Shaken with half volume of 2M NaOH, and emulsion allowed to separate. Repeated 3 times, then washed twice with water, dried over CaCl₂, filtered, dried over sodium wire and finally distd from fresh sodium under N₂, using a Dean-Stark trap, samples in the trap being rejected until free from turbidity.

Dried with CaSO₄ or CaCl₂, or by refluxing with sodium or BaO with crystalline FeSO₄ or by passage through an alumina column. Traces of phenols have been removed by prior shaking with 2M NaOH, followed by washing with water. (CAS NO. ) can be purified by zone refining.