_Treatment._—The first object must be to expel the poison from the stomach, for which purpose the stomach-pump may be advantageously employed, or emetics of sulphate of zinc, mustard, or ipecacuan administered, unless vomiting is already present. The sickness must be promoted by the free use of albuminous or mucilaginous diluents. Raw eggs beaten up in milk are particularly useful, as is likewise a mixture of albumen, milk, and limewater. Taylor advises equal parts of oil and limewater, for the oil invests the poison, and the lime renders it less soluble. A large dose of castor oil (℥j to ℥ij) may be given, to carry off any of the poison which may have passed into the intestines, as soon as sickness has subsided. Animal charcoal, calcined magnesia, &c., when taken in large quantities, may be of service by enveloping the arsenic, and preventing its contact with the mucous membrane of the stomach; but oil or milk will act more efficiently in this manner. The hydrated peroxide of iron[B] should be administered moist, and in large doses, after the stomach-pump has been used; or indeed, mixed with water, it may be first introduced and then expelled, thus washing out the stomach by means of the stomach-pump. This is the most efficient antidote known. The subsequent treatment must be conducted on general principles, according to the severity of the symptoms; but the great depression of the nervous and vascular systems must not be overlooked in combating any inflammatory action. Henbane or opium, in many instances combined with stimulants, ice internally, and hot fomentations externally, will frequently be found of great service. _Tests._—In its _solid state_ arsenious acid may be known by the following properties. Heated on platinum foil or on the point of a penknife, it produces a white smoke and is entirely volatilized. If some of the powder be heated in a small test tube, it will be sublimed, and small octahedral crystals, visible to the naked eye or by a lens, obtained. If arsenious acid be mixed with freshly-burnt powdered charcoal, and heated in a small test tube, a ring of shining metallic arsenic of a grey color will be found on the cool portion of the tube, and an odor of garlic is perceptible. If this deposit be driven about from place to place it will gradually become oxidized, and octahedral crystals of arsenious acid formed. Further, if the tube be divided and the part containing the arsenious acid be washed out with distilled water, the liquid tests may be applied to the solution. This is called the Reduction test. It is very delicate, detecting according to Christison, the 300th part of a grain.