The normal or ordinary carbonate of soda popularly known as the soda of commerce, is a colorless, inodorous salt, with a nauseous alkaline taste. It crys tallizes in large transparent rhomboidal prisms, which contain nearly 63 per cent of water, but it readily parts with all this water on the application of heat. The crystals nisi; lose the greater part of their water on mere exposure to the air, when they effloresce and fall to powder. Water at 60° dissolves half its weight of the crystals, and boiling water considerably more, the solution acting like an alkali on vegetable colors. This salt occurs native in the natron-lakes of Hungary, Armenia, etc., in association with sulphate of soda and chloride of sodium. In other regions it appears in an efflorescent form on the surface of the earth. It is now, however, almost entirely manufactured from sea salt. See SODA, MANUFACTURE OF.
Saguia! rbomzte of soda 3Aq) occurs native in the form of large, hard, non-efflorescent prisms, in Hungary, Egypt, Mexico, etc., under the name of trona or natron. When strongly heated, it loses one-third of its carbonic acid, and becomes converted into the preceding salt.
Bicarbonate of soda may be formed by passing a current of carbonic acid through a strong solution of carbonate of soda, till saturation takes place, and allowing the mixture to crystallize; or it may be produced on a large scale by t xposing crystals of carbonate of soda to a prolonged current of carbonic acid. The bicarbouic crystallizes in four-sided prisms, which require 10 parts of water at an ordinary tempera ture for their solution. This salt is used largely in medicine. Sec AERATED WATERS.
Sulphuric acid forms with soda a normal and an acid sulphate.
The normal or ordinary sulphate()) soda (Na0,S03 10Aq) has been already described under its synonym of Glauber's salt (q.v.). The acid salt, or bisulphate of soda (NaO,H0,2.',602) is of no special interest.
The hypusulphite of soda (NaO, SO22 5Aq), occurs in large colorless, striated, rhombic prisms, of a cooling a sweet taste. When strongly heated in the air, it burns with a blue flame. It dissolves readily in water, depositing sulphur if the solution be kept in a closed vessel. It may be obtained by digesting a solution of sulphite of soda on powdered sulphur. The sulphur is gradually dissolved, and formsa colorless solution, which, on evaporation, yields crystals of hyposulphite of soda. This salt is largely employed in photography, and is occasionally prescribed medicinally. Sulphurous acid forms two salts with soda —viz., a sulphite and a bisulphite. The sulphite of soda 7Aq) is obtained by passing sulphurous. acid over carbonate of soda, dissolving the resulting mass in water, and crystallizing; when the salt is obtained in efflorescent oblique prisms, which fuse at 113', and are soluble in 4 parts of cold water, the solution having a slightly alkaline reaction. and a sulphurous taste. This compound is commercially known as antieldore, and is largely used in paper-manufactories for the purpose of removing the last trace of chlorine from the bleached •ag-pulp. The bisulphite is of no importance. _Nitrate of soda known also as cubic niter or Cali saltpeter, occurs as a natural product on the surface of the soil of certain South American districts. In most of its properties, excepting its crystalline form, and further in its being deliquescent, it resembles nitrate of potash. It is used to a considerable extent as a manure. Tile phosphates of soda, though comparatively numerous, do not call for notice here. Sec PHOSPHATES. Hypo chlortte of soda (NaO,C10) is at present only known in solution, in which it occurs as a yellowish-green fluid, evolving a smell of chlorine; it has strong bleaching power, and, when boiled, becomes decolorized, and evolves chlorine freely. It is formed by passing
a stream of 'chlorine gas through a solution of carbonate of soda, the resulting solution containing the hypochlorite, together with undecomposed carbonate of soda and chloride of sodium. This solution is useful as a bleaching agent, as an oxidizing agent m analytical chemistry, and as a disinfectant agent. There are two borate.s of soda, of which the only important one, the biborate, is already described under its ordinary name of bores (q.v.). Various silicates of soda have been formed. In reference to the proper. tics of these salts, see the articles FUCIT'S SOLUBLE GLASS and GLASS.
The lat'oid salts of sodium resemble, in their general characters, the corresponding salts of potash. Of these by far the most important is,chloride of sodium or common salt, formerly known as mu riate of soda. (NaCI). It OCCIII'S naturally in far greater quantity than any other soluble salt. See RoCE-SALT, SEA, WATER. The following are its leading properties: It crystallizes in colorless, transparent pubes, which are anhydrous, soluble in about 3 parts of cold water, and scarcely more soluble in boiling water. A saturated solution has a specific gravity of 1.205, the specific gravity of the salt being 2.125. It is insoluble in pure alcohol, is inodorous, and has a purely saline taste, unmingled with bitterness, unless chloride of magnesium be mixed with it. At a red heat it fuses, and becomes converted into a transparent brittle mass. The well-known decrepitation which occurs when salt is thrown On the fire, or otherwise strongly heated, 'results from the sudden expansion of water mechanically entangled among its particles. The uses of this salt have been known from the earliest times. It is an essential constituent of the food both of man and animals. From want of space we must refer our readers to Liehig's Letters on. Chemistry (hitter xxviii.) on this subject. in which the functions of salt in the food and in the blood arc clearly pointed out. It is regarded as a necessity even by the rudest nations. "In several countries of Africa men are sold for salt; among the Gallas and on the coast of Sierra Leone the brother sells his sister, the husband his wife, and parents their children, for salt: in the district of Accra (Gold coast), a handful of salt, the most valuable mer chandise after gold, will purchase one. or even two slaves."—Note to Liebig's op. cit., p. 413. Chloride of sodium is employed in the process of salting meat in consequence of its powerful antiseptic properties. Meat thus prepared loses, however, a considerable portion of its nutritive jukes, which pass into the brine, and is less digestible than in its natural state. Among the purposes for which this salt is mainly employed may be mentioned the manufacture of the various salts of soda, especially the carbonate; tact preparatiou of hydrochloric acid; the glazing of stoneware; the preparation of soap, The other haloid salti—the iodide, bromide, and fluoride of sodium—require no notic Sodium has been recently found to enter into various groups of organic bodies. We shall take time sodiumadeohols as au example. Whim sodium or potassium 1: gradu ally added to anhydrous alcohol, the temperature rapidly rlses, the metal is dissolved, hydrogen is evolved, and a fusible deliquescent compound 13 formed, which lies received the name of sodiuni-alcohol (or potassium-alcohol), or of ethylate of soda (or potash), its composition being such that it may be regarded as alcohol iu which ouc atom of Lydro gen is replaced by one of the metal; as shown in the equation: The action of sodium or potassium on the other alcohols is of an analogous nature.