CATALASE REACTION OF MILK. B29 
Evidence of this increase is well shown by the foregoing 
figures, which show an increase for the value of A, and the 
total hydrogen peroxide decomposed, until the milk is 22 
hours old: after this the value for A shows a decrease. 
This decrease being probably due to the inhibiting action 
of the lactic acid formed. The total decomposition is 
expressed in ces. of standard hydrogen peroxide solution. 
From these results it seems highly probable that there 
are ordinarily bacteria in the air which on gaining access 
to the milk are able to produce a substance having the 
power of catalysing the decomposition of hydrogen peroxide. 
In order to study the action of catalase in as pure a state 
as possible, the following method of purification was arrived 
at. To 500ccs. of milk enough acetic acid, 5H, was slowly 
added to precipitate the caseinogen; sodium hydrate was 
then added until the resulting solution was acid to phenol- 
phthalein and alkaline to methyl red. This brought the 
milk back to its original acidity. The liquid was then 
filtered. To the resulting filtrate, which was quite clear, 
800 — 900 ccs. of 90% alcohol were added until a precipitate 
was formed. This precipitate was filtered off, freed from 
alcohol by drying, in vacuo, and treated with water in the 
presence of chloroform. The resulting solution contained 
catalase, and readily decomposed hydrogen peroxide. 
Table IV. 
Temperature 25° C. 
tO ts lene: Ee a — « K x10+ 
M/300 0) 14:16 a 
20 10-00 189 
30 8-25 196 
40 7-20 177 
45 6°35 185 
te 5-80 184 
60 4°80 185 
