216 Testing Milk and Its Products. 



Concentration (c)=^j- 



where a and s designate the solids not fat and specific 

 gravity, respectively of the condensed milk, and a l and 

 s l the corresponding data for the milk used. If s 1 =1.030 

 and a 1 9 per cent., then c = <^ gives the concentration. 



C. BUTTER. 



262. Sampling. A four- to eight-ounce sample of but- 

 ter is melted in a tightly- closed pint fruit jar, shaken 

 vigorously and cooled until the butter is hardened, the 

 jar being shaken vigorously at short intervals during the 

 cooling so as to keep the water of the butter evenly dis- 

 tributed in the mass. 



263. a. Determination of water. Small pieces of but- 

 ter (about 2 grams in all) are taken from the sample by 

 means of a steel spatula and placed in glass tubes, seven- 

 eighths of an inch in diameter and two and a half inches 

 long, closed at the bottom by a layer of stringy asbestos, 

 and filled two- thirds full of asbestos prepared as for milk 

 analysis (250). The tubes are dried at 100 C. in a water 

 oven, until no further loss in weight takes place, and are 

 then cooled and weighed. The loss in weight shows the 

 per cent, of water present. 



264. b. Fat. The tubes are placed in CaldwelPs ex- 

 tractors and extracted for four hours with anhydrous 

 ether; the ether is then distilled off, and the flasks dried 

 in the steam bath and weighed, the increase in weight 

 giving the fat in the samples of butter weighed out. 



265. c. Casein. 10 grams of butter are weighed into 

 a small beaker provided with a lip, and treated twice 

 with about 50 cc. of gasoline each time; the solution is 



