682  Study  of  Strophanthus  Kombe  Seeds.    {  AlgctJ0°£r,  ^J"* 
acid  test;  (3)  the  sulphuric  acid  and  potassium  dichr.omate  test; 
(4)  the  phosphomolybdic  acid  test;  (5)  Keller-Kiliani's  test;  (6) 
Kiliani's  reagent;  (7)  Keller's  test;  (8)  the  tannic  acid  test;  and 
(9)  a  new  delicate  test  which  is  as  follows:  Sulphuric  acid  concen- 
trated (2  drops)  and  ammonium  molybdate  (0.10  Gm.)  on  a  slab 
gave  with  a  trace  of  strophanthin — or  residue  containing  strophan- 
thin — a  light  brownish  green  color  which  gradually  developed  into 
blue  after  ten  minutes.  The  intensity  of  the  blue  color  reached  a 
maximum  in  twenty  minutes,  and  remained  permanent.  This  in- 
tense blue  color  was  instantaneously  destroyed  by  a  trace  of  concen- 
trated nitric  acid.  This  test  is  based  on  the  reducing  power  of  the 
glucose  portion  of  the  strophanthin  molecule,  and,  therefore,  this 
test  would  be  positive  with  other  active  principles  of  a  reducing 
nature. 
This  test  may  be  used  as  a  comparative  test  for  different  varieties 
of  strophanthus  seeds. 
Several  active  principles,  particularly  the  glucosides,  were  tested 
with  this  test. 
Some  of  these  results  may  be  interesting  in  connection  with 
strophanthin : 
Digitalin  (verum) — Garnet  red  at  once,  going  to  deep  blue  in  a 
minute. 
Digitalein  (Merck) — Orange  at  once,  going  to  orange  red  in  two 
minutes,  then  deep  blue  in  twenty  minutes. 
Digitoxin  (Merck) — Olive  green  at  once,  going  to  dirty  black  in  a 
minute,  then  changing  to  deep  blue. 
Digitalin  pur.  (Merck) — Orange  at  once,  going  to  violet  in  half  a 
minute,  and  gradually  to  blue  in  five  minutes. 
Digitonin  (Schuchardt) — Nothing  at  first;  blue  color  appears  in 
two  minutes,  reaching  a  maximum  in  eight  minutes. 
Salicin — Violet  immediately,  going  to  blue  in  eight  minutes. 
Santonin — Light  blue,  deepening  on  keeping. 
Part  II. 
The  determination  of  the  M.L.D.  of 
(I)  K.  Strophanthin  isolated  in  the  laboratory. 
(II)  Strophanthin  Merck,  and 
(III)  Tincture  of  Strophanthus  B.P.,  1914. 
English  frogs  were  chosen  for  these  experiments,  and  the  usual 
