82 MODERN METHODS OF TESTING MILK 



are seen in the liquid, 17.5 cc. of sulj)huric acid is 

 added. The test is then completed in the usual way. 

 To obtain tl:e per cent, of fat in the cheese, if less 

 than 18 grams is used, multiply the reading of fat 

 by 18 and divide by the number of grams of cheese 

 used in the test. 



METHOD OF TESTING BUTTER 



The Rabcock test has not been adapted to deter- 

 mine accurately the amount of fat in butter. A mass 

 of butter is so variable in its composition, owing to 

 the uneven distribution of water, that it is difficult to 

 obtain a representative sample when only a small 

 amount is used. Since butter contains over 80 per 

 cent, of fat, a sample of less than 9 grams must be 

 used in a test-bottle made to measure less than 40 

 per cent, of fat. Approximate results can be obtained 

 by observing certain precautions. 



Preparing sample of butter. — With a butter-trier 

 draw several samples, aggregating 4 to 8 ounces. 

 Place these samples in a fruit- jar or composite-sam- 

 ple bottle, melt completely by placing in fairly hot 

 w ater with the jar closed ; then remove from hot wa- 

 ter and shake vigorously for one or two minutes, after 

 which moderate agitation is continued until the but- 

 ter solidifies. The cooling may be hastened by hold- 

 iilg the jar under a stream of cold water, continuing 

 to shake the bottle vigorously until the butter hardens. 



Testing sample of butter. — On a cream-scale place 

 a cream-bottle (Fig. 29, p. 70), in wdiich is placed a 

 long-stemmed cylindrical funnel (Fig. 36). After 

 balancinsf the bottle and funnel, one takes on the 



