DETECTION OF ADULTERATION 59 
known amounts of the preservative estimations 
may be made. 
Hydrogen Peroxid.—Many tests have been 
devised for detection of this substance. Among 
the most convenient and satisfactory is the 
reaction with vanadic acid first given by Werther. 
It may be carried out by adding to ro c.c. of the 
milk, ro drops of a 1% solution of vanadic acid 
in dilute sulfuric acid. This solution may be 
conveniently made by dissolved commercial 
sodium orthovanadate in the dilute acid. 
In the presence of hydrogen peroxid a distinct 
red will appear promptly. Barthel states that a 
proportion of o.o10 gram of the peroxid in 100 
c.c. of milk can be detected positively using only 
10 c.c. of the sample. 
Benzoates and Salicylates—The following 
method covers both these preservatives. 
to c.c. of dilute sulfuric acid (5%) are added 
to 20 c.c. of 95% alcohol and into this 50 c.c. of 
the milk are poured in a fine stream with constant 
stirring. After a few moments, the mixture is 
filtered, the filtrate being returned until it passes 
clear. A sufficient volume of the filtrate is 
extracted in the usual manner with an equal 
volume of ether or similar solvent. The solvent 
is divided into two portions that are separately 
evaporated and tested for benzoic and salicylic 
acids respectively as given below. 
