577 



increased acidity also increased the resistance of tlie milk. But in spite 

 of these facts the author believes that the test may furnish valuable 

 indications as to whether a sample is watered. A milk which under 

 conditions similar to those prevailing in this experiment shows a resist- 

 ance of over 220 ohms, he claims may be safely assumed to have been 

 watered. To what extent this watering has been carried it is impossible 

 to determine by this method, since the electrical resistance of different 

 samples of poor milk varies by about 20 ohms, and that of different 

 waters which might be used for adulteration may vary as widely as 

 100 ohms. 



The method of W. Schmid for estimating fat in milk, J. Pinette 



{Chcm. Zt(/., 15 {1S91),2>' 1S33). — Sclimid's method as modified by the 

 author, is described by the latter as follows : Ten c. c. of milk are heated 

 in an Erlenmeyer flask with 10 c. c. concentrated crude hydrochloric 

 acid till tlie curd is dissolved, but not too long, lest traces of the fat be 

 decomposed. The contents of the flask are partially cooled and then 

 poured into a graduated burette, the flask being thoroughly rinsed out 

 with a mixture of equal parts of ether and j)etroleum ether. The burette 

 is then nearly tilled with the mixture of ether and petroleum ether, 

 reversed, and agitated, and the solution containing the fat allowed to 

 rise to the surface, where it is read off. An aliquot part of the fat layer 

 is pipetted off, evaporated to dryness, and the residue weighed. It is 

 advisable to allow the fat layer to thoroughly separate, so that it con- 

 tains no water when the aliquot is taken. If insufficient time is allowed 

 for a complete separation, it is suggested to filter through a dry, fat-free 

 filter to remove the water. 



