Open AccessOn the direct determination of the electrostatic moments of molecules
Author(s) -
Robert Clark
Publication year - 1929
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1929.0146
Subject(s) - dielectric , condensed matter physics , constant (computer programming) , field (mathematics) , debye , debye model , molecule , thermodynamics , chemistry , physics , quantum mechanics , mathematics , computer science , pure mathematics , programming language
According to Faraday's ideas, the specific inductive capacity of a substance is due to the polarisation of the molecules as wholes. This is the basis of the old Clausius-Mosotti theory of dielectrics, on which it is shown first that the polarisation P is proportional to the polarising field,i. e. , P =k E,k being the dielectric constant, and second that δ being the density of the dielectric,k - 2/k + 2 ·1/δ = constant. Now it is known that some substances have large negative temperature coefficients for their dielectric constants which cannot thus be accounted for. To provide for this Debye proposed the theory that the molecules were permanently polarised and that they were systematically orientated in the field. This leads to the equationk - 2/k + 2 =a T-1 +b T-2 , to represent the change of specific inductive capacity with temperature. This theory has been developed by Gans and others, and a number of measurements have been made by Smyth and others, who have found the molecular moments of many substances by measuring the dielectric constants at different temperatures.