Principles of Milk Preservation. 89 



Formalin has been extensively advertised of late, but 

 even though this agent does not exert as prejudicial an 

 effect on human tissues as some of the other disinfectants, 

 yet it must be regarded with the remainder of chemical 

 preservatives as undesirable. 



These substances can be added to milk in quantities 

 not recognizable to the taste, and they will materially in- 

 crease the time that milk will remain sweet, but their 

 general use in milk is to be strongly deprecated. In 

 many European countries their use is prohibited entirely. 

 A large number of the preservatives are sold under pro- 

 prietary names, and as a rule for extremely high prices, 

 but they all depend for their efficiency upon the anti- 

 septic action of chemicals. 



87. Detecting- preservaline. The detection of these 

 various preservatives in milk does not come within the 

 general province of this work, but Farrington 1 has 

 suggested such a simple means for the determination 

 of the presence of preservaline and other boracic acid 

 compounds that is so intimately connected with the de- 

 velopment of acid that it is given here. When the acidity 

 of a normal milk reaches 0.3-0.4%, it tastes sour, but 

 when boracic acid is added to fresh milk, the acidity is 

 much increased without affecting the taste. In fact, for 

 some reason not yet explained, the acidity of the milk is 

 increased considerably more than that due to the chemical 

 added. Therefore milks having a high acid reaction (ex- 

 ceeding 0.3-0.4% ) and not tasting perceptibly sour have in 

 all probability been treated with preservatives. Failure to 

 sour, especially when milk is kept at room temperatures 

 for several days, is pretty conclusive evidence that chem- 

 icals have been used. The sale of these preparations for 

 use in milk finds its only outlet with those dairymen who 



1 Farrington, Journ. Amer. Chem. Soc., Sept., 1896. 



