CARE OF MILK ON THE FAEM 339 



for several days it should be stored in a cold place and in an 

 earthenware or glass vessel rather than in one of tin or wood. 



THE BABCOCK TEST^ 



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

 inventor, Dr. S. M. Babcock, chief chemist of the Wisconsin 

 agricultural experiment station, is based upon the fact that 

 strong sulphuric acid ^\411 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 quantity of sulphuric acid. The acid performs 

 other functions than the simple solution of the serum solids. 

 Much heat is developed by its action, and this causes the fat 

 globules to lose their individuality and run together, a condition 

 which greatly facilitates the separation from the serum. This 

 separation is still further accelerated by the increase in specific 

 gravity of the sermn caused by the presence of the heav}^ sul- 

 phuric acid. When the solution of the serum solids is effected, 

 the complete separation of the fat and serum is accomplished by 

 whirling in a centrifuge. The fat is gradually driven into the 

 graduated neck of the bottle and the percentage read directly. 



Test bottles. — The Babcock test bottle for milk consists of a 

 body holding about fifty cubic centimeters and the neck grad- 

 uated so that the percentage of fat may be read directly. Seven- 

 teen and one-half cubic centimeters is used in the test, and this 

 vohmie of average milk weighs almost exactly eighteen grams. 



Milk pipette. — The charge for the Babcock test for milk is 

 measured rather than weighed, the measuring instrument being 

 a pipette graduated to deliver 17.5 cubic centimeters of milk. 

 These pipettes, filled to their graduation mark, hold 17.6 cubic 

 centimeters. The extra 0.1 cubic centimeter is allowed for the 

 milk which clings to the walls. Pipettes may be obtained which 

 conformi to the requirements of the United States Bureau of 

 Standards. 



Acid measure. — For farm testing this may be a simple glass 

 cylinder graduated to deliver 17.5 cubic centimeters. 



The centrifugal machine. — This is commonly called the Bab- 

 cock tester, and various types are on the market, ranging from 

 the small, two-bottle hand tester to the large steam turbine or 

 electric tester, accommodating twenty-four or more bottles. 

 They all consist mainly of a horizontal revolving disk or wheel 



'In preparing this material free use has been made of Bulletin A-12, U. S. Depart- 

 ment of Agriculture, by Roscoe H. Shaw. 



