Enzymes  in  Milk. 
(Am.  Jour.  Pharm. 
\    February,  1909. 
In  view  of  the  assertion  that  hydrogen  dioxide  disappears  entirely 
upon  standing,  some  experiments  were  made  with  the  purpose  of 
ascertaining  whether  this  were  true.  Varying  amounts  of  solution 
of  hydrogen  dioxide  were  added  to  milk,  making  dilutions  from  15 
parts  absolute  H202  in  100,000  up  to  3  parts  in. 1000.  Upon  allow- 
ing these  to  stand  over  night  it  was  found  that  by  neither  of  the 
tests  could  as  much  as  3  parts  in  10,000  be  detected  after  standing 
twenty-four  hours,  although  the  milk  thus  treated  remained  sweet 
for  three  or  four  days  standing  at  room  temperature.  The  most 
surprising  results,  however,  were  obtained  when  the  milk  in  which 
no  reaction  could  be  obtained  for  H202  was  tested  by  both  methods 
for  the  presence  of  the  enzyme. 
With  the  Dupouy  test  positive  results  were  obtained,  while  with 
the  Wilkinson  and  Peters  test  negative  results  were  shown.  In 
the  presence  of  15  to  30  parts  of  hydrogen  dioxide  per  100,000,  this 
differentiation  was  most  marked.  In  the  presence  of  larger  amounts 
up  to  3  parts  in  1000,  the  Dupouy  test  applied  for  the  enzyme 
was  also  inhibited  after  several  days.  In  the  presence  of  the  larger 
amounts,  the  Wilkinson-Peters  test  was  inhibited  immediately.  A 
tabular  statement  of  the  experiments  may  serve  to  illustrate  more 
fully : 
Wilkinson-Peters'  Test  ,        Dupouy 's  Test 
Strength  of  H202  in  milk  Test  for  enzyme  applied  immediately 
15  parts  to  100,000  positive  positive 
30  parts  to  100,000  positive  positive 
15  parts  to    10,000  negative  positive 
Test  for  enzyme  applied  after  24  hours 
15  parts  to  100,000  negative*  positive* 
30  parts  to  100,000  negative*  positive* 
15  parts  to    10,000  negative  positive 
Test  for  enzyme  applied  after  96  hours 
15  parts  to  100,000  negative*  negative* 
30  parts  to  100,000  negative*  negative* 
15  parts  to    10,000  negative  negative 
*  Ho02  no  longer  detectable  by  reversal  of  test. 
The  foregoing  results  indicate: 
First,  that  hydrogen  dioxide,  when  added  in  small  amounts  to 
milk,  can  only  be  detected  within  a  few  hours  after  such  addition, 
and  that  the  resulting  milk  remains  sweet  for  several  days  at  ordi- 
nary temperatures. 
