Description of the experimental data of water in the wicinity of the critical point on the basis of algebra of fluctuation variables

Abstract

The system of algebraic equations of the algebra of fluctuating variables, proposed by V.L. Pokrovsky, has been directly applied for the first time to quantitative describing experimental data in close vicinity of the liquid-vapor critical point. Based on the literature data for water, the thermodynamic variables were subsequently converted into variables of the symmetric three-dimensional Ising model with using software. This transformation of variables was carried out until the following conditions were simultaneously fulfilled: 1) until the equation of the coexistence curve for the order parameter was symmetrized; 2) until the entropy jump along the coexistence curve was disappearanced. Within experimental errors for the initial experimental water data, it has been additionally shown next conditions fulfilled: 1) simultaneously with the symmetrization of the coexistence curve equation for the order parameter, the critical isotherm equation becomes symmetric 2) simultaneously with the disappearance of the entropy jump, the ordering field along the coexistence curve reaches zero. These properties of the transforming from experimental variables to variables of the symmetric three-dimensional Ising model indicate the thermodynamic consistency of the applied approach. According to the proposed methodology, the coefficients of equations of the algebra of fluctuating variables have been quantitatively determined for water. It is established that, in contrast to the initial idea of V.L. Pokrovsky, the condition for the smallness of both cross coefficients of the algebra of fluctuating variables simultaneously is not fulfilled, and also the signs of these coefficients can be different. On the example of water, it has been concluded that the transforming from thermodynamic variables of molecular liquids determined from experiment to variables of the Ising model does not significantly affect the disordering field and the order parameter, but significantly changes the ordering field and the disordering parameter. It is this behavior that characterizes the qualitative difference between the properties of liquids in the vicinity of the critical point and the properties of the symmetric three-dimensional Ising model.