466 
Assay  of  Heart  Tonics. 
j  Am.  Jour.  Pharm. 
(     October,  1909. 
tration  already  cited,  Table  I.  According  to  the  formula,  the 
minimum  fatal  dose  of  standard  divided  by  the  minimum  fatal  dose 
of  unknown 
M.F.D.  of  standard 
/M. 
F.D.  of  unknown 
—  per  cent,  unknown  is  of  standard^ 
equals  the  percentage  value  of  unknown.  The  percentage  value  of 
the  unknown  can  easily  be  converted  into  H.T.U.s  by  multiplying 
the  number  of  H.T.U.s  in  standard  by  the  per  cent,  value. 
LOSS  IN  POTENCY  OF  PREPARATIONS  OF  THE  HEART  TONICS  WITH  AGE. 
A.  Preparations  of  Digitalis. 
TABLE  III. 
LOSS  OF  POTENCY  OF  DIGITALIS  PREPARATIONS  WITH  AGE. 
Av.  yearly- 
loss  %. 
8% 
4% 
Prep. 
No. 
sample. 
Av.  No.  H.  T.  U.s 
per  Cc.  when  mfg. 
Years 
later. 
Av.  No. 
H.  T.  U.s 
Extract 
94% 
Alcohol  + 
II 
260 
5 
160 
47%  Alcohol 
Fl.  Ext. 
U.  S.  P.  8 
7th  Rev. 
72 
6 
55 
Fl.  Ext. 
U.  S.  P. 
8th  Rev. 
II 
55 
3/2 
35 
Tincture 
U.  S.  P. 
8th  Rev 
8 
7 
3 
5 
10% 
9% 
1.  Extract  of  digitalis  made  by  using  94  per  cent,  alcohol  fol- 
lowed by  47  per  cent,  alcohol  as  menstruum. 
Average  potency  of  eleven  samples  at  the  time  of  manufacture 
in  round  numbers  contained  260  H.T.U.s  per  gramme  of  extract. 
Five  years  later  the  average  strength  had  fallen  to  160  H.T.U.s 
per  gramme — a  loss  of  nearly  40  per  cent.,  or  about  8  per  cent,  each 
year. 
2.  Fluidextract  digitalis.  U.S. P.  7th  Rev.,  62.7  per  cent,  alcohol. 
Average  potency  of  eight  samples  at  the  time  of  manufacture  720 
H.T.U.s  per  cc.  Six  years  later  the  strength  had  fallen  to  550 
H.T.U.s  per  cc. — a  loss  of  about  one-fourth,  or  4  per  cent,  per  year. 
3.  Fluidextract  digitalis.  U.S. P.  8th  Rev.,  48  per  cent,  alcohol. 
Average  potency  of  eleven  samples  at  time  of  manufacture  550 
