The official preparations of magnesia are all derived, directly or indirectly, from the sulphate.
Magnesia, in the form of the oxide and carbonates, forms insoluble and comparatively harmless compounds with the mineral acids. It is therefore used as an antidote for these poisons, the oxide being preferable, and to be very freely given.
Magnesia has antacid, purgative, and diuretic qualities. Entering the circulation, it increases the alkalinity of the plasma, and is partly excreted by the kidneys, rendering the urine more abundant and less acid.
Made from dolomite, or magnesian limestone, by solution in sulphuric acid and purification. A quickly acting hydragogue cathartic, easily borne by the stomach, though of nauseous taste. Ordinary laxative doses act in a few hours. Large doses (℥ i.-ii.) produce a result almost immediately, and cause griping and abdominal distension. It should be given well diluted and on an empty stomach. It is soluble in 2 1/2 parts of water. Dose, ℥ ss. (15 Gm.) in carbonated, Seltzer, or Vichy water.
In small doses a laxative, in large ones cathartic, acting in from four to six hours. It is effervescent, and should be kept cold and taken at the moment it is poured out. If the whole amount is not taken at once the bottle should be stood on the corked end or laid on its side. Average dose, ℥ xii.-350 mils.
Dose, ʒ i.-iv. stirred up in cold water. (4-15 Gm.)
Cerium (Cerium). A metal of which the oxalate only is used