Surface tension regularity of non-polar, polar, and weak electrolyte liquid hydrocarbons

The correlation of reduced surface tension σ sc * versus reduced temperature T sc * which produces family of linear curves is investigated for universality. Each curve is characterized by the reduced temperature index T index * which is included in T sc * . The correlation is based on phenomenological scaling law and consideration of law of corresponding states. The reduced temperature T sc * , scaled distance from the boiling temperature Tb, has the practical advantage of being independent of critical temperature. The correlation is highly accurate when applied to 10 classes of non-polar, slightly polar, polar, and weak electrolyte liquid hydrocarbons. The slopes of linear curves of each class of liquids at given T index * ʹs are rather constant and a universal regularity among all liquid is very likely, however small differences identify three classes of non-polar, slightly polar, and polar plus weak electrolytes. Consideration of the pervious application to molten alkali halides, molten salts, and molten metals, and considering that the reduced surface entropy S s * = ( ∂ σ sc * / ∂ T sc * ) is rather constant for all liquid tested, strengthen the idea that σ sc * – T sc * correlation is likely universal.