.  4  Proximate  Analysis  of  Cinchona  Bark,  {^"^■j^^Z^^^^''''' 
water  :  this  precipitate,  contains  the  alkaloids,  and  the  filtrate,  a, 
contains  the  acids. 
The  washed  precipitate,  is  exhausted  with  (much)  ether,  giving  an 
ether-solution,  containing  the  quinia  and  quinidia,  while  cinchonia 
and  cinchonidia  are  left  undissolved.  Precipitate  a  is  again  washed  with 
water,  and  then  treated  with  90  per  cent,  alcohol,  which  dissolves  the 
cinchonidia  with  a  little  cinchonia  :  solution  c.  Precipitate  washed 
again  with  water,  remains  as  nearly  pure  cinchonia.  The  residue  of 
solution  is  the  cinchonidia  with  a  little  cinchonia.  (Cinchonia  is 
soluble  in  about  120  parts  of  90  per  cent,  alcohol  ;  cinchonidia  in  about 
12  parts  of  the  same  solvent.) 
The  quinia  and  quinidia  of  solution  are  separated  from  each  other 
by  the  unlike  solubilities  of  their  oxalates,  as  follows  :  A  moderately 
dilute  water  solution  of  oxalic  acid  is  added  to  an  acid  reaction  ;  the 
ether  is  allowed  to  evaporate  or  is  distilled  ofF ;  and  the  residue  is  treated 
with  water.  The  solution  ^,  contains  the  quinidia  as  oxalate,  together 
with  a  very  little  oxalate  of  quinia.  The  residue  is  not  soluble  in 
water,  is  dissolved  with  dilute  sulphuric  acid,  as  acid  sulphate  of  quinia,, 
solution  e.  By  precipitation  with  aqueous  alkali,  quinia  is  obtained 
from  solution     and  quinidia  from  solution  d. 
Each  of  the  four  alkaloids  may  be  obtained  in  crystals  from  a  satur- 
ated alcoholic  solution. 
In  the  work  for  acids,  the  quinovic  acid  is  precipitated  with  normal 
lead  acetate,  leaving  quinic  acid  in  solution.  Also,  if  the  lead  acetate 
is  added  short  of  saturation,  the  quinotannic  acid  remains  in  solution. 
To  accomplish  this  result,  two-thirds  of  solution  a  is  treated  with  neutral 
acetate  of  lead  solution  just  to  complete  saturation,  and  immediately 
mixed  with  the  remaining  one-third.  The  precipitate  of  quinovate  of 
lead  is  filtered  out,  washed  with  water,  suspended  in  water,  and  decom- 
posed by  dropping  in  very  dilute  sulphuric  acid,  until  the  precipitate 
turns  white,  carefully  avoiding  an  excess  (which  would  decompose  the 
quinovic  acid).  The  liquid  is  decanted  from  the  lead  sulphate,  upon  a 
/  filter,  and  the  filtrate  concentrated  and  left  some  time  to  crystallize  as 
quinovic  acid. 
The  filtrate  from  the  precipitate  by  acetate  of  lead  is  concentrated 
to  the  consistence  of  a  thin  syrup,  and  set  aside  to  crystallize.  It  may 
require  the  insertion  of  a  nucleus  for  crystallization.  There  should 
now  form  a  crystalline  mass  (quinic  acid),  mixed  with  yellowish  drops 
