Brønsted, Johannes Nicolaus

views updated May 18 2018

Brønsted, Johannes Nicolaus

(b. Varde, Denmark, 22 February 1879; d. Copenhagen, Denmark, 17 December 1947)

chemistry.

Brønsted entered the Faculty of Chemical Engineering at the Technical University of Denmark in 1897. Two years later he received his degree, then left the Technical University and entered the Faculty of Natural Sciences at the University of Copenhagen, from which he obtained the M.S. in chemistry in 1902. After a period of nonchemical research he was appointed assistant at the university’s chemical laboratory in 1905, and from then on he was attached to the university, serving as professor of physical chemistry from 1908.

Since the conclusion of Julius Thomsen’s studies on thermochemistry in 1886, physical chemistry had been somewhat neglected in Denmark. although the work of Ostwald, Arrhenius, and Nernst was followed up in most other countries. Brønsted took over Thomsen’s idea of determining chemical affinity by measuring the maximum work of a chemical process, but instead of using calorimetric determinations, he used electromotive force measurements for galvanic cells, which give correct values at room temperature, whereas the calorimetric method gives values that are in error by an amount proportional to the entropy changes taking place for the process in the chemical reaction. He published the results in a series of thirteen monographs on chemical affinity (1906–1921). He defended the third paper of this series, on the affinity of mixing in binary systems, for the Ph.D. at the University of Copenhagen in 1908.

Other aspects of physical chemistry aroused Brønsted’s interest after 1913: not only the determination of specific heats but also the determination of affinity constants, published in a series of studies on solubility (1921–1923) and on the specific interaction of ions (1921–1927). These studies evoked considerable interest among physical chemists, especially in the United States and in England, and from 1921 to about 1935 Brønsted’s laboratory was crowded with foreign guests desiring to study under his guidance. The poor laboratory conditions were considerably improved when the International Education Board offered to defray the expenses connected with the building of a new Institute of Physical Chemistry, provided the Danish government would take over the operation of the institute, which began operation in 1930. Famous among these studies is a paper, written with V. K. la Mer, on the relation between activity coefficients and the ionic strength of the solution, a relation derived theoretically at the same time by P. Debye and E. Hückel.

Other achievements, too, deserve to be mentioned: Brønsted’s definition of acids and bases (1923), simultaneously suggested in almost identical form by T. M. Lowry and in an extended version by G. N. Lewis; his studies on catalysis (1924–1933); and his work on the separation of isotopes of mercury and chlorine (1920–1922, 1929), done with G. von Hevesy.

In 1912 Brønsted published a short manual of physical chemistry, based on the thermodynamic cycle of Carnot. Before 1936, when a new edition had to be written, Brønsted had become convinced of the superiority of J. W. Gibbs’s approach to thermodynamics, and the new, substantially enlarged edition was based on Gibbs’s ideas.

Brønsted was unhappy with the classical formulation of the laws of thermodynamics, according to which heat is not directly comparable to other forms of energy. To him, heat, like other forms of energy, can be considered as composed of a quantity factor (the entropy) and an intensity factor (the temperature). In this way it was possible to formulate the first law of thermodynamics as a work principle, whereas the second law was broadened to a heat-and-equivalence principle, including also irreversible reactions. A characteristic of this approach is that it relates thermodynamics to physical concepts rather than to mathematical complexities.

Brønsted’s formulations, especially his use of the principles “work” and “heat,” were not approved by the physicists, and angry discussions took place. He tried to concrete his principles in later works (1940, 1941, 1946), but no agreement had been reached by the time of his death.

BIBLIOGRAPHY

A list of 103 of Brønsted’s 120 papers (i.e., those written up to 1935) is in Stig Veibel, Kemien i Danmark, II (Copenhagen, 1943), 80–88. Among his works are Blandingsaffiniteten: binaere Systemer (Copenhagen, 1908); Grundrids of den fysiske kemi (Copenhagen, 1912), new ed. entitled Laerebog i fysisk kemi (Copenhagen, 1936, 1943), also trans. into English by R. P. Bell (London, 1937); “Einige Bemerkungen über den Begriff der Säuren und Basen,” in Recueil des travaux chimiques des Pays-Bas et de la Belgique, 42 (1923), 718–728; “The Activity Coefficients of Ions in Very Dilute Solutions,” in Journal of the American Chemical Society, 46 (1924), 555–573, written with V. K. la Mer; “Die katalytische Zersetzung des Nitramids und ihre physikalisch-chemische Bedeutung,” in Zeitschrift für physikalische Chemie, 108 (1924), 185–235, written with K. Pedersen; Om syre- og basekatalyse (Copenhagen, 1926); “The Fundamental Principles of Energetics,” in Philosophical Magazine, 7th ser., 29 (1940), 449–470; “On the Concept of Heat,” in Kongelige Danske Videnskabernes Selskabs Skrifter, 19 , no. 8 (1941), 79 ff.; and Principer og problemer i energetiken (Copenhagen, 1946), trans. by R.P. Bell as Principles and Problems in Energetics (New York, 1955), with an enthusiastic foreword by V. K. la Mer. There is an obituary with a complete bibliography by J. A. Christiansen in Oversigt Danske Videnskabernes Selskabs 1948–1949, pp. 57–79.

Stig Veibel

Complete Dictionary of Scientific Biography

Brønsted, Johannes Nicolaus

views updated May 14 2018

Brønsted, Johannes Nicolaus

DANISH CHEMIST
1879–1947

Johannes Nicolaus Brønsted was a physical chemist whose work resulted in a new theory of acids and bases. He was born in the town of Varde in Jutland (Denmark), where his father was an engineer for the Danish Heath Society. His mother died shortly after his birth. When his father died in 1893, young Brønsted relocated to Copenhagen, where he was admitted to the old Latin school (high school), the Metropolitanskolen. He passed the school's final examinations in 1897.

Brønsted studied chemistry at the University of Copenhagen. He received a master of science degree in 1902 and a doctorate degree in 1908. After receiving temporary appointments at the University of Copenhagen, he became an assistant professor there in 1905, and full professor in 1908. Brønsted studied chemical affinity, electrolytes, isotope separation, reaction kinetics, thermodynamics, and acid-base catalysis .

On May 4, 1923, the Dutch chemical journal Receueil des Travaux Chimiques des Pays-Bas (42:718) received a paper from Brønsted on existing concepts of acids and bases. In this paper Brønsted demonstrated how useful it was to define an acid as a proton donor and a base as a proton acceptor. In the Brønsted scheme, acid-base reactions are proton transfer reactions. Every acid is related to a conjugate base, and every base to a conjugate acid. Also in this paper he pointed out that there is an analogy between the proton transfer that is characteristic of acid-base reactions and the electron transfer that is characteristic of oxidation -reduction reactions.

On January 19, 1923, an article by Thomas Martin Lowry (1874–1936) was published in the English journal Chemistry and Industry, in which the idea of proton transfer between acids and bases was launched. In spite of this, Brønsted's theorizing work has been recognized, and the terms Brønsted acid and Brønsted base have had wide usage.