SODA

Natron; mineral alkali. This important and useful substance is an oxide of sodium. Sodium was discovered by Davy in 1808. It is a metal much resembling pota ium in its general characters. It is soft, malleable, fusible at 190°, and burns when heated in contact of air. When tlirown upon water it does not burn, but floats about upon the surface, and rapidly disappears, being converted into soda, which is di olved in the water, and gives it an alkaline reaction. The specific gravity of sodium is 0"97. By the quantity of hydrogen evolved during the action of sodium on water, we learn that soda, or oxide of sodium, consists of 1 equivalent of sodium = 24, and 1 of oxygen = 8. The equivalent of soda, therefore, is 32. The commercial demands for soda are chiefly supplied from two sources: the combustion of marine vegetables, such as common sea-weed and the Salsola soda, which furnish the impure alkalies called kelp and barilla; and the decomposition of common salt, or rather perhaps of sulphate of soda, obtained by the decomposition of salt by sulphuric acid. Carbonate of soda forms large rhombo-prismatic crystals, composed of 32 soda + 22 carbonic acid + 90 water. They fuse in their water of crystallization at about 150°, and it may be entirely expelled by exposure to heat. They effloresce when exposed to air. Sulphate of soda, or Glauber's salt, is the result of the action of sulphuric acid upon common salt. {See Muriatic Acid.) It consists of 32 soda -I- 40 sulphuric acid; and the crystals are constituted of 72 dry sulphate and 90 water: they are efflorescent, and soluble in about 3 parts of cold w'ater. When sodium is introduced into chlorine it immediately combines with it to form chloride of sodium, or common salt; if heated in the gas, it burns very vividly: 24 parts of sodium combine with 36 of chlorine to form 60 parts of this important and well-known compound. {See Salt.) When chlorine gas is pa ed into a weak solution of caustic soda it is absorbed, and a useful bleaching and disinfecting solution is obtained, which has been called Labarracqiie's disinfecting soda liquid. [s. 1141]