DECOMPOSITION. 51 DECORATED STYLE. (CjHiOH) and carbon dioxide (CO,), and the couimou decompositious known as putrefaction and decay. In modem theoretical eheniistry, a nuuiber of decompositions have been chissed as chemical "dissociations.' The difference between a decom- position proper and a dissociation may be under- stood from the following examples. When sal ammoniac (ammonium cliloride) is heated in a closed vessel, it parth' breaks up into ammonia gas and hydrochloric acid, and partly remains unchanged. On the contrary, if equal volumes of ammonia gas and hydrochloric acid were confined in a closed vessel at the same temperature and under the same pressure as in the first experi- ment, the two substances would partly combine chemically into ammonium chloride and partly remain in a state of mechanical mixture. Quan- titative investigation would show that the ratio of the combined to the uncombined products is the same in both experiments, i.e the final state is the same, whether ^^•e start with sal ammoniac or with ammonia and hydrocliloric acid. The decomposition of sal ammoniac is therefore called a reversible reaction and is classed as a chemical dissociation. Consider now the ease of ammonia alone. Under the influence of electric sparks, anunonia breaks up, .at elevated temperatures, into its elements, nitrogen and hydrogen. But these cannot by any n:cans be caused to re-com- bine into ammonia. The breaking up of auraionia is therefore called a non-revei-sible reaction and is classed as a true decomposition. Xow, the prin<dples of thermodynamics, combined with the study of a large number of reversible reactions, led to the conclusion that two changes of an op- posite character are involved in eveiy chemical reaction whatever, and that the final state of equilibrium is determined by the relative speeds with which the two changes take place. In the ca.se of sal ammoniac this is almost self-evident. In that case the final state, as expressed by the ratio of the dissociated and undissociated prod- ucts, depends on nothing but the two speeds: viz. that with which, under a given pressure, the sal ammoniac is capable of dissociating, and that with which the products of dis.sociation are capa- ble of re-combining: it was seen above that the ratio remains the same whether we start with sal ammoniac or witl equivalent amounts of ammonia gas and hydrochloric acid. Further, the state of equilibrium is described as diinamic, not static. In other words, action is supposed to go on even after the state of equilibrium has been reached: only, under the conditions of pres- sure prevailing in that state, the speed of disso- ciation is equal to the speed of re-combination. In other words, while some amount of sal ammoniac is being broken up into ammonia and hydrochloric acid, a precisely equivalent amount of these is re-combining into sal ammoniac, and henee no change can be actually observed, al- though the two reactions are taking place con- tinually. These principles, being deduced from the laws of so absolutely general a science as thermodvnamics, must of course hold good in all cases without exception. When they are applied to cases of true decomposition, i.e. cases in which the reaction seems to take place only in one direction, the inference must necessarily be drawn that in those cases, too, both of the oppo- site reactions really take place simultaneously; only the speed of one of the reactions is so much greater than that of the opposite reaction that the amount of the product of re-combination, found after the state of equilibrium has been reached, is practically nothing. In the case of ammonia decomposed by electric sparks, the process is found to be complete and incapable of being reversed only because the amount of ani- luonia is so small compared to the amount of nitrogen and ox'gen formed, that it can hardly be detected liy the ordinary tests. It must, there- fore, be remendiered that while it is convenient, for certain purposes, to distinguish between the processes of decomposition and dissociation, the two kinds of processes are really identical in their nature. See also Dissociation ; Reaction. DE CONINCK, de ko'naNk', Pierre Louis Joseph (1S2S— ). A French genre painter, born at Meteren (Xord). He studied in Paris under Leon Cognict and won the second prix de Rome in 1S55. lie was awarded medals in the salons of ISOO and 1SC8, and a second-class medal at the Paris Exposition of 1S80. Among his pictures are "The Trappist" (1885) and At the Foun- tain," in the Volfe collection at the iletropoli- tan JIuseum in Xew York City. In 1887 he was made a member of the Legion of Honor. His pic- tures are aiiiiiuiled and good in color. DE CONSOLATIONE PHILOSOPHIC, de kOn'so-Ia'shi-C/ne fil'6-so'fi-e (Lat., on the con- solation of philosophy). A philosophical work interspersed with verse by Boethius, • written about 52.5, in prison. Alfred the Great trans- lated it into Anglo-Saxon, and Chaucer trans- lated it into English before 1382. Caxton print- ed it in 1480. Its influence in spreading Platonic thought in the Middle Ages is almost incalcula- ble. It was one of Dante's great thought-sources. DECO'RAH. A city and county-seat of Win- nc-liiek County. Iowa, 110 miles northwest of Dubuque; on the Iowa River, and on the Chicago, ililwaukee and Saint Paul and other railroads (Jlap: Iowa. F 1). It contains a Norwegian Lutheran college and Breekenridge Institute. The city has stock-raising, farming, and milling interests, and manufactures of paper, wagons, windmills, etc. Settled in 1849, Decorah was incorporated as a town in 1857, and was char- tered as a city in 1S71. Its government is admin- istered under a general law by a mayor elected biennially and a city council. The city owns and operates its water-works. Population, in 1S90, 2801 ; in 1900, 3246. DECORATED STYLE OF GOTHIC AR- CHITECTURE. The style of architecture in England immediately following the Early English stvle (q.v.). During the reigns of the first three Edwards, from about 1280 to 1380, Gofliic archi- tecture may be said to have been in full Itlooni in England. It arose so giadually out of the style which preceded it. and merged so gradually into that wiiich followed it, that it is not wonderful that dill'erent periods of duration should be as- signed to it by different writers. In fixing on the middle of the fourteenth century as its highest point, liowever, they are all pretty much agreed, and the same agreement is exhibited in recogniz- ing it as ihe most perfect of the English. Gothic styles, although Jloore, in Gothic Architecture, does not alhiw any perfectly national English Gothic until the Perpendicular (q.v.). Tliis middle period of Englisii Gothic corresponds to the earlier developed Gothic of France, repre-
