In general, purification methods of (CAS NO. 78-93-0) are the same as for acetone. Aldehydes can be removed by refluxing with KMnO₄ + CaO, until the Schiff aldehyde test is negative, prior to distn. Shaking with satd K₂CO₃, or passage through a small column of activated alumina, removes cyclic impurities. The ketone can be dried by careful distn (an azeotrope containing 11% water boils at 73.4°C), or by CaSO₄, P₂O₅, Na₂SO₄, or K₂CO₃, followed by fractional distn. Purification as the bisulfite addition compound is achieved by shaking with excess satd Na₂SO₃, cooled to 0 °C, filtering off the ppte, washing with a little ethyl ether and drying in air; this is followed by decomposition with a slight excess of Na₂CO₃ soln and steam distn, the distillate being satd with K₂CO₃ so that the ketone can be separated, dried with K₂CO₃. filtered, and distd.

Purification as the Nul addition compound (m 73-74 °C) is more convenient. Small quantities of 2-butanone can be purified by conversion to the semicarbazone, recrystn to constant melting point, drying under vac over CaCl₂ and paraffin wax, refluxing for 30min with excess oxalic acid, followed by steam distn, salting out, drying and distilling.