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but meadows and pastures are rare. Maize, millet, rye, flax, liquorice and fruits of all sorts—especially nuts, almonds, oranges, figs, walnuts and chestnuts—are produced. Wheat sufficient for one-fourth of the population is grown, and the vine is extensively cultivated. Few cattle, but numbers of sheep, goats and swine are reared. Game is plentiful, and the fisheries on the coast are excellent. The wines are for the most part rough and strong, though some are very good, especially when matured. They are much used to adulterate those of Oporto, or, after undergoing the blending operation termed compage, are passed off as Bordeaux wines in France. The best of them, priorato, is chiefly known in England, under the disguise of second or third-rate port; it was much used in the military hospitals of America during the Civil War.

The Catalonians are a frugal, sharp-witted, and industrious people, having much national pride, and a strong revolutionary spirit. They are distinct in origin from the other inhabitants of Spain, from whom they differ in their dialect and costume. In their great energy and their love of enterprise they resemble the Basques. Irrigation, careful husbandry and railroad communications have much developed the resources of their country, in themselves excellent; and there are many manufacturing towns and industrial establishments.

Catalonia was one of the first of the Roman possessions in Spain, and formed the north-eastern portion of Hispania Tarraconensis. About 470 it was occupied by the Alans and Goths. It was conquered by the Moors in 712, but these invaders were in turn dispossessed by the Spaniards and the troops of Charlemagne in 788. Catalonia was subsequently ruled by French counts, who soon, however, made themselves independent of France. By the marriage of Count Raymond Berenger IV. of Barcelona with Petronilla of Aragon, Catalonia became annexed to Aragon; but this union was frequently severed. In 1640, when Philip IV. attempted to deprive Catalonia of its rights and privileges, it gave itself up to Louis XIII. of France. It was restored to Spain in 1659, and was once more occupied by the French from 1694 to 1697. Under Philip V. Catalonia, in 1714, was deprived of its cortes and liberties. From 1808 to 1813 it was held by France. It was the scene of civil war in 1823, and of important revolutionary operations in the Carlist wars.

The history and literature of Catalonia have been closely studied, and in many cases the results of research are published in the Catalan language. See Cataluña, sus monumentos y artes, su naturaleza e historia (2 vols. of the illustrated series España), by P. Pifferrer, F. Pi Margall, and A. A. Pijoan (Barcelona, 1884); Historia de Cataluña, by V. Balaguer (11 vols., Madrid, 1886, &c.); Historia de Cataluña, by A. Bori y Fontestá (Barcelona, 1898); Origines históricos de Cataluña, by J. Balari y Jovany (Barcelona, 1899); Coleccio dels monografias de Catalunya, by J. Reig y Vilardell (Barcelona, 1890); Historia del derecho en Catalonia, Mallorca y Valencia, by B. Oliver (Madrid, 1876–1880); and Antigua marina catalana, by F. de Bofarull y Sans (Barcelona, 1898). The Revista catalana (Catalan Review), published at Barcelona from 1889, contains many valuable papers on local affairs. See also Spain: sections Language, Literature and History, and Barcelona.

CATALPA, in botany, a genus belonging to the family Bignoniaceae and containing about ten species in America and eastern Asia. The best known is Catalpa bignonioides, a native of the eastern United States which is often cultivated in parks and gardens. It is a stately tree with large heart-shaped pointed leaves and panicles of white bell-shaped flowers streaked with yellow and brown purple.

CATALYSIS (from the Gr. κατά, down, and λύειν, to loosen), in chemistry, the name given to chemical actions brought about by a substance, termed the “catalyst,” which is recovered unchanged after the action. The term was introduced by Berzelius, who first studied such reactions. It is convenient to divide catalytic actions into two groups:—(1) when the catalyst first combines with one of the reaction components to form a compound which immediately reacts with the other components, the catalyst being simultaneously liberated, and free to react with more of the undecomposed first component; and (2), when the catalyst apparently reacts by mere contact. The theory of catalysis is treated under Chemical Action; in this article mention will be made of some of the more interesting examples.

A familiar instance of a catalytic action is witnessed when a mixture of potassium chlorate and manganese dioxide is heated to 350°, oxygen being steadily liberated, and the manganese dioxide being unchanged at the end of the reaction. The action may be explained as follows:—part of the chlorate reacts with the manganese dioxide to form potassium permanganate, chlorine and oxygen, the chlorine subsequently reacting with the permanganate to produce manganese dioxide, potassium chloride and oxygen, thus

2KClO3 + 2MnO2 = 2KMnO4 + Cl2 + O2 = 2KCl + 2MnO2 + 3O2.

This explanation is supported by the facts that traces of chlorine are present in the gas, and the pink permanganate can be recognized when little dioxide is used. Other oxides bring about the same decomposition at temperatures below that at which the chlorate yields oxygen when heated alone; but since such substances as kaolin, platinum black and some other finely powdered compounds exercise the same effect, it follows that the explanation given above is not quite general. Another example is Deacon’s process for the manufacture of chlorine by passing hydrochloric acid gas mixed with air over heated bricks which had been previously impregnated with a copper sulphate solution. The nitrous gases employed in the ordinary chamber process of manufacturing sulphuric acid also act catalytically. Mention may be made of the part played by water vapour in conditioning many chemical reactions. Thus sodium will not react with dry chlorine or dry oxygen; carbon, sulphur and phosphorus will not burn in perfectly dry oxygen, neither does nitric oxide give red fumes of the peroxide. In organic chemistry many catalytic actions are met with. In the class of reaction known as “condensations,” it may be found that the course of the reaction is largely dependent upon the nature of some substance which acts catalytically. One of the most important is the Friedel and Craft’s reaction, in which an aromatic compound combines with an alkyl haloid in the presence of aluminium, zinc or ferric chloride. It seems in this, as in other cases, that additional compounds are first formed which subsequently react with the re-formation of the catalyst. The formation of benzoin from benzaldehyde in the presence of potassium cyanide is another example; this action has been investigated by G. Bredig and Stern (Zeit. Elektrochem., 1904, 10, p. 582).

The second class of catalytic actions, viz. those occasioned by the presence of a metal or some other substance which undergoes no change, is of especial interest, and has received much attention. The accelerating influence of a clean platinum plate on the rate of combination of hydrogen and oxygen was studied by Faraday. He found that with the pure gases the velocity of reaction increased until the mixture exploded. The presence of minute quantities of carbon monoxide, carbon disulphide, sulphuretted hydrogen and hydrochloric acid inhibited the action; in the case of the first two gases, there is no alteration of the platinum surface, since the plate brings about combination when removed to an atmosphere of pure hydrogen and oxygen; with the last two gases, however, the surface is altered, since the plate will not occasion the combination when placed in the pure gases. M. Bodenstein (Zeit. phys. Chem., 1904, 46, p. 725) showed that combination occurs with measurable velocity at ordinary temperatures in the presence of compact platinum. More energetic combination is observed if the metal be finely divided, as, for instance, by immersing asbestos fibres in a solution of platinum chloride and strongly heating. The “spongy” platinum so formed brings about the combination of ammonia and oxygen to form water and nitric acid, of nitric oxide and hydrogen to form ammonia (see German Patent, 1905, 157,287), and of sulphur dioxide and oxygen to form sulphur trioxide. The last reaction, which receives commercial application in the contact process of sulphuric acid manufacture, was studied by M. Bodenstein and W. Pohl (Zeit. Elektrochem., 1905, 11, p. 373), who found that the equilibrium followed the law of mass-action (see also F. W. Küster, Zeit. anorg. Chem., 1904, 42, p. 453, R. Lucas, Zeit. Elektrochem., 1905, 11, p. 457). Other metals, such as nickel, iron, &c., can also react as catalysts.