Reliable azeotropic data have been measured for the binary systems ethanol + diethoxymethane, diethoxymethane + 1-propanol, diethoxymethane + heptane, and cyclohexane + diethoxymethane with the help of a wire band column. Additionally molar excess enthalpies (HF) for the binary mixtures of diethoxymethane with hexane, 1-octene, methanol and ethanol at 363.15 K have been determined with an isothermal flow calorimeter. The experimental data were compared with the results using the available "ether" main group of the group contribution method Modified UNIFAC (Dortmund), which is a well-known model for the prediction of phase equilibria and excess properties. For the description of the HE data a Redlich-Kister polynomial was also used. The aim of this work is to supplement the available data base for acetal systems required for the introduction of a new "acetal" group in the Modified UNIFAC (Dortmund) model.