ANTIDOTE TO POISONS.—The antacid properties of magnesia make it valuable as a antidote in cases of poisoning by the strong mineral or vegetable acids. It neutralizes the acids and acts as a me chanical protective to the tissues against the corrosive action of the acid-poisons. Its value as an antidote in poisoning by metallic salts depends upon the fact that it precipitates many metals from their acid of combination, and thus renders the metal less soluble and, therefore, less poisonous. In poisoning by arsenic, freshly-prepared hydrate of magnesia is an antidote of no mean value, but is not so effective as the official hydrate oxide of iron with magnesia, of which doses of 1 to 4 drachms are given.
PUROATIVE.—Magnesia and carbonate of magnesia are often used as purgatives in children, as before mentioned. The neutral salts, the citrate and sulphate, are more generally used for this purpose. Magnesia and the carbonate are hardly suitable for continuous administration, as, being insoluble, they may accumulate in the intestines and form concretions consisting of the hydrate of magnesia. The citrate and sulphate of magnesia cause little, if any, irritation, and are on that account valuable as laxatives in en teritis and peritonitis. In febrile affec
tions, given in small doses, they exert a refrigerant and slight diuretic action. Combined with iron, they are useful in constipation associated with atonic con ditions. In anmmia and chlorosis, which Clarke attributes to fmcal intoxication, the "mistura ferro-salina" is a useful tonic laxative.
4 Sulphate of magnesia, 1 ounce. Cream of tartar, 1 drachm.
Dried sulphate of iron, 10 grains. Water, 2 pints.-111.
Of this a wineglassful should be taken a half-hour before breakfast each morn ing.
The constipation of lead poisoning is relieved best by magnesium sulphate as follows:— 4 Magnesium sulphate, 2 drachms.
Morphine sulphate, 1 grain. Peppermint-water, 3 ounces.
Mix and give a tablespoonful every two hours in lead colic.
The purgative mineral waters (Fried richshall, PuUna, Seidlitz, and Hunyadi waters) owe their purg,ative action prin cipally to the presence of magnesium sulphate.