METHODS  FOE,  DISCRIMINATING  CINCHONA  ALKALOIDS.  245 
fluid  containing  only  1  grain  of  alkaloid  in  800  grains  of  water, 
and  very  readily  detects  immediately  1  part  in  350.  It  does 
not  precipitate  quinidin  or  cinchonidin,  but  it  produces  a  white 
precipitate  in  concentrated  solutions  of  cinchonine. 
XII.  De  Vry's  test  for  quinidin  by  hydriodic  acid,  or  iodide  of 
potassium  in  neutral  solutions,  produces  a  well-marked  crystal- 
line precipitate  as  a  colorless  salt,  when  1  part  of  the  alkaloid  is 
present  in  1000  of  the  fluid ;  the  crystals,  being  short  hemihe- 
dral  prisms,  are  readily  recognized ;  the  neutral  hydriodates  of 
cinchonidin  are  colorless,  silky,  prismatic  needles,  and  much 
more  soluble.  If  to  a  solution  of  the  sulphate  of  quinidin  in 
dilute  spirit  (i)  we  add  hydriodic  acid  and  expose  to  the  action 
of  light  during  some  days,  there  is  formed  the  red  iodo-sulphate 
of  the  author. 
The  neutral  hydriodate  of  quinine  appears  as  lemon-yellow 
prisms.  The  neutral  hydriodate  of  cinchonine  appears  as  long, 
thick,  colorless  prisms,  and  is  very  soluble. 
XIII.  Leibig's  ether  test  dissolves  quinine,  quinicine,  and  cin- 
chonicine,  and  therefore  does  not  discriminate  between  them,  as 
they  are  all  uncrystallizable.  It  dissolves  also  a  portion  of  the 
quinidin  and  cinchonidin.  Should  the  proportions  of  these  alka- 
loids not  exceed  the  solvent  powers  of  the  ether  employed,  they 
will  not  be  indicated  by  this  test.  When  crystallization  occurs, 
the  rhombic  prisms  indicate  cinchonidin  ;  the  long  slender  aci- 
culse,  quinidin ;  whilst  an  amorphous  powder  is  demonstrative  of 
cinchonine.  Ether  also  extracts  cinchonidin  from  cinchonine ; 
but  its  sparing  solubility  in  ether  necessitates  the  employment 
of  warmth,  and  a  large  quantity  of  ether. 
XIV.  Leer's  combination  of  the  ether  test  with  that  of  Bran- 
des  can  readily  detect  small  portions  of  quinine,  quinidin,  or 
quinicine  in  cinchonine  or  cinchonidin,  especially  when  used  in 
the  manner  as  modified  by  the  author. — Proceedings  of  the 
Royal  Society,  from  London  Pharm.  Journal,  March  18589 
