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Rh in beehive ovens, but the waste being less there is a decided saving, apart from the value of the condensed products. In one instance the coke was found to be about 5% less efficient in the blast furnace, while the yield on the coal charged was increased 10%. In the further treatment of the condensed products by distillation the tar gives burning oil and pitch, the benzene is separated from the creosote oil by steam-heated stills, and the ammoniacal liquor, after some lime has been added to decompose fixed ammonium compounds, is heated to vaporize the ammonia, which is condensed in lead or copper-lined tanks containing strong sulphuric acid to produce a crystalline powder of ammonium sulphate, which accumulates in the receiver and is fished out from time to time. The yield of by-products averages about 1% of ammonium sulphate, about 3½% of tar, and 0.6 to 0.9% of benzene, of the weight of the coal carbonized. After the ovens have been heated and steam supplied for the machinery of the condensing plant and the coke ovens, there is usually a surplus of gas, which may be used for lighting or driving gas-engines. For the latter purpose, however, it is necessary to remove the last traces of tar, which acts very prejudicially in fouling the valves when the gas is not completely purified. The gas given off during the earlier part of the coking process is richer in heavy hydrocarbons and of a higher illuminating value than that of the later period when the temperature is higher. This property is utilized in several large coking plants in America, where the gas from the first ten hours’ working is drawn off by a second hydraulic main and sent directly to town gas-works, where it passes through the ordinary purifying treatment, the gas from the second period being alone used for heating the ovens.

Coke is essentially a partially graphitized carbon, its density being about midway between that of coal and graphite, and it should therefore occupy less space than the original coal; but owing to the softening of the charge a spongy structure is set up by the escaping gases, which acts in the other direction, so that for equal bulk coke is somewhat lighter than coal. It is this combination of properties that gives it its chief value in iron smelting, the substance being sufficiently dense to resist oxidation by carbon dioxide in the higher regions of the furnace, while the vesicular structure gives an extended surface for the action of heated air and facilitates rapid consumption at the tuyeres. Compact coke, such as that formed on the inner sides of gas retorts (retort carbon), can only be burned with great difficulty in small furnaces of special construction, but it gives out a great amount of heat.

The most deleterious constituents of coke are ash, sulphur and volatile constituents including water. As the coke yield is only from two-thirds to three-quarters of that of the coal, the original proportion of ash is augmented by one-third or one-half in the product. For this reason it is now customary to crush and wash the coal carefully to remove intermingled patches of shale and dirt before coking, so that the ash may not if possible exceed 10% in the coke. About one-half of the sulphur in the coal is eliminated in coking, so that the percentage in the coke is about the same. It should not be much above 1%. According to the researches of F. Wuest (Journ. Iron and Steel Inst., 1906) the sulphur is retained in a complex carbon compound which is not destroyed until the coke is actually consumed.

The older methods of coking and the earlier forms of retort ovens are described in J. Percy, Metallurgy, Jordan, Album du cours de metallurgie; Phillips and Bauerman, Handbook of Metallurgy, and other text-books. A systematic series of articles on the newer forms will be found in The Engineer, vol. 82, pp. 205-303 and vol. 83, pp. 207-231; see also Dürre, Die neuern Koksöfen (Leipzig, 1892); D. A. Louis, “Von Bauer and Brünck Ovens,” ''Journ. Iron and Steel Inst.'', 1904, ii. p. 293; C. L. Bell, “Hüssener Oven,” id., 1904, i. p. 188; Hurez, “A Comparison of Different Systems of Vertical and Horizontal Flue Ovens,” ''Bull. soc. industrie minérale'', 1903, p. 777. A well-illustrated description of the Otto system in its American modification was issued by the United Gas & Coke Company of New York, in 1906.

COL (Fr. for “neck,” Lat. collum), in physical geography, generally any marked depression upon a high and rugged water-parting over which passage is easy from one valley to another. Such is the Col de Balme between the Trient and Chamounix valleys, where the great inaccessible wall crowned with aiguilles running to the massif of Mt. Blanc is broken by a gentle downward curve with smooth upland slopes, over which a footpath gives easy passage. The col is usually formed by the head-waters of a stream eating backward and lowering the water-parting at the head of its valley. In early military operations, the march of an army was always over a col, which has at all times considerable commercial importance in relation to roads in high mountain regions.

 COLBERT, JEAN BAPTISTE (1619–1683), French statesman, was born at Reims, where his father and grandfather were merchants. He claimed to be the descendant of a noble Scottish family, but the evidence for this is lacking. His youth is said to have been spent in a Jesuit college, in the office of a Parisian banker, and in that of a Parisian notary, Chapelain, the father of the poet. But the first fact on which we can rely with confidence is that, when not yet twenty, he obtained a post in the war-office, by means of the influence that he possessed through the marriage of one of his uncles to the sister of Michel Le Tellier, the secretary of state for war. During some years he was employed in the inspection of troops and other work of the kind, but at length his ability, his extraordinary energy and his untiring laboriousness induced Le Tellier to make him his private secretary. These qualities, combined, it must be confessed, with a readiness to seize every opportunity of advancement, soon brought Colbert both wealth and influence. In 1647 we find him receiving the confiscated goods of his uncle Pussort, in 1648 obtaining 40,000 crowns with his wife Marie Charron, in 1649 appointed councillor of state.

It was the period of the wars of the Fronde; and in 1651 the triumph of the Condé family drove Cardinal Mazarin from Paris. Colbert, now aged thirty-two, was engaged to keep him acquainted with what should happen in the capital during his absence. At first Colbert’s position was far from satisfactory; for the close wary Italian treated him merely as an ordinary agent. On one occasion, for example, he offered him 1000 crowns. The gift was refused somewhat indignantly; and by giving proof of the immense value of his services, Colbert gained all that he desired. His demands were not small; for, with an ambition mingled, as his letters show, with strong family affection, he aimed at placing all his relatives in positions of affluence and dignity; and many a rich benefice and important public office was appropriated by him to that purpose. For these favours, conferred upon him by his patron with no stinted hand, his thanks were expressed in a most remarkable manner; he published a letter defending the cardinal from the charge of ingratitude which was often brought against him, by enumerating the benefits that he and his family had received from him (April 1655). Colbert obtained, besides, the higher object of his ambition; the confidence of Mazarin, so far as it was granted to any one, became his, and he was entrusted with matters of the gravest importance. In 1659 he was giving directions as to the suppression of the revolt of the gentry which threatened in Normandy, Anjou and Poitou, with characteristic decision arresting those whom he suspected, and arranging every detail of their trial, the immediate and arbitrary destruction of their castles and woods, and the execution of their chief, Bonnesson. In the same year we have evidence that he was already planning his great attempt at financial reform. His earliest tentative was the drawing up of a mémoire to Mazarin, showing that of the taxes paid by the people not one-half reached the king. The paper also contained an attack upon the superintendent (q.v.), and being opened by the postmaster of Paris, who happened to be a spy of Fouquet’s, it gave rise to a bitter quarrel, which, however, Mazarin repressed during his lifetime.

In 1661 the death of Mazarin allowed Colbert to take the first place in the administration, and he made sure of the king’s favour by revealing to him some of Mazarin’s hidden wealth. It was some time before he assumed official dignities; but in January 1664 he obtained the post of superintendent of buildings; in 1665 he was made controller-general; in 1669 he became minister of the marine; and he was also appointed minister of commerce, the colonies and the king’s palace. In short, he soon acquired power in every department except that of war.

A great financial and fiscal reform at once claimed all his energies. Not only the nobility, but many others who had no legal claim to exemption, paid no taxes; the weight of the burden fell on the wretched country-folk. Colbert sternly and fearlessly set about his task. Supported by the young king, Louis XIV.,