SALTS, THEORY OF. Any substance which is produced by the combination of a base with an acid, is commonly termed a salt. The base is in most :oases a metallic oxide, which is capable of uniting with an acid, and of more or less completely neutralizing the distinctive properties of the latter; in some cases, however, the base is non-metallic and organic in its nature, as in the case of ammonia, morphia, quinia, strychnia, ereatipine, etc.
The salts derive their generic name from common salt, now known as chloride of sodium, but till the dine of Davy regarded as a compound resulting from the union of hydrochloric (or as it was then termed, muriatie) acid and soda. See SODIU31. Davy, however, showed that during their action upon each other, both the acid and the alkali undergo decomposition, and that while water is formed by the union of the oxygen of the alkali (Na0) and the hydrogen of the acid (HCI), the sodium of the former combines with the chlorine of the latter to form chloride of sodium (NaCI). Hence, strangely enough, the very substance from which the salts derive their name as a class, was the means of overthrowing the old idea that a salt, as a matter of necessity, must result from the union of a base ivith an acid. It was then proposed to divide salts into two classes—those formed by the union of a base with an oxyacid, such as nitrate of potash (KO,N0,,), formed by the union of oxide of potassium with nitric acid, sulphate of soda carbonate of lime etc., which were termed arysaits; while the
other class consisted, like chloride of sodium, of a metal combined with the characteristic element (chlorine, iodine, bromine, fluorine) in a hydrogen acid or hydracid (as, for example, hydrochloric, hydriodic, hydrobromic, or hydrofluoric acid). The salts of this second class, of which chloride of potassium (ICCI) and fluoride of calcium (Us F) may be quoted as examples, being constructed on the same plan or type as sea-salt, were termed ha!oid salts (q.v.), from the Greek word hats, the sea. The chlorine, iodine, bromine, or fluorine, which, in combination with a metal, forms a haloid salt, is. by some writers termed a "The great resemblance in properties between the two classes of saline compounds, the haloid and oxysalts, has very naturally led to the supposition that both might possi bly be alike constituted; and that the latter, instead of being considered compounds of an oxide and an acid, might with greater propriety be considered to contain a metal in union with a compound salt-radical, having the chemical relations of chlorine and iodine. On this.supposition, sulphate and nitrate of potash will be constituted in the same man ner as chloride of potassium. the compound radical replacing the simple one.
Old View. New view.