(a) The following liquid will dissolve silver without attacking copper, brass, or German silver, so as to remove the silver from silvered objects, plated ware, etc. It is a mixture of 1 part nitric acid with 6 parts sulphuric, heated in a water-bath to 160° F., at which temperature it operates best.

(6) Mix sulphuric acid, 1 part; nitric acid, 1; water, 1; boil the metal in the mixture till it is dissolved, and throw in a little salt to cause the silver to subside.

(c) Nearly fill a flat pan of enamelled cast iron with concentrated sulphuric acid, and heat to a temperature of 300°-400° F.; at the moment of using it, pinches of dry powdered saltpetre are thrown into it; then hold the article with copper tongs in the liquid. The silver rapidly dissolves, and the copper or its alloys are not sensibly corroded. According to the rapidity of the solution, more or fewer pinches of saltpetre are added. All the silver has been dissolved when, after rinsing in water and dipping the articles into the cleansing acids, they present no brown or black spots, that is, when they appear like new metals.

(d) For removing the silver from wrought and castiron, zinc, or lead, it is preferable to invert the electric current in a cyanide bath, or to use mechanical processes. Old desilvering liquors become green after use; to recover the silver they are diluted with 4 or 5 times their volume of water, then add hydrochloric acid or common salt. The precipitation is complete when the settled liquor does not become turbid by a new addition of common salt or hydrochloric acid. The resulting silver chloride is separated from the liquid either by decantation or filtration, and is afterwards reduced, to the metallic state.

(e) For dissolving silver in the cold the objects are hung in a large vessel filled with the following mixture: - Sulphuric acid at 66° B., 10 parts; nitric acid at 40° B., 1, in which they remain for a greater or less length of time, according to the thickness of the coat of silver to be dissolved. This liquid, when it does not contain water, dissolves the silver without sensibly corroding copper and its alloys; therefore avoid introducing wet articles into it, and keep the liquid perfectly covered when not in use. As far as practicable, place the articles in the liquid so as not to touch each other, and in a vertical position, so that the silver salt will fall to the bottom. In proportion as the action of the liquor diminishes, pour in small and gradual additions of nitric acid. Dissolving silver in the cold is regular and certain, but slow, especially when the proportion of silver, is great.