magnesia, common name for the chemical compound magnesium oxide, MgO. It occurs as colorless, cubic crystals. It is refractory, melting at about 2,800°C. It is very slightly soluble in pure water but is soluble in acids and solutions of ammonium salts. The magnesia of commerce is a fine white powder used in soaps, cosmetics, pharmaceuticals, and as a filler in rubber goods. Magnesia is used to make crucibles and other ceramic goods. Crude magnesia is prepared by roasting dolomite (calcium magnesium double carbonate) or magnesite (magnesium carbonate). Pure magnesia is prepared by refining the crude product. Magnesia is also extracted from seawater. It occurs in nature as the mineral periclase.
Magnesium oxide; aperient and antacid.
an antacid pill
A food or drug that stimulates evacuation of the bowels.
- Stimulating evacuation of the bowels.
- Causing looseness or relaxation, especially of the bowels.
[Middle English, from Old French laxatif, from Medieval Latin laxātīvus, preventing constipation, from Late Latin, assuaging, from Latin laxātus, past participle of laxāre, to relax, from laxus, loose. See lax.]