Nitro-Mriatic Acid, a mixture of nitric and hydrochloric acids, called by the alche-mists aqua regia, because it possesses the power of dissolving the "king of metals," gold. Both platinum and gold are insoluble in either acid separately, but are readily attacked by the mixture, forming chlorides. Chlorine is liberated, the action being assisted by the presence of the metal, and polarization of the molecules of the acid is produced, the chlorine in its nascent state combining with the metal. Red fumes also appear, which were at one time mistaken for peroxide of nitrogen, it being supposed that the liberated hydrogen simply deoxidized the nitric acid; but it has been found that two gases, nitric oxychloride (NOCl2) and nitrous oxychloride (NOCl), are formed instead, the former in the earlier and the latter in the later stages of the process. The action of aqua regia on metals produces perchlorides, and the oxides which may be formed by the addition of an alkali to their solutions are corresponding peroxides.

Minors ACID. See Nitrogen.