1 86  Assay  of  Belladonna  Plasters.       { Xm ^  ™£rm- 
or  any  other  convenient  receptacle  the  acid  solution,  which  contains 
most  of  the  alkaloid.  Wash  out  the  empty  separator  with  10  c.c. 
of  water  containing  a  few  drops  of  dilute  acid,  draw  the  washings 
off  into  the  second  separator  and  agitate  this  as  before.  Draw  off 
the  chloroform-alcohol  into  the  first  separator  and  add  the  water 
solution  to  the  first  portion.  If  the  contact-line  of  the  two  liquids 
is  perfect,  so  as  to  permit  a  complete  separation  of  them,  only  a  third 
portion  of  acidulated  water  will  be  required  to  remove  all  alkaloid 
from  the  chloroform,  notwithstanding  the  presence  of  a  large  pro- 
portion of  alcohol;  but  if  any  considerable  amount  of  solid  matter 
collects  at  the  line  of  contact,  a  fourth  or  even  fifth  portion  will  be 
necessary. 
Make  the  combined  acid  solutions  alkaline  with  ammonia-water  and 
wash  out  the  alkaloid  in  a  separator  with  3  successive  portions  of  20, 
10,  and  10  c.c.  of  chloroform,  observing  the  same  precautions  to  avoid 
emulsions  as  before.  Wash  the  combined  chloroform  solutions  with 
10  c.c.  of  water  to  remove  any  adhering  ammonium  salts  or  other  im- 
purities drawn  off  with  the  chloroform,  and  after  complete  separation 
transfer  the  chloroform  solution  to  a  small  flask.  Agitate  the  water 
in  the  separator  with  10  c.c.  of  chloroform  and  after  separation  add 
the  latter  to  that  in  the  flask. 
Evaporate  or  distil  off  the  chloroform.  If  distilled,  great  care 
must  be  taken  that  the  tube  and  cork  connecting  the  flask  with  the 
condenser  are  perfectly  clean,  as  the  estimation  would  be  vitiated 
by  the  presence  of  even  minute  quantities  of  acids  or  alkalies.  If 
the  chloroform  is  to  be  evaporated,  precautions  are  necessary,  in 
view  of  the  observations  of  Dieterich,  that  alkaloids  may  become 
partially  neutralized  by  hydrochloric  acid,  which  is  formed  through 
the  action  of  the  gas  flame  on  chloroform  vapors.  It  is  advisable, 
therefore,  not  to  conduct  the  evaporation  in  shallow  vessels,  unless 
it  can  be  done  through  a  source  of  heat  not  necessitating  the  use  of 
a  flame.  It  is  considered  safe,  however,  to  evaporate  on  a  water- 
bath  over  a  gas  flame,  if  the  chloroform  solution  is  contained  in  a 
flask  having  a  narrow  neck,  and  evaporation  carried  on  rapidly  by 
boiling. 
N 
To  the  alkaloidal  residue  add  4  c.c.  of  —  acid  and  agitate  by 
20 
rotation  until  all  alkaloid  is  dissolved.  This  is  not  always  easy  to 
decide,  as  there  is  nearly  always  more  or  less  of  an  insoluble  resi- 
