Cadmium, METALLURGY

OF. Found in nature as a constituent of many zinc ores, but only in small proportion. Silesian calamine (zinc silicate) carries up to 5 per cent; Hungarian blende (zinc sulphide) averages almost 2 per cent; and similar quantities are found in zinc ores in many parts of the world. In the U. S. noticeable amounts are found on the zinc ore from Friedensville, Pa., and on blende from Mi ouri. The cadmium occurs as a thin, yellow incrustation, chemically consisting of cadmium sulphide, known mineralogically as Greenockite. When zinc ore is being reduced in retorts, a yellowish-brown smoke coming off before the bluish-green flame of zinc appears indicates the presence of cadmium, the smoke being a mixture of the oxides and carbonates of zinc and cadmium, and its early formation being due to the fact that cadmium is more easily reduced and is more volatile than zine. Zinc fumes from lead smelting furnaces, as well as the accretions sometimes forming directly in the upper part of blast-furnaces ( cadmia ) , frequently contain cadmium.