Interfacial Tension of 3-Methylpentane–Nitroethane near the Critical Point

Experimental data are reported for the capillary rise of the interface between the two liquid phases of 3‐methylpentane–nitroethane as a function of temperature. The data are interpreted in terms of a power law currently proposed for the behavior of the interfacial tension near the critical mixing point. The results seem to indicate that for 3‐methylpentane–nitroethane the region of asymptotic behavior is limited to rather small values of ${\mathrm{\Delta T*\hspace{0.17em}=\hspace{0.17em}(T}}_c{\mathrm{\hspace{0.17em}-\hspace{0.17em}T)\hspace{0.17em}/\hspace{0.17em}T}}_c$ . For ${\text{ΔT*\hspace{0.17em}≥\hspace{0.17em}10}}^{\text{−2}}$ Sugden's parameter $a^2$ can be represented by a power law $a^2{\mathrm{\hspace{0.17em}=\hspace{0.17em}A}}^2{\mathrm{\Delta T*}}^{\phi }$ with an exponent $\text{φ\hspace{0.17em}=\hspace{0.17em}1.00\hspace{0.17em}±\hspace{0.17em}0.01}$ . A comparison is made with the behavior of the surface tension of simple one‐component liquids near the gas–liquid critical point.