Sodium dithionite

Physical Nature: This product is white crystalline powder, it is odorless or slightly sulfur dioxide. It has strong reducibility, in air it can be oxidized into sodium bisulfite and sodium bisulfate.

If it met a small amount of water or exposed to humid air, it would break down and fever, then it fumed, fevered and gave off SO2, when 250℃ it would be spontaneous combustion. If it contacted with oxidants would caused violent reaction then led to combustion and explosion. In alkaline, it is usually more stable than in neutral medium.