Excerpt from the report Introduction: The principal purpose of this study was to test the accuracy of the Jacobson equation relating the solids-not-fat to the fat of milk, and of the Babcock formula relating solids-not-fat to fat and specific gravity. These are the most widely known and used of the various formulas and equations of both types, but there had been no previous comprehensive study of their validity under commercial conditions. A secondary purpose was to obtain data on the average solids-not-fat content of milk in some important dairy areas in the United States.