text: In its main applications, dithionite is generally prepared in situ by reduction of sulfur dioxide by sodium borohydride, described by the following idealized equation:.
  Dithionite is a reducing agent.  At pH 7, the potential is −0.66 V vs NHE.  Redox occurs with formation of sulfite:
  :  +  2 HO   →   2   +  2 e +  2 H
  Dithionite undergoes acid hydrolytic disproportionation to thiosulfate and bisulfite:
  :2  + HO →  + 2 
  It also undergoes alkaline hydrolytic disproportionation to sulfite and sulfide:
  :3 NaSO + 6 NaOH → 5 NaSO + NaS + 3 HO
  It is formally derived from dithionous acid (HSO), but this acid does not exist in any practical sense.