Should it be desired to change the color of an article made of brass to a dark bronze or black, the following compound will be found to give good results, espe-cially if the metal has a polished surface. First make up a solution of 120 grains of nitrate of silver and 5 ounces of water; then dissolve 120 grains of copper nitrate in 5 ounces of water. Mix the two solutions together in equal parts, making a quantity sufficient to immerse the articles. Clean the brass articles to be blackened thoroughly in hot soda water, and then dip in the above compound. Remove and heat in an oven until the proper shade of color appears. T. E. O'Donnell.
To color brass blue black make a solution of ammonia and copper carbonate in the approximate proportion of 10 parts of ammonia and one part of copper carbonate by weight. Shake the mixture well until the copper carbonate is dissolved, adding the copper carbonate to the ammonia little by little until the ammonia will not dissolve any more; then add a volume of clear water equal to about one-fourth of the mixture. The brass to be colored should be polished bright, either with fine dry emery cloth, taking care not to touch the polished surface with the fingers, or made clean and bright by dipping in a strong solution of caustic soda. Before dipping agitate the compound thoroughly and then immerse the pieces of brass, keeping them in motion two or three minutes, rinse off in clean water, and dry in sawdust or clean cotton waste. When not in use the solution should be kept in a tightly-corked bottle. I have used it on instrument work very successfully. H. M. Weber.