Physical Properties of Aqueous N-Methyl Pyrrolidone at Different Temperatures

Many physical properties of aqueous N-Methyl pyrrolidone mixtures were determined for molar fraction X_NMP = 0.02, 0.05, 0.125, 0.32, 0.37 at different temperatures ranging from 15-65°C. From the result we noticed that the viscosity coefficient was increased with increasing the molar fraction X_NMP and reached a maximum value at X_NMP = 0.25-0.37, and decreased with temperature. We observed the same relationship of the thermodynamic properties for the mixture at different temperatures and for excess activation function was positive. They reached maximum value at the X_NMP = 0.25-0.37. The same relationship was observed for excess dielectric constant. The results were explained according to hydrogen bonding effects and dipole-dipole interactions. This binding is stronger than binding between water molecules which may be let to form a complex at the molal fraction ratio 2:1 of water-NMP solution. We noticed that an increase in temperature may be let to tighten the interaction between water and NMP.