Kurnakov, Nikolai Semyonovich

(b. Nolinsk, Vyatka guberniya, Russia, 6 December 1860; d. Mopscow, U. S. S. R., 19 March 1941)

chemistry.

Kurnakov graduated from the St. Peterburg Institute of Mines in 1882. From 1893 he was a professor of inorganic chemistry there and also (1899–1908) professor of physical chemistry at the St. Peterburg Polytechnic Institute. On 7 December 1913 Kurnakov was elected a member of the Academy of Sciences. In 1918, at Kurnakov’s suggestion, the Academy created the Institute of Physical and Chemical Analysis; in 1934 it became the Institute of General and Inorganic Chemistry, and in 1944 it was renamed the N. S. Kurnakov Institute of General and Inorganic chemistry.

Kurnakov’s first scientific interest was in salts. In the 1890s he completed a series of experiment on the chemistry of coordination complexes that were generalized in his inaugural dissertation, “O slozhnykh mettalicheskikh osnovaniakh” (“On Complex Metallic Bases,” 1893). Kurnakov discovered the reaction of cis- and trans-isomers of divalent platinum with thiourea; this reaction is named for him. He showed that trans-isomers form a coordination complex with two molecules of thiourea in an internal sphere, while cis- compounds react with four particles of thiourea. This reaction permits question concerning the structure of derivatives of bivalent platinum.

Kurnakov’s main scientific accomplishment was the creation of physicochemical analysis based on the study of equilibrium systems by measuring their characteristics in relation to changes in compositiojn and by constructing appropriate phase diagrams. Beginning in 1898, Kurnakov carried on a systematic study of heterogeneous systems (initially of metallic alloys, later of organic and salt systems). Developing the work of Chernov, Le Châtelier, Osmond, and Roberts-Austen in thermal analysis, in 1900 Kurnakov developed the means of finding the composition of specific compounds in alloys by using the method of fusibility.

In 1903 Kurnakov invented a self-registering pyrometer—a device for recording heating and cooling curves—with the aid of which he significantly improved the methodology of thermal analysis. In 1906 he introduced the measurement of electroconductivity as a method of studying the change in the characteristics of a system in relation to changes in its composition. With S. F. Zhemchuzhny he demonstrated that in the formation of solid solutions of two metals there is a reduction in electroconductivity. They established the basic composition electroconductivity diagrams for systems of two metals which form continuous solid solutions.

In 1906 Kurnakov established that technical alloys of high electric resistance, which are are widely employed in the manyfacture of rheastats and resistance boxes, consist of solid solutions. Expandiong his research on alloys, Kurnakov applied the measurement of hardness and the determination of flow pressure as a new method of physicochemical analysis (1908–1912).

In 1912, while studying the viscosity of two-liquid systems in relation to their composition, Kurnakov found that the formation of specific compounds in the given systems corresponds tp special points (which he called singular or Dalton points) on the phase diagrams. These results permitted Kurnakov to formulate the general conclusion that “a chemical individuum belonging to a specific chemical compound represents a phase, which possess singular or Dalton points on the lines of its characteristics” (1914). The composition corresponding to these points remains constant even with a change in the facts of the system’s equilibrium. Through investigation of tellurium-bismuth, iron-silicon, antimony, aluminum-iron, and lead-sodium systems, using all methods of physicochemical discovered that, according to Kurnakov, belonged to the berthollide type. These phases were not characterized by singular points on the phase diagrams. According to Kurnakov, the berthollides are crystalphase nonstoichiometric compounds, the variable composition of which cannot be expressed by simple integer relationship.

Kurnakov ascribed great significance to the study of the genetic connection between daltonides adn berthollides chemical compounds. “In equilibrium systems,” he said, “discreteness adn continuity are intercombined and coexist.”

Kurnakov and his students proposed methods of physicochemical analysis for the study of a great variety of systems formed by salts, metals, and inorganic compounds. without destroying the system under investigation, Kurnakov precisely specified teh conditions od separation of the various phases for intermetallic compounds and for the hydrate forms of doubt salts; he also found the limits of their stable state—unobtainable with the common methods of chemical investigation then in use.

Investigation of the salt equilibrium in the system 2 NaCl + MgSo₄ ⇌ Na₂ SO₄ + MgCl₂ (at 25°C, and 0° C.) enabled Kurnakov to clarify the mechanism of deposition of Glauber’s salts in kara-Boraz-Gol Bay (1918); the results provided the scientific basis for teh industrial exploitation of rich deposits of natural salts. In 1917 he published “Mestorozhdenia Khloristogo kalia Solikamskoy solenosnoy tolshchi” (“Deposits of Potassium chloride in the Solikamsk Saliferous Mass”), written with K. F. Beloglazov and M. K. Shmatko; this work played a conspicuous role in the industrial exploitation of the rich Solikamsk potassium deposits.

Studies of the salt lakes in the Crimea and in the Volga basin, of the Tikhvin bauxite deposits, and of other valuable sources of minerals are associated with Kurnakov.

Kurnakov was an active participant in the introduction of chemicak processes into Soviet agriculture and helped to organize many scientific conventions and conferences. He also fostered a large school of inorganic chemists and metallurgists, includings G. G. Urazov, S. F. zhemchuzhny, N. I. Stepanov, and N. N. Efremov.

BIBLIOGRAPHY

I Original Works. Kurnakov’s writings include Sobranie izbrannykh rabot (“Collection of Selected Works”), 2 vols. (Leninggrad, 1938–1939); Vvedenie v fiziko-khimichesky analiz (“Introduction to Physicochemical Analysis”), 4th ed. (Moscow, 1940); and Izbrannye trudy (“selected Papers”), 3 vols. (Moscow, 1960–1963).

II. Secondary Literature. See L. Dlougatcyh, “N. S. Kournakow, sa vie, son oeuvre, son école,” in Revue de métallurgie, 21 (1925), 650–662, 722–732; G. B. Kauffman and A. Beck, “Nikolai Semenovich Kurnakov,” in Journal of chemical Education, 36 (1962), 521; Y. I. Soloviev, Ocherki istorii fiziko-khimicheskogo analiza (“Essays on the History of Physicochemical Analysis”; Moscow, 1955); Y. I. Soloviev adn O. E. Zvyagintsev, Nikolay Semyonovich Kurnakov. Zhizn i deyatelnost (“Nikolai Semyonovich Kurnakov. Life and Work”; Moscow, 1960); and G. G. Urazov, “Akademic N. S. Kurnakov—osnovatel fizikokhimicheskogo analiza i glava nauchnoy shkoly” (“Academician N. S. Kurnakov—founder of Physicochemical Analysis and Head of a Scientific School”), in izvestiys Sektora fiziko-khimicheskogo analiza, Institut obshchei i neorganicheskoi khimii, 14 (1941), 9–35, which includes a bibliography of Kurnakov’s papers.

Y. I. Soloviev