Speed of ultrasound, density, and adiabatic compressibility for 2-methylpyridine plus heavy water in the temperature range 293 K to 313 K

The speed of ultrasound and density for 2-methylpyridine (1) + heavy water (2) were measured at atmospheric pressure and at temperatures ranging from 293 K to 313 K over the entire composition range. Parabolic equations approximating the dependencies of speed and density on temperature were determined. The adiabatic compressibility was calculated from the Laplace formula. The speed of sound, density, and compressibility isotherms were plotted as functions of the mole fraction x(1). The density decreases monotonically with increasing 2-methylpyridine concentration, while both the speed and compressibility isotherms show single extrema (maxima and minima, respectively). The speed of sound and compressibility isotherms cross one another in a narrow concentration interval in the vicinity of x(1) approximate to 0.04. The mixture of 3-methylpyridine with heavy water shows similar features although its phase properties differ from those of the 2-methylpyridine solution.