Onsagern.
/ˈɒnsɑːɡə/, U.S. /ˈɔnˌsɑɡər/ 1. Physical Chemistry. Onsager equation n. (also Onsager's equation) an equation that relates the conductance of an electrolytic solution to that of the pure solvent.
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1929 Proc. Royal Soc. A. 126 99 There is good reason to suppose that the Onsager equation expresses the behaviour of a completely dissociated electrolyte in dilute solution.
1961 Proc. Royal Soc. A. 260 414 For solutions it is more correct to use Onsager's equation and to assume additivity of molar polarizations of the solute and the solvent.
1991 Acta Metallurgica et Materialia 39 2535/2 We present the microscopic kinetics equations as Onsager equations in which relaxation parameters are occupation probabilities.
2. Physics. Used attributively and in the genitive with reference to a theorem originally obtained for the thermodynamics of irreversible processes, but of wide applicability in physics and biophysics.
a. Onsager's principle n. (also Onsager principle, Onsager's law) a statement of the reciprocal nature of the interference between two irreversible processes occurring simultaneously, spec. that the Onsager coefficients for each direction of flow between the two processes are equal. Cf. reciprocity theorem n. at reciprocity n. Compounds 2.
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the world > matter > chemistry > physical chemistry > [noun] > laws and rules
Raoult's law1886
Le Chatelier1910
Onsager's principle1945
the world > matter > physics > mechanics > dynamics > thermodynamics > [noun] > specific theorems or principles
reciprocity theorem1878
Nernst heat theorem1912
Onsager's principle1945
1945 Rev. Mod. Physics 17 343 (heading) On Onsager's principle of microscopic reversibility.
1965 A. K. Katchalsky & P. F. Curran Nonequilibrium Thermodynamics in Biophysics x. 120 Onsager's law provides a quantitative relation between the phenomena of ultrafiltration and osmotic flow.
1968 Times 31 Oct. 5/4 In the simplest terms possible, the Onsager principle or ‘reciprocity theorem’, as it is sometimes called, asserts that where two or more kinds of flow affect each other the equations describing them will be reciprocally related in a specific way.
1994 Proc. Royal Soc. A. 445 681 The jumps in chemical potential are defined as ∆μ=μ1−μ2, and Lws=Lsw, by Onsager's principle.
b. Onsager relation n. (also Onsager's relation, Onsager reciprocal relation, Onsager reciprocity relation) a relation that is a mathematical statement of Onsager's principle.
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the world > matter > physics > mechanics > dynamics > thermodynamics > [noun] > specific theorems or principles > mathematical statement of Onsager's principle
Onsager relation1952
1952 Physica 18 182 Verschaffelt has given an example of a linear transformation of flux and force variables which leaves the entropy production invariant and yet which destroys the Onsager relations.
1955 I. Prigogine Introd. Thermodynamics Irreversible Processes iv. 46 These Onsager reciprocity relations express that when the flux, corresponding to the irreversible processes i, is influenced by the affinity Xk of the irreversible process k, then the flux k is also influenced by the affinity Xi through the same interference coefficient Lik.
1978 B. H. Lavenda Thermodynamics Irreversible Processes ii. 29 The derivation of the Onsager reciprocal relations was based on an apparent analogy between the conditions of chemical equilibrium and the ‘principle of detailed balance at equilibrium’.
1993 Proc. Royal Soc. A. 442 665 When the underlying dynamics has time-reversal symmetry, the linear response tensor..is symmetric. This is an example of Onsager's relation.
c. Onsager coefficient n. a tensor coefficient expressing the degree of interference between two irreversible processes.
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the world > matter > physics > mechanics > dynamics > thermodynamics > [noun] > specific theorems or principles > mathematical statement of Onsager's principle > coefficient
Onsager coefficient1958
1958 Proc. National Acad. Sci. U.S.A. 44 28 For low concentrations of salts in which association is slight, the conductance equation assumes the approximate limiting form A = A9 − S √c + Ec log c + J1c − KAA0c − FAoc, where S is the Onsager coefficient.
1977 S. H. Chue Thermodynamics ii. 248 In the Onsager coefficients the subscript i refers to the flux and the subscript j to the driving force.
1995 Ann. Probability 23 725 The Onsager coefficient a is introduced into the model to break the gradient structure.
This entry has been updated (OED Third Edition, June 2004; most recently modified version published online March 2022).
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n.1929