331 SEMENOV 



chemical reaction, because the heat liberated does not have 

 time to leave the reaction zone. Semenov and his students 

 studied energy distribution in a flame, detonation, and com- 

 bustion of explosives and powders. The investigations of Seme- 

 nov on the theory of chain reactions is particularly significant. 

 On the basis of the study of critical phenomena, such as limit 

 of ignition, observed during oxidation of vapors of phosphorus, 

 hydrogen, carbon monoxide and other compounds, he discovered 

 branching reactions. In his monograph, * Chain Reactions" 

 (1934), he developed the theory of non-branching reactions and 

 showed the wide distribution of chain reactions in chemistry. 

 He and his associates developed theoretically and checked ex- 

 perimentally many ideas of the chain theory: the breaking of 

 reaction chains on walls and in the volume of a container, de- 

 generate chain branching, positive and negative interaction of 

 chains. Also, he established the detailed mechanism in a series 

 of complex chain processes, and studied the properties of free 

 atoms and radicals with the aid of which the elementary stages 

 of these processes were realized. Semenov took active part 

 in organizing a physico-mechanical department at the Lenin- 

 grad Polytechnic Institute and in starting scientific journals. 

 He trained many specialists in physics, chemical kinetics, and 

 the combustion theory. 



In March 1962, Semenov was elected a delegate from 

 R.S. F.S.R. to the Supreme Soviet. As of 1961, he was Secretary 

 of the Department of Chemical Sciences of the U.S.S.R. Acade- 

 my of Sciences. 



In 1961 he was elected Candidate Member of the Central 

 Committee of the Communis* Party. 

 Bibliography: 



Chain Reactions. Leningrad: 1934. 



Thermal theory of burning and explosions. Uspekhi Fiz. 



Nauk, 1940, 23, #3; 24, #4. 



On Some Problems of Chemicai Kinetics and Reaction Abili- 

 ty. Moscow: 1954. 

 Biography: 



Nikolai Nikolaevich Semyenov, compiled by N. M. Emanuel. 



Moscow-Leningrad: 1946. 



Yu. B. Khariton . Creator of the theory of chain chemical 



reactions. Soviet Science, 1941, #4, p. 1621. 



N. M. Emanuel . Contribution to the world of science. On 



the awarding of the Nobel Prize to Academician N. M. 



Semyonov. Priroda, 1957, #2. 



