Abstract
The vapor pressures of platinum, iridium, and rhodium have been measured using a microbalance technique based on the Langmuir method. Heats of sublimation at 298 °K were calculated with the aid of free energy functions. The least square lines for the vapor pressure data, the heats of sublimation, and the normal boiling points obtained were as follows: Platinum: [Formula: see text] Iridium: [Formula: see text] Rhodium: [Formula: see text] The indicated uncertainties are estimates of the overall limits of error. The value of the gas constant R used in the calculation of ΔHs° is 1.98726 cal/degree mole.