Commonly, washed with conc H₂SO₄ until the washings are colourless, followed by water, aq Na₂CO₃ or 5% NaOH, and again water until neutral. It is next dried with P₂O₅, Linde type 4A molecular sieves, CaCl₂, or MgSO₄ then Na and distd. (CAS NO. ) has been refluxed with, and distd from Na, CaH₂, LiAlH₄ (which also removes peroxides), sodiudpotassium alloy, or P₂O₅. Traces of benzene can be removed by passage through a column of silica gel that has been freshly heated: this gives material suitable for ultraviolet and infrared spectroscopy. If there is much benzene in the cyclohexane, most of it can be removed by a preliminary treatment with nitrating acid (a cold mixture of 30mL conc HNO₃ and 70mL of conc H₂SO₄) which converts benzene into nitrobenzene. The impure cyclohexane and the nitrating acid are placed in an ice bath and stirred vigorously for 15min, after which the mixture is allowed to warm to 25 °C during 1h. The cyclohexane is decanted, washed several times with 25% NaOH, then water dried with CaCl₂, and distd from sodium. yl-containing impurities can be removed as described for chloroform. Other purification procedures include passage through columns of activated alumina and repeated crystn by partial freezing. Small quantities may be purified by chromatography on a Dowex 710-Chromosorb W gas-liquid chromatographic column.

Rapid purification: Distil, discarding the forerun. Stand distillate over Grade I alumina (5% w/v) or 4A molecular sieves.