The Collaborative International Dictionary
Magnesia alba
Magnesia \Mag*ne"si*a\ (?; 277), n. [L. Magnesia, fem. of Magnesius of the country Magnesia, Gr. h` Magnhsi`a li`qos a magnet. Cf. Magnet.] (Chem.) A light earthy white substance, consisting of magnesium oxide ( MgO), and obtained by heating magnesium hydrate or carbonate, or by burning magnesium. It has a slightly alkaline reaction, and is used in medicine as a mild antacid laxative. See Magnesium.
Magnesia alba [L.] (Med. Chem.), a bulky white amorphous substance, consisting of a hydrous basic carbonate of magnesium, and used as a mild cathartic.
Wiktionary
magnesia alba
n. (context chemistry obsolete English) A bulky white amorphous substance, consisting of a hydrous basic carbonate of magnesium, and used as a mild cathartic.