400  Stability  of  Digitalis  Leaf  Extracts.    [^'^-  ^"^f^vl^i^^: 
From  these  curves  it  is  shown  that  four  infusions  passed  a  point 
of  20  per  cent,  deterioration  as  follows : 
(a)  Which  molded  in  about  2V2  days. 
(6)  At  room  temperature  and  warm  weather  in  3-4  days. 
{c)  At  10°  C.  in  8  days. 
id)  At  room  temperature  in  cooler  weather;  7  days. 
C.  Observations  on  Deterioration  of  1.5  Per  Cent.  Infusion  {U.  S.  P.). 
— We  purposely  began  this  investigation  with  10  per  cent,  infusions 
because  it  was  found  that  in  using  1.5  per  cent,  solutions  that  con- 
siderable concentration  was  required  before  injection,  i.  e.,  1.5  per 
cent,  solutions  are  poorly  absorbed.  It  might  be  objected  that  this 
concentration  rather  than  the  storage  produced  deterioration. 
Expt.  I  {1-1^-20). — A  fresh  1.5  per  cent,  infusion  U.  S.  P.  was 
prepared  (F2190),  and  two  aliquots  of  100  Cc.  were  concentrated  to 
exactly  15  Cc.  thus  making  the  final  concentration  10  per  cent. 
One  concentration  was  made  upon  the  steam  bath,  while  the  second 
was  concentrated  at  40°  in  a  vacuum  distillation  apparatus.  Both 
solutions  showed  the  same  activity,  i.  e.,  0.00667  Mil  per  Gm.  frog 
or  90  per  cent,  of  the  standard  for  the  tincture. 
Expt.  II. — Adopting  the  process  of  concentration  upon  the  steam 
bath,  we  took  at  intervals  100  Cc.  of  the  sterile  1.5  per  cent,  infusion 
and  assayed  these  with  the  following  results : 
Date.  Time.  Activity,  %.  %  Deterioration. 
1-16-20   At  beginning  90  o 
1-  26-20   After  10  days  75  17 
2-  6-20   After  21  days  60  33 
2-24-20   After  39  days  35  61 
The  curve  during  the  first  20  days  is  exactly  like  those  described 
for  the  10  per  cent,  infusions  "c"  and  "<i"  and  it  passes  the  point 
recording  20  per  cent,  deterioration  at  about  the  nth  day,  but  we 
consider  the  assay  upon  the  10  per  cent,  infusion  of  the  fresher  drug, 
which  brings  this  point  earlier,  as  more  accurate. 
D.  Observations  on  the  Advisability  of  Adding  10  Per  Cent.  Alcohol. — 
In  the  U.  S.  P.  of  1890,  infusion  digitalis  is  made  with  the  addi- 
tion of  10  per  cent,  alcohol.  It  is  true  that  the  addition  of  alcohol 
clarifies  the  solution,  and  tends  to  prevent  turbidity,  but  the  better 
appearance  tends  to  delude  the  pharmacist  to  accept  an  inaccurate 
belief  that  the  stability  is  thereby  increased.    The  following  will 
