sodium hydrosulfite


noun Chemistry.

a white, crystalline, water-soluble powder, Na2S2O4, used as a reducing agent, especially in dyeing, and as a bleach.
Also called hydrosulfite, so·dium di·thi·o·nite [dahy-thahy-uh-nahyt] /daɪˈθaɪ əˌnaɪt/, sodium hyposulfite.