SULPHURIC ACID, a very important acid which occurs in nature in large quantities, both in the vegetable and mineral kingdoms, in combination with the various bases, more particularly the alkalies, alkaline earths, and the oxides of iron, copper, lead, zinc, alumina, etc. Its mineral combinations are generally known as vitriols, a name which, in the case of the sulphates of iron, copper, and zinc, has been transferred to the manu factured products. Sulphuric acid is formed by the oxidation of sulphurous acid, or some other oxide of sulphur. In its perfectly anhydrous condition, it oc curs as a white crystalline fibrous mass, somewhat resembling asbestos in appear ance. It can be molded in the fingers like wax without charring the skin; it fumes in the air, and is very delique scent, hissing violently when thrown into water; thereby becoming sulphuric acid. It chars wood, paper, sugar, and other similar substances, by abstracting water from them. It melts at 65° F., and boils at 110° F., forming a colorless vapor. It possesses no acid properties whatever, and is not regarded as such by the fol lowers of Gerhardt, by whom it is called sulphuric anhydride. The vapor, when passed through a red-hot tube, is resolved into a mixture of one volume of oxygen with two volumes of sulphurous acid. With sulphur it forms several more or less definite compounds, of a brown, green, and blue color respectively, which have not as yet received sufficient in 7estigation. There are two varieties of tulphuric acid in commerce. The first of these, fuming or Nordhausen sul phuric acid, is obtained by the distilla tion of the basic sulphate of iron formed by heating crystals of common green vitriol. It is a somewhat viscid liquid, generally of a light-brown color, from containing traces of organic matter, and has a sp. gr. of 1.896. It is believed to be a combination of equal parts of the anhydrous and monohydrated sulphuric acid, and may be represented by the formula H2SO.S0,. It solidifies at 32° F. into a mass of transparent colorless crystals. It is chiefly used in the arts for dissolving indigo. The second variety is the ordinary sulphuric acid, or oil of vitriol, of commerce. It is prepared in
immense quantities by burning sulphur or roasting pyrites, and oxidizing the re sulting sulphurous acid by means of aqueous vapor and certain oxides of nitrogen. When pure, sulphuric acid is a heavy, oily, colorless, inodorous liquid, and having a sp. gr. of 1.842. It is in tensely caustic, and chars almost all organic substances, by abstracting water from them. Sulphuric acid is the start ing point of nearly every important chemical manufacture. Acetic, nitric, and hydrochloric acids are made by its means; and it will be only necessary to allude to the important part it plays in the manufacture of soda from common salt, to appreciate the saying of Liebig, "that the amount of sulphuric acid made in a country is a sure index of its wealth and prosperity." In the hands of the chemist it has numerous and important uses. Its salts, the sulphates, are among the most important chemical agents in the laboratory. In its concen trated form, it is in daily use by the scientific chemist to promote the crys tallization of deliquescent substances in vacuo, from its intense avidity for water. Besides the monohydrate above described, sulphuric acid forms several other well marked hydrates; among which may be noticed the bihydrate, a colorless liquid, having a sp. gr. of 1.78, and solidifying in transparent colorless prisms at about 40° F.; hence it is often called glacial sulphuric acid. It may be easily formed by mixing the monohydrate with water, till the proper specific gravity is reached. The sulphates are a numerous and im portant class of salts. They are mostly, composed of an equivalent of acid and an equivalent of the metallic oxide. They vary somewhat in the numbers of atoms of water of crystallization, some being anhydrous, others containing as many as 12 equivalents. Sulphuric acid also forms acid bisalts, of which bisulphate of potash may be taken as an example, KO.H2 0.2S02. In a few instances, basic salts are formed; as for instance, the basic sulphate of copper, CuS0.51120. Sulphuric acid and its salts are recog nized by giving a white precipitate with a soluble salt of barium, insoluble in nitric acid. Formula, MO'.