The partial churning of the samples is not a frequent 

 occurrence and with proper care can always be avoided. 

 When samples are to be sent a considerable^distance, the 

 containers should be completely filled so that no space is 

 left at the top. A good way is to fill a bottle to overflowing 

 with the mixed sample and then to insert a rubber or cork 

 stopper having a hole about one-eighth of an inch in diame- 

 ter. As the stopper goes to its place the milk will spurt 

 out through the hole; the hole is then filled with a piece 

 of glass rod or a wooden plug. When treated in such 

 manner milk will not churn. 



Sour milk. While the souring of milk does not affect 

 the fat, it is impossible to obtain a representative charge 

 from curdled milkVithout special treatment. In order to 

 obtain a good mixture, it is necessary to dissolve the curd. 

 This may be accomplished by adding 5 or 10 per cent by 

 volume of a strong solution of either caustic soda or potash ; 

 strong ammonia water may also be used. The alkali must 

 be thoroughly mixed with the milk until it is completely 

 liquid. The charge for test must be immediately meas- 

 ured out and a correction made in the final percentage for 

 the volume occupied by the alkali solution. If desired, 

 the powdered alkali may be added directly to the milk in 

 small portions at a time, being sure that one portion is dis- 

 solved before another is added, and agitating until the milk 

 has become liquid. No correction is necessary for the 

 volume occupied by the powdered lye. When making a 

 fat test on milk containing alkali, special precautions 

 must be observed in adding the sulphuric acid, as an ex- 

 cessive amount of heat is generated and the contents of 

 the test bottle may be thrown out. When alkali is used, 

 slightly more acid is required. 



THE BABOOCK TEST. 



The Babcock test for fat in dairy products, named for its 

 inventor, Dr. S. M. Babcock, chief chemist of the Wiscon- 

 sin agricultural experiment station, is based upon the 

 fact that strong sulphuric acid will dissolve the serum 

 solids in milk and set the fat free from its emulsion. In 

 conducting the test the charge is placed in a specially 

 constructed test bottle and mixed with the proper quan- 



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