Vanadyl(IV) sulfate, VOSO4, is a well known of vanadium. This blue solid is one of the most common sources of vanadium in the laboratory, reflecting its high stability. It features the vanadyl ion, VO2+, which has been called the "most stable diatomic ion." Vanadyl sulfate is an intermediate in the extraction of vanadium from petroleum residues, a major commercial source of the vanadium. Vanadyl sulfate is a component of some food supplements and drugs. Vanadyl compounds mimic the effects of insulin, although humans have no requirement for vanadium.