Popular Science Monthly/Volume 19/August 1881/Sketch of Robert Wilhelm Bunsen
IT has been given to few scientific investigators to be more closely identified through their discoveries with the practical progress of the world, to see the fruits of their researches taken up and applied, made appreciable and beneficial in a greater diversity of lines, than to Robert Wilhlem Bunsen.
Professor Bunsen was born in Göttingen, March 31, 1811. His father was Professor of Theology, and of the Oriental Languages and Literature, in the University of Göttingen. Having passed through the course of the gymnasium, he entered the university, devoted himself to the study of chemistry and physics, and was graduated as a Doctor of Philosophy in 1830, publishing as his inaugural dissertation, "Enumeratio ac Descriptio Hygrometorum," or, "Enumeration and Description of Hygrometers." He afterward studied in London, Paris, and Vienna, and became, in 1833, tutor at the University of Göttingen; in 1836 he was appointed Professor of Chemistry at the Polytechnic school in Cassel; took the corresponding chair at the University of Marburg in 1838, and remained there thirteen years; then went, in 1851, to Breslau, where he planned a famous working laboratory; and in the next year went to Heidelberg, where he has for thirty years added to the fame of the great university.
His works in his chosen field have been numerous; their value, whether they are measured in relation to the advance of theoretical science, or as factors in the perfection of the operations of practical art, has been very great.
In 1834, in conjunction with Berthold, he published a research upon hydrated peroxide of iron as an antidote to arsenical poison, introducing a remedy which, having become universally known and universally accessible, may be regarded as a positive addition to the security of human life against a certain class of dangers.
He next, in 1835, described some singular compounds which the double cyanides form with ammonia, and the crystals of many of the double cyanides. In 1837 he began a series of investigations of the liquid called Cadet's fuming arsenical liquid—the product of heating a mixture of acetate of potash and white arsenic, discovered in 1760—and brought out the radicle cacodyl, the first of a series of organometallic compounds which exhibit striking analogies with the metals. These bodies are unpleasant in every way, extremely poisonous, dangerously explosive, highly inflammable, and often, like cacodyl, insufferably offensive in odor. "It is difficult enough nowadays," says Professor Roscoe, in "Nature," "for a chemist to work with such substances, armed as he is with a knowledge of the danger which he has to encounter, as also with improved appliances of every kind to assist him in overcoming his difficulties. But Bunsen, forty years ago, was a traveler in an unknown and treacherous land, without sign-posts to guide him, or more assistance on his journey than was furnished by his own scientific acumen and his unfaltering determination. Nor did he escape scot-free from such a labor, for, in analyzing the cyanide of cacodyl, the combustion-tube exploded, Bunsen lost the sight of an eye, and for weeks lay between life and death, owing to the combined effects of the explosion and the poisonous nature of the vapor. 'This substance,' he writes, 'is extraordinarily poisonous, and for this reason its preparation and purification can only be carried on in the open air; indeed, under these circumstances, it is necessary for the operator to breathe through a long open tube so as to insure the inspiration of air free from impregnation with any trace of the vapor of this very volatile compound. If only a few grains of this substance be allowed to evaporate in a room at the ordinary temperature, the effect upon any one inspiring the air is that of sudden giddiness and insensibility, amounting to complete unconsciousness.'"
His next research, published in 1838, was into the chemical changes which occur in the blast-furnace. In it he showed that at least forty-two per cent, of the heat evolved from the fuel employed in the furnace was lost, and pointed out that a great economy might be effected by collecting the combustible gases which escaped, and saving them for subsequent use. The investigation led to the introduction of improved methods by which the waste gases were utilized, and the cost of the manufacture of iron was cheapened. The experiments made in this research were the first in which an accurate method of gas-analysis was employed, and entitle Bunsen to the credit of having introduced new and valuable processes in that line to chemistry.
In 1841 he invented the Bunsen battery, an apparatus which has come into general use as a scientific instrument, and in telegraphy. Its chief peculiarity is the substitution of carbon for copper or platinum as the negative pole.
He visited Iceland in 1846-'47, and devoted special attention to the study of the volcanic phenomena of the island, particularly of the geysers. The memoirs which he published on the subjects of these studies contain the analyses of the volcanic rocks occurring in the island, which led him to the theory that all the eruptive rocks that reach the surface consist either of an acid or a basic silicate, or a mixture of the two, that has been formed and crystallized within the interior of the earth. Other papers relate to the formation of various crystalline minerals by the joint action of heat, acid gases, and moisture, on the rocks, and the theory of the geysers.
With the aid of his battery, Bunsen performed the electrolysis of some of the rarer metals. He began with magnesium, which he prevented from taking fire as soon as it came to the surface by the ingenious device of catching the metal as it rose in a cup, which he formed in his carbon pole for the purpose, while it was still under the salt. He then proceeded to the reduction, in conjunction with the late Dr. Matthiessen, of the alkaline-earth metals, and, with Hillebrand and Norton, of the metals of the cerium group. Applying metallic magnesium in photo-chemical researches and in comparison of the light of its flame with that of the sun, he gave the impulse which induced the undertaking of the commercial preparation of the metal.
Other researches, with which his name is connected, are those of Kolbe on the electrolysis of the fatty acids, of Kolbe and Frankland on the isolation of the organic radicals, the explanation of a new method of determining vapor densities, the investigation and correction of Dalton and Henry's law of absorption of gases in water, experiments on laws of gaseous diffusion, on applications of gaseous diffusion in gasometric analysis, on the phenomena of the combustion of gases, and on the temperature of ignition of gases; all of which were performed by himself or his pupils, or both.
In analytical chemistry Bunsen has contributed something valuable to the solution of nearly every important problem, and the best methods in complicated laboratory processes like those of the analysis of silicates and mineral waters, methods for the estimation of nitrogen and sulphur, and a method of volumetric analysis, which, though requiring considerable time for its completion, leaves little to be desired in point of accuracy and simplicity of manipulation. He introduced a general method for the separation of the rare earths, by which he for the first time prepared pure yttria and erbia, and by which several new metals have been discovered by other chemists.
In connection with his investigations on the measurements of the chemical action of light. Professor Roscoe, who was associated with him, speaks admiringly of his untiring energy and wonderful manipulative power, and says that, in all the difficulties and perplexities by which the experimental investigation of such a subject is beset, he never knew Bunsen discouraged, or at a loss for an expedient by which an obstacle could be overcome. "Cheerful and self-reliant under the most depressing circumstances, he never gave up hope, and thus it was that these somewhat intricate and difficult investigations were brought to a successful close."
Perhaps none of his labors are more distinguished than the experiments with which he and Kirchhoff laid the foundation of the new science of spectrum analysis. Among his own most important transactions in this work was the discovery, by means of the spectrum lines, of the metals cæsium and rubidium. He first saw the cæsium lines, says Professor Roscoe, in a few milligrammes of the alkaline residue obtained in an analysis of the Dürkheim mineral waters, and the discovery of a second new metal (rubidium) soon followed that of the first. "So certain was he of the truth of his spectroscopic test, that he at once set to work to evaporate forty tons of the water, and with 16·5 grammes of the mixed chlorides of the two new metals which he thus obtained he separated the one metal from the other (no easy task) and worked out completely their chemical relationship and analogies; so much so, that the labors of subsequent experimenters have done little more than confirm and extend his observations." Another research in this direction was that on the spark spectra of the metals contained in cerite and other rare minerals, which he carefully mapped in such a manner as to make the separation and identification possible.
Bunsen's name is identified with two instruments which he has devised, which have come into general use in science and the arts; the Bunsen gas-burner, which is almost indispensable in laboratories and in many processes of manufacturing, and is used in many households; and the Bunsen pump for accelerating filtration, which those who employ it could likewise hardly do without.
His published writings are many. Most of them are special papers relating to the subjects of investigation that have been already mentioned; others embody more general results of his studies. His visit to Iceland gave rise to several papers on the various physical, geological, and volcanic phenomena of the island; his studies in metals to a number of monographs; his spectroscopic studies to "Chemical Analysis based on Observations of the Spectrum," published by him and Kirchhoff. Besides these, we may mention "Researches on Chemical Affinity"; "On a New Volumetric Method"; and "A Treatise on Gas Analysis."
Concluding his notice in "Nature," from which we have drawn liberally in the preparation of this article. Professor Roscoe says: "The many hundreds of pupils who, during the last half-century, have been benefited by personal contact with Bunsen will all agree that as a teacher he is-without an equal. Those who enjoy his private friendship regard him with still warmer feelings of affectionate reverence. All feel that to have known Bunsen is to have known one of the truest and noblest-hearted of men."