Aqua Regia is a compound of the nitrous and marine acids, in different proportions, according to the purpose for which it is required; and usually made, by dissolving sal ammoniac, or common salt, in nitrous acid. When the former is employed, the usual proportion is one of this salt to four of the acid ; but equal parts will be necessary to dissolve plalina.

Aqua regia is used as a menstruum for gold ; it likewise dissolves all other metals, silver alone excepted. The best kind for the above-mentioned purpose, is a preparation of three parts of the pure marine, with one of the nitrous, acid. One hundred grains of gold require for their solution, two hundred and forty-six of this mixture. - Con-cerning the nature and cure of those casualties which may arise from an improvident use of this powerful solvent, we refer to the preceding article.