a term frequently met with in the writings of physicians, chemists, &c. for certain medicines, or menstruums, in a liquid form, distinguished from each other by peculiar epithets, as AQUA Alexiteria, AQUA Aluminosa, AQUA Mirabilis, &c. for which see PHARMACY.

AQUA Extincta, or Extinguished Water, is aquafortis into which some river water has been poured, in order to qualify it, and render it less corrosive. Its use is to get the silver from the aquafortis that served to part gold from it.

Aqua Fortis, a name given by artists to nitric acid of a certain strength, from its dissolving power. See CHEMISTRY Index.

Aqua Marina, a name by which the jewellers call the beryl, on account of its sea-green colour. See BERYL.

Aqua Regia, a compound of nitric and muriatic acid, in different proportions according to the purpose for which it is intended. It is usually made by dissolving in nitric acid, sal ammoniac, or common salt, both which are combinations of muriatic acid with alkali. When made with sal ammoniac, the common proportion is one part of this salt to four parts of nitric acid; but to dissolve platina, equal parts are requisite. A purer aqua regia may be made by simply mixing the two acids. It is particularly used as a menstruum for gold; it likewise dissolves all other metals, except silver. The gold dissolved in aqua regia is, in fact, dissolved in the oxygenated muriatic acid only, which gives out its oxygen to the gold, and then dissolves the oxide: for metals are not soluble in acids until they are oxidated. See CHEMISTRY Index.

Aqua Secunda, aquafortis diluted with much pure water. It is employed in several arts, to clear the surface of metals and certain stones.