Note 30 — MINERALS.

1430. Nitric Acid is a compound of oxygen and azote, or nitrogen, in the proportion of twenty-five parts, by weight, of the latter to seventy-five of the former. It is one of the constituent parts of nitre, or saltpetre (206); and, in a pure state, is transparent and colourless, like water. By the action of light, however, it soon becomes yellow; and, if exposed to the air, it emits yellow fumes, which even tinge the air of the same colour. To the taste it is extremely acid. It dyes the skin a yellow colour, which is very difficult to be removed; and it is so corrosive as to destroy almost every substance into which it penetrates. If poured upon oils, it sets them on fire. With various bases it forms compounds called nitrats. This acid, which hitherto has never otherwise been obtained than mixed with water, is chiefly known in commerce by the name of aqua fortis (206).