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.)
n. (Chem.) A slightly alkaline chemical substance,
n. (Chem.) Magnesia. [ WordNet 1.5 ]