3633. To Coat Copper Plates with Brass

3633.    To Coat Copper Plates with Brass. Expose the plates, heated sufficiently, to the fumes of zinc. Zinc boils and is vaporized by heating it to a white heat.

3634. To Coat the Inside of Copper Vessels with Brass

3634.    To Coat the Inside of Copper Vessels with Brass. Dissolve 1 part zinc amalgam (see No. 3539 (To Make Zinc Amalgam for Electrical Machines)) in 2 parts muriatic acid ; add 1 part argol (crude tartar), and add sufficient water to fill the vessel; then boil it in the vessel.

3635. To Deposit Copper upon Cast Iron

3635.    To Deposit Copper upon Cast Iron. The pieces of cast iron are first placed in a bath made of 50 parts hydrochloric acid, specific gravity 1.105, and 1 part nitric acid; next, in a second bath, composed of 10 parts nitric acid, 10 parts of chloride of copper, dissolved in 80 parts of the same hydrochloric acid as just alluded to. The objects are rubbed with a woolen rag and a soft brush, next washed with water, and again immersed until the desired thickness of copper is deposited. When it is desired to give the appearance of bronze, the copper surface is rubbed with a mixture of 4 parts sal-ammoniac and 1 part each oxalic and acetic acids dissolved in 30 parts water.

3636. Graeger's Process for Covering Iron and Steel with Copper without a Battery

3636.    Graeger's Process for Covering Iron and Steel with Copper without a Battery. The objects are first well cleaned, and then painted over with a solution of protochloride of tin, and immediately afterward with an ammoniacal solution of sulphate of copper. The layer of copper thus produced adheres so firmly to the iron or steel, that the different objects can be rubbed and polished with fine chalk without injuring the deposit. The tin solution is prepared with 1 part crystallized chloride of tin, 2 parts water, and 2 parts hydrochloric acid. The copper solution, with 1 part sulphate of copper, 16 parts water, adding ammonia sufficient to redis-solve the precipitate first thrown down by it. Zinc and galvanized iron can be treated, according to Boettger, directly by the copper solution, without using the tin salt. The above process may be found useful by gilders, and for various ornamental purposes.

3637. Weil's Process for Coating Iron with Copper

3637.      Weil's Process for Coating Iron with Copper. This process yields a coating of copper of great brightness and strong cohesion. The object, whether of cast or wrought iron, is freed from rust by immersion for from 5 to 10 minutes in water containing 2 per cent, of muriatic acid, and subsequent scrubbing for 1/4 hour with a wire brush and sand, then washing in water until all traces of acid are removed. It is then covered with zinc wire in spiral turns of about 6 inches from each other, which also serves as a means of suspension. The bath consists of a solution of 8 parts caustic soda in 100 parts water, of which 11 quarts are mixed with 50 ounces Rochelle salts and 121/2 ounces sulphate of copper, making a liquid of a density equal to 19° Baum6. It retains its activity as long as the copper is kept replaced, and deposition from it proceeds with great regularity. The material of the vessel is best when made of wood, lined with guttapercha, and covered with a wooden lid. When the coating is of sufficient thickness, the object is removed from the bath, first washed with water slightly acidified with sulphuric acid, and then with pure water until the disappearance of all traces of acid; after this it passes into a drying room heated to 132° Fahr. The bronzing, when required, is obtained by a bath of sulphide of sodium, or by means of the same bath as above, somewhat modified, that is, by increasing the proportion of copper to a threefold, in which case the bath no longer deposits copper, but, to all appearances, bronze. By reducing the points of contact between the iron and wire, though retaining the spiral turns at uniform distances, the deposit gradually assumes a number of colors in the following series, viz.: orange, silver-white, pale yellow, golden yellow, carmine, green, brown, and dark bronze. As soon as the desired color is attained, the object is washed in warm water, and again dried at 132°. Between each subsequent change of color is an interval of about 5 minutes. The reaction is more decided when the alkaline reaction of the bath is stronger. For indoor work or ornaments the time of immersion may vary from 3 to 72 hours; . for outdoor objects a much longer time would be necessary.