Am.  Jour.  Pharm.l 
March,  18S9.  f 
Assay  of  Belladonna  Leaves. 
113 
The  question  suggested  itself:  "To  what  extent  does  the  stearic 
acid  interfere  with  the  accuracy  of  the  assay?"  The  following 
experiments  answer  this  question  : 
(1)  O-ioo  gramme  stearic  acid  (a  quantity  far  in  excess  of  that 
actually  used  in  the  assays)  was  dissolved  in  10  c.c.  alcohol,  1  c.c.  of 
a  diluted  ammonia  water,  30  c.c.  water,  and  3  drops  hematoxylin 
indicator  added,  required  0-75  c.c.  HC1. 
(2)  In  a  similar  experiment,  omitting  the  stearic  acid  075  c.c. 
HO  were  needed. 
(3)  0100  gramme  stearic  acid  dissolved  in  10  c.c.  alcohol,  0-5  c.c. 
of  a  more  dilute  ammonia  water,  30  c.c.  water,  and  3  drops  indi- 
cator added,  required  0  2  c.c.  HC1. 
(4)  A  similar  experiment,  omitting  the  stearic  acid  required 
0-3  c.c.  HC1. 
(5)  0.100  gramme  stearic  acid  in  very  small  fragments  agitated  with 
25  c.c.  water,  and  3  c.c.  ammonia  water  (10  per  cent.)  were  extracted 
with  the  several  portions  of  alkaloidal  solvent  as  in  an  assay ;  the 
residue  obtained  dissolved  in  8  c.c.  alcohol  and  diluted  with  30  c.c. 
water  required  after  addition  of  3  drops  indicator  and  0.5  c.c.  diluted 
ammonia  water  (same  as  used  in  (3)  and  (4))  0-25  c.c.  HC1.  In  this 
last  experiment,  as  in  assays  proper,  only  a  small  portion  of  the 
stearic  acid  used  was  extracted  by  the  alkaloidal  solvent. 
These  experiments  prove  that  the  influence  exerted  by  the  stearic 
acid  does  not  exceed  005  c.c.  of  the  HC1  used  in  these  assays 
corresponding  to  about  0-005  Per  cent,  alkaloid  on  the  basis  of  20 
grammes  leaves,  or  about  o-oi  per  cent,  on  the  basis  of  10  grammes 
leaves ;  the  interference  is  so  slight  that  no  correction  was  made  in 
any  assay  in  which  stearic  acid  was  used. 
While  stearic  acid  has  not  been  tried  in  the  assay  of  other  drugs, 
there  is  no  doubt  but  that  it  will  prove  quite  successful  in  case  the 
alkaloids  can  be  titrated  with  haematoxylin  as  the  indicator. 
The  results  of  the  preceding  work  are  given  in  tabular  form 
(Table  No.  I),  from  which  it  will  be  seen  that  all  assays  were  made 
in  duplicate  ;  where  calculations  involve  such  assays  the  average 
was  used.  Comparing  the  yield  of  alkaloids  in  the  extracts  with 
the  calculated  yield  based  upon  the  assay  of  the  leaves  and  the 
yield  of  extract,  it  will  be  seen  that  the  former  exceeds  the  latter 
by  from  20  to  33  per  cent-.;  whilst  the  assay  of  the  plasters  ran  a 
trifle  higher  than  the  calculated  amount  based  upon  the  assay  of 
the  extract. 
