Gold will not dissolve ia muriatic acid alone, although it will be attacked by chlorine. To dissolve it in muriatic acid, therefore, a substance must be added to liberate the chlorine. Peroxyd of manganese does this, and the gold dissolved in such a solution is a sub-chloride. The most useful and important vehicle for dissolving gold is aqua regia, (royal water), composed of two parts of hydrochloric (muriatic) acid, and one part of nitric (aquafortis). Gold is dissolved readily in this liquid; the nitrous gas escapes in dense yellow fumes while the gold is being eaten up, or dissolved, and the chlorine is set free, and unites with the gold, forming the per-chloride of the metal. The per-chloride of gold dissolves in alcohol and ether, in which condition it is employed as a gold wash for steel instruments. By dipping a polished steel instrument into an ethereal solution of gold, on the evaporation of the ether, the metal is found in a pure state adhering in a fine thin coat; delicate cutting instruments are gilt in this manner. Lackers are sometimes called gold washes, but there is not a particle of gold in them. They are made of lac varnish, colored yellow with turmeric, or gamboge. Applied to polished metal or wood, they resemble bright brass more than gold. They Rre made by dissolving lac in alcohol—about half a pound to the gallon of spirits, adding half a pound of turmeric and one ounce of gamboge, then straining the mixture, after it is about a day old, through a clean piece of cotton cloth. It is then ready for use, to be put on with a brush, or the article to be lacquered dipped into it.
This article was originally published with the title "Gold Washes"