398  Stability  of  Digitalis  Leaf  Extracts.    {^""- ^J^nl^i'-g^i: 
The  infusion  in  this  case  represents  about  90  per  cent,  of  the  total 
activity  of  the  leaves  as  represented  in  the  official  tincture. 
In  order  to  find  out  whether  an  aged  drug  would  behave  differ- 
ently we  reexamined  D1625  on  this  point.  A  sample  of  this  lot  has 
been  stored  since  December  5,  1916. 
10%  Tincture  (A').        10%  Infusion  (A).  A/A'. 
Date.  %  % 
3-  1-17   135  ...   
4-  19-20   50  ...  .... 
4-16-20   35  0.70 
From  this  result  it  would  appear  that  the  activity  of  the  water 
soluble  principles  of  an  old  drug  represented  less  of  the  total  activity 
than  in  the  fresher  leaf. 
B.  On  the  Deterioration  of  lo  Per  Cent.  Aqueous  Infusions. — The 
infusion  prepared  from  Drug  F2190  was  allowed  to  stand  at  room 
temperature  (4-1- 19). 
Time.  Activity,  %.  %  Deterioration. 
At  beginning   130  o 
After  18  hours   120  8 
After  24  hours. ..  .■   120  8 
After  48  hours   no  15 
After  72  hours   95  27 
This  infusion  molded  on  the  3d  day,  and  the  work  was  repeated 
by  filtering  a  fresh  infusion  (4-9-19)  through  porcelain  and  collecting 
the  filtrate  under  sterile  conditions. 
Date.                                    Time.                         Activity,  %.         %  Deterioration. 
4-8-19   At  beginning  i3o(?)   
4-  9-19   After  18  hours  120  0-8 
After  48  hours  no  8-15 
After  90  hours  100  17-23 
After  144  hours  80  33-38 
After   8  days  76  37-41 
After  II  days     '  67  44-48 
After  16  days  48  60-63 
5-  3-19                         After  25  days  40  66-70 
After  43  days  30  75-77 
After  63  days  30  75 
After  87  days.  27  78 
It  is  thus  shown  that  this  elaborately  sterilized  solution  should 
have  been  discarded  after  3-5  days. 
We  next  proceeded  to  determine  the  rate  of  deterioration  when 
