342 
TESTS  FOR  THE  CINCHONA-ALKALOIDS. 
for  several  years  past,  devised  and  employed  a  method  by  which 
not  only  the  proportion  of  the  alkaloid,  but  also  that  of  the 
kinovic  acid  may  be  quantitatively  and  qualitatively  determined, 
whilst  at  the  same  time  the  proportion  of  both  kinic  acid  and 
oxidized  tannin  (cinchona  red)  is  indicated.  So  that  all  those 
constituents  of  the  bark,  which  are  of  importance  for  medical 
practice,  are  determined. 
The  barks  tested  by  this  method,  yield,  when  employed  for  the 
manufacture  of  the  alkaloid  on  a  large  scale,  exactly  the  same 
quantity  which  they  yield  by  the  experiment,  generally  one-eighth 
to  one-quarter  per  cent,  more,  the  loss  in  working  with  large 
quantities  being  naturally  less  in  proportion,  and  this  indeed  is 
the  best  proof  of  the  efficiency  of  this  method. 
In  the  qualitative  examination  of  cinchona  barks,  a  number  of 
tests  have  hitherto  been  employed,  which  have  not  only  [not]  aided 
this  examination,  but  have  rendered  it  much  more  difficult. 
The  efficacy  of  the  bark  depends,  as  is  well  known,  chiefly  on 
the  proportion  of  alkaloid,  and  of  that  of  pure  and  oxidized  cin- 
chona-tannin. Of  the  kinovic  acid,  we  only  know  that  it  does 
not  act  as  a  febrifuge.  The  medicinal  virtues  of  kinic  acid  or 
kinate  of  lime  have  not  yet  been  determined.  We  must,  there- 
fore, confine  ourselves  to  the  application  of  those  tests  by  means 
of  which  these  compounds  can  be  detected  in  an  infusion  of 
bark,  and  their  quantitative  proportion  at  least  approximative^ 
determined.  These  are,  as  has  been  before  stated  in  my  mono- 
graph on  genuine  barks,  as  follows  : — 
1.  Tannin,  for  detecting  the  alkaloids.  The  more  abundant 
the  precipitate  produced  Jby  this  reagent  in  the  aqueous  filtered 
infusion,  the  more  alkaloid  do  the  barks  contain. 
2.  Chloride  of  iron  determines  the  proportion  of  oxidized  tan- 
nin by  the  more  or  less  intensely  dark-grey  coloration,  which 
speedily  becomes  brown,  and  by  the  subsequent  more  or  less 
abundant  pulverulent  precipitate  of  a  dark,  dirty,  brownish-green 
color. 
3.  G-elatine  {solution  of  isinglass,)  like  chloride  of  iron,  occa- 
sions the  oxidized  tannin  to  be  precipitated.  In  the  liquid 
filtered  from  the  magma,  the  proportion  of  non-oxidized  cinchona- 
tannin  may  be  determined  by  iodic  acid.  The  latter  oxidizes 
the  tannin,  and  causes  the  precipitation  of  a  yellowish  brown 
