SULPHURIC ACID

n. Suslf-u3r'isk. Lat., acidum sulphur i cum (seu sulfur i cum). Fr., acide sulfur i que (ou vitriol i que). Ger., Schwefelsaure. Oil of vitriol. The name was originally applied to sulphur trioxide (SO3), still sometimes called anhydrous s. a., but is now given to the compound, H2SO4, of this substance with water. When obtained perfectly pure and free from water, by strongly cooling the distilled acid, s. a. forms crystals, melting at 105 C., and after fusion remaining liquid even when cooled below C. As ordinarily obtained by distillation, it contains about 2 per cent, of water. It is a colorle , oily liquid, of strongly acid reaction, powerfully corrosive, and fuming when raised to a temperature of 30 C. It has a strong affinity for water, absorbing it from the atmosphere and from solids, with considerable evolution of heat. When hot, the strong acid attacks many metals (silver, mercury, copper, lead, tin. bismuth, and antimony), but does not affect gold or platinum. The dilute acid di olves zinc, iron, manganese, etc. S. a. also combines with many organic radicles. Informing compounds with metals or radicles, s. a. acts as a powerful dibasic acid, producing a series of sulphates. Commercial s. a. (Lat., acidum siilfuricum crudum [Ger. Ph.]; Fr., acide sulfur i que du commerce [Fr. Cod.]) contains various impurities, chiefly lead sulphate and other sulphates, arsenic, traces of other elements, various oxides of nitrogen, and an exce of water. Official s. a. (Lat., acidum sulphur i cum [U. S. Ph., Br. Ph.], acidum sulfur i cum [Ger. Ph.]; Fr., acide sulfur i que officinal; Ger., reine Schwefelsaure) is distilled from the commercial acid, and contains not le than 96 per cent. [U. S. Ph.] (96'8 per cent. [Br. Ph.], 94 to 97 per cent. [Ger. Ph.]) of the pure acid. The Fr. preparation is repreE, he; E, ell; G, go; I, die; I2, in; N, in; N2, tank; [s. 568]