C *3 1 ? SECTION IV. fi On Saline Subjlances. h 28. SALINE fubftances, or falts, are either jj of a four tafte and corrofive quality, in a fluid form commonly, when pure, and then they are called acids ; or they have an acrid, fiery and [I fomething fweetifh tafte, and then they are called alkalis or alkalines. 2f). Acids are not to be met with in the whole extent of nature in their pure ftate, unlefs in fome mineral vapours ; and even then they are allied either to water, inflammables, or fome other volatile principles. Acids, mixed with earthy, bituminous, alkaline, and me- ' tallic particles, are frequently obvious, and from thefe mixed fubftances they may be extradbed in their purity; that is to fay, as i far as poflible; for appearing conftantly in a L fluid form, they are blended more or lefs j with aqueous particles. j EXPERIMENT IX. . 30. Take fyrup or tindlure of violets, and put in it a few drops of any fluid you fufpedt to be a mineral acid; and it will turn the fyrup or tindture of violets red, if it really be an acid. 31. The tindture of litmus, or fuccus heliotropii, i or turnefol, has the fame property in trying acids. But it is ftill better to take common t radifhes, and rub with the fine purple on if the upper part of their roots fome linen rags, fo that they may be thus tinged purple. If a drop of any acid whatfoever falls on the purple fpot, it turns irjftantly red, and brightens