MAGNESIUM, inng-ne'zhi-Sini or -shi-firn (Neo-Lat., from nlagnesia, from Gk. Acemio-la [Sc. Alan], [cc. lithos], magnesian [Sc. stone], magnet, from Malevuo-la. Maglu7sia, a dis trict ill Thessaly. where magnetic stones abound ed). A metallic element first isolated by Davy and Bussy. Certain isolated salts of magnesium were known in the seventeenth century, the sul phate, for instance ('Epsom salt'), having been found in the mineral waters at Epsom, England. The element is not found native, but its com pounds are widely distributed as the minerals magnesite or magnesimn carbonate, dolomite or magnesium-calcium carbonate, kieserite or mag nesium sulphate, kainite or masmesium sulphate with potassium chloride, earnallite or maple sium-potassium chloride, as well as numerous other minerals, containing smaller quantities. Magnesium also forms the chief constituent of many silicates:, such as aught'-, horebletule, alining, serpentine, tourmaline, and meerschaum. It is further found in the bones of animals and in the seeds of the cereals. The metal itself WaS originally obtained by heating magnesium chloride with potassium in a platinum crucible. and washing out the resulting potassium chloride with water. It may he made by the action of metallic sodium on magnesium chloride, but it is more cheaply obtained electrolytically.
Magnesium (symbol. Mg: atomic weight. 24.36) is a silver-white, lustrous, hard metal that is malleable and ductile, has a specific gravity of 1.75, melts at about 500° C.. and boils at about 1000° C. It finds use as an illuminant, burning readily when in the form of filings, wire, or ribbon, with a white light of great brilliancy: thus, a burning magnesium wire of 0.297 millimeters thickness produces a light equal to 74 stearin candles; hence its application for flashlights iu photography, for signals, and in fireworks. Magnesium combines with various other metals to form alloys, the most interesting of which are those with potassium and sodium.
which decompose water at ordinary temperatures. A silver-white alloy of aluminum and magnesium. called magnalium, has been recommended for lens mountings, spectacles. etc. When ignited in the air or oxygen it forms an oxide,. MgO, which is a white, light, infusible. amorphous powder that is extensively used in the manufacture of cruci bles, cupels, fire bricks, etc. It is also used, like lime, for the production of a light similar to the calcium light. (See DRUMMOND LIGHT.) The commercial article is obtained by prolonged igni tion of the carbonate or the hydrate. both of which are derived from the saline deposits of Stassfurt. Germany. The oxide, as well as the carbonate. of magnesium finds use in medicine as a laxative and antacid. When mixed with water, the oxide gradually changes into the hydrate, which is also found native as the mineral brucite. The hydrate is used for ex tracting sugar from molasses, forming an insolu ble, granular, crystalline magnesium saccharate. which, When decomposed by corhon dioxide. yields pure sugar. The carbonate, which is known commercially as magnesia alba, is pre pared by precipitating either the sulphate or the ehloride with sodium (mrbonate. The sulphate, or Epsom salt, which occurs as the purgative principle of various spring waters, is obtained commercially from the minerals kieserite and ep somite, or by decomposing dolomite with sul phuric acid. This salt is largely used as a fer tilizer. as a refrigerant cathartic in medicine. for dyeing with aniline colors. and for warp sizing cotton. The rhlorirb, which occurs native with potassium chloride as earnallite in the Stassfart deposits. is used by cotton spinners as a thread lubricator. and as a source for other magnesium salts. The citrate, which is official in the United States Pharmacopasia. is used in medicine as a laxative.