Page:EB1911 - Volume 11.djvu/371

 such as furfuracrolein, C4H3O·CH:CH·CHO, and furfuracetone, C4H3O·CH:CH·CO·CH3. With alcoholic potassium cyanide It changes to furoin, C4H3O·CHOH·CO·C4H3O, which can be oxidized to furil, C4H3O·CO·CO·C4H3O, whilst alcoholic potash converts it into furfuryl alcohol. With fatty acids and acid anhydrides it gives the “Perkin” reaction (see ). Furfurol is shown to have its aldehydic group in the a position, by conversion into furfurpropionic acid, C4H3O·CH2·CH2·CO2H, which on oxidation by bromine water and subsequent reduction of the oxidized product is converted into n-pimelic acid, HO2C(CH2)5CO2H. Furfurol in minute quantities can be detected by the red colour it forms with a solution of aniline acetate.

FURIES (Lat. Furiae, also called ), in Roman mythology an adaptation of the Greek (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 th of the statute mile. “Furlong” was as early as the 9th century used to translate the Latin stadium, th 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 and ), 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:— &emsp;(1) Fuel and substance in contact. (a) Height of furnace greater than diameter = shaft furnaces. No blast = kilns. With blast = blast furnaces. (b) Height not much greater than diameter = hearth furnaces. &emsp;(2) Substance heated by products of combustion = reverberatory furnaces. (a) Charge not melted = roasting or calcining furnaces. (b) Charge melted = melting furnaces. &emsp;(3) Substance is not directly heated by the fuel or by the products of combustion. (a) Heating chamber fixed and forming part of furnace = muffle furnaces. (b) Crucible furnaces. (c) Retort furnaces. Another classification may be based upon the nature of the heating agent, according as it is coal (or some similar combustible) oil, gas or electricity. In this article the general principles of metallurgical furnaces will be treated; the subject of gas- and oil-heated furnaces is treated in the article Fuel, and of the electric furnace in the article Electrometallurgy. For special furnaces reference should be made to the articles on the industry concerned, e.g., , § Manufacture, &c.

Shaft, Blast and Hearth Furnaces.—The blast furnace in its simplest form is among the oldest, if not the oldest, of metallurgical contrivances. In the old copper-smelting district of Arabia Petraea, clay blast-pipes dating back to the earlier dynasties of ancient Egypt have been found buried in slag heaps; and in India the native smiths and iron-workers continue to use furnaces of similar types. These, when reduced to their most simple expression, are mere basin-shaped hollows in the ground, containing ignited charcoal and the substances to be heated, the fire being urged by a blast of air blown in through one or more nozzles from a bellows at or near the top. They are essentially the same as the smith’s forge. This class of furnace is usually known as an open fire or hearth, and is represented in a more advanced stage of development by the Catalan, German and Walloon forges formerly used in the production of malleable iron.

Fig. 1 represents a Catalan forge. The cavity in the ground is represented by a pit of square or rectangular section lined with brick or stone of a kind not readily acted on by heat, about 1 or 2 ft. deep, usually somewhat larger above than below, with a tuyere or blast-pipe of copper penetrating one of the walls near the top, with a considerable downward inclination, so that the air meets the fuel some way down. In iron-smelting the ore is laid in a heap upon the fuel (charcoal) filling up the hearth, and is gradually brought to the metallic state by the reducing action of the carbon monoxide formed at the tuyere. The metal sinks through the ignited fuel, forming, in the hearth, a spongy mass or ball, which is lifted out by the smelters at the end of each operation, and carried to the forge hammer. The earthy matters form a fusible glass or slag melt, and