Commonly known as vanadium pentoxide, it is a dark yellow solid, although when freshly precipitated from aqueous solution, its colour is deep orange.

Further reduction using hydrogen or excess CO can lead to complex mixtures of oxides such as V4O7 and V5O9 before black V2O3 is reached.

Thus V2O5 reacts with strong non-reducing acids to form solutions containing the pale yellow salts containing dioxovanadium(V) centers: It also reacts with strong alkali to form polyoxovanadates, which have a complex structure that depends on pH.

If acid is slowly added to a solution of Na3VO4, the colour gradually deepens through orange to red before brown hydrated V2O5 precipitates around pH 2.

Technical grade V2O5 is produced as a black powder used for the production of vanadium metal and ferrovanadium.

A more satisfactory laboratory preparation involves the decomposition of ammonium metavanadate at 500–550 °C:[13] In terms of quantity, the dominant use for vanadium(V) oxide is in the production of ferrovanadium (see above).

The oxide is heated with scrap iron and ferrosilicon, with lime added to form a calcium silicate slag.

[8] Vanadate (VO3−4), formed by hydrolysis of V2O5 at high pH, appears to inhibit enzymes that process phosphate (PO43−).