Ferric Chloride Solution, 10 % Iron: Iron in Hydrochloric Acid, Oxidised with Nitric Acid (Ph. G. 1882)

Iron dissolves in hydrochloric acid as the green ferrous salt; nitric acid then turns it to the brown ferric chloride. The German Pharmacopoeia of 1882 weighs every stage so that the finished solution holds exactly 10 per cent iron. Work outdoors or under a hood: the oxidation gives off red nitrous fumes. Source: Pharmacopoea Germanica, ed. II (1882), English ed. New York 1884, Liquor Ferri sesquichlorati. The gram example and the heat source are ours. Picture: iron(III) chloride solution (Chemicalinterest, public domain).