Am'ju7y?i899arm"}     Acetic. Acid  in  Extracting  Drugs.  315 
degree  of  bitterness  of  the  final  percolate,  which  is  not  quite  bitter- 
free  when  the  cotton  and  the  lower  part  of  the  powder  is  quite  bit- 
ter-free though  not  tasteless.1 
The  entire  percolate  is  evaporated  in  a  flat-bottom  capsule  to  the 
condition  of  a  soft  solid  when  cold,  capable  of  being  stirred  when 
hot.  This  extract  usually  weighs  35  to  38  per  cent,  of  the  cin- 
chona and  it  retains  a  small  amount  of  acetic  acid.  While  heated 
on  the  water-bath,  30  c.c.  of  a  previously  made  mixture  of  5  vol- 
umes of  10  per  cent,  water  of  ammonia  and  15  volumes  of  91  per 
cent,  alcohol  is  added,  the  mixture  is  stirred  to  a  uniform  condition 
and  poured  into  a  separator  of  160  to  180  c.c.  capacity.  The  cap- 
sule is  rinsed  into  the  separator  with  a  mixture  of  10  c.c.  of  the  am- 
monia mixture  and  10  c.c.  of  alcohol,  and  the  whole  is  well  shaken 
together.  If  much  ammonia  has  been  lost  in  dissolving  the  extract 
— if  much  acetic  acid  should  have  been  retained  in  the  extract,  or  if 
the  cinchona  should  be  very  rich  in  alkaloids,  the  40  c.c.  of  am- 
monia mixture  may  be  insufficient  to  set  the  alkaloids  free.  This 
point  is  always  to  be  assured  by  the  smell  of  ammonia  at  the  mouth 
of  the  separator,  or  by  holding  a  strip  of  wet  and  neutral  litmus 
paper  in  the  air  space  of  the  separator.  If  the  alkaline  reaction  be 
not  full  and  prompt,  5  c.c.  more  of  the  ammonia  mixture  is  added 
and  the  shaking  and  testing  repeated. 
Then  40  c.c.  of  chloroform  (96  per  cent.)  is  poured  into  the  separa- 
tor, the  whole  is  vigorously  shaken  for  five  minutes  and  then  allowed 
to  separate.  This  separation  requires  ten  to  fifteen  minutes  and 
then  the  chloroform  solution  is  drawn  off  into  a  tared  flask  of  about 
100  c.c.  capacity,  and  is  put  upon  the  water-bath  to  boil  off  the 
chloroform.  Then  5  c.c.  of  alcohol  (91  per  cent.)  is  added  to  the 
residue  in  the  separator,  is  shaken  in,  and  then  a  second  40  c.c.  of 
chloroform  is  added,  and  the  whole  is  again  shaken  for  five  minutes, 
allowed  to  separate,  the  chloroform  drawn  off  into  the  tared  flask 
1  In  these  percolations,  especially  when  on  a  larger  scale,  it  is  difficult  to  get 
a  bitter-free  final  percolate  and  residue,  so  that  it  was  desirable  to  know  how 
much  bitterness  was  consistent  with  practical  exhaustion.  A  solution  of  total 
alkaloids  of  cinchona  of  one  part  in  100,000  of  water  was  made,  and  this  was 
perceptibly  though  faintly  and  transiently  bitter  to  several,  but  not  to  all  or- 
dinary tastes.  This,  therefore,  is  not  bitter-free.  One  part  in  10,000  was  dis- 
tinctly and  rather  permanently  bitter,  and  as  this  is  buto'oi  of  1  per  cent.,  it  is 
considered,  on  the  large  scale,  as  practical  exhaustion. 
