Properties: Also known as niobic acid, commonly known as earth acid together with tantalic acid. In fact, it is hydrated niobium oxide Nb?O?·xH?O, where the number of hydration depends on the preparation method, the degree of aging and other factors. Niobium hydroxide removes most of the water at 150-200°C, but the remaining water and niobium oxide combine very strongly and must be heated to above 400-450°C to finally remove all the water and turn it into Nb2O5. Niobium hydroxide has amphoteric properties. It is decomposed by Nb(OH)5Nb(OH)4++OH— in acidic medium, and decomposed by Nb(OH)5NbO3—+H++2H2O in alkaline medium. Niobium hydroxide is insoluble in water, insoluble in inorganic acids such as HCl and HNO3, and easily soluble in organic oxyacids such as hydrofluoric acid, oxalic acid, and citric acid. Niobium hydroxide is prepared by hydrolysis, and various niobium compounds can be hydrolyzed to obtain Niobium hydroxide. Niobium hydroxide is the raw material for preparing various niobium compounds.