The adoption of any standard of purity of butter requires a knowledge of the effects of the different constituents of butter upon its quality. This knowledge, in so far as the effect of different percentages of water is concerned, has been, up to the present time, somewhat meager.

In fixing the moisture standard considerable controversy has arisen as to whether or not 16 per cent is the most desirable amount. The evidence available goes to show that so far as quality is concerned, butter containing from 14¹/₂ to 16 per cent water is not inferior to that containing a lower percentage. Butter is not bought on a basis of its actual food value. This is confirmed by the high prices consumers are willing to pay for this article in comparison with prices paid for other equally nutritious food products. The marked differences in value of butter of different grades would indicate that butter is bought primarily as a relish. Its food value should not, however, be overlooked in a consideration of this question.