LmAprn;f898rm-}       Assay  of  Belladonna  Plasters.  183 
(see  Proc.  A.  Ph.  A.,  1890,  pp.  1 55— 173  ;  Pharm.  Record,  ii 
At  the  suggestion  of  Prof.  Virgil  Coblentz,  the  writer  called  upon 
these  gentlemen,  who  very  kindly  communicated  their  present  pro- 
cess, which  differs  in  important  features  from  that  published  by  them 
in  1890,  and  also  offered  to  furnish  any  other  assistance  in  their 
power.  The  writer  takes  much  pleasure  in  acknowledging  the  valu- 
able aid  rendered  to  him  by  Mr.  Williams  and  Mr.  Parker. 
The  method,  as  obtained  from  the  authors,  has  been  deviated 
from  in  the  writer's  work  only  in  minor  details,  and  is  in  outline  as 
follows :  The  plaster  is  cut  in  strips  and  the  mass  disintegrated  and 
partially  dissolved  by  stirring  with  chloroform  made  alkaline  with 
ammonia  water.  The  chloroform  mixture  is  decanted  and  the  cloth 
washed  with  successive  small  portions  of  chloroform.  The  rubber 
is  precipitated  from  the  chloroform  with  alcohol,  the  solution 
decanted  and  the  rubber  re-dissolved  with  chloroform  and  re-pre- 
cipitated with  alcohol  repeatedly  to  recover  any  alkaloid  retained  in 
it.  The  alkaloid  is  washed  out  from  the  united  alcohol-chloroform 
solutions  with  acid  water,  the  acid  solution  of  alkaloid  made  alkaline 
with  ammonia  and  extracted  with  chloroform.  After  distillation  of 
the  chloroform  the  alkaloidal  residue  is  titrated  with  acid. 
This  method  was  critically  tested  as  to  its  degree  of  accuracy  in 
the  following  manner.  Extract  of  belladonna  leaf  was  assayed  by 
the  "  shaking  out  "  process,  1-19  and  ri  5  per  cent,  of  alkaloid  being 
N 
obtained  in  duplicate  estimations,  by  titration  with  —  acid.  The 
v  *  20 
extract  was  then  mixed  with  twice  its  weight  of  a  rubber  combina- 
tion, such  as  is  used  in  the  manufacture  of  belladonna  plasters,  and 
for  which  the  writer  is  indebted  to  Mr.  S.  W.  Williams.  The  mix- 
ture was  then  assayed  by  the  above  outlined  method  and  yielded 
0  393  and  0  377  per  cent,  of  alkaloid,  the  amount  calculated  from 
the  mean  result  of  assaying  the  extract  being  0-390  per  cent.  These 
estimations  were  made  without  use  of  heat,  except  in  distilling  the 
chloroform  during  the  final  stage  of  the  process.  A  third  deter- 
mination, during  which  the  lumps  of  plaster  mass  were  heated  with 
the  alkaline  chloroform  on  a  water-bath  for  a  considerable  time,  to 
hasten  their  disintegration,  but  otherwise  conducted  in  the  same 
manner,  gave  only  0-353  per  cent. 
Repeating  the  above  experiment  with  extract  of  belladonna  root, 
one  part  of  an  extract  assaying  2-49  and  2-53   per  cent,  was 
