SALT, SEDATIVE, is boracie acid. SALT. This term, though in ordinary language limited to common salt, or sea salt, is applied in chemistry to all combi nations of acids with alkaline or salifiable bases. The term has also been extended to certain binary combinations of chlo rine, iodine, bromine, and fluorine with the metals ; and these have been called haloid salts (from As, sea salt, and cubes, form), inasmuch as modern chemistry has taught us that sea salt belongs to this class. Certain definite combinations of sulphurets with each other have of late been called sulphur salts; but the former appellation of double sulphurets is, per haps, more properly applicable to such compounds.
Sea salt is a compound of 1 equivalent of sodium = 24, and 1 of chlorine = 36 ; its equivalent, therefore, is (24 + 36)= 60: and it is a chloride of soda.
The nomenclature of salts has reference to the acids which they contain ; sulphates, nitrates. carbonates, &c., implying salts of the sulphuric, nitric, and carbonic acids. The termination ate implies the maximum of oxygen in the acids, and ito the mini mum: thus the salts of sulphurous and nitrous acids are called sulphites and nitrites. When salts contain 1 equivalent of acid and 1 of base, they are called neutral salts ; where 1 equivalent of acid is combined with 2 of base, they are termed bask salts, submits or disalts ; and where there are 2 equivalents of acid and 1 of base, the salt is a supersalt or bkalt. Thus, the terms subacetate and diacetate of lead are synonymous ; so are supercar bonate and bicarbonate of potash. Many salts are hydrous ; that is, they contain a definite proportion of water of crystalli zation ; others are destitute of water, and are dry or anhydrous salts. Some salts attract moisture when exposed to air, and are said to be detiquese; others suffer their water to escape and become opaque, or pulverulent: these are called salts.
Salt is, next to bread, the most impor tant necessary of life. It is one of the most important British minerals, and is procured in great quantities, both from fossil beds and brine springs, in Cheshire and Worcestershire. Previously to the
discovery of the fossil beds during the 16th century, and subsequently, a good deal of salt continued to be made by the evaporation of sea water in salt pans, at Lymington and many other places ; but the works at these places are now all but abandoned; while not only has the quali ty of the article in question become great ly improved, but, instead of being im ported as formerly, it is now largely exported. The consumption of Great Britain only, exclusive of Ireland, a mounts to about 180,000 tons ; and the foreign exports to about 300,000 tons per year of which the United States, Canada, the Low Countries, Russia, Prussia, and Denmark are the chief consumers. The geological position of rock-salt is between the coal formation and the lias. The great rock-salt formation of England occurs within the red snarl, or new red sandstone, the buziter-aandstein of the Germans, so called, because its colors vary from red to salmon and chocolate. This mineral stratum frequently presents streaks of light blue, verdigris, buff, or cream color ; and is chiefly remarkable for containing considerable masses or beds of gypsum. At Northwich, in the vale of Weaver, the rock salt consists of two beds, together not less than 60 feet thick, which are supposed to constitute large insulated masses, about a mile and a half long, and nearly 1300 yards broad. There are other deposits of rock salt in the same valley, but of inferior impor tance. The uppermost bed occurs' at 75 feet beneath the surface, and is covered with many layers of indurated red, blue, and brown clay, interstratified more or less with sulphate of lime, and inter spersed with argillaceous marl. The second bed of rock-salt lies Kb feet be low the first, being separated from it by layers of indurated clay, with veins of rock-salt running through them. The lowest bed of salt was excavated to a depth of 110 feet, several years ago.