In chemistry, a plumbate is a salt having one of the several lead-containing oxoanions. Although the term plumbate can refer either to plumbate(II) or plumbate(IV), it traditionally refers specifically to plumbate(IV), whereas plumbate(II) is referred to as plumbite.
Plumbates are formed by the reaction of lead(IV) oxide, PbO2, with alkali. Plumbate salts contain either the hydrated plumbate anion, Pb(OH)2−
6, or the anhydrous anions PbO2−
3 (meta-plumbate) or PbO4−
4 (ortho-plumbate). For example, dissolving PbO2 in a hot, concentrated aqueous solution of potassium hydroxide forms the potassium salt K2Pb(OH)6. The anhydrous salts may be synthesized by heating metal oxides or hydroxides with PbO2. All plumbate(IV) salts are very strong oxidising agents. Some hydrated plumbate(IV) salts decompose upon dehydration. They are also decomposed by carbon dioxide.
Red lead, a mixed oxide with formula Pb3O4, may be thought of as lead(II) ortho-plumbate(IV): [Pb2+]2[PbO4]4−. This structure is demonstrated by its reaction with nitric acid, which yields the lead(II) nitrate salt, Pb(NO3)2, and PbO2. Lead sesquioxide, Pb2O3, is also known, and likewise has the structure lead(II) meta-plumbate(IV): [Pb2+][PbO3]2−.
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