Temperature dependence of the extinction coefficient of mercuric iodide vapor. Heat of sublimation and vapor pressure of solid mercury(II) iodide

The temperature dependence of the extinction coefficient of HgI/sub 2/ vapor has been determined at a single wavelength of 342 nm where the data can be represented by the equation epsilon(lambda 342 nm, T) = (0.803 +- 0.008)T/K - (273.1 +- 4.1). Measurements of the absorbance of the vapor in equilibrium with the solid as a function of temperature yielded the following vapor pressure equation, where the pressure is in millimeters of Hg (reduced to 273.15 K and standard gravity) and the temperature is in Kelvins: ln P = -(9959 +- 71)K/T + (23.28 +- 0.16), 417 less than or equal to T less than or equal to 509. The heat of sublimation calculated from this equation is 82.80 kJ mol/sup -1/. The linear dependence of ln P vs. l/T also establishes Beer's law for the vapor.