108 GRADING AND TESTING MILK AND CREAM 



50 c.c. of ether are poured into the cylinder and at once siphoned 

 off without being mixed with the other liquid. Finally, the 

 residual liquid is shaken with a mixture of 25 c.c. ether and 25 c.c. 

 petroleum ether, and, after settling, the ethereal layer is drawn 

 off. The three portions of ether are naturally all placed in 

 the same tared flask, which is weighed again after the ether has 

 been evaporated and the fat dried. 



These repeated extractions with ether and petroleum ether 

 are necessary if exact results are to be obtained. If the above 

 directions are carefully followed, it will be found that the Rose- 

 Gottlieb method, while easier and more convenient, and also 

 considerably quicker than the extraction method, gives results 

 which are in very close agreement with those obtained by the 

 latter. 



The Mojonnier test is a modification of the foregoing, and 

 possesses several features which greatly facilitate the work and 

 shorten the time required to make the test. In the method 

 known as the " Indirect Determination of Fat," the percentages 

 of moisture, casein and salt are carefully determined. These 

 are then added together and their total is subtracted from 100 to 

 determine the per cent of fat in the butter. 



Practical Methods. There are several practical methods that 

 are made use of to a greater or less extent. We shall briefly 

 outline two of these. 



For making a Babcock test of butter, using the Illinois g-inch, 

 g-gram, 90 per cent butter test bottle devised by Dr. N. W. 

 Hepburn, University of Illinois, the following directions are given: 



" Taking the Sample. In testing butter it is necessary to 

 exercise great care both in securing and in preparing the sample. 



" Sampling from a Churn. With an ordinary ladle cut off 

 the surface of the butter in several places, including each end and 

 the middle of the churn. Then make a composite sample by 

 taking, with a spatula or common case knife, a small sample 

 (10 to 20 grams each) from six or eight different places in the 

 churn where the surface has been removed, putting them into 

 an 8-ounce wide-mouthed glass-stoppered bottle. 



