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chemist , professor of physics

Robert Wilhelm Eberhard Bunsen was a German chemist.


Robert Bunsen was born at Göttingen, Germany in 1811, in what is now the state of Lower Saxony in Germany.

Bunsen was the youngest of four sons born to Christian Bunsen, chief

librarian and professor of modern languages at the University of Göttingen.

His ancestors on his father’s side had lived in Arolsen, where many of them held public office, frequently as master of the mint; his mother was the daughter of a British-Hanoverian officer named Quensel.


Bunsen began school in Göttingen but transferred to the Gymnasium at Holzminden, from which he graduated in 1828.

His chemistry teacher was Friedrich Stromeyer, who had discovered cadmium in 1817.

Returning to Göttingen, Bunsen entered the university, where he studied chemistry physics, mineralogy, and mathematics.

Later that year, in Berlin, he studied Christian Weiss’s geognostic and mineralogic collections; met Freidlieb Runge, the discoverer of aniline, and Gustav Rose; and worked in Heinrich Rose’ laboratory.

From May to July 1833, he traveled to Vienna, where he toured several industrial plants. In the fall of 1833 Bunsen became Privatdozent at the University of Göttingen.

He presented 100 hours of lectures during each of seventy-four semesters in a course entitled “Allgemeine Experimentalchemie”.


Bunsen received his doctorate in 1830, presenting a thesis in physics: “Enumeratio ac descriptio hygrometrorum”.

Aided by a grant from the Hanoverian government, Bunsen toured Europe from 1830 to 1833, visiting factories, laboratories, and places of geologic interest.

In May 1832, he saw a new steam engine in K. A. Henschel’s machinery factory in Kassel.

In September 1832, Bunsen arrived in Paris.

There he worked in Gay-Lussac’s laboratory and met such prominent scientists as Jules Reiset, Henri-Victor Regnault, Théophile Pelouze, and César Despretz.

He succeeded Friedrich Wöhler at the Polytechnic School in Kassel in January 1836.

In 1852 he succeeded Leopold Gmelin at the University of Heidelberg.

Although offered a position as Mitscherlich’s successor at the University of Berlin in 1863, Bunsen remained at Heidelberg until he retired in 1889, at the age of seventy-eight.

The lectures, which changed little through the years, were concerned with inorganic chemistry; organic chemistry was excluded.

Theoretical aspects were at a minimum: neither Avogadro’s hypothesis nor the periodic law of the elements–developed by his own students, Dmitri Mendeleev and Lothar Meyer–was mentioned.

He enjoyed designing apparatus and, being a skilled glassblower, he frequently made his own glassware.

Bunsen developed and improved several pieces of laboratory equipment, including the Bunsen burner, the Bunsen battery, an ice calorimeter, a vapor calorimeter, a filter pump, and a thermopile.

While involved in this work, Bunsen discovered that hydrated ferric oxide could be used as an antidote for arsenic poisoning.

The ferric oxide is effective, he explained, because it combines with arsenic to form ferrous arsenite, a compound insoluble in both water and body fluids.

This finding, still used today, was Bunsen’s only venture into physiological chemistry.

In other early research, he analyzed a sample of allophane, an aluminum silicate, taken from a lignite bed near Bonn.

In 1835 and 1836 Bunsen set forth the compositions and crystal measurements of a new series of double cyanides, showing, for example, that ammonium ferrocyanide and potassium ferrocyanide are isomorphous.

He also discovered the double salt of ammonium ferrocyanide and ammonium chloride. Bunsen’s only work in organic chemistry was an investigation of compounds of cacodyl, an arsenic-containing organic compound, the results of which appeared in five papers published between 1837 and 1842.

In 1843, Bunsen lost the use of his right eye in an explosion of cacodyl cyanide.

The first known cacodyl compound, alkarsine, had been prepared in 1760 by L. C. Cadet de Gassicourt, by distilling a mixture of dry arsenious oxide and potassium acetate.

Alkarsine is a highly reactive, poisonous, spontaneously inflammable substance having heavy brown fumes and a nauseating odor.

Berzelius called the compound kakodyl oxide (from the Greek κακóδηs, “stinking”).

Bunsen conducted a detailed study of cacodyl derivatives, obtaining the chloride, iodide, cyanide, and fluoride by reacting concentrated acids with the oxide.

This conclusion supported the radical theory of organic compounds advocated by Liebig and Berzelius.

After presenting his papers, Bunsen withdrew from the controversy over the merits of the radical theory and turned to inorganic chemistry.

It remained for his students, Adolph Kolbe and Edward Frankland, to show in 1853 that cacodyl compounds contain dimethylarsenic, As(CH3)2, and for Auguste Cahours and Jean Riche to demonstrate that free cacodyl is A62(CH3)4.

Finally, in 1858 Adolph von Baeyer, another of Bunsen’s students, clarified the relationships among the members of the cacodyl series.

Between 1838 and 1846, Bunsen developed methods for the study of gases while he was investigating the industrial production of cast iron in Germany and, in collaboration with Lyon playfair, in England.

He demonstrated the inefficiency of the process; in the charcoal-burning German furnaces, over 50 percent of the heat of the fuel used was lost in the escaping gases; worse, in the coal-burning English furnaces, over 80 percent was lost.

Valuable by-products, such as ammonia, went unrealized and were among the gases lost to the atmosphere.

Further, it was accidentally discovered that potassium cyanide was formed from potassium carbonate and atmospheric nitrogen at high temperatures.

In an 1845 paper, “On the Gases Evolved From Iron Furnaces With Reference to the Smelting of Iron, ” Bunsen and Playfair suggested techniques that could recycle gases through the furnace, thereby utilizing heat otherwise lost.

They also dicussed ways by which valuable escaping materials could be retrievedBunsen compiled his research on the phenomena of gases into his only book, Gasometrische Methoden (1857).

The expedition, sponsored by the Danish government, lasted three and one-half months and included Sartorius von Waltershausen and Bergmen, both from Marburg, and Alfred DesCloizeaux, a French mineralogist.

Bunsen collected gases emitted from the volcanic openings and studied the action of these gases on volcanic rocks.

He performed extensive chemical analyses of eruptive rocks, insisting that instead of determining what minerals were in a rock, the chemical composition of the rock as a whole should be ascertained.

Bunsen concluded that volcanic rocks are mixtures, in varying proportions, of two exteme kinds of rock; one kind acidic and rich in silica (trachytic).

The other kind basic and less rich in silica (Pyroxenic).

Although this explanation is no longer accepted, his observations contributed a great deal to the development of modern petrology.

Bunsen also explored geysers, and at the Great Geyser made daring temperature measurements at several depths shortly before it erupted.

He found that the temperature of water in the geyser tube, although high, did not reach the boiling point for a particular depth and corresponding pressure.

He concluded that the driving force for eruption is supplied by steam that enters the tube under great presure from volcanic vents at the bottom.

As the steam lifts the column of water, the effective pressure above the water is reduced.

This change in the water’s depth results in a lowering of the boiling point and enables the already not water to boil. Through the 1840’s and 1850’s Bunsen made a number of improvements in the galvanic battery.

In 1841 he made a battery, known since as the Bunsen battery, with carbon, instead of the more expensive platinum or copper, as the negative pole.

To prevent disintegration of the carbon pole by the nitric acid electrolyte, Bunsen treated the carbon, a mixture of coal and coke, with high heat.

Forming a battery from forty-four subunits.

Later, the made a battery with zinc and carbon plates in chromic acid.

He pressed magnesium into wire and used it as a light source in his subsequent photochemical experiments.

With the assitance of Augustus Matthiessen, Bunsen isolated lithium and several alkaline earth metals-barium, calcium, and strontium-from their fused chlorides.

Bunsen, with William hillebrand and T. H. Norton, prepared the rare earth metals of the cerium group-cerium, lanthanum, and didymium.

To obtain the specific heats of these rare elements, Bunsen devised a sensitive ice calorimeter that measured the volume rather than the mass of the ice melted and requried only a small sample of the metal.

From the specific heats, the atomic weights of these elements and the formulas of their compounds were calculated.

For this experiment they altered a reaction vessel devised by John Draper in 1843.

Bunsen and Roscoe found that for some time after the experiment started—a time they called the induction period—no reaction took place; then the reaction rate slowly increased until a constant rate, Proportional to the intensity of the light source used, was reached.

The effect of the incident light was related to the wave- length and followed a law of inverse squares.

Further, the illumination of chlorine alone before it entered the reaction chamber did not alter the length of the induction period.

While variations of temperature within the range 18°–26° had little effect on the reaction, the presence of oxygen appeared to have a catalytic effect.

The Bunsen burner, with its nonluminous flame, quickly supplanted the blowpipe flame in the dry tests of analytical chemistry.

Bunsen used his burner to identify metals and their salts by their characteristic colored flames.

Other experiments with the burner yielded data for melting points and rate of volatility of salts. In the 1860’s Bunsen and Kirchhoff worked together to develop the field of spectroscopy.

Bunsen saw that analyses of absorption spectra could be made in order to determine the composition of celestial and terrestrial matter.

He further predicted that spectral analysis could aid in the discovery of new elements that might exist in too small quantities or be too similar to known elements to be identifiable by traditional chemical techniques.

The element was named cesium (from the Latin caesius, “sky blue”) because of its brilliant blue spectral lines.

Cesium salts had previously been mistaken for compounds of potassium.

The following year the element rubidium (from the Latin rubidus, “darkred”)was detected from the spectrum of a few grains of the mineral lepidolite.

By comparison, forty tons of mineral water were needed to yield 16. 5 grams of cesium chloride and rubidium chloride that could be used in the chemical investigation of the compounds of these new elements.

In 1862 Bunsen succeeded in isolating metallic rubidium by heating a mixture of the carbonate and charcoal.

During the yeaars that followed, several other elements were identified by spectroscopic methods: thallium (Crookes, 1861), indium (Reich and Richter, 1863), gallium (Lecoq de Boisbaudran, 1875), scandium (Nilson, 1879), and germanium (Winkler, 1886).

Bunsen was concerned with a variety of additional analytic work.

In 1853 he developed a technique for the volumetric determination of free iodine using sulfurous acid.

In 1868 he worked out methods for separating the several metals—palladium, ruthenium, iridium, and rhodium—that remain in ores after the extraction of platinum; as part of this project Bunsen constructed a filter pump for washing precipitates.

With the assistance of Victor Meyer, he conducted a government–sponsored study of the mineral water of Baden; results were published in 1871.

He described the spark spectra of the rare earths in 1875.

Late in his life Bunsen used a steam calorimeter that he had built to measure the specific heats of platinum, glass, and water. Bunsen was honored by several European scientific societies.

I. Original Works.  Bunsen’s Writings include Gasometrische Methoden (Brunswick, 1857; enl.  ed. , 1877), trans.  by Henry E. Roscoe as Gasometry; Comprising the Leading Physical and Chemical Properties of Gases (London, 1857); Photochemical Researches, 5 Pts.  (London, 1858–1863), written with Henry E. Roscoe and pub.  in German as Photochemische Untersuchungen (Leipzig, 1892); Chemische Analyse durch Spectralbeobachtungen (Vienna, 1860), written with Kirchhoff; and Gesammelte Abhandlungen, Wilhelm Ostwald and Ernst Bodenstein, eds. , 3 vols.  (Leipzig, 1904).  Also of interest, all in Klassiker der exacten Wissenschaften, are Untersuchungen über die Kakodylreihe, Adolf von Baeyer, ed. , no. 27; and Photo-chemische untersuchungen, W. Ostwald, ed. , nos. 34, 38.  II.  Secondary Literature.  Works on Bunsen are Theodore Curtin’s article in Eduard Farber, Great Chemists (New York, 1961), pp. 575–581, a trans.  from Journal für praktische Chemie (1900); O. Fuchs’s article in F. D. G. Bugge, Das Buch der grossen Chemiker, II (Berlin, 1930), 78–91; Georg Lockemann, Robert Wilhelm Bunsen.  Lebensbild eines deutschen Forschers (Stuttgart, 1949); Ralph E. Oesper, “Robert Wilhelm Bunsen, ” in Journal of Chemical Education, 4 (1927), 431–439; W. Ostwald’s article in Zeitschrift für Elektrochemie, 7 (1900), 608–618; J. R. Partington, A History of Chemistry, IV (London, 1964), 281–293; H. Rheinboldt, “Bunsens Vorlesung über allgemeine Experimentalchemie, ” in Chymia, 3 (1950), 223–241; Henry E. Roscoe, “Bunsen Memorial Lecture” (delivered 29 Mar. 1900), in Journal of the Chemical Society, 77, pt.  I (1900), 513–554; and Bunseniana.  Eine Sammlung von humoristischen Geschichten aus den Leben von Robert Bunsen (Heidelberg, 1904).


  • He investigated emission spectra of heated elements, and discovered caesium (in 1860) and rubidium (in 1861) with the physicist Gustav Kirchhoff. Bunsen developed several gas-analytical methods, was a pioneer in photochemistry, and did early work in the field of organoarsenic chemistry.

    With his laboratory assistant, Peter Desaga, he developed the Bunsen burner, an improvement on the laboratory burners then in use. The Bunsen–Kirchhoff Award for spectroscopy is named after Bunsen and Kirchhoff.

    To measure this light he designed in 1844 another instrument, which in various modifications has come into extensive use-the grease-spot photometer.                      He thought that the formation of different kinds of rock could be traced to their differences in meltingpoint behavior under pressure.

    Five years later he studied the volcanic rock formations and geyser action in Iceland, doubtless laying thereby the foundation of modern petrology.



A man of wide scientific interests, Bunsen did some early research in organic chemistry but later abandoned this field and concentrated on inorganic chemistry.


In 1842 he was elected a foreign member of the Chemical Society of London.


He was also one of the first to appreciate the value of practical work to the student, and he instituted a regular practical course at Marburg so far back as 1840.


Bunsen never married; his teaching and research consumed most of his time, and he traveled widely, either alone or with friends. Bunsen was a most devoted teacher.

Christian Bunsen

Eilhard Mitcherlich