The second division of the class of Corrosives has now to be considered. It contains the Caustic Alkalies, and some of their Salts. Poisoning by any of these agents is rare.

Potash.—This substance, in its caustic state, as found in commerce, is in the form of grey-colored cakes. It has an acrid taste, is soapy to the touch, and very deliquescent. Moulded in cylinders, it is often employed as a caustic (Potassa fusa). In solution (Liquor potassÆ) it is strongly alkaline, and imparts a brown stain to black cloth.

Potassium carbonate or Carbonate of Potash (Pearlash) is extensively used by laundresses and in the dressing of woollen cloth. It is generally sold in a granular condition, white, inodorous, and strongly alkaline; it is soluble in water, but not in alcohol.

Caustic Soda.—This agent resembles potash in its general properties. The Sodium Carbonate or Carbonate of Soda (Soap-lees) bears a similar resemblance to the carbonate of potash, except that it crystallizes easily, and effloresces on exposure to the air.

Ammonia.—When pure, ammonia is a colorless, pungent gas; but it is commonly met with dissolved in water, as the liquor ammoniÆ. Its vapor is poisonous, and may prove fatal by producing inflammation of the larynx and trachea, and even of the lungs. A case is recorded of a French boy, Æt. six, who killed his younger sister by making her swallow several teaspoonfuls of a solution of ammonia. Other instances have also occurred where the liquor ammoniÆ has either been taken in mistake for the aromatic spirit of ammoniÆ, or purposely, to destroy life. An instance is recorded by Dr. Taylor, as occurring in the practice of Mr. Hilton, where liquor ammoniÆ, given by mistake, caused corrosion of the throat and gullet and obstruction of the bronchial tubes by false membrane. The oesophagus was completely dissolved at its junction with the stomach, and there was an aperture in the anterior wall of that organ such as might have been caused by oil of vitriol.

The Ammonium Carbonate or Carbonate of Ammonia (Hartshorn, Smelling Salts) has been used as a poison. It may be distinguished from other salts by its being alkaline, by its entire volatility, and by its pungent odor. A young woman in a state of unconsciousness, was made to swallow a quantity of hartshorn. In an hour there was great pain, sickness, and vomiting of blood. The hÆmatemesis continued for some days, and then feebleness and emaciation set in, death occurring in three months. On examination the pylorus was found contracted to the size of a crow-quill, while there was a large cicatrix on the posterior wall of the stomach.

Symptoms.—The chief symptoms occasioned by the foregoing poisons are, an acrid, burning taste, with a sensation of excoriation and burning extending along the mouth and throat, to the stomach. There soon ensue exquisite pain in the epigastrium, and tenderness on pressure. Frequently there is cough, hoarseness, dyspnoea, as well as vomiting of altered mucus mixed with blood and detached portions of the mucous membrane. The tongue, mouth, and fauces become swollen, soft, and flabby, and deglutition is difficult. The surface of the body gets cold and moist, the pulse small and feeble, and there is great pain over the abdomen, with diarrhoea. Death took place, in the case of a boy, in three hours from the time of swallowing a strong solution of carbonate of potash. Ammonia, by its effect on the air passages, has proved fatal in four minutes. When recovery from the immediate effects of the poison has taken place, death has subsequently ensued from stricture of the oesophagus, producing starvation. By the proper use of bougies, &c., life may occasionally be prolonged for many months, or even for years. In some instances, however, it is almost impossible to effect dilatation, owing to the whole of the gullet becoming thickened and contracted, so that the opening into the stomach will hardly admit a crow-quill. The pylorus may also be contracted in like manner.

Post-mortem Appearances.—The mucous membrane of the mouth and gullet is softened and inflamed, and portions of it detached. The coats of the stomach and intestines are inflamed, stained of a dark color, and sometimes ulcerated. When death has resulted from ammonia, signs of inflammation are usually found in the larynx and bronchial tubes. The other caustic alkalies may also destroy life by producing inflammation of the glottis, which consequently may be found thus occluded after death.

Treatment.—The object must be to neutralize the poison, which may be effected by a weak acid. Vinegar and water is perhaps the best antidote, and that most readily procurable; its administration may be followed up by freely allowing acidulated demulcent drinks, orange juice, &c. The use of oil has been recommended, on the principle that it converts the alkali into a soap. But that its efficacy is doubtful has been in some measure shown by the death of two young children from swallowing a mixture of ammonia and oil. In one of these cases nearly two ounces of linimentum ammoniÆ (made of one part of liquor ammonia to two of olive oil) were poured down an infant’s throat by a child five years old. Were, however, the oil given in much greater abundance, the result would probably be different. At all events, its administration should not be neglected.

Tests.—The specific character of these substances is their strongly marked alkalinity, ammonia possessing, over and above, that of volatility. Potash is known from soda by being precipitated of a creamy yellow by platinum perchloride, soda remaining unaffected by that reagent.