Pyroligneous acid - Aldehydes and Ketones
Pyroligneous acid consisting of acetic acid, acetone and methyl alcohol that is distilled in copper vessel and the vapours are passed via hot milk of lime. Acetic acid combines to make nonvolatile calcium acetate. The methanol and acetone's unabsorbed vapours are condensed and fractionally distilled. Acetone distills at 56° C.
So the acetone obtained is purified with the help of sodium bisulphite.