Effect of temperature on the density and surface tension of aqueous solutions of HMT

In this study, a systematic study of the effect of the temperature on the density and surface tension of HMT (hexamethylentetramine) in water was developed. The density and surface tension were determined at temperatures of 288.15, 293.15, 298.15, 303.15, and 308.15 K. Precise data of surface tension have not been reported previously in literature. From the density measurements, the apparent molar and partial molar volumes were calculated. The apparent molar volume decreases with concentration, the molar partial volume increases with temperature. The surface tension of the aqueous solutions of HMT decreases with concentration. The excess surface concentration was calculated, the values increase with concentration, indicating that the amount of HMT that goes to the interface gas liquid increases at higher concentrations of HMT.