SODIUM (Neo-Lat., from It. soda, soda, saltwort, glasswort). A metallic element iso lated by Sir Humphry Davy in 1807. (See POTASSIUM; CHEMISTRY.) Compounds of sodium occur distributed in large quantities, especially sodium chloride, which is found in nature as halite or rock salt. and in solution in sea and other natural waters. Sodium also occurs in the form of nitrate (soda nitre, or Chile saltpetre), which is found abundant ly in superficial deposits in the rainless dis tricts of the Pacific coasts of Chile, Peru, and Bolivia; as the sulphate (Glauber's salt) or mirabilile: as the carbonate; and in numer erous minerals of more complex composition, such as cryolite, the various feldspars. in eluding albite, labradorite. oligoelase, and the zeolites. Sea plants, as well as animal or ganisms, likewise contain sodium salts. The preparation of the metal itself may be accom plished by decomposing sodium hydroxide by electrolysis. It was first prepared on a large scale by Sainte-Claire Devine. who reduced sodium carbonate with coal and chalk at a white heat, and collected the resulting metallic sodium under coal oil in suitable condensers. A commercial process now extensively employed was invented in MSG by Castner, and consists in re ducing sodium hydroxide by an iron carbide pre pared by adding finely divided iron to melted pitch and coking the mixture in large cylinders. The metal is distilled over into condensers and is purified by passing through linen under petro leum at about 100° C. (212° F.).
Sodium (symbol, Na; atomic weight, 23.05) is a very soft white metal possessing a silvery white lustre when freshly cut. Its specific grav ity is 9.85. and its melting point is 95.0° C. (204° F.). It is one of the best conductors of heat and electricity, and is one of the most eleetro-positive metals. Its vapor is colorless when seen in thin layers, but has a purple or violet tinge by transmitted light when seen in quantity. Sodium burns with a bright yellow flame when heated in the air. When thrown into cold water it. decomposes it. liberating hydrogen, but not with sufficient heat to ignite the latter, unless the temperature of the water is above GO° C. F.). The metal readily takes up oxygen, and in consequence finds its chief use in the preparation of aluminum, boron. mag nesium, and silicon by reduction from the oxides. Sodium forms alloys with many metals. and the amalgam with mercury is employed in the ex traction of gold. It combines with oxygen to form a monoxide (Na,)) and a peroxide (NaA), of which the former may be obtained by heating sodium hydroxide with sodium. yield ing a gray mass, which melts at a dull red heat : while the latter. which is a white solid that delignesecs in the air, is formed by heating metallic sodium in oxygen.
The salts of sodium are among the most im portant of the commercial chemicals. Chief
among them is sodium acetate, which is pre pared by treating acetic acid or vinegar with sodium carbonate, filtering the solution and con centrating to crystallization. Sodium arsenate is prepared by fusing arsenious acid, sodium car bonate, and sodium nitrate, dissolving the result ing mixture in hot water. filtering, and crystal lizing. The colorless crystals thus obtained are official in the pharmaeopwin and are used in skin diseases and as a substitute for arsenic. Nixed with sugar this salt is frequently em ployed as a poison for flies. Sodium. bromide and sodium iodide, which are prepared by decompos ing, respectively, ferrous bromide and ferrous iodide with sodium carbonate, are white crystal line compounds that find some use in medicine as nervous sedatives. Sodium carbonate. which is the soda of commerce, is a colorless crystalline odorless compound with a strong alkaline taste, which is found native in many mineral waters and as effloreseences in the neighborhood of soda lakes. Sodium bicarbonate o• 'acid' sodium car bonate is made by passing a current of carbon dioxide through a strong solution of sodium carbonate until it is saturated and then allowing, the mixture to crystallize. a colorless compound which finds extensive use in the mann factnre of baking powders and of artificial min eral waters, and also in medicine as an antacid. Sodium. hypophosphite is prepared by treating calcium bypophosphite with sodium carbonate and recrystallizing the resulting product from alcohol. It forms small colorless crystals that are deliquescent and finds some use in medicine as a restorer in exhausted conditions of the nerv ous system, and as an ingredient in the syrup of hypophosphites. Sodium hyposulphite, or more correctly sodium thiosulphate, is prepared by decomposing soluble calcium thiosulphate with either sodium sulphate or sodium carbonate, resulting in the formation of a colorless crystal line compound that is efflorescent in dry air. and is used in photography as a solvent for the unal tered silver chloride or bromide on the film, and in medicine as an alterative and resolvent. Sodi um silicate is prepared commercially by fusing sodium carbonate with sand and a small quan tity of charcoal in a reverberatory furnace and then dissolving by prolonged boiling in water. (See 'WATER-GLASS.) Sodium sulphite is ob tained by passing gaseous sulphur dioxide into a solution of sodium carbonate and evaporating the mixture to dryness or crystallization, result ing in a colorless, transparent, efflorescent com pound that is used as a bleaching agent under the name of antichlore, in the manufacture of paper, for the purpose of removing the last traces of chlorine from the bleached pulp; it is also employed in medicine as an antiferment. See also SODA; SALT; SALTPETRE; CLABBER'S SALT; etc.