Vapor Pressures, Heats of Vaporization, and Entropies of Some Alkali Halides

Vapor pressures of crystalline KCl, KBr, KI, and NaCl have been measured in the pressure range of 10−1 to 10−7 mm by a surface ionization method. Heats and entropies of vaporization are calculated from the data. The heats of vaporization at 0°K and entropies at 298°K are also calculated. From the data, saturated KCl vapor is shown to be less than 2 percent associated at 800°K and the heat of dissociation of (KCl)2 is shown to be less than 47 kcal.