Tin dioxide

Tin(IV) oxide, also known as stannic oxide, is the inorganic compound with the formula SnO2. The mineral form of SnO2 is called cassiterite, and this is the main ore of tin. With many other names, this oxide of tin is an important material in tin chemistry. It is a colourless, diamagnetic, amphoteric solid. Tin(IV) oxide, also known as stannic oxide, is the inorganic compound with the formula SnO2. The mineral form of SnO2 is called cassiterite, and this is the main ore of tin. With many other names, this oxide of tin is an important material in tin chemistry. It is a colourless, diamagnetic, amphoteric solid. Tin(IV) oxide crystallises with the rutile structure. As such the tin atoms are six coordinate and the oxygen atoms three coordinate. SnO2 is usually regarded as an oxygen-deficient n-type semiconductor. Hydrous forms of SnO2 have been described as stannic acid. Such materials appear to be hydrated particles of SnO2 where the composition reflects the particle size. Tin(IV) oxide occurs naturally. Synthetic tin(IV) oxide is produced by burning tin metal in air. Annual production is in the range of 10 kilotons. SnO2 is reduced industrially to the metal with carbon in a reverberatory furnace at 1200–1300 °C. Although SnO2 is insoluble in water, it is amphoteric, dissolving in base and acid. 'Stannic acid' refers to hydrated tin (IV) oxide, SnO2, which is also called 'stannic hydroxide.' Tin oxides dissolve in acids. Halogen acids attack SnO2 to give hexahalostannates, such as 2−. One report describes reacting a sample in refluxing HI for many hours. Similarly, SnO2 dissolves in sulfuric acid to give the sulfate: SnO2 dissolves in strong base to give 'stannates,' with the nominal formula Na2SnO3. Dissolving the solidified SnO2/NaOH melt in water gives Na22, 'preparing salt,' which is used in the dye industry. In conjunction with vanadium oxide, it is used as a catalyst for the oxidation of aromatic compounds in the synthesis of carboxylic acids and acid anhydrides.