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In page Tin:

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Tin can form many oxides, sulfides, and other chalcogenide derivatives. The dioxide SnO2 (cassiterite) forms when tin is heated in the presence of air.[1] SnO2 is amphoteric, which means that it dissolves in both acidic and basic solutions.[3] Stannates with the structure [Sn(OH)6]2−, like K2[Sn(OH)6], are also known, though the free stannic acid H2[Sn(OH)6] is unknown.[citation needed]