The presence of lead or any metal deleterious to health is detected, by shaking in a stopped phial some of the suspected oil with a quantity of water impregnated with sulphuretted hydrogen, in the proportion of one part of the former to two parts of the latter ingredient; when the oil, if adulterated, will become of a dark brown or black colour. When the oil of poppy seed, or the decoction of cucumber, is supposed to have been made use of in the adulteration, their presence may be ascertained by exposing the mixture to a freezing temperature, when the olive oil will become frozen, while the adulterating ingredient will remain fluid. The best olive oil is of a bright pale amber colour, somewhat inclining to a greenish cast; free from sediment, bland to the taste, and without smell. SALT. Salt is frequently adulterated with sulphate of lime, for the purpose of making it weigh heavier, appear lighter, and less liable to become moist. MUSTARD. “Genuine mustard,” says Mr. Accum, (Culinary Poisons, p. 330) “either in powder, or in a state of paste ready made, is perhaps rarely to be met with in the shops.” Whether “_patent_,” “_best Durham_,” or of any other pretty and imposing name, it generally consists of a composition of mustard flour and wheaten flour; only for the additional cost of the “patent mustard” of the respective manufacturers, the purchaser is treated with a little cayenne pepper, a large quantity of bay salt, and a quantum sufficit of “aqua pura.” Turmeric is the grand adulterant of the merchant for giving the yellow colour to factitious mustard. The _flour_ of mustard of the shops generally consists of the produce of mustard seed, cayenne pepper, wheat flour, and turmeric; and the _essence_ of mustard of the fashionable oilmen is composed of camphor and oil of rosemary, dissolved in oil of turpentine, with the addition of a little of the _flour_ of mustard! ANCHOVY SAUCE. Anchovy sauce is frequently contaminated with the pigments denominated Venetian red or Armenian bole, which are rubbed into the mass, while the operator is triturating the anchovy in his mortar. The Venetian red, which is frequently adulterated with red lead, affords the deepest and finest colour, and is accordingly used by the _fashionable_ oilman; the aid of the Armenian bole is invoked by his more conscientious and less aspiring brethren. But the anchovy itself is not exempt from the sophisticating ingenuity of the trade; for sprats are frequently prepared and sold for anchovies. The best way of discovering the fraud is by the appearance of the back bone, which in the anchovy is triangular for some space from the head, while that of the sprat is flat. The test for detecting the fraud practised in the manufacture of anchovy sauce is the same as that which will be presently stated for discovering the adulteration of mushroom catsup. MUSHROOM CATSUP.