Vanadyl Sulphites

Normal sulphites containing tetravalent vanadium have not hitherto been prepared in consequence of the readiness with which hydrolysis takes place. A considerable number of vanadyl sulphites are, however, known, as well as their double salts, which, no doubt, are heteropoly-acid compounds.

When a mixture of the oxides V₂O₃ and V₂O₄, resulting from the decomposition of ammonium metavanadate, is treated in boiling aqueous solution with sulphur dioxide, a blue liquid is obtained from which under suitable conditions the following blue, crystalline hydrates of vanadyl sulphite, VOSO₃, can be isolated: VOSO₃.3H₂O; VOSO₃. 4H₂O; VOSO₃.8H₂O. The liquid also gives rise to an amorphous, green, hydrated, basic vanadyl sulphite, VO₂.VOSO₃.4½H₂O or 2VO₂.SO₂.4½H₂O. Another blue, crystalline complex sulphite, having the composition 4VO₂.3SO₂.10H₂O, has been prepared by a similar process, and by reducing barium metavanadate in aqueous suspension, the blue, crystalline compound 3VO₂.2SO₂.4½H₂O results.

By the action of sulphur dioxide on vanadates in the presence of varying molecular proportions of alkali sulphites, two series of alkali vanadyl sulphites have been obtained.

This consists of blue compounds having the general formula R₂O.3VO₂.2SO₂.xH₂O, which can be regarded as derivatives of the vanadyl sulphite, 3VO₂.2SO₂.4½H₂O, which can be alternatively written, H₂O.3VO₂.2SO₂.3½H₂O. The following have been prepared: (NH₄)₂O.3VO₂.2SO₂.H₂O; Na₂O.3VO₂.2SO₂.3H₂O; K₂O.3VO₂.2SO₂; and ZnO.3VO₂.2SO₂.

This comprises green substances which are generally less stable than the members of former series, and have the general formula R^•₂O.VO₂.2SO₂.xH₂O. The following are known:

(NH₄)₂SO₃.VOSO₃.1 or 2 H₂O or (NH₄)₂O.VO₂.2SO₂.1 or 2H₂O.
Na₂SO₃.VOSO₃.5H₂O or Na₂O.VO₂.2SO₂.5H₂O.
K₂SO₃.VOSO₃.2H₂O or K₂O.VO₂.2SO₂.2H₂O.

In addition to the foregoing, Gain has prepared a large number of alkali vanadyl sulphites in which the proportions of basic oxide, vanadium dioxide, and sulphur dioxide vary considerably:

2(NH₄)₂O.10VO₂.7SO₂.16H₂O;
2K₂O.6VO₂.5SO₂.5H₂O;
(NH₄)₂O.6VO₂.4SO₂.4H₂O;
K₂O.4VO₂.3SO₂.2H₂O;
5Li₂O.2VO₂.6SO₂.8H₂O;
K₂O.6VO₂.4SO₂.5H₂O;
Na₂O.4VO₂.3SO₂.4H₂O;
2Rb₂O.4VO₂.3SO₂.2H₂O;
Na₂O.10VO₂.6SO₂.2H₂O;
Rb₂O.2VO₂.3SO₂.4H₂O;
3Cs₂O.2VO₂.4SO₂.8H₂O;
2Tl₂O.2VO₂.3SO₂.4H₂O;
Tl₂O.6VO₂.4SO₂.8H₂O;

It is improbable that these are all true individual chemical compounds.