This having been the first solvent that was discovered for gold, the king of metals, was called by this name, signifying the king'3 water. The original and proper aqua regis is made by adding four ounces of common salt to an avoirdupois pound of aqua fortis. Homberg says, aqua regis is of proper strength to dissolve gold, when a bottle, holding sixteen ounces of water, holds seventeen ounces of the acid; that is to say, when it is of the specific gravity 1.062.