Carbonyl compounds (aldehydes) form solid additive products with $NaHSO _{3}$ which get separated out. The solid bisulphites of carbonyl
compounds on hydrolysis by dilute acid regenerate carbonyl compound. Thus, this property is used for purification of carbonyl compounds. Aldehyde and ketones form addition compounds with $NaHSO _{3}$ where as impurities donot. On hydrolysis, we get pure aldehyde and ketone back.
