Vanadium compounds (pentoxide and certain vanadates) are used as catalyst in the oxidation of SO2 to SO3; ethanol to acetaldehyde; in the syntheses of phthalic and maleic anhydrides; in the manufacture of polyamides (nylon); sugar to oxalic acid, and anthracene to anthraquinone. It is also used for the manufacture of yellow glass; inhibiting UV light transmission in glass; depolarizer; as developer in photography; and as mordant in dyeing and printing fabrics and in manufacture of aniline black in form of ammonium vanadate.