344 THE HANDBOOK FOR PRACTICAL FARMERS 



in the test bottle before being mixed. The third trouble 

 is caused by one or more of the following: The acid was 

 too weak; too little acid was used; the acid was too cold when 

 added to the milk; the milk was too cold when the acid was 

 added ; or the mixing was not continued long enough to dissolve 

 all the serum solids. 



TESTING CREAM FOR FAT 



Cream is tested by the Babcock test in much the same manner 

 as milk, but there are some modifications that must be observed. 

 The range of fat in cream, and consequently the specific gravity, 

 is much greater than in milk, so that 17.5 cubic centimeters do 

 not necessarily represent eighteen grams, as in the case of milk. 

 Cream also varies in consistence, some being thin and some 

 thick ; therefore in some cases much more would adhere to the 

 walls of the pipette than in others. For these reasons cream 

 can not be accurately measured. The charge for the test must 

 be weighed into the test bottle. 



Cream-test bottles. — The cream-test bottles used in the Bab- 

 cock test are of various designs. Those conforming to the 

 requirements of the United States Bureau of Standards differ 

 from milk bottles only in the graduations and in the length and 

 diameter of the neck. Test bottles are made for both an eighteen- 

 gram and a nine-gram charge. 



Cream-test balances. — Several types of balances designed for 

 weighing cream charges are on the market. The small torsion 

 balances prove to be very satisfactory if care is taken that the 

 important metal parts are not allowed to rust. Balances should 

 be tested for sensitiveness from time to time and should always 

 be kept in perfect condition. 



Preparing" cream for testing. — In testing cream or milk the 

 small quantity taken for the test must be truly representative. 

 No matter how carefully the test is carried out, if the charge 

 taken does not accurately represent the cream or milk to be 

 tested, the results will be worthless. The preparation of cream 

 for testing does not differ materially from that of milk. The fat 

 must be evenly distributed, and if there are no lumps this can 

 be accomplished by pouring from one receptacle to another, 

 warming the cream slightly, if cold. If lumps are present, it 

 has been advised to pass the cream through a fine sieve, rubbing 

 the lumps through Avith the fingers and then mixing as usual. 

 If the cream has stood for some time in the sample jar, the top 

 may have become hard, leathery, and difficult to remove. In this 



