Electric Permittivity Anomaly Close to the Critical Consolute Point of a Nitrobenzene + Octane Liquid Mixture

Abstract

Electric permittivity and density were measured in a nitrobenzene and octane mixture in the vicinity of the upper critical consolute point. Measurements were conducted in the one-phase region, at the critical concentration. The possibility of stirring in the course of measurements allowed us to check if the density and concentration gradients had any influence on the obtained results. No signs of the presence of the gradients mentioned above were found. Using the data obtained in the reported measurements, different methods of the fitting of the equation describing the permittivity anomaly were tested. The calculation of a reliable value of the critical amplitude, used to estimate the critical temperature shift under the influence of the electric field, was of particular interest. The derivative (∂T(c)/∂E(2)) was found to be (-3.9 ± 0.3) × 10(-16) K m(2) V(-2).

Liquid-vapor interface of the Stockmayer fluid in a uniform external field

“…the sign of the change in T c ), such as for pure SF 6 [6]. However, most experiments on polar liquids have been for liquid mixtures [2][3][4]8], and additional factor(s) can alter the sign of the change in T c [53]. For more complicated experimental systems, our results provide a base to understand the effect of additional characteristics beyond the simple dipolar model.…”

“…The presence of an external field brings an additional control that can be used to switch or modify the statistical states of the fluid. Liquid-vapor coexistence is a key aspect of the phase diagram of any liquid, and there has been much interest in liquid-vapor coexistence in dipolar systems in an external field both experimentally [2][3][4][5][6] and theoretically [5,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

“…Mean field theory predicts that the sign of the critical temperature shift also depends on the second derivative of the dielectric constant with respect to composition (i.e. density for a pure fluid), which for most fluids is positive [8]. This leads to an increase of critical temperature for constant surface potential [5].…”

The super- and sub-critical effects for dielectric constant in diethyl ether

“…In critical solutions of limited miscibility the anomalous decrease below the extrapolated linear dependence is observed. 16,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] This can be associated with the fact that generally for critical mixtures dT C /dE 2 < 0. 53 The only exception, still not explained ultimately, was obtained in nitromethane -3-pentanol critical mixture.…”

“…This can be linked to the fact that they can be conducted under atmospheric pressure and for near-room temperatures. 16,[21][22][23][24][25][26][27][28][29][30][31][32][33] Relations analogous to Eqs. (3)-(5) can be also expected for the isothermal, pressure path of approaching the critical point.…”