The Romance of Modern Chemistry

THE ADULTERATION OF FOOD Since, then, the appearance of the milk and even the determination of its specific gravity may fail to give any proof of adulteration, further examination is necessary. The analyst must proceed to find also what is the amount of fat present in the milk. This is very quickly ascer- tained by treating a measured quantity in a centrifugal machine; the fat or cream under these circumstances separates almost immediately, and its bulk may be deter- mined. If the amount of fat is less than 3 per cent., the milk has certainly been tampered with, since the normal product never contains a smaller percentage of fat than this. A thorough examination would include also the determination of the non-fatty solids, consisting chiefly of casein and milk-sugar; but a description of this would take us rather far. Butter is another household article that is readily and frequently adulterated, although the recent Butter and Margarine Act should do something to protect the public. The usual frauds practised in the case of butter are (1) the sale of “renovated” or “process'” butter as fresh butter, and (2) the substitution of a certain amount of cheap beef fat or lard for the true butter fat. Reno- vated butter is obtained from rancid butter by a pro- cess in which the objectionable matter is removed; the product is rendered sweet for the time being, and is sold as choice butter. Artificial butter, on the other hand, or margarine, as it is commonly called, is prepared from beef fat or lard, which is worked up with ordinary butter and colouring matter so as to resemble the real article. Besides a certain difference in the taste of butter and margarine, there is one very simple method, known as the spoon test, by which they may be distinguished. If a 264