Stability constants (K1) for the reaction of acetaldehyde and hydroxyacetaldehyde with NaHSO3, determined spectrophotometrically in aqueous solution, were found to be (6.90 ± 0.54) × 105 M-1 (2.0 ± 0.5) × 106 M-1 respectively, where K1 (corrected for aldehyde hydration) = [RCH(OH)SO3-]/[RCHO][HSO3-] (μ = 0.2 M; 25 °C). Acid dissociation constants (pKa3) of a series of α-hydroxyalkanesulfonate salts, RCH(OH)SO-3, were found to be 11.46 (CH3-), 11.28 (H-), 10.30 (HOCH2-), 10.33 (C6-H5-), 10.31 (CH3CO-), and 7.21 (Cl3C-) (μ = 0 M; 25 °C). Simple straight-line relationships were found to exist between Taft's σ* parameter and a number of thermodynamic and kinetic properties of some aldehydes. K1 Ka3, and the rate constant for nucleophilic addition of SO2-3 all increase linearly with σ*. Carbonyl species such as halogenated derivatives of acetaldehyde, certain β- and γ-dicarbonyl aldehydes, and perhaps also some highly (halogen) substituted ketones, i.e., all those species with ∑σ* ≥ ~1.5 (aldehydes) or ∑σ* ≥ ~2.5 (ketones), could be important S(IV) reservoirs.