Sodium bisulfite (chemical formula: NaHSO3), white crystalline powder, sulfur dioxide odor, soluble in water, also slightly soluble in alcohol. It is easily oxidized to sulfate in the air. Sodium bisulfite reacts with active aldehydes and ketones to produce sodium bisulfite additive. The reaction can be used to avoid the use of highly toxic HCN of carbonyl and HCN, by adding carbonyl compounds and sodium bisulfite, and then adding the amount of NACN. Can be prepared by pyrosulfite sodium sulfate, chemical formula: NA2S2O5 (s) +H2O (L) →2NAHSO3 (aq)