-magnes-

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. [ 1913 Webster ]

Magnesia alba [ L. ] (Med. Chem.), a bulky white amorphous substance, consisting of a hydrous basic carbonate of magnesium, and used as a mild cathartic. [ 1913 Webster ]

a. Pertaining to, characterized by, or containing, magnesia or magnesium. [ 1913 Webster ]

Magnesian limestone. (Min.) See Dolomite. [ 1913 Webster ]

a. (Chem.) Pertaining to, or containing, magnesium; as, magnesic oxide. [ 1913 Webster ]

n. [ Cf. F. magnésite. ] (Min.) Native magnesium carbonate occurring in white compact or granular masses, and also in rhombohedral crystals. [ 1913 Webster ]

n. [ NL. & F. See Magnesia. ] (Chem.) A light silver-white metallic element of atomic number 12, malleable and ductile, quite permanent in dry air but tarnishing in moist air. It burns, forming (the oxide) magnesia, with the production of a blinding light (the so-called magnesium light) which is used in signaling, in pyrotechny, or in photography where a strong actinic illuminant is required. Its compounds occur abundantly, as in dolomite, talc, meerschaum, etc. Symbol Mg. Atomic weight, 24.305. Specific gravity, 1.75. [ 1913 Webster ]

Magnesium sulphate. (Chem.) Same as Epsom salts. [ 1913 Webster ]

n. (Chem.) A slightly alkaline chemical substance, Mg(OH)2, the active principle in the antacid milk of magnesia, also used as a laxative. [ WordNet 1.5 ]