The rapid growth of the dairy industry which began in the latter half of the nineteenth century necessitated the development of chemical tests for determining the composition of dairy products. Chemists devoted much study and labor in devising methods which would be both accurate and rapid. As a result of these researches a large number of tests were developed. Many of the methods possessed considerable merit and a few were so satisfactory that the rest did not come into general use. The basic principles of all the tests now in use were discovered between 1880 and 1890
