Crystallized muriate of soda contains 53 of soda, and 47 of acid, containing, how ever, some water of composition, so that of real acid the quantity is 38.83. Its specific gravity is 2.12. This salt is de composed by the sulphuric and nitric acids, in the same manner as the muriate of potash is. It is from its decomposition by the sulphuric acid, that the muriatic acid is best obtained ; as has already been observed. When decomposed by the nitric acid, part of the latter is de composed, a quantity of its oxygen being transferred to the muriatic. One of the most important practical problems in chemistry is, to decompose this salt so as to obtain its alkali. It abounds so much in nature, that if such a process, capable of being carried on to advantage, could be discovered, a vast supply of soda would be obtained ; and as this alkali can he em ployed for every purpose that potash can, and is even much superior to it for some uses, such a discovery would be of much importance to the chemical arts. Salt is decomposed in the usual mode by sulphu ric acid ; and to defray the expense, the touristic acid is collected and employed in the manufacture ot'sal ammoniac, in the preparation of oxymuriatic acid for bleaching, or for any other useful pose to which it can be applied. The
sialphate of soda is calcined in a reverbe ratory furnace, to free it from any super fluous acid. It is then to be decomposed. It is of very extensive use. Its applies tion to preserve animal substances from putrefaction is well known ; the theory of its antiseptic quality has never yet been properly explained. It is also taken uni versally as a seasoning to food, and seems to be very necessary to promote diges tion, as even the lower animals, it has been proved, languish, when altogether deprived of it. It is employed in a varie ty of arts. In the manufacture of pottery of the coarser kind, when it is thrown in to the oven in which the ware is baked, it is converted into vapour, and, being ap plied in this state to the surface of the vessels, glazes them, an effect probably owing to the combination of its alkali with the silicious earth of the pottery. It is employed in the manufacture of glass, which it is said to render whiter and clearer; in that of soap, which it makes harder; as a flux, in the melting of metals from their ores ; and in a variety of che mical and pharmaceutical processes.