Mixture containing three parts hydrochloric acid and one part concentrated nitric acid. Already noted by alchemists, aqua regia allows precious metals, including gold, to corrode and turns them into liquid form. Aqua regia was used to produce tin chloride, also called killed spirits, in the 18th century. This dark red colorant was made by dropping a block of tin in the aqua regia solution. Aqua regia will dissolve all metals except silver. Synonyms: nitrohydric acid; yellow fuming liquid; nitro-muriatic acid; nitrohydrochloric acid; chloronitrous acid; chlorazotic acid. Museum of Fine Arts, Boston (2000). [J. Cassar, R. de Angelis]