1902 Encyclopedia > Friedrich Wohler

Friedrich Wohler
German chemist

FRIEDRICH WOHLER, (1800-1882), chemist, was born on July 31, 1800, in Eschersheim, near Frankfort-on-the Main. While attending the village school of Rödelheim, he received valuable additional instruction from his father, a man of more than ordinary acquirements. In 1812 the family removed to Frankfort, where he entered the gym-nasium, and by the kindness of a scientific friend, Dr Buch, was introduced to the study of mineralogy, chemistry, and physics. He afterwards studied medicine at Marburg and Heidelberg, graduating in that faculty at the latter university. Having, on the advice of Leopold Gmelin, decided upon devoting himself henceforth to chemistry, he completed his chemical education at Stock-holm, under Berzelius, in whose laboratory he worked for a considerable time, and with whom, during his subsequent life, he maintained the most friendly relations. While in Sweden he took part in a scientific expedition through Norway, which made him acquainted with the brothers Brongniart and with Humphrey Davy.
After his return from Sweden in 1825, he accepted a call to Berlin as teacher of chemistry in the then newly-erected " gewerbschule," and remained there until 1832, when family affairs caused him to take up his abode in Cassel. In 1836 Wöhler became professor of chemistry in the medical faculty of the university of Göttingen, which office, in his case, was combined with that of inspector-general of pharmacy for Hanover. He held his chair till his death, which occurred, after a short illness, on the 23rd September 1882.
Wbhler's career as a chemist extends over two generations. Some sixty years ago, when the elementary nature of chlorine had just been established, and the isolation of cyanogen was still a novelty, young Wohler already worked as an investigator, the same Wohler who rejoiced with the chemists of to-day over the synthesis of indigo. Of the world of chemical discoveries that lie between he magna pars fait. Within the limits of the present article, however, it is impossible to do more than indicate briefly the nature of some of his greater achievements. Amongst these his discovery of cyanic acid, and what it led him to, occupy a prominent place. From these investigations of his the science of organic chemistry may be said to date.
When, in 1828, Wohler prepared the ammonia salt of his acid, he was astonished to find that the salt, although made by what appeared to be a straightforward double decomposition, did not exhibit the character of an ammonia salt at all, but turned out to be identical with urea, a substance which heretofore had been known only as one of the organic components of urine. Prior to this discovery a wide and impassable gulf had in the minds of chemists separated the mineral from the organic kingdom. Inorganic bodies all appeared to be derivable from their elements by a succession of acts of binary combination ; the full analysis of such a body contained in itself the full instruction for its synthetical production in the laborator}7. Organic substances, on the ether hand, were supposed to be things of an entirely different order; in them the few elements which they all consist of were assumed to be united with one another, each with each, in a mysterious manner, which could be brought about only by theagency of "vital force." Vital force, it was now seen, had nothing to do with the formation of urea at any rate. The gulf was bridged over, and a great and new morning full of the highest promise dawned over chemistry. If the promise was more than fulfilled, if organic chemistry from a mere possibility developed into a reality, we owe this chiefly to the great researches which were carried out con-jointly by Wohler and Liebig.
One of the first, if not the first, of these was an investigation on the oxygenated acids of cyanogen, which they published in 1830. In their research they proved, both analytically and synthetically, that cyanic and cyanuric acid, although distinct bodies, have the same elementary composition, and that the former, when simply kept in a sealed-up tube, gradually passes wholly into a porcelain-like neutral solid, cyamelide, which is widely different from either. By these discoveries, and by Wbhler's synthesis of urea, the fact of isomerism was firmly established. Compared with this great conquest their joint work on mellitic acid (1830) and on sulpho-vinic acid (1831) appears small; it sinks into insignificance wdien viewed in the light of their immortal researches on bitter-almond oil and on uric acid.
In 1832 bitter-almond oil was supposed to be to bitter almonds what a hundred and one other essential oils are to their vegetable sources. Of its chemistry nothing was known except the fact that it contains loosely combined prussic acid, and that, when kept for a long time, it is liable to deposit a crystalline solid, as various other essential oils do. Liebig and WT6hler, being struck by the absence from even powdered bitter almonds of the intense smell characteristic of the oil, set about tracing the latter to its origin, and soon solved the question. In 1830 Robiquet and Boutron-Charlard had succeeded in extracting from bitter almonds a crystal-line nitrogenous solid, soluble without decomposition in alcohol and in water, which they called amygdaline. What Liebig and Wohler found was that, when bitter-almond meal is mashed up with water, this amygdaline, by the action of the water and a ferment (common to both sweet and bitter almonds), breaks up into sugar, prussic acid, and bitter-almond oil. They also succeeded in separating the prussic acid from the distilled oil, and found the thus purified oil to be a non-poisonous liquid of the composition C7H60. This liquid, when exposed to the air, readily takes up oxygen and assumes the form of a solid, which is identical at the same time with the quasi-stearopteue of the oil and with Scheele's benzoic acid, C7HB02. When treated with chlorine, the purified oil yields a chloride, C7H50.C1,—the chlorine of which, by treatment with the respective potassium compounds, is displaced by its equivalent in bromine, iodine, sulphur, cyanogen, and, on treat-ment with ammonia, by the group NH2. Water converts it into hydrochloric and benzoic acids. In all these reactions the group C7H50 holds together; it moves forwards and backwards as if it were a compound element,—a common-place enough fact in the eyes of the chemical student of 1882, but a most wonderful revelation to the chemist of 1832. Berzelius, who certainly was not much given to dealing in superlatives, greeted the discovery in his Jahresbericht as opening up a new era in organic chemistry, and, rejecting the prosaic name of benzoyl which Wohler and Liebig had given to their radical, proposed to name it proine, from wpai, early in the day, or orthrine, from tipOpos, the dawn.
Equally important in a scientific sense, but greater as a piece of experimental work, was their joint research on URIC ACID (q.v.). After their uric acid research the ways of Wohler and Liebig

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 narcotine (which was carried out in his laboratory, partly by -himself partly by Blyth, and published in 1848) is alone sufficient to prove.
Amongst Wohler'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 he 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 Wohler found was that this chloride, when heated with potassium or sodium, readily gives up its chlorine and assumes the elementary form. The aluminium which Wohler thus obtained was a grey powder ; but in 1845 he succeeded in producing the metal in the shape of well-fused, fully metallic globules. Wohler, on this second occasion, correctly ascertained all the properties wdiich 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 Wohler taught us how to prepare real titanium and really pure titanic acid.
In 1854 Dcville'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 Wohler, 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, SiH4, which body Wohler subsequently, with the co-operation of Martius, obtained in a state of greater purity. Wohler 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 Wohler, 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 f IT 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 Wohler 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 Wohler, and all, as well as the fifth or sixth, would find themselves in the right place. That Wohler in these circumstances was able to do much literary work is truly marvellous. His Grundriss der 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 Practische Uebungen in der cheinischen Analyse (entitled in the second edition Mineral-Analyse in Bei-spielen), 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 Lehrbuch der Chemie, and of all the successive volumes of Berzelius's Jahresberieht, which only thus became really available to the scientific world at large. From 1838, too, Wohler was one of the editors of Liebig's Annalen.
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 Wohler by Hofmann is published in the Berichte
der deulschen chemischen GeseHscfia/t for 1882. (W. D.)

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