The New Student's Reference Work/Babcock Test

Babcock Test, a method of determining the amount of butter-fat in milk, named after Prof. S. M. Babcock, of Wisconsin Agricultural Experiment Station, who invented it in 1890. It depends upon (i) the separation of light from heavy parts by centrifugal force and (2) the action of sulphuric acid on all the solids of the milk other than butter-fat. The machine consists of deep brass cups attached to an upright revolving shaft, so that they will swing out horizontally when the machine is rotated by hand or steam power. In the cups are placed Babcock milk bottles.

These are vase shaped with long narrow necks, and hold about 2½ cubic inches. Almost equal parts of milk and acid are mixed in the bottles in a special way. The acid decomposes the other solids and frees the fat. Being warmed by the chemical action, the fat particles run together, and being so much lighter than the acid mixture, the fat rises into the neck, which is so graduated that the amount of fat can be read off in percent. The rapid rotation of 900 to 2,000 or more revolutions per minute separates practically all the fat. The Babcock test was the first practical method of testing milk for commercial use. It has made it possible for creameries to pay for milk on a basis of cream value and has made it possible for the dairyman to estimate accurately the performance of each of his cows and so tell the amount of cream produced by each. Milk from different cows may vary in amount of butter-fat from 2% to 8%. Some cows will test less than others, but may, by reason of a greater quantity of milk, produce the same amount of butter. Milk for retailing is usually required by law to test at least 3% of cream. Cream is sold in different grades, as 12%, 18%, etc. See Cream Separator. Ref.: L. L. Van Slyke: Modern Methods of Testing Milk and Milk Products.