Soda, Fossil, or Mineral Alkali, a peculiar salt, which is found native in various parts of the world; but, as the quantity thus obtained, is inadequate to its extensive consumption, various methods have been devised, for procuring it from sea-salt; and also by the burning of the salt-wort, together with other saline plants, which grow in the vicinity of the sea-coast. - See Barilla, and Fossil Alkali.

Few articles are of greater importance to the arts, manufactures, and domestic economy, than soda. It is indispensably necessary for making hard soap; and also forms an excellent substitute for this article ; as four ounces of the former, and six of the latter, are fully equal to 1(5 ounces, or one pound of soap, for cleansing 14lbs. of cloth, by hand; while it softens the hardest water : thus, a saving will arise in the expence of from one-third to one-half, accordingly as that operation is performed by the hand, or by machines. - The superior effects of soda are fully evinced in the cleansing of fleecy hosiery, flannels, or worsted stockings ; which, when managed with warm water, soap, and pot-ash, acquire an unpleasant odour, and are: apt to shrink, in consequence of the rubbing, particularly if they be immersed in cold water: whereas, by using the fossil alkali, these inconveniencies are said to be completely avoided, and neither the quality of the goods Will be impaired ; nor the hands of women, when the soda is employed, be injured in the same manner, as generally happens by the common ley.

Farther, as frequent bathing or washing of the body greatly conduces to health, it has been recommended to dissolve a small portion of soda in the water thus employed ; or, at least to pass a towel wetted with a solution of soda and soap, over the surface; for such practice opens the pores, and removes the disagreeable odour arising from profuse perspiration : - a similar application will be produc-tive of equal advantage to horses that are employed for racing, post-chaises, or other purposes, where great exertions are required.

If a weak solution of soda be poured into foul bottles or casks, in which wine has been kept for a considerable time, it will completely dissolve the tartarous crust that is formed on their inner surface : - boot-tops, saddles, or bridles, may with such liquid be effectually cleansed, while the original colour of the leather is preserved.

This alkali may, likewise, be employed for sweetening kitchen-utensils, and particularly for removing grease or acids from copper vessels ; because these concretions, when suffered to remain, form a strong poison, and may be productive of deleterious effects. In a similar manner, it may be used for tin and iron vessels, to prevent them from becoming rusty. Lastly, as the utensils of the dairy are apt to acquire an acid, disagreeable smell, during the summer, and particularly after a thunder-storm, though every attention be bestowed on them, such fetor may be completely removed by a small portion of soda, which will render the milk-vessels perrfectly sweet; while it neutralizes and dispel the acid ferment imbibed by the wood, and which might otherwise taint the milk.

The crystals of soda arc not less useful in a medicinal point of view. Thus, a solution of this salt, is an excellent gargle for cleaning the throat, mouth, and gums, both in a sound and in a diseased or ulce -rated state ; while it whitens the teeth ; and dissolves all incrustations that may be formed on their surface, without injuring their enamel. And, if a small quantity of this liquid be occasionally swallowed, after washing the fauces, it said effectually to remove & fetid breath. Soda is, in many instances, preferable to magnesia, for correcting acidity in the stomach; nay, it is even asserted, that it prevents the gout, gravel, stone, and similar disorders : lastly, if the fossil alkali be mixed with cream of tartar, in the proportion of 14 parts of the former to 12 of the latter, it furnishes one of the mildest laxatives; namely, the Rochelle Salt. - See also Glauber's Salt.