436  Stability  of  Digitalis  Leaf  Extracts.  {Am-j^-^m- 
cent.)  yielded  an  extract  which  came  into  equilibrium  with  52/76  or 
69  per  cent,  permanent  activity.  The  following  table  summarizes 
the  work  in  respect  to  this  point,  Tincture  5  being  out  of  order  and 
possibly  not  yet  at  equilibrium. 
Sample. 
Activity  of 
Drug. 
Gm.  Drug  in 
1,000  Cc. 
Activity  =  100. 
Activit} 
Per  Cent. 
Stable. 
r  =  100. 
Per  Cent. 
Lost. 
Calculated  Per 
Cent.  Stable  in 
100  Per  Cent. 
Activity. 
135 
74 
37-5 
62.5 
2  
I30 
77 
37-5 
62.5 
$  IOO 
^  100 
37-5 
62.5 
(51 
3  
t  113 
i  89 
;  (45 
5  
90 
in 
81 
29 
56 
F.  E.  1  
130 
770 
37  ; 
:  63  • 
2  
130 
770 
40 
60 
3  
113 
885 
49 
51 
45 
4  
76 
1,320 
69 
31 
67* 
*  Leaf  is  at  least  18  months  old. 
4.  The  above  conclusions  may  agree  with  the  hypothesis  that 
"  digitoxin  "  is  the  stable  and  that  the  so-called  "  digitalein  "  is  the 
less  stable  part,  the  equilibrium  point  corresponding  roughly  with 
the  percentage  of  "  digitoxin  "  often  found. 
5.  This  work  indicates  the  futility  of  conclusive  pharmacological 
work  on  Galenical  digitalis  preparations  and  certainly  points  out  a 
very  good  reason  for  the  failure  of  pharmacologists  to  agree  among 
themselves  on  many  points. 
The  authors  wish  to  expressly  indicate  that  the  above  work  was 
carried  out  incidental  to  the  commercial  production  of  the  products 
and  that  further  experimental  work  involving  temperature  control, 
percolation  on  smaller  scale,  etc.,  is  desirable.  The  results  are  pub- 
lished as  they  clear  up  somewhat  the  very  conflicting  views  found 
in  the  literature  and  in  the  profession,  concerning  the  stability  of 
this  important  drug. 
Research  Laboratory,  The  Upjohn  Company, 
Kalamazoo,  Michigan,  May  2,  1919. 
