Silver(I,III) oxide

Silver(I,III) oxide or tetrasilver tetroxide is the inorganic compound with the formula Ag₄O₄. It is a component of silver zinc batteries. It can be prepared by the slow addition of a silver(I) salt to a persulfate solution e.g. AgNO₃ to a Na₂S₂O₈ solution. It adopts an unusual structure, being a mixed-valence compound. It is a dark brown solid that decomposes with evolution of O₂ in water. It dissolves in concentrated nitric acid to give brown solutions containing the Ag²⁺ ion.

Structure

Although its empirical formula, AgO, suggests that the compound tetrasilver tetraoxide has silver in the +2 oxidation state, each unit has two monovalent silver atoms bonded to an oxygen atom, and two trivalent silver atoms bonded to three oxygen atoms, and it is in fact diamagnetic. X-ray diffraction studies show that the silver atoms adopt two different coordination environments, one having two collinear oxide neighbours and the other four coplanar oxide neighbours. tetrasilver tetraoxide is therefore formulated as Ag^IAg^IIIO₂ or Ag₂O·Ag₂O₃. It has previously been called silver peroxide, which is incorrect since it does not contain the peroxide ion, O₂^{2−}.

Uses

Tetrasilver tetroxide has been marketed under a trade name "Tetrasil." In 2010, the FDA issued a warning letter to an American company concerning the firm's marketing of Tetrasil and Genisil ointments of tetrasilver tetroxide for herpes and similar conditions.

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