A standard has been developed for calibrating uranium hexafluoride pressure gauges in the micron region. The device employs the equilibrium dissociation pressure of uranium hexafluoride furnished by the sodium fluoride complex salt at easily controlled temperatures above ambient. The pressure signal obtained is in good agreement with reported dissociation pressure measured by the transpiration method. The principles are applicable to noncorrosive gas‐solid systems; for example, some oxides, carbonates, and hydrates dissociate to reversibly give a definite oxygen, carbon dioxide, or water vapor pressure at a given temperature.