MURIATIC ACID. Under CrukanTE the chemical nature of this valuable acid has been described; but it will be instructive to trace the mode of manufacturing the acid, as con ducted at the great chemical works of St. Rollox, near Glasgow.
The same chemical operation which pro duces soda will also produce muriatic acid. Common salt is chloride of sodium ; and by a certain train of operations, the chloride com bines with hydrogen to form muriatic acid, while the sodium combines with oxygen to form soda, and with carbonic acid to form carbonate of soda. Common Cheshire salt is put into a pan in a reverberatory furnace, and sulphuric acid is slowly dropped upon it through a leaden pipe passing through the roof of the furnace. The action of the acid on the heated salt generates a new product, muriatic acid gas, by bringing into play the various degrees of chemical affinity between the substances employed. The substance then remaining in the furnace is, by further treatment, converted into soda: In the infancy of the manufacture, when the soda was the chief object of attention, the muriatic acid gas was a source of infinite trouble to the manufacturer. It is so deleterious, that if allowed to mingle with the atmosphere near the ground it would do great mischief: hence we have a clue to the history of the lofty chimneys which distinguish chemical works.
But after a time it was fcund that this delete rious gas might be made a valuable commer cial article, by changing it into liquid muriatic acid, or spirit of salt, as it is somewhat expres sively termed, in familiar use. This change has been brought about as follows all the soda furnaces discharge their muriatic acid gas into a bulky stone tower, about 40 feet high, by 8 feet square; this tower is filled with coke, upon which a stream of water is constantly falling from above ; and the gas, ascending the tower from the flues of the furnaces, meeting with an innumerable series of little streams of water trickling through the coke, becomes absorbed by the water, and thus gives rise to the formation of liquid mu riatic acid, which falls to the bottom of the tower.
The tendency of modern chemistry has been to change the name of Muriatic to Hydrochloric acid, since the latter name ex presses the composition of the acid (hydrogen and chlorine). In the same way the salts formed by the combination of the acid with gases are gradually changing their names ; instead of the muriates of soda, potash, ammo nia, tin, &c., we have the hydrochlorates of those substances.