SALT.
Salt is one of the most widely spread and plentiful minerals which the earth gives for the use of man; all the water of the ocean derives its saline taste from salt; many springs are completely saturated and are hence called “brine springs,” and it also exists crystallized in beds within the earth of immense thickness and extending for miles each way. The salt mines of Cheshire are the finest and most extensive in England, and in some places the stratum or layer of salt is more than one hundred feet thick, perfectly white and crystallized. Salt is not a simple body, but is composed of two simple bodies or elements, chlorine and sodium, hence it is called by chemists the chloride of sodium, it can be formed by putting carbonate of soda into hydro-chloric acid (sometimes called muriatic acid,) until no more effervescence takes place, the result will taste salt and yield pure salt on evaporation. The waters of the sea are in some places evaporated by the heat of the sun in shallow hollows dug out in the beach, this is called “bay salt” and is very impure; but the chief part of the salt of commerce is procured by evaporating the waters of brine springs; this water is pumped up into large iron cisterns placed beneath slight sheds to keep the rain off, and having flues running beneath them, the first impurities are thrown away, and as evaporation goes on, the salt crystallizes and falls to the bottom of the cistern in a fine white powder; this is taken out with wooden shovels and placed in conical vessels with a hole in their lower part to drain off all the moisture; it is then dried by stoves and is fit for use; when no more salt falls down, the impure liquor, called “bittern,” is drawn off and used to procure Epsom salts from, by mixing it with sulphuric acid. The bittern contains chloride of magnesium, and the sulphuric acid changes it into sulphate of magnesia, which, when purified, forms the Epsom salts sold by druggists.
About half a million tons of salt are made in England every year. Salt, besides its general use as a condiment, and in preserving food for storing ships, &c., is also used for several manufacturing purposes. By adding sulphuric acid and heating it, the acid called “hydrochloric” is given off, which is largely used for many purposes; but the chief use made of salt by the manufacturing chemist is to prepare soda for cleansing and soap making.