Popular Science Monthly/Volume 24/April 1884/Sketch of August Wilhelm Hofmann
THE recent visit of this distinguished scholar and chemist to our city is worthy of more than a passing notice, and we would commemorate it in a feeble manner by placing before our readers a sketch and portrait of the man who has contributed so much to the advancement of science and of human progress.
August Wilhelm Hofmann was born in Giessen, April 8, 1818. After completing the usual gymnasium course, he entered the University of Giessen at the age of eighteen. Having acquired a taste for the modern languages during his travels in Italy and France, he at first took up the study of philology, to which he devoted himself assiduously for several years. To this we may undoubtedly attribute much of his power as a writer and speaker. At this time his father, who was an architect, was engaged on the plans for Liebig's new laboratory, and thus young Hofmann became acquainted with that famous chemist. His influence turned the whole course of Hofmann's life, for he at once took up the study of chemistry, and we next hear of him as the assistant of Liebig. He remained in this position until the spring of 1845, when he was appointed professor in Bonn, but he was not destined to remain long upon the Rhine, for, in the latter part of the same year, he was called to London and placed in charge of the newly established Royal College of Chemistry. Through the exertions of Professor Hofmann, and his popularity as a lecturer and teacher, this school soon acquired such a prominence that, in 1853, the Government united it with the Royal School of Mines. It was during this time that he made several of those important researches which have resulted in discoveries of the greatest importance. In addition to his other labors, he found time to deliver courses of lectures to working-men, which were well attended, and to investigate various technical and sanitary questions upon which his opinion was sought. His success in solving difficult expert problems soon won for him an influential position in England. In 1856 he was appointed Warden of the English Mint, which position he continued to hold until he left England. He was made a fellow of the Royal Society in 1861, and ten years later was nominated President of the London Chemical Society. He served on the jury in the International Exhibitions held in London in 1851 and 1862. Among the important investigations of public interest was a chemical examination of the waters of London, and, with Professor Graham, an investigation of the bitter ales at a time when the brewers were suspected of using strychnine as an adulterant.
His early philological studies enabled him rapidly to master the intricacies of the English language, so that he became a fluent speaker and a correct writer in our tongue. Several of his works have appeared in English first, and subsequently been translated into German.
His reputation as one of the most successful teachers of chemistry of the present day brought him many offers from German governments, for at that time he stood almost alone as a teacher of organic chemistry according to modern ideas. In 1862 he was called to Bonn, where he undertook the building of a fine chemical laboratory, but he was not permitted to finish his undertaking, for in 1803 he was appointed the successor to Mitscherlich at the Frederick William University in Berlin.
His first work in Berlin likewise consisted in the planning, erecting, and equipping of a new chemical laboratory, which was opened in 1868. It consists of a substantial brick edifice, built in the form of a hollow square, in the center of which is a large, airy, and well-lighted lecture-room, capable of seating about two hundred students. Two large courts, one on each side of the lecture-room, afford abundant light to the various work-rooms, laboratories, and smaller lecture-rooms. The entire structure occupies a lot of ground one hundred and forty by one hundred and sixty-five feet on Georgen Strasse, with an extension seventy feet wide running through to the Dorothean Strasse. On the latter are the library and residence of the professor. The situation is a central one, near the principal station of the elevated railroad (Stadtbahn), and but five minutes' walk from the university building on Unter den Linden.
Professor Hofmann's lectures are illustrated by very elaborate experiments, and the fundamental laws of the science are demonstrated by means of apparatus devised by himself for this special purpose. No other living chemist, Bunsen perhaps excepted, has invented so many new and useful forms of lecture apparatus as Hofmann. Besides his earlier papers on this subject, a season rarely passes, even now, without some new contribution to this kind of literature from his fertile pen. His lectures are so interesting, his manner so animated, that his lecture-room is thronged with students from all parts of the globe.
Soon after his removal to Berlin, Professor Hofmann founded the German Chemical Society, of which he has several times been president, and the growth of which has been largely due to his efforts. Although German in name and in language, it numbers among its twenty-seven hundred members persons of every nation where chemistry is cultivated, and its proceedings are the chief means of communication between a large portion of the chemists of this and other countries. The number of original papers published by it is larger than that of the English, French, and American chemical societies combined.
Although Hofmann excels as a lecturer and teacher, his reputation rests chiefly on his valuable and numerous contributions to the science of organic chemistry, foremost among which are his investigations on the coal-tar colors.
He first began the study of the bases in coal-tar under the direction of Liebig, and in 1843 we find him publishing his first original paper on this subject. One of these bases, then known as "cyanol," attracted his special attention, and by working over half a ton of coal-tar he succeeded in obtaining this rare base in sufficient quantity to investigate its properties, which he found to be the same as those of "benzidam." Further investigation also enabled him to prove that "aniline," the name then given to a substance that had only been obtained from indigo by distillation, was identical with both cyanol and benzidam. Here, then, were three sources for obtaining this rare material. Evidently there could not be much of it in coal-tar, when only three pounds could be separated from half a ton of tar indigo, too, was an expensive source; hence it was a fortunate circumstance that Zinin had discovered another method of making it, and that too from a far more abundant constituent of coal-tar, namely, benzol; it is from that all the aniline of the present day is prepared.
Hofmann, it is said, noticed that aniline gave rise, under certain conditions, to the production of a red color, but he failed to publish the fact, and to Perkin belongs the credit of having discovered the first aniline dye mauvine. This took place in 1856, and two years later Hofmann discovered a red dye, then called Hofmann's red, which was formed by the action of chloride of carbon upon aniline. Aniline was beginning to attract the attention of manufacturers as well as of chemists, and many different methods were devised for making what seemed to be the same substance, a fine red dye variously known as magenta, solferino, fuchsine, and aniline red. Hofmann undertook a careful investigation of the dye, which resulted in his discovery of the surprising fact that the red dye was in reality the salt of an organic base, like an alkaloid, and that this base, to which he gave the name of "rosaniline," was colorless. From this base he prepared another which he called "leucaniline" by reducing it with zinc. Turning his attention to the blues, greens, and purples, he found them to be derivatives from this same base, but of more complex construction. The importance of these investigations can scarcely be overestimated. The production of dyes from aniline was no longer a matter of blind experimentation; empirical methods gave place to scientific ones, and the process of making dyes has gone on to the present day nearly in the same direction. One of the earliest practical results of this discovery was the invention of a series of most beautiful purples which still bear the name of Hofmann. Like Leverrier's discovery of Neptune, their elements had been calculated beforehand, their existence foretold, and they needed only to be made.
Before taking up the investigation of the aniline dyes, Hofmann had been engaged in a line of research, which, though apparently of mere theoretical interest, had especially fitted him for this work, namely, the study of organic ammonias, or amines. In 1849-'50 Hofmann made the discovery that when ammonia was acted upon by certain alcoholic iodides, such as methyl iodide, one, two, or three of the hydrogen-atoms of the ammonia could be replaced by the alcoholic radical. In this way he prepared trimethylamine, a substance which he subsequently found to exist ready formed in herring-pickle, and from which it is still obtained for medicinal purposes. For his investigations on the molecular constitution of the organic bases, he was awarded the Royal Medal in 1854, and in 1887 he received the great prize of the World's Fair at Paris.
Engaged in studies of this sort, the resemblances between aniline oil and ordinary ammonia, and more especially between their respective salts, could not escape his notice. Each contains one atom of nitrogen; the substitution of a certain group of atoms known as the phenyl group for one of hydrogen will convert ammonia into aniline. In the more complex molecule of rosaniline, with its three atoms of nitrogen, he naturally sought for a triple ammonia, but he found the phenyl group alone incompetent to form this base, which led to his discovery of the very important fact that no dyes can be made from pure aniline, an admixture of its homologue, toluidine, being essential to the production of the rosaniline and its derivatives.
Organic bases, containing other elements than nitrogen, have also attracted his attention, and through his labors much has been added to our knowledge of the "phosphines," phosphonium, etc.
Another class of subjects, to which Hofmann has devoted much attention, includes the mustard-oils, both natural and artificial, and the sulpho-cyanides of organic bodies. These researches have resulted in the artificial production or synthesis of many pungent oils and ethers. He has also fearlessly attacked the cyanides themselves, and succeeded in producing some new organic compounds that fairly rival Bunsen's well-known cacodyle in their repulsive odors.
Among the analytical processes introduced by Dr. Hofmann are several of importance, including the separations of arsenic from antimony, and of copper from cadmium, and the detection and estimation of carbon disulphide. Hofmann's method of determining the specific gravity of vapors is as remarkable for its simplicity as for its accuracy.
Although a fertile writer, Professor Hofmann is not given to writing books. He has, however, contributed a great many original papers to various chemical journals, of which the "Journal of the London Chemical Society" contains more than ninety, and nearly two hundred more are to be found in the "Berichte" of the Berlin Chemical Society. He was for a time one of the editors of Fowne's "Manual of Chemistry," and since 1874 has also been one of the editors of the "Annalen der Chemie und Pharmacie," established by Liebig.
A portion of the course of lectures upon inorganic chemistry, which he had delivered so acceptably before the Royal College of Chemistry in London, was published in book form in 1866, under the title of "Lectures on Chemistry." It was soon after translated into German, and has passed through several editions under the more appropriate title of an "Introduction to Modern Chemistry." We know of no other book in any language on this trite subject that exhibits so much originality of treatment, or that is more pleasing in style, convincing in its demonstrations, and logical in method. Taken in connection with the ingenious apparatus therein described, it has had avery beneficial effect upon the methods of teaching chemistry.
The substance of his lectures upon organic chemistry was published in 1872 by one of his former assistants, Dr. A. Pinner, and during the past year it has been translated into English by Professor P. T. Austen, one of his American pupils.
Hofmann's "Life-Work of Liebig" is a worthy monument to the great chemist; while his biography of the great French chemist, Jean Baptiste Andre Dumas, in the "Nature" series of scientific worthies, is a charming specimen of English composition. His memorials of deceased scientists are worthy of more than passing mention. Among those whose memories have been perpetuated by his pen are Thomas Graham, Gustav Magnus, and last of all Friedrich Wohler.
Several of his addresses delivered upon special occasions have been published, among which are two academical orations delivered recently in Berlin, which have appeared under the title of "Chemische Erinnerungen aus der Berliner Vergangenheit." His inaugural address upon assuming the rectorship of the Berlin University has provoked some discussion, owing to the position taken in regard to classical studies, and has already been referred to in our pages. His largest and most important work is his "Report on the Development of Chemical Industries," which first appeared in 1875-'76.