Three pieces of -3/8 in. brass or copper rod should be procured, long enough to reach across the vat. These are termed slinging rods, from which the anodes and articles to be plated are hung. Suitable suspending rods for the articles are made of small bent glass tubing.
This is a mercury salt with three acids, and is composed of the sulphate, nitrate, and' bichloride of this metal. It is liquid, more or less coloured, very dense, and gives in water a yellow precipitate, which is dissolved by an excess of acid. It produces a violet stain oh the skin, and amalgamates copper and its alloys thoroughly and rapidly. It is used for amalgamating the zincs of batteries, and dispenses with the metallic mercury; it is more easily applied, and prevents much trouble in gilding works. It is prepared by boiling the nitrate of bin oxide of mercury upon an excess of a powder composed of equal parts of bisulphate- and bichloride of mercury; the liquor only, remaining after cooling, is used.
-(a) This has all the brightness of polished cast iron. Its dead lustre is a slate grey, and it may be easily scratch-brushed and polished; it resembles black platinum, and may take its place in many cases. Boil for an hour, in a porcelain dish or enamelled cast iron vessel; - 2 1/5 gal. water, 70 oz. soda carbonate, 17 1/2 oz. finely-powdered antimony sulphide. Filter the boiling solution through paper or fine cloth; by cooling it deposits a reddish-yellow powder of antimony oxysulphide. Boil this powder again in the same liquor, and the new solution is the antimony bath. It is necessary to use the bath constantly boiling. For the anode, use either a plate of antimony or a platinum wire.
(ft) Copper may also be covered with a layer of antimony by the following process: - Dissolve antimony chloride in alcohol, and add hydrochloric acid until the mixture becomes clear; clean the copper well, and leave it in the bath for | hour. The effect of the alcohol is thus explained: it moderates the precipitation of one metal from its solution by another metal, and causes the precipitate to fall in an extremely divided state; when alcohol is used alone, without water, the coating of copper thrown down is reduced to the last degree of tenuity. It is recommended that when the work is finished it should be well washed, first in water, and afterwards several times successively with a solution of soda carbonate, and with weak hydrochloric acid, and finally carefully dried in a warm place.
Bertrand has succeeded in producing a galvanic deposit of bismuth on the surfaces of other metals. He uses a double chloride of bismuth and ammonia. The operation is performed cold, with a solution containing 25-35 gr. of chloride per litre. A single Bunsen pile should be used. On coming out, the objects are coated with a dark-looking slime, beneath which the sheen of the bismuth may be detected. The latter adheres very closely to the subjacent metal, and takes a fine polish, the colour being intermediate betwixt antimony and old silver.
All the manufactures of bronze composition made of zinc or cheap alloys, have a brass deposit placed on before the bronze lustre is given, as the bronzing operation is more easy and satisfactory upon brass deposits. The preliminary and finishing operations and the disposition of the baths are the same for brass as for copper deposits. Heat is employed for brass deposits by those who electroplate coils of iron or zinc wire with this alloy. The proper temperature varies from 130° to 140° F., and the coils of wire dip only onehalf or two-thirds of •their diameter into the bath. The bath is put into an oblong open iron boiler heated by fire, steam, or hot water. The inside is lined with brass sheets connected with the positive pole of a battery. A stout copper or brass rod, in the direction of the length of the boiler, rests upon the edges, and the contact of the two metals is prevented by pieces of rubber tubing. The rod is connected with the negative pole by a binding screw. Remove the binding wire from the coils, and loosen the wires, bending the ends together into a loop. Dip the wire in a pickle of dilute sulphuric acid, and hang it on a strong round peg held in the wall, so that the coil may be made to rotate easily.
After a scrubbing with wet, sharp sand and a hard brush, give the coil a primary deposit of pure copper. It is then suspended from the horizontal rod over the brass bath, where only a part of the coil at a time dips into the solution and receives the deposit; the coil must, be turned now and then J or J of its cir-cumference: by dipping the coil entirely into the liquid, the operation is not so successful. The wires are washed,, dried in sawdust, and then in a stove, and lastly passed through a draw-plate; to give them the fine polish of true brass wire. Copper and brads wires are also covered with brass electro-deposits, in order to give them various shades.