Furfurane—αα′-dicarboxylic acid or dehydromucic acid, C4H2O(CO2H)2, is formed when mucic acid is heated with hydrochloric acid at 100° C. On being heated, it loses carbon dioxide and gives pyromucic acid. By digesting acetoacetic ester with sodium succinate and acetic anhydride, methronic acid, C8H8O5, is obtained; for the constitution of this acid, see L. Knorr, Ber., 1889, 22, p. 152, and R. Fittig, Ann., 1889, 259, p. 166.
Di- and tetrahydrofurfurane compounds are also known (see A. Lipp, Ber., 1889, 22, p. 1196; W.H. Perkin, junr. Journ. Chem. Soc., 1899, 57, p. 944; and S. Ruhemann, ibid., 1896, 69, p. 1383).
FURIES (Lat. Furiae, also called Dirae), in Roman mythology an adaptation of the Greek Erinyes (q.v.), with whom they are generally identical. A special aspect of them in Virgil is that of agents employed by the higher gods to stir up mischief, strife and hatred upon earth. Mention may here be made of an old Italian deity Furina (or Furrina), whose worship fell early into disuse, and who was almost forgotten in the time of Varro. By the mythologists of Cicero’s time the name was connected with the verb furere and the noun furia, which in the plural (not being used in the singular in this sense) was accepted as the equivalent of the Greek Erinyes. But it is more probably related to furvus, fuscus, and signifies one of the spirits of darkness, who watched over men’s lives and haunted their abodes. This goddess had her own special priest, a grove across the Tiber where Gaius Gracchus was slain, and a festival on the 25th of July. Authorities differ as to the existence of more than one goddess called Furina, and their identity with the Forinae mentioned in two inscriptions found at Rome (C.I.L. vi. 422 and 10,200).
FURLONG (from the O. Eng. furlang, i.e. “furrow-long”), a measure of length, originally the length of a furrow in the “common field” system. As the field in this system was generally taken to be a square, 10 acres in extent, and as the acre varied in different districts and at different times, the “furlong” also varied. The side of a square containing 10 statute acres is 220 yds. or 40 poles, which was the usually accepted length of the furlong. This is also the length of 1⁄8th of the statute mile. “Furlong” was as early as the 9th century used to translate the Latin stadium, 1⁄8th of the Roman mile.
FURNACE, a contrivance for the production and utilization of heat by the combustion of fuel. The word is common to all the Romance tongues, appearing in more or less modified forms of the Latin fornax. But in all those languages the word has a more extended meaning than in English, as it covers every variety of heating apparatus; while here, in addition to furnaces proper, we distinguish other varieties as ovens, stoves and kilns. The first of these, in the form Ofen, is used in German as a general term like the French four; but in English it has been restricted to those apparatus in which only a moderate temperature, usually below a red heat, is produced in a close chamber. Our bakers’ ovens, hot-air ovens or stoves, annealing ovens for glass or metal, &c., would all be called fours in French and Öfen in German, in common with furnaces of all kinds. Stove, an equivalent of oven, is from the German Stube, i.e. a heated room, and is commonly so understood; but is also applied to open fire-places, which appears to be somewhat of a departure from the original signification.
Furnaces are constructed according to many different patterns with varying degrees of complexity in arrangement; but all may be considered as combining three essential parts, namely, the fire-place in which the fuel is consumed, the heated chamber, laboratory, hearth or working bed, as it is variously called, where the heat is applied to the special work for which the furnace is designed, and the apparatus for producing rapid combustion by the supply of air under pressure to the fire. In the simplest cases the functions of two or more of these parts may be combined into one, as in the smith’s forge, where the fire-place and heating chamber are united, the iron being placed among the coals, only the air for burning being supplied under pressure from a blowing engine by a second special contrivance, the tuyere, tuiron, twyer or blast-pipe; but in the more refined modern furnaces, where great economy of fuel is an object, the different functions are distributed over separate and distinct apparatus, the fuel being converted into gas in one, dried in another, and heated in a third, before arriving at the point of combustion in the working chamber of the furnace proper.
Furnaces may be classified according as the products of combustion are employed (1) only for heating purposes, or (2) both for heating and bringing about some chemical change. The furnaces employed for steam-raising or for heating buildings are invariably of the first type (see [Boiler] and [Heating]), while those employed in metallurgy are generally of the second. The essential difference in construction is that in the first class the substances heated do not come into contact with either the fuel or the furnace gases, whereas in the second they do. Metallurgical furnaces of the first class are termed crucible, muffle or retort furnaces, and of the second shaft and reverberatory furnaces. The following is a detailed subdivision:—