548 ANNUAL RECOBD OF SCIENCE AND INDUSTRY. 



trogen, equivalent to 13.40 per cent, of albuminoids, or flesh 

 formers. 18 A, August 25, 562. 



TESTING ADULTERATION OF MILK. 



In a recent report by Professor Chandler, of Columbia Col- 

 lege, upon the quality of the milk supply of New York, it is 

 stated, as the result of numerous experiments made in his 

 official capacity as chemist to the Board of Health, that the 

 milk used is generally free from injurious adulteration and 

 untainted with disease, but mixed with water in the propor- 

 tion of one quart to every three quarts of milk. The quan- 

 tity of water thus paid for as milk, at ten cents per quart, 

 costs consumers about $12,000 a day, or over four and a quar- 

 ter millions of dollars annually. In view of this fact, it is 

 important to have some simple method of testing the amount 

 of this adulteration, which, according to Professor Chandler, 

 may be done by taking the specific gravity of the milk and 

 determining the amount of water it contains by evaporating 

 a weighed sample to dryness. Assuming the specific gravity 

 of pure milk to be from about 1.029 to 1.032, whenever the 

 gravity falls much below this the milk may be considered as 

 adulterated with water. Dr. Davies, however, dissents from 

 this statement, and asserts that the specific gravity can not 

 be relied upon as a test either of freedom from adulteration 

 or of natural richness. A sample known to him as perfectly 

 pure and of excellent quality, rich in the solid constituents 

 of milk, and especially butter, possessed a specific gravity of 

 only 1.0246. He therefore concludes that the specific gravity 

 test does not indicate whether the milk is naturally poor or 

 lias been rendered so by the addition of water. Cases have 

 even been known of pure milk containing 90 per cent, of wa- 

 ter. Dr. Davies therefore recommends as a test to show 

 whether the milk has been purposely diluted with water, 

 and if so to what extent, to take the specific gravity of the 

 serum, or the liquid portion of the milk from which the case- 

 ine and fat have been removed by coagulation and straining. 

 The gravity of this he finds to be remarkably constant, and 

 ranging, in that obtained from pure milk, from 1.026 to 1.028. 

 By carefully ascertaining the specific gravity of the serum 

 of thin milk, diluted with various quantities of water, we 

 may obtain a standard of comparison which will enable us to 



