Measurements of the binary mixture {water (1) + 1,3-dimethylurea (2)} density within the temperature range of 274.15 to 333.15 K were performed within a wide range of compositions at the atmospheric pressure by using the density gauge with a U-shaped vibrating tube. There are calculated apparent and partial molar volumes of water and 1,3-dimethylurea (1,3-DMU) in the mixture, limiting (standard) partial molar volumes of 1,3-DMU in water, molar isobaric thermal expansion of the mixture and molar isobaric thermal expansion of 1,3-DMU at infinite dilution. It is shown that concentration dependences of partial molar volumes of the water and 1,3-DMU are characterized by the presence of extremums thus revealing manifestation of hydrophobic nature of the 1,3-dimethylurea molecule. Limiting partial molar volumes of 1,3-DMU increase with the increase of the temperature. Increasing both the temperature and the concentration of 1,3-DMU lids to the increasing of the molar isobaric expansion of the mixture. The obtained results are discussed in terms of the solute – solvent and solute – solute interactions. A comparison of the obtained characteristics with similar characteristics of the urea, N-methylurea and tetramethylurea is performed.
