216 MILK HYGIENE 



the fats from the other ingredients and ascertaining 

 their weight. 



Gottleib's method gives results sufficiently accurate for our use. 

 For this method one requires, as apparatus, only a cylinder of 40 c.c. 

 capacity, divided to measure quantities of 0.5 c.c., some glass flasks 

 and a long, thin glass syphon. 10 grm. of milk are accurately weighed 

 into one of the small flasks and poured into the glass cylinder; the 

 amount of milk left adhering to the walls of the flask is determined 

 by a second weighing, so that one may know exactly how much 

 has been poured into the cylinder. 1 c.c. of 10 per cent, ammonia 

 water (specific gravity 0.96) is mixed with the milk and shaken, 

 then 10 c.c. alcohol (95 per cent.) are added and it is shaken again, 

 after which 25 c.c. ether are added. The cylinder is well closed with 

 a cork that has been moistened in water, and shaken hard. 25 c.c. 

 petroleum benzine are added and, after repeated shaking, the bottle 

 should be allowed to stand undisturbed at least 6 hours. By that 

 time, the fluid is separated into two sharply marked layers; the 

 upper one is the ether-benzine-fat mixture, the under one contains 

 the water, the lactose and proteids; a whitish sediment consists of 

 phosphates. The volume of the upper layer of the fluid is read off 

 and a determined quantity of it is syphoned off into a small weighed 

 flask. The ether and benzine are now evaporated by mild heat. 

 Thereupon, the flask is allowed to stand a couple of hours in a drying 

 chamber at 100 C., is cooled in an exsiccator and, finally, weighed. 

 From the total volume of the mixture of ether, benzine and fat, 

 and from the quantity of fat in the portion evaporated, the weight of 

 the total fat content of the milk sample can be calculated, and thus 

 the percentage is determined. 



/. Determination of the total solids in milk. The total 

 solids in milk are determined chemically in the following 

 way : Exactly 10 c.c. of milk are measured into a plat- 

 inum or porcelain vessel, the weight of which is already 

 known; the vessel is heated in a water bath to 100 C. 

 until all the water is evaporated. After cooling in an 

 exsiccator, the vessel and its contents are weighed. The 

 difference between the weight found and the original 

 weight of the dish gives the total amount of solids in 

 the milk. If the amount of fat, found in another way, is 



