48 MILK 
blue, sucrose a weaker blue and dextrose the’ 
weakest blue, corresponding in intensity as 
10:3 51. 
Stannous chlorid and ferrous sulfate give this 
color, but the reaction takes place in the cold, 
and with small quantities the color disappears on 
heating. In order for the color to persist after 
heating the sample of cream must contain these 
substances to the extent of 1% calculated as the 
metal. In this case the sample will be completely 
coagulated and the taste will be disagreeable. 
Hydrogen sulfid will also give the blue, but it will 
disappear on heating. If the solution does not 
show blue before heating, it is free from hydrogen 
sulfid, ferrous sulfate or stannous chlorid. 
As a confirmatory test for sugar, the resorcinol 
test may be applied to the serum prepared with 
uranium acetate as described. This test is given 
by sucrose and levulose, but not by dextrose or 
lactose. 
The quantitative estimation of sucrose in milk 
is given under Milk Products (page 74). 
Detection of Heated Milk.—Fresh milk con- 
tains one or more enzyms of the ‘‘peroxydase’”’ 
type, that is, having power to bring about 
transfer of oxygen from peroxids to oxidable 
substances. As the function of these enzyms 
is destroyed by temperatures near 100°, it be- 
comes possible to utilize the reaction for deter- 
