Chloric acid + sodium chlorate mixtures have been proposed as a substitute for some of the sodium chlorate and sulfuric acid in the generation of chlorine dioxide. This paper continues our work on physical property characterization of chloric acid + sodium chlorate solutions. A dual ebulliometric setup was employed to evaluate the vapor pressure-temperature relationship of chloric acid and chloric acid + sodium chlorate solutions. The natural log of vapor pressures for chloric acid solutions (1.01-3.82) mol L(-1) over the temperature range (35-79) degrees C was a linear function of chloric acid concentration and the reciprocal of the temperature. Vapor pressures were determined for sodium chlorate + chloric acid solutions for (0.85-4.25) mol L(-1) sodium chlorate, (0.73-3.59) mol L(-1) chloric acid, and (35-83) degrees C. All of the data were well correlated by an equation relating the natural log of vapor pressure to sodium chlorate concentration, chloric acid concentration, and the reciprocal of the temperature. Some solutions with high chlorate ion concentrations at high temperatures developed a yellow or pink color. Vapor phase measurements showed that the vapor pressures determined in these experiments are due to water with a trace contribution from another component.