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Henri Moissan
(28 Sep 1852 - 20 Feb 1907)
French chemist who was awarded 1906 Nobel Prize for Chemistry for the isolation of fluorine. He also invented an electric arc furnace which made possible experimenting with reactions at much higher temperatures than had been possible before.
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Henri Moissan - Obituary
By George Fredereck Kunz
A paper read by title at the Eleventh general Meeting of the
American Electrochemical Society, in Philadelphia, Pa., May 4, 1907;
President Carl Hering in the chair.
[p.232] The untimely death of Henri Moissan has removed from the world one of the most brilliant and distinguished scientific investigators of our time. Whether regarded as a student of pure science, or as a discoverer and promoter of important practical applications, no man has exceeded him, and very few have even approached him, in the lifetime of the present generation. His [p.234] departure at the early age of fifty-five, in the very fulness of his powers, is an irreparable loss to science everywhere and peculiarly to science in France. It seems remarkable in this respect that the only other men who had attained to any similar prominence in the same domain of chemistry and physics, Dr. Pierre Curie and more recently the great Berthelot should have likewise died in the midst of their activity, within less than a year past. The whole scientific world can but join in sympathy with France, both in her grief at the loss of Moissan, and in the pride that she justly feels in one who shed such glory upon his country, whose name will be recognized in all coming time as ranking among those who have made great and permanent discoveries in the realm of chemistry and physics, and have also given to mankind practical applications of the highest importance.
It is difficult, within the limits of a brief obituary, to give adequate expression to the variety, the novelty, and the importance of the researches and discoveries of Dr. Moissan. He had found and developed fields of research that were peculiarly his own; and in those fields he vastly enlarged the scope of human knowledge, while incidentally he gave to the world results of immense economic and industrial value. The whole department of electrochemistry, with its apparently unlimited applications, had in him its pioneer explorer and its triumphant expounder. His whole magnificent scientific career was achieved within the brief limit of about twenty-five years, and we cannot but wonder what further triumphs he might have won, had his life been spared to the ordinary bounds, and lament with deepest sorrow the sudden termination of a course so fruitful already in results and still so full of promise and possibility.
Prof. Moissan was born September 28, 1852, in the city of Paris, where his whole life was spent and his whole work achieved. His scientific education was chiefly in the Musée de 1' Histoire Naturelle of that city. Here, in 1872, at the age of twenty, he entered the laboratory of Frémy, and followed up his chemical studies under such masters as Deville, Debray, Berthelot and St. Claire Deville. “His early training,” says Prof. R. S. Hutton, in an obituary notice of Moissan, “firmly fixed the direction of his life's work, for it is precisely along the lines so ably developed by this brilliant school of French chemists, that [p.235] Moissan's genius and resource in experimentation were applied. Worthily to have upheld the traditions and high quality of this school required powers of no mean order.”1
In the very next year, 1873, be became an assistant in the laboratory of Decaisne and Dehérain, in the same great Academie. Here his studies were directed toward vegetable chemistry, and his first formal contribution to science, published in 1874, was a joint study with M. Dehérain upon the action of plants in the dark, in absorbing oxygen and giving out carbon dioxide. But the bent of his mind was more toward inorganic chemistry, and he ere long withdrew from this association and established a laboratory of his own, where he began some of his most important investigations. He subsequently entered into connection with the laboratory of Debray and Troost, where he continued his researches until, in 1879, be was appointed instructor and demonstrator in the laboratory of the École superieure de Pharmacie. In 1887, after his great success in isolating fluorine, he was made professor of toxicology in the same institution, and later was transferred to the chair of mineralogical chemistry.
All these earlier years were full of scientific activity. In 1877 he began investigations upon the salts of chromium, which, in the words of Becquerel, “signalized him as an able experimenter.” These, extended into a series of valuable papers upon the oxides of iron, manganese, nickel and chromium, were presented in 1880 as his thesis for the degree of Doctor in Science. He had already begun his investigations in regard to the electric furnace, and was also engaged in the effort to achieve the isolation of fluorine. Prof. Becquerel, speaking on the death of Moissan before the French Academy of Sciences, depicts vividly this remarkable quest, carried on through years, for the “unattainable body which had eluded his predecessors and his masters.” He conducted the siege systematically, and each unsuccessful endeavor brought him nearer to his object, until the day when, in an electrolysis of hydrofluoric acid, which was accidentally impure, a gas appeared at the positive pole—and this was fluorine! A powerful current was employed, at a low temperature (—23º C), and the impurity which determined the fortunate success was a small amount of potassium bi-fluoride, which had been added to [p.236] the anhydrous acid. He had previously made many skilful efforts to separate fluorine from its combinations with silicon, boron and arsenic; but now at last he had reached a result which Prof. Hutton calls “one of the greatest achievements of chemistry in the nineteenth century.” The first notice of the experiment was made to the Academy of Sciences on June 28, 1886, and fuller details were presented a few weeks later. On November 8th, Prof. Debray announced to the Academy the complete acceptance of Moissan's results by the section of chemistry.
The demonstration was now given, for the first time, of the reality and the properties of this previously theoretical element, and of the exact composition of hydrofluoric acid, and its precise correspondence to the other halogen acids. These results and experiments led him to further studies of fluorine compounds and to the discovery and preparation of a number of new ones. From these he naturally passed to the study of other binary compounds, especially those of boron, silicon and carbon, in which he afterwards attained results that were scarcely less important and novel.
“This great triumph in the isolation of fluorine at once made Moissan famous in the world of chemistry, and won for him the Lacaze prize from the French Academy, and the professorship of toxicology in the École de Pharmacie. Twenty years later, in the last year of his life, a medal was given him by students and friends in commemoration of this early achievement, and he received also the great Nobel prize, which was largely due to this discovery, though it also recognized his later work in many forms.
As Prof. Moissan's interest inclined chiefly toward the study of the elements and their inorganic compounds, toxicology was evidently not to be his best field of activity. So in 1889 he was transferred to the chair of mineralogical chemistry in the École de Pharmacie. Here he remained for a number of years, and carried out much of his finest and most conspicuous work. In 1897 he lectured upon fluorine at the Royal Institution in London, and on the following day, in conjunction with Sir James Dewar, he accomplished the liquefaction of fluorine in the laboratory of that institution. His extended researches upon this notable element and its combinations were published in 1900, in a volume entitled “Le Fluor et ses Composés.”
[p.237] In the same year he was appointed professor of general chemistry in the Sorbonne, and speedily became Director of the Institute of Applied Chemistry.
It is largely, however, to his remarkable work upon carbon and the carbides, and his triumphs with the electric furnace, that Prof. Moissan's fame is due with the general public. Very interesting it is to trace the connection between these and his earlier studies. His peculiar interest in the elements and their problems has already been mentioned, and after his great success with fluorine, and indeed before, his mind was powerfully drawn toward the mystery of the diamond and its origin—the problem of the crystallization of carbon. With this object in view, he sought to reach some results from combinations of carbon with fluorine, and succeeded in producing two gaseous compounds of those elements, but their decomposition set free the carbon only in the amorphous form. He was thus led to extended studies upon the three modifications of carbon, the conditions of their formation, and their possible production from one another. This investigation was in itself of great value in adding largely to the knowledge of these varieties of carbon and their relations and metamorphoses. Gradually he came to recognize the fact that the crystallization of carbon as diamond, the hard and heavy form, instead of graphite, the soft and less dense variety, must be dependent upon great pressure. He was now on the road that led him to the actual production of diamonds.
The problem before him thus became that of causing carbon to solidify under great compression. The only way seemed to lie in the direction of the solubility of carbon in fused metals, and for this very high temperatures were necessary. He had long been much interested in the electric furnace and its possibilities, and conducted a host of experiments with it and obtained important results. Among these were especially the carbides of many metals, formed at the enormous temperatures attainable by the electric furnace. The solubility of carbon in molten iron had long been known, but whenever it separated out in cooling it took the form of graphite. If the solidification could be made under extreme pressure, he reasoned, diamond carbon should be obtained. Here was the key to the long-sought mystery. Availing himself of the well-known property of iron, of expanding in [p.238] solidification (like water), he melted iron in a crucible in the electric furnace, at a temperature of 4000°, introduced pure carbon in the form of sugar charcoal, and when it was freely dissolved, removed the crucible and quickly immersed it in cold water. The exterior of the mass of course solidified at once, leaving the interior portion confined and unable to expand, so that it was forced to solidify under enormous pressure. The result followed as he had expected, part of the carbon being found to have crystallized in the form of minute diamonds.
This was the great success, achieved in 1893, which interested the whole world and made the name of Moissan familiar to multitudes who had known little of his previous scientific researches. He had produced real diamonds by an artificial process. They were minute, indeed, and could only be obtained by dissolving the enclosing mass of iron with powerful acids, but they were true diamond crystals. The value of the experiment was theoretical only, for the cost of producing them was very great, and their size too small for any practical use. But the discovery was one of extreme interest in itself, and was a remarkable example of a scientific study carried on through years, with great skill and indomitable perseverance, to the attainment of a desired end.
Three years later, in 1896, Prof. Moissan visited the United States, and repeated these experiments in several brilliant lectures. One of these was given in New York, before a joint meeting of the American Chemical Society, the Academy of Sciences, the American Institute of Electrical Engineers, and the College of Pharmacy. It was a remarkable occasion in every way. Dr. Charles A. Doremus thus describes one of the principal incidents: “As he removed the glowing crucible from within the furnace and plunged it into a mass of water, some of his audience, all scientists, involuntarily moved, as if expecting an explosion. ‘Have no fear,’ said he, ‘I have performed this experiment without accident, over 300 times.’” Of course, it was possible on such an occasion to show the process only, not the results, as the mass of iron must have time to cool completely, and then must be slowly dissolved in the strongest acids, before any diamonds present could be found and tested, but it was very striking to witness the calm confidence of Prof. Moissan in the success [p.239] which he had so often proved. Laying his hand upon the non-conducting cover of the crucible, he referred again to his oft-repeated experiments, and remarked, “I know that this regulus contains diamonds, for I have never had a failure.” To one who looked on that commanding figure and noble countenance, it seemed that Moissan might well have been made the subject of a picture, representing “The Triumphant Chemist,” as a counterpart to the one known as “The Doubtful Alchemist.” The two would illustrate impressively the contrast between modern science, with its clearness and precision, and the indefinite groping of the early period of chemistry.
The studies and experiments that preceded this remarkable achievement had taken a very wide range and led him into some peculiar fields. His researches on the three varieties of carbon have already been mentioned, but in addition to these he had laboriously investigated all the occurrences and associations of diamonds in nature, and, in particular, the presence of carbon in meteorites. The discovery of diamond carbon in the great iron meteorite of Cañon Diablo, which was made by Foote and Koenig in this country in 1891, and verified by Moissan himself and by others abroad, is thought to have had special influence in giving him the conception of the combined agency of great heat and great pressure in the production of diamonds. His examination of the ash of diamonds, and also of the minerals associated with the diamonds of South Africa, impressed him further with the frequent presence of iron in connection with them, and led him on in the line of his endeavors. Nor did the researches cease when he had achieved success; he kept them up year after year, and one of his latest important papers, in 1904, was the record of an elaborate reexamination of the Cañon Diablo iron and its carbon and diamond inclusions.
But apart from these special researches, Moissan's general fame will always be connected with the electric furnace. His experiments with this wonderful appliance, though largely incidental to his diamond quest, led to many other results, among which are those that have proved most important in their practical bearing, apart from their scientific interest. His production of a whole body of new compounds, formed at temperatures never before attained, marks an epoch in the history of chemical science. These [p.240] are chiefly silicides, borides, and carbides of various metals, among which two have become especially prominent—the calcium and the silicon carbides. It is true that neither of these was strictly a new discovery by Moissan. Calcium carbide had been well known before, and its property of yielding acetylene gas upon contact with water, but it had been too expensive to be available for that purpose on any considerable scale. In 1892, however, Moissan proved that it could be easily and cheaply produced in the electric furnace, and thus made possible the important industry of acetylene lighting. In the year previous, he had noticed the accidental formation of a compound of carbon and silicon in some of his early experiments with the furnace, but he did not publish it or give it special attention until two years later (1893). By that time the same substance had been independently discovered in this country by Cowles and Acheson, and the latter had described it and given it the name of carborundum. Moissan has freely accorded to Acheson the credit of priority, but he has given much attention to the substance and its important properties, in later publications, especially in his great volume on the electric furnace and its products.2 This body, known as both silicon carbide and carbon silicide, is now manufactured on a large scale, and has great value as an abrasive, being harder than any substance previously known, except diamond itself. Eleven years afterward, in 1904, during his reexamination of the Cañon Diablo meteorite, Moissan discovered this identical substance in very small crystals, associated with the diamond carbon present in that iron. Being now found for the first time as a natural product, it became entitled to a scientific name, as a true mineral, and the writer took pleasure in proposing for it the name of Moissanite, in honor of his eminent friend, the discoverer.3
But beside these two, Prof. Moissan was the actual discoverer and producer of a number of metallic carbides before entirely unknown, some of which possess remarkable properties. After his visit to the United States in 1896, in recognition of many honors and courtesies extended to him here, he presented to the National Museum, at Washington, a full set of these new and most interesting products, sixteen in number, each with his [p.241] signature. These were secured largely through the friendly influence of the late Prof. R. Ogden Doremus, of New York, and are a permanent treasure of great interest.
In the following year Moissan published his most important work, Le Four Electrique, in which the instrument of his researches and all its products and applications were treated of systematically and fully.4 This was the great record of his lifework. “Here,” Prof. Hutton says, “his preeminent position is due, not to the design or discovery of a special form of furnace, but rather to the skill with which he investigated in detail a number of individual chemical reactions,” and also to the extreme care and accuracy with which all his work was conducted.
Since the opening of the new century Moissan had been gaining honors rapidly, while ever actively engaged in continuing and extending his researches. He had been the recipient of honors from scientific bodies in almost every land. In 1900 he was president of the International Congress of Chemists, held at Paris. In 1904, as already stated, he revisited America, and addressed the scientific convention at St. Louis by invitation of the Government. In 1906, he was awarded the great Nobel prize, his highest honor, and alas! his last.
The economic and industrial results of Prof. Moissan's studies and discoveries have been of the highest practical importance. His friend and co-laborer, Prof. Becquerel, in a most beautiful obituary address before the Académie des Sciences, dwells with great emphasis upon these aspects of his work. Moissan himself, while ever deeply interested in the practical side of his researches, and anxious to establish and enlarge the industries of his country, was not ambitious for rewards or distinctions as an economic scientist, and let this be known as his feeling. All his achievements were inspired by pure love for science, and he gave his results freely to the world, unrestricted by patents or personal limitations, for the use and the profit of others. In this respect, his character and spirit are a noble example of the highest type of scientific devotion. His great success was due to a remarkable combination of faculties—daring conception, fertile imagination, skilful manipulation and extreme accuracy in work, together with indefatigable patience and lofty aim. Prof. Becquerel closes his [p.242] obituary by quoting a beautiful and noble expression which he had employed: “We should always place our ideal so high that we never can attain it.” Such a combination of qualities enabled him to conceive and plan his work, to persevere in the face of countless obstacles, and to bring it to a triumphant issue, in fields that had never before been explored and that had seemed almost hopeless of attainment.
We can but lament that so brilliant a career has been cut short in the very midst of its achievements, after accomplishing so much in a brief quarter-century since the name of Henri Moissan first came into prominence. He died from an operation for appendicitis, in the fulness of his powers and his fame, but his work is immortal in the history of science, and his methods and his character should alike be an inspiration to those who survived and who succeed him.
Of late years, Prof. Moissan had undertaken, with the aid of a group of co-workers and assistants, the preparation of a general treatise upon mineralogical chemistry. Had he lived, this would have been the grand summing-up of all his studies and conclusions, past and prospective, and the fact that it has been interrupted is an irreparable loss to science. At the conference of chemists, held at St. Louis in connection with the Exposition of 1904, Prof. Moissan delivered an address by invitation of the United States. Government, which has since been published in Paris, and which was essentially the opening chapter of this great work.5 It is impossible to read this noble address without feeling that it is the product of a master mind. It begins with a broad and very clear outline of the growth of chemistry from the earliest times to its present position, by the successive labors and investigations of many men in many lands, and shows admirably the progress of thought and the widening of scope in the history of the science. His own experiments and results are next described, in their logical connections with each other and with the problems of chemistry during his lifetime; and then follows the extension of his thought and his forecast into the field of mineralogical chemistry proper, closing with a brief but very broad outlook as to the relations of chemistry with other fields of scientific investigation, especially in physiology and astronomy.
[p.243] Dr. Moissan's presentation of the development of his own remarkable body of researches and discoveries, as a chapter in the history of chemistry, is of great interest, and may well be briefly reviewed. After tracing the progress of the science, step by step, and its extension into various kindred fields, up to the latter part of the nineteenth century, he proceeds to the subject of thermochemistry—the relations of reactions to temperatures either very high or very low. The great importance of this subject had long been recognized, but the possibilities of experiment were limited. The highest temperatures attainable were those produced by the oxy-hydrogen blowpipe, first used in 1802 by Dr. Hare, of Philadelphia, and later followed up by Deville and Debray in France. But the limit of temperature thus obtained was 1800°—just high enough to admit freely the fusion of platinum, which takes place at 1775°—and was among the first notable results achieved by Hare.
In his desire to produce the crystallization of carbon in the form of diamond, the problem which had such special attraction for Moissan, he undertook minute and comprehensive studies of all the forms in which carbon is known to occur, and of the whole question of its solubility in fused metals. He began his experiments on this latter point with the oxy-hydrogen blowpipe, but found that not only were higher temperatures necessary, but also more exactness and uniformity of conditions. His results were uncertain and variable.
Attempts had repeatedly been made to utilize for both scientific and industrial purposes the much higher temperature of the electric arc, discovered by Davy about the same time with Hare's invention of the oxy-hydrogen blowpipe. But little practical success had attended these attempts, until the comparatively recent invention of the dynamo-electric machine, which opened a new era in the development of chemistry, by the transformation of the current into a source of continuous heat before unattainable.
Prof. Moissan omits any description of his own special type of furnace, passing at once to a general statement of the results which he obtained. The furnace itself is extremely simple, but many questions arose in its application, requiring new study and leading to new results. The temperature of the arc increases with the intensity of the current, and the limit attained, or [p.244] attainable, has never been exactly determined. In this respect, Moissan says, he was less fortunate than Dewar, who was able to fix definitely the lowest temperature reached, that of the solidification of hydrogen, at —252.5°, only 20.5° above the “absolute zero” of theoretical physics. All the conditions of the current—amperage, voltage, etc.—together with the size of the electrodes, the duration of the experiment, and every circumstance involved, had to be most carefully noted as factors. The volatilization of carbon, as determined by Violle, at 3500°, gives one definite point of temperature, up to and above which Moissan's experiments ranged widely.
His general summary of results is essentially as follows: Most of them are well known, but certain aspects are presented in a very striking manner. He found it possible to decompose readily many metallic oxides before considered irreducible, to dissociate a great number of other compounds, and to produce a whole series of entirely new combinations. In particular, he thus prepared the numerous body of carbides, borides and silicides, that will forever remain associated with his name. Many of these same bodies, moreover, though stable and well-defined compounds, he found to be dissociated again at still higher temperatures, the limits of their formation and destruction both lying within the range of his electric furnace. He was able to prove that the same general laws that regulate the decomposition of ordinary substances at lower degrees of heat prevail with these new compounds at temperatures in the vicinity of 3000° C. In the same way he found that in vaporizing mixtures of metals, such as copper and lead, lead and tin, and copper and tin, the same laws appear, between 2000° and 3000°, as when mixtures of liquids (such as water with alcohol, with ether, and with formic acid), are subjected to fractional distillation at ordinary temperatures. In short, he was enabled to show the unity and constancy of chemical law in the new realm that was thus opened to science, as compared with those already familiar. This result, which he mentions but briefly, though citing several illustrations, is itself of the highest interest, and surpasses in its scope any of his separate discoveries, however novel and valuable.
Prof. Moissan's remarks upon biological chemistry are again highly suggestive. He sums up briefly the body of little-known [p.245] facts regarding the presence of minute amounts of various metallic elements in many organic structures, both animal and vegetable, where they evidently serve some important functions as yet wholly or almost wholly unknown. In this direction, he recognizes a vast and untrodden field of research. In biology, mineral chemistry and organic chemistry meet. “In fact,” he says, “there is only one science of chemistry; all separation is artificial. As energy is one, chemistry is one.”
But mineral chemistry, in order to attain to its proper and possible development, must, he urges, be carried out with more exactness and minuteness in the matter of experiment and analysis, than it has heretofore generally received. “It must attain the precision . of physics.” He cites several striking examples in illustration of this point, and dwells upon it at some length.
The relations of chemistry to astronomy through the spectroscope are briefly alluded to, as showing the unity of chemical law to extend to the farthest visible limits of the universe. Its relations to mathematics, in stereo-chemistry, and the grouping of atoms in space in the molecule, are also touched upon, and some of its more obvious connections with geology, though Prof. Moissan speaks very generally and apparently with no special interest.
As to mineralogy, he says it must rest upon chemical analysis as its foundation, because the species is thus determined. This has been the general view, but there are broad fields of research in geological mineralogy, wherein not merely the composition, but the manner of origin, of mineral species must be considered, and their alterations and replacements under a variety of conditions as yet little investigated. Of these, there is no suggestion or apparent recognition. The artificial synthesis of minerals is referred to more than once, and its great interest fully appreciated. Prof. Moissan would go even farther, and have mineralogy to include not only natural substances, but the countless host of laboratory products. In this view, he is no doubt correct from a theoretical and philosophical standpoint, but how far it may be possible thus to extend the scope of mineralogy practically, is a matter of serious question.
But alas! the grand chemist is no more! How we long, in [p.246] reading this noble introduction, to see the great work itself, that he had planned arid outlined, but was not permitted to complete! It would have marked a new era in mineralogical chemistry, and opened to science a storehouse of treasures, to which he alone had the key.
His last, a posthumous paper on “A Property of Platinum Amalgam,”6 was read at the Academy of Sciences March 18, 1907, in which he states: “Pure mercury shaken with water, as is well known, forms no mixture with it, but an amalgam of mercury and platinum after being shaken for a few seconds with water forms a semi-solid mass, of the consistency of butter, and of about five times the volume of the original amalgam. This emulsion is stable, and exhibits no change after standing for a year; it resists the action of heat and of cold. Microscopic examination shows droplets of water disseminated through the mass, giving it a cellular appearance. Copper, silver and gold amalgams do not form emulsions with water. Platinum amalgam forms emulsions with other liquids also, such as sulphuric acid, solutions of ammonia, ammonium chloride, sodium chloride, glycerin, acetone, alcohol, ether, carbon tetrachloride, chloroform. All are stable. Emulsification is also produced when mercury is shaken with water to which a 10 per cent. solution of platinum chloride has been added.”
1 Nature, Feb. 28, 1907, pp. 419, 420.
2 Le Four Electrique, Paris, G. Steinheil, 1897, pp. 385, 8vo.
3 Am. Jour. Science, vol. XIX, May, 1905.
4 Le Four Electrique; Paris, G. Steinheil, 1897; pp. 385, 8vo.
5 La Chimie Minérale; ses relations avec les autres sciences; Paris, 1904; pp. 31, roy. oct.
6 Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. Vol. CXLIV, No. 11, March 18, 1907. Chemical News, April 3, 1907.
Henri Moissan, His Laboratory and His Work, Nature, Jan. 16, 1902. London Times, Feb. 20, 1907.
Henri Moissan, H. S. Hutton, Nature, Feb. 28, 1907.
Henri Moissan, Chemical News, March 1, 1907; March 8, 1907.
Henri Moissan, Scientific American, March 9, 1907.
Henri Moissan, Engineering Mining Journal.
Comptes Rendus de l'Académie de Sciences. Tome cxliv, No. 8 (Feb. 25, 1907). 4°. Paris, 1907, pp. 409-411. Henri Becquerel.
Berichte der Deutschen Chemischen Gesellschaft. 40th Jahrgang, No. 4 (March 9, 1907), 8°. Berlin, 1907, pp. 759-61. C. Graebe, President.
Bulletin de la Societé Chemique de France. 4 eme Série. Tome I-II, No. 6 (March 20. 1907), 8°. Paris, 1907, p. 242. Louis Bouveault, President.
Journal of the Society of Chemical Industry. Vol. xxvi, No. 5 (March 15, 1907). 8°. London, 1907. No name.
Journal of the American Chemical Society. Vol. xxix, No. 5 (May, 1907). 8°. Easton, Pa., pp. 51-52. Felix Lengfeld.
- Science Quotes by Henri Moissan.
- 28 Sep - short biography, births, deaths and events on date of Moissan's birth.
- Fluorine - Lecture by Henri Moissan in which he describes first-hand his work on fluorine to the Royal Institution (1897).
- Booklist for Fluorine.
