Hydrogen diselenide is an inorganic selenium compound with a chemical formula or . At room temperature, hydrogen diselenide dissociates easily to hydrogen selenide () and elemental selenium, and is therefore not stable. When an aluminum-reduced hydrochloric acid solution of selenium dioxide is reacted with lead acetate, the resulting black precipitate contains lead diselenide ()ï¼Âthis proves that hydrogen diselenide exists in the gas mixture.However, hydrogen diselenide can be stable in some solutions.