BRASS BATH

( FOR ELECTRO-PLATING ). For steel, wrought and cast iron, and tin; using ordinary cyanide of pota ium. Di olve together in 14 pints of distilled or rain water:—Bisulphite of soda, 7 oz. ; cyanide of pota ium (containing 75 per cent. of real cyanide), 17 oz. ; carbonate of soda, 34 oz. To this solution add the following, made up to 3 1 ⁄ 4 pints of water:—Acetate of copper, 4 1 ⁄ 2 oz. ; neutral pro to chloride of zinc, 3 1 ⁄ 2 oz. ; the two liquors become colourle when mixed. Ammonia must not be used for bra electro-plating baths for iron, especially for solutions worked in the cold.