456 MILK AND MILK PRODUCTS; DAIRY FARMS 



will answer the purpose. Heat the sample in a water oven at the tem- 

 perature of boiling water for eight hours. Cool the dish, weigh and 

 divide the loss in weight by the three grams of cheese taken. Multiply 

 the quotient by 100. This quotient is the percentage of moisture in the 

 cheese. Care should be taken to place the cheese in the dish in as thin a 

 layer as possible. This will make it easier for the moisture of the 

 cheese to escape. 



The Babcock test for fat in cheese (Ross). 



Secure a representative sample of the cheese. This is best done by 

 means of a cheese trier, taking a plug from the center of the cheese one- 

 half way between the center and the outside of the cheese and one 

 very near the outside of the cheese. Using a knife, mince these three 

 plugs as fine as possible and mix them thoroughly. After the sample 

 is minced very fine and thoroughly mixed, weigh out on a set of cream 

 balances in a cream bottle 4 grams of the cheese. Add 5 cc. of 

 warm water and shake thoroughly for one or two minutes. Then 

 make the sample up to approximately 18 grams by the addition of 

 water, and add 17.5 cc. sulfuric acid. After the acid is added, shake 

 the sample thoroughly for from two to three minutes. The purpose 

 of this shaking is to dissolve all of the cheese curd. If this is not done, 

 the fat column will be cloudy. Then place the bottles in the machine 

 and proceed with the test in the ordinary way. 



Test for determining casein in milk (Van Slyke and Bosworth). 



A given amount of milk, diluted with water, is made neutral to phe- 

 nolphthalein solution by addition of a solution of sodium hydroxid. 

 The casein is then completely precipitated by addition of standardized 

 acetic acid ; the volume of the mixture is made up to 200 cc. by ad- 

 dition of water, thoroughly shaken, and then filtered. Into 100 cc. of 

 the filtrate a standardized solution of sodium hydroxid is run until 

 neutral to phenolphthalein. The solutions are so standardized that 1 cc. 

 is equivalent to 1 per cent of casein when a definite amount of milk 

 is used. The number of cubic centimeters of standard acid used, divided 

 by 2, less the amount of standard alkali used in the last titration, 

 gives the percentage of casein in the milk examined. When one uses 

 17.5 cc. (18 grams) of milk, the amount used in the Babcock milk- 



