_Tests._—Zinc is distinguished from all other substances by giving a white precipitate with sulphuretted hydrogen. The solution containing it must not be too acid or no precipitate will be formed. Zinc also gives white precipitates with ferrocyanide of potassium and ammonia. NITRATE OF SILVER (_Lunar Caustic_).—This is a powerful irritant, and has proved fatal in at least two instances. The antidote is common salt, which must be given immediately, followed by emetics. TIN.—The chlorides of tin being employed in dyeing, color-making, &c., may lead to their being used as poisons, or being taken accidentally. Death from their use is rare. They are decomposed by magnesia, which should therefore be freely administered, followed by albuminous and mucilaginous drinks. BISMUTH.—The nitrate or magistery of bismuth has caused death in nine days, after a dose of two drachms. The symptoms were those of a strong irritant, but in all probability were caused by some impurity in the substance. Arsenic is frequently present in this way. As no antidote is known, vomiting must be promoted and emollient drinks freely given. CHROME.—The bichromate of potassium is found in the form of orange-red crystals, which yield a yellow acid solution. It is used as a dye, and has caused death in more than one instance. Emetics and magnesia or chalk, must be the remedies employed. It is well to know that this substance is apt to produce troublesome sores on the hands of those engaged in its manufacture. Some slight abrasion begins the lesion, which does not heal, but forms on its surface a tough slough, which separating, leaves a foul ulcer with hard edges, and most untractable, behind it. SULPHATE OF IRON (_Green Vitriol_, _Copperas_).—Although not a powerful irritant, sulphate of iron has proved fatal when taken in a large dose. It is sometimes given to procure abortion. The _perchloride of iron_ has also produced alarming symptoms, after being taken for the same purpose. Dr. Christison relates the case of a man who died in five weeks from an ounce and a half of the tincture. Magnesia and diluents, freely administered, must constitute the treatment. CHAPTER XI. SIMPLE VEGETABLE AND ANIMAL IRRITANTS. This division of the class of simple irritants is an important one, on account of the substances composing it consisting in considerable part of ordinary remedies or drugs, which given in over doses, may produce symptoms of poisoning. They chiefly give rise to vomiting and purging. VEGETABLE IRRITANTS.