3719. Dead Silvering for Medals

3719.     Dead Silvering for Medals. The perfect smoothness which a medal generally possesses on the surface, renders it very difficult to obtain a coating of dead silver upon it, having the beautiful silky lustre which characterizes that kind of work, except by giving it a very thick coating of silver, which takes away the sharpness of the imELECTRO - GILDING.

pression. This dead appearance can be easily obtained by putting the medal, previous to silvering, in a solution of copper, and depositing upon it, by means of a weak current, a mere blush of copper, which gives the face of the medal that beautiful crystalline richness that deposited copper is known to give. The medal is then to be washed from the copper solution, and immediately to be put into the silver solution. A very slight coating of silver will suffice to give the dead frosty lustre so much admired, and in general so difficult to obtain.

3720. To Recover Silver from Old Plated Goods

3720.    To Recover Silver from Old Plated Goods. Oil of vitriol, together with 5 per cent, of nitrate of soda, is heated in a cast-iron boiler, or a stoneware pan, to 212° Fahr. The silver-plated clippings are placed in a sheet-iron bucket or cullender, which is fastened to a pulley that it may be moved about in the acid. As soon as the silver is removed, the cullender is raised, allowed to drain, then immersed in cold water and emptied, to be again used in the same manner. When the acid bath is fresh, the desilvering proceeds very rapidly, and even with heavy plated ware takes but a few minutes; with the gradual saturation of the bath more time is required, and it is readily perceived when the acid must be renewed. The small amount of acid solution adhering to the copper, precipitates its silver when brought into the water. To obtain its complete removal, the clippings, when raised from the desilvering bath, and before immersion in water, may bo dipped into a second bath prepared in the same manner, which is afterwards to be used in place of the first. The saturated bath, on cooling, congeals to a crystalline semi-fluid mass of sulphate of copper and of soda. The silver is removed by chloride of sodium (common salt) which is added in small portions at a time, while the solution is yet warm. The chloride of silver separates readily, and is washed and reduced in the usual manner. The acid solution contains but a very small portion of copper, hardly enough to pay for recovering.

3721. To Recover Silver from Copper

3721.     To Recover Silver from Copper. This process is applied to recover the silver from the plated metal, which has been rolled down for buttons, toys, etc., without destroying any large portion of the copper. For this purpose, a dissolving solution is composed of 3 pounds oil of vitriol, 11/2 ounces nitre, and 1 pound water. The plated metal is boiled in it till the silver is dissolved, and then the silver is recovered by throwing common salt into the solution. {See No. 3214 (To Purify and Reduce Silver).)