SPECIFIC-HEAT CAPACITY AT CONSTANT VOLUME FOR (XNH(3)-X)H2O) AT TEMPERATURES FROM 300 TO 520 K AND PRESSURES TO 20 MPA((1)

Specific heat capacities at constant volume (c(v)) of {xNH(3) + (1 - x )H2O} (x approximate to 0.7, 0.8, 0.9) mixtures were measured with an adiabatic calorimeter. Temperatures ranged from 300 K to 520 K, and pr essures ranged from 3 MPa to 20 MPa. Measurements were conducted on si ngle-phase liquid and compressed gaseous samples. The mixtures were gr avimetrically prepared from high-purity substances and verified by che mical analysis. Density was reported for initial and final end points during each calorimetric experiment. The principal sources of uncertai nty are the temperature rise measurement and the change-of-volume work adjustment. The expanded relative uncertainty (with a coverage factor k = 2 and thus a 2-standard-deviation estimate) for c(v) is estimated to be 1% for liquid phase and 4% for gaseous results, and for density it is 0.2%.