EXAMINATION OF MILK. 



The adulteration of inilk in this country consists usually either in the 

 removal of cream or the addition of water. 



Without making any attempt whatever to notice the prolific litera- 

 ture of this subject, which has accumulated during the past few years, 

 such portions thereof as seem to be most helpful in the work of analy- 

 sis will be cited. Those who care to study the subject in greater detail 

 are referred to the periodical literature, especially to the "Analyst" and 

 " Milch Zeitung." 



The constituents of milk which are to be determined by analysis are 

 (1) water 5 (2) sugar; (3) nitrogenous constituents; (4) ash, and (5) fat. 



Water. The simplest method for estimating water in milk consists 

 in evaporating one or two grams in aflat platinum dish. The larger 

 the diameter of the dish the quicker and more accurate will be the re- 

 sults. 



If larger quantities of milk be used or the dish have not a flat bot- 

 tom, the film which forms over the surface of the milk during evapora- 

 tion will prevent complete desiccation. To avoid this many plans have 

 been proposed. The milk may be mixed with gypsum, and then a larger 

 surface be exposed and more rapid and complete drying secured. 



Instead of gypsum, sulphate of barium, pure quartz sand, sulphate of 

 strontium, and powdered glass have been used. All of these methods 

 are capable of giving fairly accurate results when properly conducted. 



The addition of acetic acid or alcohol to coagulate the albuminous 

 matter before desiccation has been largely practiced, but Gerber and 

 Eadenhausen have shown 1 this treatment is without influence on the re- 

 sults. Jenks has also shown 2 that simple evaporation without any treat- 

 ment whatever gives results which agree well with those obtained by 

 using sand. 



In fifty determinations the maximum and minimum difference between 

 the two methods was only .14 per cent, and the mean difference .003 

 per cent. 



Babcock 3 has proposed an ingenious and accurate method of determ- 

 ining the water in milk : 



About two grams of rather coarse asbestos are placed in a platinum evaporator of 

 30cc. capacity, ignited and weighed. Five cubic centimeters of inilk from the pipette, 



1 Bied. Centralblatt, 1876, p. 22. 



2 Chem. Centralblatt, 1882, p. 13. 



3 Second Ann. Kept. Bd. Control N. Y. Exp. Sta., pp. 167-8. 

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