkaloids  have  been  proposed  : — 
To  Bouchardat  and  Pasteur  we  are  indebted  for  the  use  of 
polarized  light  as  a  means  of  discriminating  these  alkaloids  by 
the  rotary  power  which  they  exercise  upon  its  plane. 
Liebig  employs  the  difference  of  their  solubility  in  ether  for 
the  same  purpose. 
Almost  all  the  other  tests  proposed  have  for  their  object  only 
the  discovery  of  quinine. 
Professor  Stokes  employs  fluorescence,  combined  with  the  pecu- 
liar reaction,  in  respect  to  this  phenomenon,  of  hydrochloric 
acid,  alkaline  chlorides,  &c.  Brandes,  the  green  reaction  pro- 
duced by  the  successive  addition  of  chlorine  and  ammonia,  whilst 
Vogel  has  modified  the  latter  test  in  several  ways. 
Pelletier  has  employed  the  agency  of  a  stream  of  chlorine  gas, 
and  Marchand  uses  nascent  oxygen,  obtained  from  puce-colcred 
oxide  of  lead  and  sulphuric  acid  for  the  discovery  of  quinine. 
Leers  first  proposed  a  combination  of  Liebig's  ether  test,  with 
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