Determination of the Components of the Surface Tension of Some Liquids from Interfacial Liquid-Liquid Tension Measurements

Abstract

Measurements of the surface tension of glycerol, ethylene glycol, formamide, α-bromonaphthalene, and benzene, as well as of the interfacial tension of polar liquid-apolar liquid, were made. On the basis of the surface tension of n -alkane and the interfacial tension of n-alkane-polar liquid the dispersion and nondispersion or Lifshitz-van der Waals and acid-base components of glycerol, formamide, and ethylene glycol were calculated and compared with those obtained in different ways. Then using the surface tension values of benzene and diiodomethane and the interfacial tension of polar liquid-benzene and polar liquid-diiodomethane, the values of electron-acceptor and electron-donor parts of acid-base components of glycerol, ethylene glycol, and formamide were calculated and compared with those obtained from contact angle measurements. The Lifshitz-van der Waals and the electron-acceptor and electron-donor components of the liquids mentioned above were also calculated solving a system of equations obtained on the basis of the measurements of their surface tension and interfacial tensions for polar liquid-diiodomethane and polar liquid-benzene systems. These calculations were made either on the assumption that there is acid-base interaction across the interface for the polar liquid-diiodomethane system, or on the assumption that there is not. The Lifshitz-van der Waals and acid-base components for α-bromonaphthalene were calculated from the interfacial tensions of glycerol-α-bromonaphthalene, ethylene glycol-α-bromonaphthalene, formamide-α-bromonaphthalene, and water-α-bromonaphthalene. On the basis of the measurements and calculations we found that the values of the dispersion and nondispersion components of glycerol, ethylene glycol, and formamide differ depending on the kind of n-alkane. These components differ from those obtained in another way. The electron-acceptor and electron-donor parts of the acid-base components differ also from those obtained from contact angles. It was found that using the dispersion and nondispersion components of the surface tension of the liquids studied for calculation of the interfacial tension for some liquid-liquid systems gave almost the same results as using Lifshitz-van der Waals and acid-base ones. On the basis of measurements and calculations it is stated that the specific orientation of molecules at the liquid-liquid interface and the mutual solubility of phases that are in contact influence the values of components of liquid surface tension calculated from liquid-liquid interface tension measurements.