When temperature (t°) increases from 100 to 175°C empirical constants of etherification equilibrium reaction in mixtures with excess of acetic acid decrease (ΔH⁰ < 0), with excess of ethyl alcohol - increase.

This anomaly is explained by the fact that ethyl alcohol has negative temperature coefficient of static dielectrical permeability (like most other liquids), while acethic acid and other carbon acids (except for formic acid) - positive. Different behaviour of examined liquids is caused by molecule chain association of aliphatic alcohols and cyclic association of carbon acids (except for formic acid) and disconnection of their dimeasures under rising temperature.