Vapor Pressure of Magnesium Fluoride

The vapor pressure of MgF 2 was measured over the temperature range 1413° to 1614°K by the Knudsen effusion and torsion‐effusion methods. Experimental data could be expressed by the equations log P Knudaen = 9.147 ‐ 20,183/T and log P Toraion = 8.311 ‐ 18,960/T in the temperature range of solid magnesium fluoride (1413° to 1536°K) and by the equations log P Knudaen = 6.065 ‐ 15,44O/T and log P Toraion = 6.737 ‐16,480/T in the temperature range of liquid magnesium fluoride (1536° to 1614°K). The MgF 2 vapor was shown to be essentially monomeric. The heat of vaporization (or sublimation) at 298°K was calculated to be 88.0 ± 1.0 kcal per mole. A continuous weighing procedure was devised for use with the Knudsen effusion method. An electromagnetic torque method of measurement was developed for use with the torsion‐effusion method.