344 
TESTS  FOR  THE  CINCHONA-ALKALOIDS. 
supernatant  liquid  becomes  perfectly  decolorized.  In  the  cage 
of  most  of  the  genuine  barks,  this  takes  place  in  a  short  time ; 
but  the  alcoholic  tinctures  of  the  spurious  barks,  which  contain 
kinovic  acid,  as  well  as  those  which  contain  paricin,  are  very  im- 
perfectly decolorized  by  this  process,  a  circumstance  which 
serves  to  distinguish  the  paricin  barks  and  spurious  barks  from 
the  genuine  ones. 
The  decolorized  liquid  is  now  to  be  removed  from  the  residue, 
and  the  latter  repeatedly  shaken  with  small  quantities  of  alcohol 
washed  on  the  filter  with  spirit  of  wine  and  dried.  From  the 
mixed  filtered  alcoholic  tinctures  the  greater  portion  of  the 
alcohol  can  be  recovered  by  distillation  in  the  water-bath.  Bein- 
dorfFs  distillatory  apparatus  with  Liebig's  refrigerator  is  well 
adapted  for  this  purpose — a  similar  and  much  cheaper  apparatus 
can  be  constructed  of  tin.  The  whole  quantity  of  alkaloid  which 
was  contained  in  the  bark  is  now  in  the  residue,  and,  if  the  bark 
contained  kinovic  acid,  in  combination  with  the  latter,  and  a 
peculiar  fatty  substance.  Small  proportions  of  oxidized  tannin 
are  frequently  mechanically  mixed  with  it.  In  order  to  purify 
the  alkaloid  of  the  latter  and  to  remove  the  kinovic  acid  and 
fatty  matter,  the  residue  is  to  be  placed  in  a  small  evapora- 
ting basin,  the  distilling  vessel  is  to  be  washed  with  a  small 
quantity  of  water,  slightly  acidulated  with  sulphuric  acid,  and  the 
solution  added  to  the  residue.  A  small  excess  of  diluted  sulphuric 
acid  is  to  be  dropped  into  this  mixture,  which  is  to  be  heated,  and 
when  it  again  becomes  cold  is  to  be  filtered,  and  by  this  means 
the  precipitated  kinovic  acid  and  fatty  matter  are  removed  and 
washed  with  distilled  water.  From  the  filtered  acid  solution  the 
alkaloid  is  to  be  thrown  down  by  a  slight  excess  of  ammonia ; 
and  the  mixture  evaporated  by  a  slight  heat  to  dryness.  The 
sulphate  of  ammonia  contained  in  the  cold  residue  is  to  be 
removed  by  a  small  quantity  of  very  cold  water,  and  the  residual 
alkaloid  dried  and  weighed  in  this  impure  state  ;  for  the  perfect 
purification  of  small  quantities  is  attended  with  too  great  a  loss 
to  admit  of  the  exact  determination  of  the  quantity  of  alkaloid 
contained  in  small  quantities  of  bark.  After  having  thus  deter- 
mined the  weight  of  the  alkaloid,  the  further  examination  of  it  is 
proceeded  with,,  the  cinchonine  and  quinine  are  seperated  by 
ether,  &c. 
