magnesia (redirected from Magnisia Prefecture)

Magnesia, ancient cities, Lydia

Magnesia (măgnē`zhə), two ancient cities of Lydia, W Asia Minor (now W Turkey). They were colonies of the Magnetes, a tribe of E Thessaly. One city (Magnesia ad Maeandrum), SE of Smyrna (Izmir), was later colonized by Ionians and given by Artaxerxes I to Themistocles, who died there. There are important ruins on the site, including the celebrated temple of Artemis Leucophryene, built in the 2d cent. B.C. Magnesia ad Sipylum, on the Hermus River at the foot of Mt. Sipylus, NE of Smyrna, was (190 B.C.) the scene of the defeat of Antiochus III (Antiochus the Great) by the Romans. The modern Manisa is nearby.

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magnesia, chemical compound

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.

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magnesia [mag′nē·zhə]

(inorganic chemistry)

Magnesium oxide that is processed for a particular purpose.