FURFURAN or FURAN (Tetrol, tetraphenol), a colour less liquid boiling at 317750 mm., slightly soluble in water but miscible in all proportions with alcohol or ether. Its specific gravity is 0.9444 at 15° C. It occurs in the most volatile portions of pine-wood tar and is prepared synthetically by heating pyro mucic or furoic acid at 26o-275° C ; by the dry distillation of barium or calcium pyromucate (furoate); and by digesting succinic dialdehyde with water at 180° C. Furfuran develops an emerald-green coloration on a chip of pine wood moistened with hydrochloric acid. It is regarded chemically as a cyclic com pound containing four carbon atoms and one oxygen atom: Furfurol (f urf uraldehyde, furfural, or f urol) , the most im portant derivative in the furan series, is a colourless liquid which turns brown when exposed to air and light; it boils at 161.7°/ C76o mm., freezes at _36.5° C; its specific gravity is 1.1598 at 20° C. It dissolves in water to the extent of 8.3% at 20° C and is also soluble in alcohol and ether. Furfural is obtained from bran, corn cobs, gums, jute, oatmeal, oat hulls and straw when these materials are digested with dilute mineral acids and the consequent mixture is distilled. An effective procedure for the manufacture of furfural has been developed. Oat hulls, obtainable throughout the year in large quantities (200 ton lots), are subjected to the action of steam and acid in large rotary digesters. The distillate from these digesters has a relatively high furfural content, and is neutralized with lime and distilled in a fractionating still; furfural of 95% purity is thus separated and is refined by further rectification at 16o° C. Technical fur-. f ural of 98-99% purity is now marketed in considerable quan tities. Its presence in beer or spirits is detected by the cherry-red coloration developed with aniline acetate or hydrochloride.
Resinous materials are produced by condensing furfural with phenols or aromatic amines. A wide variety of moulded products are manufactured from furfural-phenol resins. Furfural and its organic derivatives are solvents for cellulose esters and ethers, and are applicable to the preparation of cellulose ester plastics. Furfural has been used as a substitute for turpentine in varnish manufacture and as a solvent in the lacquer industry. Hydrofur amide ("vulcazol"), the condensation product of furfural and ammonia, is an active indiarubber accelerator. Furfural exhibits the characteristic properties of aldehydes (q.v.) forming a bi sulphite compound, an oxime, and a hydrazone. With potassium cyanide furfural polymerizes to furoin (m.p. 135° C) , and with aqueous alkali it yields f urf uryl alcohol and furoic acid. The latter compound, which is also termed pyromucic acid, is pre pared either by the dry distillation of mucic acid (q.v.) or by mild oxidation of furfural. It is a tasteless, inodorous solid melting at 132° C and has useful germicidal properties. Ethyl furoate is a solid melting at 34° C. The other esters, including furyl furoate, are fragrant oily liquids useful as solvents for cellulose esters and for paints and varnishes. Electrolytic oxidation of furfural leads successively to furoic acid and then to maleic and succinic acids (E.P., BIBLIOGRAPHY.-A. Bender, Das Furfuran and seine Derivate Bibliography.-A. Bender, Das Furfuran and seine Derivate (1889) ; E. Abderhalden, "Furfurol," Biochemischen Handlexikon, vol. i. (191I) , pp. 852 et seq.; "Furfural and its Derivatives," the Miner Laboratories, Chicago, Bulletin No. 2 (1925), an informative brochure with comprehensive bibliography. (G. T. M.)