628  Extraction  of  Alkaloids  from  Cinchona.  {^"'•£^1885^'"'*' 
mixed  benzolic  solutions  may  now  be  determined  either  directly  or 
indirectly  in  the  manner  following,  viz. : 
Direct  Determination. 
The  benzolic  solution  is  shaken  with  30  cc.  very  dilute  nitric  acid^ 
the  acid  solution  is  drawn  off  and  replaced  by  20  cc.  water,  which  is 
again  shaken  and  added  to  the  first.  The  liquors  are  heated  to  drive 
off  traces  of  benzol,  and  when  cool  transferred  to  a  separator  and 
shaken  Avith  200  cc.  ether,  and  an  excess  of  caustic  soda.  In  this  way 
all  the  alkaloids  are  dissolved  by  the  ether/  leaving  generally  a  slight 
brown  film  on  the  surface  of  the  alkaline  liquor,  which  is  almost 
entirely  soluble  in  chloroform.^  After  separating  the  ethereal  solution 
a  further  100  cc.  ether  is  shaken  with  the  alkaline  liquor,  and  is  then 
added  to  the  first.  By  distillation  of  the  ether,  the  whole  of  the  alka- 
loids are  left  in  a  state  of  greater  purity  thai)  I  have  ever  obtained 
them  by  any  other  process. 
Indirect  Determination. 
The  benzolic^  solution  is  well  shaken  with  70  cc.  deci-normal 
sulphuric  acid.  The  acid  solution  is  drawn  off"  and  replaced  by  30  cc. 
water,  which  is  again  shaken  and  added  to  the  other.  The  aqueous 
liquors  arc  heatetl,  and  accurately  neutralized  by  deci-norraal  solution 
of  caustic  soda  until  the  color  of  reddened  litmus  is  affected  by  it» 
The  quantity  of  soda  solution  required  for  saturation  is  now  to  be 
deducted  from  70  cc.  (the  equivalent  of  70  cc.  deci-normal  sulphuric 
acid),  and  the  difference  multiplied  by  '031  ^  is  the  weight  of  alkaloid 
1  Whilst  preparing  this  paper  I  found  that  the  succirubra  bark  used  in 
Bengal  for  the  manulaeture  of  cinchona  febrifuge  proved  an  exception  to 
this  rule  ;  iov,  although  the  whole  of  the  alkaloids  are  at  first  dissolved  by 
the  ether,  a  separation  of  small  crystals  of  cinchonine  quickly  followed  to 
the  extent  of  017  gramme.  I  attribute  this  to  the  large  proportion  of  cin- 
chonine contained  in  this  bark,  which  I  have  found  to  amount  to  as  much 
as  49-3  per  cent,  of  the  total  alkaloids. 
^'This  brown  substance,  which  is  not  alkaloid,  is  the  reason  why  analyses 
of  bark,  in  which  chloroform  is  the  solvent,  yield  an  apparent  higher  per- 
centage of  alkaloids. 
3  0-031  gramme  is  the  weight  of  alkaloid  corresponding  to  1  cc.  of  a  deci- 
normal  solution.  The  molecular  weight  of  the  mixed  alkaloids  of  cinchona 
bark  being,  as  previously  stated,  310. 
