3, 3', 3"-Trihydrogyaurin was proposed as an analytical reagent for metavanadate ions.It gives a blue-black precipitate or blue colouration with metavanadate.When the reaction is carried out on spot test plate, the identification limit is 0.007γ (Concentration Limit: 1:5,000,000).Among the cations and anions tested, silver, cupric, lead, bismuth, tin (Ⅱ, IV),antimonous and iron (Ⅱ, Ⅲ) interfere.