C. A. BROWNE U. S. Department of Agriculture, Washington, D. C .
"'tis delightful to transfuse yourself into the spirit of the ages past; to see how wise men thought in olden time." And when he reads the biographies of those "wise men," in which are described the ways in which knowledge was obtained, and in which the obstacles are shown which had to be conquered, he will learn to think humbly of himself and not overrate his own accomplishments.
The publication of this paper was delayed, pending the preparation of the jol!owing one on the life and works of Ernst Cohen. Dr. Browne's unfortunate dealh, while this was i n progress, led to the third paper, on his awn activity OA an historian of chemistry. The three papers are appropriately published here together. .
The passage quoted, with its stress upon the importance of a student forminz a ~ r i v a t elibrary that has a HE recent announcement of the tragic death of place for hooks dealing wiyh (he historical i n d cultural Dr. Ernst Cohen, professor emeritus of physical aspects of his science and with its emphasis on hioand inorganic chemistry a t the University of Utrecht, graphical values, is an index of Cohen's own proclivities. in a German concentration camp in 1944, brought grief He was a most assiduous collector of books, prints, and indignation to hundreds of his friends in all parts portraits, and bther memorabilia pertaining to the lives of chemists, not only of the most eminent but also of of the world. He was especially well known in the those little known. He possessed some twelve hundred United States. His impressions of our country, formed different portraits of chemists with which he decorated chiefly during his visit in 1926 at the Fiftieth Annithe walls of the laboratories, lecture rooms, offices, versary Meeting of the American Chemical Society, and hallways of the beautiful van't Hoff Laboratory when he was made one of its honorary members, were for Physical Chemistry of which he was director. He published in 1928 as a book with the title, "Impressions of the Land of Benjamin F~anklin."~Cohen's ad- hoped, by always surrounding his students with the dresses before our Society, his introductory lecture as faces of great chemists, that they would acquire a love the first incumbent of the nonresident lectureship in for the historical side of chemistry. He once admitted chemistry a t Cornell, and his numerous speaking en- to me that he had not been wholly successful in this, gagements a t Columbia and other universities made him and then inquired what results had followed the efforts personally known to hundreds of American chemists, of Professor Edgar Smith, whom he knew and greatly some of whom had not yet become familiar with his admired, to promote in America an interest in the history of chemistry. I told him that Professor Smith researches on allotropy and piezo-chemistry, the special when lecturing on this subject, could draw large aubranches of physical chemistry for which he is best diences, but it was the magnetism of his wonderful perknown. sonality more than in interest in the historical aspects American chemists are not so well acquainted, $ow- ' of chemistry that usually filled the room, and that since ever, with Cohen's contributions to the history of his passing the movement had languished considerably chemistry, yet i t was in this field, both as student and teacher, that he had a dominant interest. In his Cor- in America. Among other historic memorabilia Cohen had a fine nell address, when speaking of the desirability of a stucollection of the medallions of famous chemists, of dent forming a library, Cohen remarked: which he praised those by French craftsmen as supreme In this library he should find a place for books which treat of in artistic merit. He was especially interested in the the history of science, as well as for those which I should like cartoons and caricatures of chemists, and his collection to call the "belles lettres" of science. . . . Historical studies are part and parcel of a scientific education. Ernst Mach, with many of these was probably one of the most complete ever others, has not only drawn attention to this fact, hut, suiting assembled. The Dutch fondness for the realistic type the action to the word, has left us many an essay which bears of picture was shared by Cohen. He had upon the wall witness to the truth of this statement. The man who studies the of his library a framed copy of Gillray's famous caricahistory of science will get a better insight into the problems that ture of a pneumatic experiment, in which Dr. Thomas are nowadays a center of interest; nay, he will be convinced Garnett is shown administering laughing gas to Sir that: John Hippesley before a fashionable London audience. ' Presented before the Division of Chemical Education at the He ridiculed the prudishness of some museum directors 109th meeting of the American Chemical Society in Atlantic in concealing the essential feature of this highly Citv. ".Aoril. . 1946. humorous, although somewhat vulgar, cartoon. a The tiiles of Cohen's publications in Dutch are given in In my exchange of history of chemistry reprints with English translations.
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Dr. Cohen, I acquired some 50 of his contributions which comprise, however, only about two thirds of the total number of articles which he wrote in this field. These 50 copies constitute, however, a good representative sample sufficientlylarge to help us form a fair estimate of his work as a historian of chemistry. Cohen's interest in the history of chemistry, like that of Professor Edgar Smith, was largely biographic, for it was not so much upon the history of chemical theories as upon the lives of the men whe made discoveries in chemistry that his attention was chiefly focussed. And as Professor Smith interested himself first in Robert Hare and other Philadelphia chemists, secondly in chemists belonging to other parts of Amefica, and thirdly in chemists of foreign countries,
so Cohen devoted his attention chiefly to van't Hoff and other chemists associated with his own University of Utrecht, secondly to chemists belonging to other parts of the Netherlands, and thirdly to chemists of foreign countries. It is under these three divisions that we can discuss most conveniently the history-ofchemistry publications of Cohen. COHEN'S INTEREST IN THE HISTORY OF UTRECHT CHEMISTS
Uurvnnsrru
OF
UTRECHI
Foremost among the chemical masters whom Cohen delighted to honor was his old teacher, J. H. van't Hoff (1852-1911), under whom he had studied a t Utrecht. Of the 50 reprints of Cohen's historical articles that I possess, 15 are devoted to van't Hoff. These comprise (1) three obituary notices written immediately after van't Hoff's death in 1911, (2) several memorial and anniversary addresses, (3) various incidental sketches, such as "The account of van't Hoff's visit to the battlefield' of Sedan in 1870!" published as Number V in his popular Chemisch Weekblud series entitled Chemisch-Historische Aanteekeninga (i. e., Chemical Historical Notes), (4) comparative studies of van't Hoff's part in the development of. important chemical theories, such as his "Fifty Years in the History of a Chemical Theory" (in which the contributions of vau't Hoff and Le Be1 to the theory of chemistry in space are respectively described, and the personalities of these two chemists vividly pictured) and "A Halfcentury of Osmotic Pressure" (in which the work and personalities of van't Hoff, Arrhenius, Ostwald, and other contributors to the theory of electrolytic dissociation are described in the genialcosmopolit& manner so characteristic of everything that Cohen wrote).
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C m c n ~ m BY~ AN UNKNOWN ARTISTOP GRRRITMOLLAND JOHN DALTON
Another teacher who attracted Cohen's attentions was Gerrit Moll (1785-1838), Professor of Natural Philosophy a t Utrecht over a century ago. His tall frame, as contrasted with the low figure of John Dalton, was made the subject of an interesting cartoon that was acquired by Coben in the course of his activities as a collector. The print bore only the legend, "Scene Royal Institution. Dedicated, but not with permission, to the British Association for the Advancement of Science," with no indication as to the identity of the two persons represented. Cohen's paper, "A PhysicalChemical Caricature" (Utrecht, 1905), tells the story of how he proved them to be Moll and Dalton and determined the place of theirmeeting to be the Royal Institution of Edinburgh where the British Association met in September, 1834, a t which time the two scientists with other celebrities were presented with the freedom of the city. Another ~rofessor ~- Utrecht ~ ~ ~ whose career interested A Cohen was Gerardus J. Mulder (1802-SO), who is best
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known for his bitter controversy with Liebig regarding the chemical nature of protein, a word coined by Mulder to denote a wide class of nitrogenous plant and animal constituent, whose importance in nutrition he was among the earliest to recognize. Extracts from Mulder's highly resentful letters to him were included in a seven page pamphlet of Liebig's entitled, "Zur Characteristik des Herr Professor Mulder in Utrecht," which he seems a t first to have intended for publication in his Annulen, but afterwards withheld. Some recipients of the circular, however, had it bound in their Volume 62 of the Annalen contrary to Liebig's stipulation that this was not to be done. One volume with this inclusion came to the notice of Cohen who, because of the ignorance among chemists of its existence, republished i t with an introduction in German in Volume 57 (June 15, 1938) of the Recueil des Travaux Chimipues des Pays-Bas under the title, "Bride, die uns nicht erreichten. Blatter zur Biographie von G. J. Mulder." It was Cohen's intention after further research to publish a complete life of Mulder, who was the teacher of many noted chemists-among them the distinguished American agricultural chemist, John Pitkin Norton of Yale. Cohen told me, during my last visit with him in August, 1938, that no reliable biography of Mnlder had yet appeared. Mulder had written an autobiography but so much of it was romance that it contained b o r e Dichtung than Wahrheit. J. M. van Bemmelen's review of Mulder's work, he said, like many eulogies, was too much of a rhapsody. The late Professor J. W. Gunning, a pupil and afterwards colleague of Mulder, intended to write a biography of him and collected much material for such a work. Gunning made the unpleasant discovery, however, that Mulder seemed to have altered some o$ his laboratory results. He thereupon abandoned the project of writing Mulder's life and destroyed all his notes and papers. Cohen did not know the nature of the s u ~ ~ o s ealterations, d his only source of information beindibe testimony of ~unning's
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son. He stated that according to tradition, Mulder was of a quarrelsome nature, his disagreements with colleagues of the University of Utrecht causing him to resign his professorship in 1868. To the series of Cohen's sketches of Utrecht professors belongs also the one in German of the physiological chemist, Hartog Jakob Hamburger (1859-1924), published-in 1908 with tributes by other colleagues in the Hamburger Festband der Biochemischen Zeitschrift. We must pass over this contribution, however, in order to consider one of the most intimate of Cohen's chemical biographies, which is that of his pupil, the well-known colloid chemist, Hugo Rudolph Kruyt (1882-19%). This sketch, written in commemoration of the twenty-fifth anniversary of the conferring upon Kmyt of the degree of Doctor of Chemistry by the University of Utrecht, is a work of 47 pages, to which is added 22 more pages of a bibliography of Kruvt's ouhlications. Written in Cohen's ha~oiest , vein, this beautifully illustrated appreciation of' the life and work of his pupil, colleague, and friend will appeal especially to ali ~rnericanchemists who remember Kruyt's extensive lecturing trip in the United States in 1927, in which year he was also a guest of honor a t the "Fifth National Colloid Symposium" a t the University of Michigan on June 22-24 of that year. &
INTEREST
COHENS IN THE HISTORY OF OTHER NETHERLANDS CHEMISTS
Cohen's historical studies of chemists in other parts were also extensive. The One of of the these having his greatest interest was Herman Boerhaave (1668-17381, who was a graduate of the University of Leyden, which he served for 32 years as professor of medicine, chemistry, and botany. I have five publications of Cohen upon Boerhaave. The earliest of these is his well illustrated and very completely annotated address on the 250th anniversary of Boerhaave's birth, entitled, "Herman Boerhaave and His Significance for Chemistry," which was printed in 1918 in both Dutch and German. This contribution was followed 20 years later by another article entitled, "Recovered Manuscripts and Correspondence of Herman Boerhaave," published also in both Dutch and German. In my last visit with Cohen, he spoke of the discovery of these forgotten Boerhaave papers which had been carried to St. Petershurg by his nephew, Abraham Boerhaave, when he went to Russia in 1740 to become Court Physician of the Czar. Cohen mentioned that he had attempted to arrange for the purchase of this new Boerhaave material by the Dutch government, but was confronted with the difficulty that therewere no diplomatic relations a t the time between the Netherlands and the Soviet Republic. Shortly after my visit with Cohen he was successful in obtaining photographic copies of some of this Boerhaave correspondence, among which was a duplicate copy of a letter in the handwriting of Anton van Leeuwenhoek, which t h i ~famous Dutch naturalist had written to Boerhaave. Dsscription: photo-repro-
GEBARDUS J. MULDER(1802-1880). PROFESSOR OF CHEMISTRY AT THE
UNIVERSITY OF UTRECHT(1x40-1868)
duction, discussion, and German translation of this letter are given by Cohen in his article in the Proceedings of the Royal Netherlands Academy of Science for 1939 under the title, "Der vermisste Brief Antoni Leeuwenhoek an Herman Boerhaave vom 26 August 1717." Another famous scientist who corresponded with Boerhaave about the same time as Leeuwenhoek was Daniel Gabriel Fahrenheit, the inventor of the thermometer that bears his name. He was born in Danzig in 1686 and spent the last 12 years of his life in Holland, dying a t The Hague in 1736; his career naturally attracted the attention of Cohen who published a 37 page careful study of his life in The Proceedings of the Royal Netherlands Academy of Science for 1936. The letters of Fahrenheit to Boerhaave, 13 in number, were written from Amsterdam in 1718, 1719, 1720, and 1729 and formed a part of the previously mentioned papers that Boerhaave's nephew took with him to Russia in 1740. The late brilliant historian of chemistry, Max Speter, made the conjecture that these papers might still exist in Leningrad, and as a result of his appeal to the Russian historian of chemistry, Professor B. Menschutkin (1874-19--), the missing documents were found. Photographs of Fahrenheit's letters to Boerhaave made by Menschntkin were sent to Speter, who generously permitted Cohen to consult them. An
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idea of Cohen's extensive correspondence in preparing his life of Fahrenheit may be formed from the fact that he expresses acknowled~ments to no less than 16 emi. nent scholars. After investigating the disputed question of "Who was the first to burn a watch snrinrr in oxvrren!" Cohen concluded that the first to cond&'tGs experiment were Lichtenberg and Pickel of Germany, who, however, were only repeating a previous demonstration by the Dqtch physician and chemist, Jan Ingen-Housz (1730-99) in which an iron wire was used [Janus, 14,21 (1909)l. In various papers Cohen stressed the great influence upon chemistry in the Netherlands of Willard Gibbs' paper, "On the Equilibrium of Heterogeneous Substances," which was published in 1876 and 1878 in the little known Transactions of the Connecticut Academy of Arts and Sciences. The great significance of the paper, at first overlooked, was first grasped by van der Walls of Amsterdam under whose stimulus Bakhuis Roozeboom (1854-1907) took up the subject and with the cooperation of F. A. H. Schreinemaker (1864-19--) and others of his students, gave the phase rule of Gibbs its most extensive applications. Cohen has given a history of the movement in his paper on "The SemiCentenary of Willard Gibbs' Phase Law," 1876-1 926"
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(Science, December 24, 1926), and in his presentation of the Roozeboom Medal to Gustav Tammann on May 26, 1923 (Chemisch Weekblud, 1923, No. 21). COHEN'S INTEREST IN THE HISTORY OF SCIENCE OUTSIDE OF THE NETHERLANDS
In a general paper on "Chemistry and Physics in the Time of Rembrandt (1607-69)," Cohen sketched the influences of Bacon, Galileo, Pascal, Descartes, Guericke, Huygens, Newton, Leibnitz, and other scientists who were more or less contemporary with the artist, Rembrandt. In another contribution he adopted the opposite procedure of following the history of a single application of chemistry or physics through several generations of scientists. This was his paper, "From Boerhaave to Kammerling Onnes," in commemoration of the fortieth anniversary of Onnes' appointment to his professorship a t Leiden, in which the history of the artificial production of cold and the liquefaction of gases by experimenters in diierent countries is traced down to the year 1908 when Onnes liquefied helium and attained the nearest approach to absolute zero. In this paper, and in his discussion of the question, "Who first liquefied a gas?" (Zeeman, Verhndelingen, 1935, pp. 39-02), Cohen revealed his characteristic freedom from national, bias by showing that the first liquefaction of a gas was not accomplished with ammonia by van Marum (1750-1837) and Paets van Troostwijk (1752-1837) in the Netherlands, as some had supposed, hut by Monge (1746-1818) and Clouet (1751-1801) in France with sulfur dioxide. We must pass over, with a bare mention, the sketches, obituaries, and anniversary tributes with which Cohen honored the memories of Black; Pasteur, Chatelier, Haber, and other chemists who were not Netherlanders. Two of his popular Chemical-Historical Notes are devoted to Faraday. The first of these (Number 9 of the series), entitled "Honderd Jaren Benzol," relates to the centenarv , 11825-1925) of Faradav's discovem of benzol. The title might seem misleading for, of the 17 pages of this article, only four actually discuss Faraday's discovery. Cohen begins by quoting a few lines from Lord Byron, one of his favorite poets, as also of his teacher van't Hoff, and proceeds to take up each of these wonders that excited wide attention in the time of Byron and Faraday, taking as his text the lines: \
What varied wonders tempt us as they passThe cowpox, tractors, galvanism, and gas.
The word "tractors" gives rise to an interesting three page discussion of the metallic tractors of the American quack doctor, Elisha Perkins (whose metallic plates for the treatment of inflammations and other ailments became a great fad in the London of the early nineteenth century), and affords Cohen an opportunity of inserting a cartoon by Gillray on the subject. The word "gas" in the quotation from Byron introduces the subject of illuminating gas, a new art in Faraday's time; CARTOON anoM Punch b~ FARADAY AND FATHER THAMESand so Cohen, by gradual steps, finally amves a t the (REPRODUCED BY COHBN IW HIS "HONDRED JARBN BENZOL") "Bicarburet of Hydrogen" or benzol that Faraday first
JUNE. 1848
isolated and which later was produced in large quantities as a byproduct of gas manufacture. Cohen's second paper on Faraday (Number 13 of the ChemiceE Historicel Notes), entitled "Faraday's Investigations of Table-turning," is of the same discursive character as the one on benzol. The reproductions of Faraday's original exposes of table-tipping in letters to the Lon& Times of June 30 and to the Athenaeum of July 2, 1853, are followed by a poetical discussion of Faraday's report by Punch, a digression on the crystal-gazing of Dr. John Dee, and a passage from a letter of the poetess, Elizabeth Barett Browning, who continued to believe in the delusions exposed by Faraday. These discursive rambles of Cohen in some of his more popular papers reveal a wide acquaintance and appreciation of the literature of foreign countries and are not to be condemned in a class of contributions which he intended to be as much diversional as scientific. Cohen was fond of tracing a chemical operation or experiment back to its original discoverer, as has been indicated by his papers on "Who 6rst burned a watch spring in oxygen?" and "Who first liquefied a gas?" Another example of this "information' please" kind of title was paper No. 14 of his Chemical-Historical Notes on "Who first made use of the floating equilibrium method for determining the specific gravity of solid substances?" Cohen gives the credit for thls to the Scotch chemist, Thomas Thomson (1773-1852), who determined the specific gravity of ice a t 32' F. by diluting alcohol with water until a mass of solid ice put into i t remained in any part of the liquid without sinking or rising. The specific gravity of the liquid, 0.92, was of course that of the ice. A sprightly spirit of good nature permeates all of Cohen's historical papers, especially those of a reminiscent character such, for example, as his article written to commemorate the twenty-fifth anniversary of the founding of the Netherlands Chemical Society in 1903 (No. 11 of his Chemical-Historical Notes) and his address, "Fifty Years of Revolution," on retiring, May 26, 1939, at the age of seventy from his professorship a t Utrecht. Next to the historical papers in his native language, Cohen published chiefly in German. Of the 50 reprints of his history of chemistry publications in my collection 27 are in Dutch, 21 in German, and two in English. Many of the German papers were simply
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his translations cf the Dutch originals. Cohen's extensive list of physical-chemical papers were nearly all published in German, Dutch being too unfamiliar for the scientific readers of other countries. The present sketch of Cohen's contributions to t h ~ history of chemistry is far from complete. It is hoped, however, that enough has been mentioned to indicate his great interest in this field. He was an ideal connoisseur of what he once so aptly called the "belleslettres of science." His passing was a great loss not only to science but to the humanities. He was a firm believer in the brotherhood of the scientific men of all nations and, after the first World War, did his utmost to reestablish friendly relations between scientists of the recently hostile nations. This was recognized in the dedication to him in 1927 of the Cohen "Festband" of Volume 130 of the Zeitschrift fiir Physikalisch~ Chemie," which is translated as follows: Dedicated by his friends and pupils to Ernst Cohen, successful investigator, and tireless champion for the reestablishment of friendly relations between the scientists of the peoples that were separated by war, on the twenty-fifthanniversary of his appointment as Professor at the University of Utrecht.
It was the cruel irony of fate that the journal which honored Cohen with so deserving a tribute, was published in the country whose later policy of inhuman persecution was responsible for the death of this peaceloving man of science.
