3699. To Dissolve Cyanide of Silver in Yellow Prussiate of Potash

3699.    To Dissolve Cyanide of Silver in Yellow Prussiate of Potash. Dissolve the cyanide of silver by yellow prussiate of potash (ferrocyanide of potassium), 3 pounds of which are required to dissolve 1 ounce of silver. This forms an excellent plating solution, and yields a beautiful surface of silver. It must have a weak battery power, and consequently the silver is very soft. The positive electrode does not dissolve in this solution; there is formed upon its surface a white scaly crust, which drops off and falls to the bottom; and the solution soon becomes exhausted of silver, and will need to be renewed.

3700. Solution Made with Oxide of Silver

3700.    Solution Made with Oxide of Silver. A good silver solution for electroplating white metal and brass is made by dissolving 1 part oxide of silver in 8 parts cyanide of potassium and 64 parts warm water. Oxide of silver is made by precipitating a solution of the nitrate by a dissolved alkali like potassa or baryta.

3701. To Make Silver Solution by the Battery

3701.    To Make Silver Solution by the Battery. The best and cheapest method of making up the silver solution is by the battery, which saves all expense of acids and the labor of precipitation. To prepare a silver solution which is intended to have an ounce of silver to the gallon, dissolve 123 ounces cyanide of potassium in 100 gallons water; get one or two flat porous vessels, submerge them in this solution to within half an inch of the rim, and fill them to the same height with the solution; in these porous vessels place small plates or sheets of iron or copper, and connect them with the zinc polo of a battery; in the solution outside the shallow vessels place a sheet or sheets of silver connected with the silver pole of the battery. This arrangement being made at night, and the power employed being a Smee's battery of 6 cells, the zincs 7 inches square, it will be found in the morning that there will bo dissolved 60 to 80 ounces of silver from the sheets. The solution is now ready for use; and by observing that the articles to be plated have less surface than the silver plate forming the positive electrode, for the first two days, the solution will then have the proper quantity of silver in it. Occasionally a little silver is found in the porous cell; it is therefore not advisable to throw away the solution in them without first testing it for silver, which is done by adding a little muriatic acid to it. The amateur electrotypist may, from this description, make up a small quantity of solution for silvering his medals or figures. For example, a half-ounce of silver to the gallon of solution will do very well; a small quantity may bo prepared in little more than an hour. As the cyanide of potassium dissolves silver without the aid of a battery, a plating liquor may be formed by merely allowing a piece of silver to steep in this solution for a few days; but this is tedious and uncertain, although for small operations, and where porous vessels are not convenient, it will servo the purpose.