(CAS NO. )  can be obtained commercially by catalytic hydrogenation of furan from pentosan-containing agricultural residues. It was purified by refluxing with, and distilling from LiAlH₄ which removes water, peroxides, inhibitors and other impurities. Peroxides can also be removed by passage through a column of activated alumina, or by treatment with aq ferrous sulfate and sodium bisulfate, followed by solid KOH. In both cases, the solvent is then dried and fractionally distd from sodium. wire or vigorously stirred molten potassium have also been used for this purpose. CaH₂ has also been used as a drying agent.

Several methods are available for obtaining the solvent almost anhydrous. Ware dried vigorously with sodium-potassium alloy until a characteristic blue colour was evident in the solvent at Dry-ice/cellosolve temperatures. The solvent was kept in contact with the alloy until distd for use. Worsfold and Bywater, after refluxing and distilling from P₂O₅ and KOH, in turn, refluxed the solvent with sodium-potassium alloy and fluorenone until the green colour of the disodium salt of fluorenone was well established. [Alternatively, instead of fluorenone, benzophenone, which forms a blue ketyl, can be used.] The tetrahydrofuran was then fractionally distd, degassed and stored above CaH₂. p- or hydroquinone inhibit peroxide formation. The method described by Coetzee and Chang for 1,4-dioxane also applies here. Distns should always be done in the presence of a reducing agent, e.g. FeSO₄. It irritates the skin, eyes and mucous membranes and the vapour should never be inhaled. It is highly flammable and the necessary precautions should be taken.

Rapid purification: Purification as for diethyl ether.