atu.  JminTMmnn.,|      Extraction  of  Alholoids  fi'om  Cinchona.  627 
without  loss,  and  transferred  to  a  small  tared  dish.  It  is  now  dried 
over  a  water-bath  until  it  ceases  to  lose  weight,  and  the  Aveight  is 
ascertained.  Add  the  compensation  above  indicated  for  mother-liquor, 
multiply  the  sum  by  five,  and  the  product  is  the  percentage  of  alka- 
loids in  the  bark  under  examination. 
The  alkaline  mother-liquor  may  now  be  used  for  ascertaining  indi- 
rectly the  percentage  of  cinchotannic  acid.  After  exposure  for  two  or 
tiiree  days  in  a  shallow  dish,  by  which  the  cinchotannic  acid  becomes 
converted  into  cinchona  red,  ^  the  liquid  is  lieated,  and  hydrochloric 
acid  cautiously  added  to  slight  acid  reaction.  After  cooling,  the  now 
turbid  liquor  is  filtered  through  a  double  filter  to  collect  the  very 
voluminous  precipitate  of  cinchona  red.  The  precipitate  is  washed, 
dried,  and  weighed,  the  second  filter  being  used  as  a  tare.^  By  multi- 
plying the  ascertained  weight  of  cinchona  red  by  1*2,  a  close  approxi- 
mation to  the  weight  of  cinchotannic  acid  is  obtained,  from  which  its 
percentage  may  be  calculated,  and  it  will  be  seen  that  the  quantity  of 
cinchotannic  acid  in  different  species  of  cinchona,  and  even  in  different 
samples  of  the  same  species,  varies  considerably. 
2.  The  acid  solution  is  mixed  with  excess  of  caustic  soda  as  before, 
and  well  shaken  in  a  bottle  with  1  litre  of  commercial  benzol,  and  left 
standing  for  not  more  than  five  minutes,  for  the  benzol,  which  now 
contains  the  alkaloids  in  solution,  to  separate.^  The  benzol  solution  is 
now  decanted  on  a  filter  previously  moistened  with  benzol,  and  the 
remainder  is  poured  into  a  separating  funnel.  After  sufficient  time 
for  separation,  the  red  alkaline  liquor  is  drawn  off  into  the  bottle 
previously  used,  and  shaken  with  other  200  cc.  benzol  to  remove 
possible  traces  of  alkaloid.,  and  this  benzolic  solution  is  also  filtered  and 
added  to  the  former.    The  amount  of  alkaloids  contained  in  the 
1  If  the  dark-red  alkaline  liquor  becomes  turbid  during  exposure  to  air 
the  quantity  of  caustic  soda  is  insufficient  for  solution  of  the  newly  formed 
cinchona  red,  and  more  soda  must  be  added. 
2  Althouj;h  I  am  opposed  to  drying  precipitates  upon  the  filter,  it  is  una- 
voidable in  this  case,  because  the  moist  cincliona  red  cannot  be  conveni- 
ently removed. 
A  litre  of  benzol  (boiling  at  from  85°  to  120°C.)  dissolves  all  the  alkaloids 
of  20  grammes  bark.  By  long  standing,  however,  a  slight  separation  of 
crystallized  benzolate  of  alkaloid,  chiefly  cinchonine,  may  sometimes  take 
place  and  affect  the  accuracy  of  the  result.  I,  therefore,  recommend  that 
it  should  not  be  allowed  to  stand  for  more  than  5  minutes  The  benzol 
may  be  used  reix^atedly,  without  redistillation,  and  with  but  little  loss. 
