Apparent Molar Heat Capacities and Apparent Molar Volumes of Aqueous Nicotinamide at Different Temperatures

Specific heat capacities and apparent molar heat capacities of aqueous nicotinamide have been determined from 25.0 to 55.0°C using microdifferential scanning calorimetry in the molality range of 0.07433 to 1.50124 mol-kg^–1. Densities and apparent molar volumes have also been determined for aqueous nicotinamide from 10.30 to 34.98°C using a digital densimeter in the molality range 0.07804–2.02435 mol-kg^–1. The results of these measurements have been used to calculate the following partial molar quantities and temperature derivatives for aqueous nicotinamide as a function of temperature: C_p,2,m^o, (C_p,2,m^o/T)_p, (²C_p,2,m^o/T²)_p, V_2,m^o, ( V_2,m^o/T)_p, and (²V_2,m²/T²)_p. The results are discussed in terms of the changes in the packing of nicotinamide molecules in the crystal, interactions in the aqueous form, and its structure-promoting ability with rise in temperature.