Note 48 — Chapter XVIII · SILICON AND THE OTHER ELEMENTS OF THE FOURTH GROUP

Few compounds are known of the lower type PbX, and still fewer of the intermediate type PbX3. To the first type belongs the so-called lead suboxide, Pb2O, obtained by the ignition of lead oxalate, C2PbO4, without access of air. It is a black powder, which easily breaks up under the action of acids, and even by the simple action of heat, into metallic lead and lead oxide. This is the character of all suboxides. They cannot be regarded as independent salt-forming oxides, neither can those forms of oxidation of lead which contain more oxygen than the oxide of lead, PbO, and less than the dioxide, PbO2. As we shall see, at least two such compounds are formed. Thus, for example, an oxide having the composition Pb2O3 is known, but it is decomposed by the action of acids into lead oxide, which passes into solution, and lead dioxide, which remains behind. Such is red lead. (See further on.)