Calcium Orthoplumbate, Ca₂PbO₄

Calcium Orthoplumbate, Ca₂PbO₄, is formed by heating lime with lead dioxide, or with the monoxide in presence of air. This latter reaction is interesting, since it is the presence of a base which secures the oxidation of monoxide completely to dioxide. The absorbed oxygen is evolved again when the salt is more strongly heated; the reaction is thus a reversible one, and it has been proposed to employ it for abstracting oxygen from the air, and also to use the salt as an oxidising agent. The dissociation pressure of calcium plumbate has been studied by Le Chatelier.

With water the crystalline hydrate Ca₂PbO₄.H₂O is formed. The salt is stable in air free from carbon dioxide, but when it is suspended in water and treated with dilute acids or carbon dioxide lead dioxide separates.

Strontium and barium plumbates are similar to the calcium salt.