Static dielectric constants of the N,N-dimethylformamide/2-methoxyethanol solvent system at various temperatures

Measurements of static dielectric constants (ε) have been made for binary liquid mixtures of N,N-dimethylformamide (DMF)/2-methoxyethanol (ME) at 19 temperatures ranging from −10 to +80 °C. Some empirical equations of the type ε = ε(T), ε = ε(X1), and ε = ε(T,X1) have been applied to check their validity. The εE values, which refer to the deviation of the dielectric constants of the binaries from the values arising from mole fraction mixture law, have been calculated. Deviations from ideal behaviour have been found to be positive at all temperatures. The positive εE values are attributed to a specific interaction between unlike molecules, which leads to the formation of complexes between DMF and ME in the liquid state. These nDMF•mME complex moieties were found to have the stoichiometric ratios 2:1, 1:1, and 1:2 in the temperature range of −10 to +80 °C.