Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/667

Rh W H W H 627 diverged. The latter continued to prosecute organic research ; the former turned his attention more to inorganic subjects, not ex clusively, however, as the well-known research on narcotiue (which was carried out in his laboratory, partly by himself partly by Blyth, and published in 1848) is alone sufficient to prove. Amongst Wbhler s inorganic publications, a short notice on the improvements in the preparation of potassium is significant as forming the small beginning of a brilliant series of researches on the isolation of elementary substances and on their properties, a subject for which he evidently had a great love, as lie always comes back to it in the intervals of other work. In 1827 he for the first time succeeded in isolating aluminium, the metal of clay, by means of a method which was soon found to be more generally applicable. Alumina, like many other metallic oxides, is not reducible by electrolysis or by the action of charcoal at any temper ature. But, when heated with charcoal in chlorine gas, it passes into the state of a volatile chloride. What Wbhler found was that this chloride, when heated with potassium or sodium, readily gives up its chlorine and assumes the elementary form. The aluminium which Wb hlcr thus obtained was a grey powder ; but in 1845 he succeeded in producing the metal in the shape of well-fused, fully metallic globules. &quot;Wohler, on this second occasion, correctly ascertained all the properties which everybody now knows to be characteristic of this metal ; and it is as well to add that where Wohler s aluminium differed from what now occurs in commerce under this name it differed to its own advantage. That Wohler should not have seen the practical importance of his discovery is not to be credited ; if he never suggested an attempt to manu facture the metal industrially, that is only the natural consequence of the circumstances in which he was placed. The earlier aluminium research was followed in 1828 by the isolation of beryllium and yttrium. These earlier metal reductions fall into the Berlin period. While in Cassel he worked out pro cesses for the manfacture of nickel free from arsenic, and this laid the foundation for what is now a flourishing chemical industry in Germany. The several methods for the analysis of nickel and cobalt ores which he describes in his Mineral- Analyse appear to be an incidental outcome of this work. This subject was one of his favourite topics ; as late as 1877 we see him coming back to it in the publication of a short process for the separation of nickel and cobalt from arsenic and iron. In 1849 metallic titanium arrested his attention. Since the days of Wollaston those beautiful copper-like cubes which are occasionally met with in blown-out blast furnaces had been sup posed to be metallic titanium pure and simple. Wohler observed that the reputed metal, when fused with caustic alkali, emitted torrents of ammonia, and on further inquiry ascertained the crystals to be a ternary compound, containing the elements of a nitride and of a cyanide of the metal. In pursuance of this research Wbhler taught us how to prepare real titanium and really pure titanic acid. In 1854 Deville s energetic attempts to produce aluminium in dustrially caused Wohler to turn his attention again to this early and almost forgotten child of his genius. His first incentive, no doubt, was the natural and just desire to claim his right as the real discoverer of what Deville, in his ignorance of foreign scientific work, quite honestly thought he had been the first to find out. This dispute came to a very satisfactory issue : Deville, after a little pardonable hesitation, fully acknowledged Wohler s priority, and the two henceforth were friends, and worked together. The first fruit of this happy union was a memorable joint re search (published in 1856 and 1857), which led to their discovery of an adamantine and of a graphitoidal (in addition to the long known amorphous) modification of boron. This graphitoidal species subsequently, in their own hands, proved to be a mistake ; but the adamantine modification lives to this day as a true analogue of ordinary (carbon) diamond. From boron to silicon is an easy transition, so we need not wonder at finding Wbhler, in 1857, engaged (conjointly with the physicist Buff) in a research on new compounds of silicon. On electrolysing a solution of common salt with silicon-containing aluminium as a positive electrode, they obtained a self-inflammable gas which they recognized as hydrogen contaminated with the previously unknown hydride of silicon, SiII 4, which body Wohler subsequently, with the co-operation of ftfartius, obtained in a state of greater purity. Wbhler and Buff also obtained, though in an impure state, what were subsequently recognized by Friedel and Ladenburg as silicon-chloroform and as silicon-formic anhydride. Space does not allow of more than a mere reference to Wohler s researches on metallic or semimetallic nitrides. What we know of this as yet little understood class of bodies, with barely an exception, came out of his laboratory, if it was not done by himself in the strict sense of the word. And only a reference can be made to the numerous processes which Wbhler, in the course of his long laboratory practice, has worked out for the preparation of pure chemicals, and for the execution of exact analytical separations. He had better work to do than to take up analytical problems for their own sake ; but what he did in this direction incidentally amounts to a great deal. The analysis of meteorites was one of his favourite specialties, one of his results being the discovery of organic matter in a meteorite which he examined in 1864. As a teacher Wbhler ranks with Liebig and Berzelius. In a sense he was the greatest of the three. Berzelius never had the opportunity to teach large numbers of students in his laboratory; and Liebig lacked the many-sidedness so characteristic of the Gbt- tingen laboratory as long as it really was under Wohler s personal direction. One student might wish to work on organic chemistry, another on minerals, a third on metallurgy, a fourth on rare ele ments; let them all go to Wbhler, and all, as well as the fifth or sixth, would find themselves in the right place. That Wbhler in these circumstances was able to do much literary work is truly marvellous. His Grundriss dcr Chemie, which he published anony mously at first, has passed through many editions, and been trans lated into various foreign languages, -never, unfortunately, into English. A more valuable teaching book still, and more unique in its character, is his excellent Pradischc Uebungen in dcr chemischcn Analyse (entitled in the second edition Mineral- Analyse in Bei- spiclcii], of which we have two English translations. To a man like him the compilation of either book probably gave little trouble ; what must have taken up a very large portion of his valuable time are his translations of Berzelius s Lehrbiich dcr Chemie, and of all the successive volumes of Berzelius s Jahrcslcricht, which only thus became really available to the scientific world at large. From 1838, too, Wbhler was one of the editors of Liultig sAimalen. Wohler s last publication (1880) treats of a new kind of galvanic element in which the one metal aluminium serves for either pole. A very excellent biography of Wbhler by Hofmann is published in the Bericlite der deutschen chemisc/ien Gesellschaft for 1882. (W. D.) WOHLGEMUTH, MICHAEL (1434-1519), an able painter of the school of Franconia, of which Nuremberg, where he was born in 1434, was the chief artistic centre. Little is known of his private life beyond the fact that in 1472 he married the widow of the painter Hans Pleyden- wurff, whose son Wilhelm worked as an assistant to his stepfather. The importance of Wohlgemuth as an artist rests, not only on his own individual paintings, but also on the fact that he was the head of a large workshop, in which many different branches of the fine arts were carried on by a great number of pupil-assistants, including Albert Dtirer (see vol. vii. pp. 555-56). In this atelier not only large altar-pieces and other sacred paintings were executed, but also elaborate retables in carved wood, consisting of crowded subjects in high relief, richly decorated with gold and colour, such as pleased the rather doubtful Teutonic taste of that time (see p. 648 infra). Wood-engraving was also carried on in the same workshop, the blocks being cut from Wohlgemuth s designs, many of which are remark able for their vigour and clever adaptation to the special necessities of the technique of woodcutting. Two large and copiously illustrated books have woodcuts supplied by Wohlgemuth and his stepson Wilhelm Pleydenwurff. The first is the Schatzkammer der ivahren Reichthiimer des Ilrils, printed by Koberger in 1491 ; the other is the Historia Ahmdi, by Schedel, 1493-94, a sort of encyclopaedia, usually known as the Nuremberg Chronicle, which attained a very high degree of popularity at the time, and is now highly valued, not for the text, but- for its remarkable collection of spirited engravings. Among the paintings ascribed to Wohlgemuth a large number are clearly the work of less able assistants, but those by the hand of the master himself possess merit of a very high order, in their rich colour, powerful drawing, and refined delicacy of finish. The earliest known work by Wohlgemuth is a retable consisting of four panels, dated 1465, now in the Munich gullery, a decorative work of much beauty. In 1479 he painted the retable of the high altar in the church of St Mary at Zwickau, which still exists, receiving for it the large sum of 1400 gulden. One of his finest and largest works is the great retable painted for the church of the Austin friars at Nuremberg, now moved into the museum ; it consists of a great many panels, with figures of those saints whose worship was specially popular at Nuremberg. In 1501 Wohlgemuth was employed to decorate the town-hall at Goslar with u