. " tantalum oxides, cobalt oxides, copper oxides, iron oxides, manganese oxides, molybdenum oxides, nickel oxides, vanadium oxides, tungsten oxides, and rare-earth metal oxides, and similar compounds, and consisting of compounds such as carbonate, sulfate, and hydroxide, and similar compounds, transformable into oxides after a heat treatment such as aluminum oxides, silicon oxides, magnesium oxides," . . .