Thermodynamics of a Fluid Substance in the Electrostatic Field

Abstract

An "apparatus" is described in which, in a thought experiment, the whole of a sample of fluid may be subjected to a uniform electrostatic field under controlled conditions. The work done in such a process can be written into fundamental thermodynamic equations so as to enable the field strength E to be a variable of state in a way which is essentially symmetrical with the way in which P and T are variables of state. This enables a variety of differential coefficients to be obtained, some of which appear to be new. A discussion is given of the relationship between "electrostriction pressure" (as derived in electrostatics) and thermodynamic pressure. Application of the formalism to systems of more than one component is illustrated by discussion of the change in composition produced by charging the plates of a small condenser immersed in a large volume of binary fluid mixture. The customary representation of the "energy density" in a field as equal to ElK/87r is discussed, and found to be limited in formal validity when the field is nonuniform, when the charging process takes place under conditions which do not hold the volume constant, or when dielectric saturation is taken into account. 1

A case against large cluster-induced nonequilibrium solvent effects in supercritical water

“…Finally, in the CC and PC models, the local density q x r is determined by the local ®eld i x r according to integration of the expression [3,37] dq…”

Properties of Hydration Shells of Protein Molecules at their Pressure‐ and Temperature‐Induced Native‐Denatured Transition

“…is equal to the value of the external pressure (a r = P) and the upper limit is b r = (P + P), where P denotes the local electrostriction pressure. [18] The latter represents the only unknown quantity in Equation (4). The permittivity e = eA C H T U N G T R E N N U N G (s,P,T) has been taken from refs.…”

“…Equation (2) represents the concise form of the thermodynamic equation of state for H 2 O in an open system, with one subsystem situated within the electric field. [18,19] Equation (4) shows a more explicit form of the equation; the solution of which leads to a relation between the mass density within the hydration shell and the surface charge density s. Knowing these values, one establishes a link between hydration shell characteristics [mass density (higher than that of the bulk water)] and protein properties (surface charge density). [14] We shall look for possible correlations between the properties of hydration water and the equilibrium line of proteins at the N-D transition (at temperature T t and external pressure P t , where t stands for transition).…”

“…The hydration shells around the protein molecules are denser than bulk water, as found experimentally by Svergun et al [17] The electric charges at the surface immersed in water exert a pull on the water dipoles into the region of the action of field E. Consequently, water within reach of the field is denser. This is due to the pressure P, termed electrostriction pressure, [18] which adds to the external pressure P in the open thermodynamic system. If one knows the total local pressure P + P, one can determine the local mass density [19] , the local coefficient of thermal expansion, the local heat capacity [20] and local compressibility of hydration water which are dependant on the charge density s at the adjacent charged or polar surface.…”

Thermodynamics of Preferential Solvation of Electrolytes in Binary Solvent Mixtures

“…Allowing r, to vary would not affect the curvature;reducing r*o would raise the predicted curve. The deficiencies of the Born treatment are well known(8) and alternative approaches to improve on the Born treatment have been attempted.Padova (36) has attempted to employ a treatment of Frank(37) to explain all solvent-sorting as arising from electrostatic contributions. It is clear that strong electrostatic fields could lead to reinforcement, or reduction, by electrostatic effects of the chemical explanation considered above.…”