Mass Spectrometric Studies at High Temperatures. II. The Sublimation Pressures of Magnesium, Strontium, and Barium Fluorides

Abstract

A mass spectrometer has been employed to measure the sublimation pressures and heats of sublimation for MgF₂ over the range 1241° to 1492°K; for SrF₂ over the range 1207° to 1563°K; and for BaF₂ from 1232° to 1505°K. For MgF₂ the results are represented by $$\log P_{\mathrm{atm}}{\text{=−[(88.3±0.9)/45.76]10}}^4{T}^{\text{−1}}\text{+8.53±0.2;}$$ for SrF₂ by $$\log P_{\mathrm{atm}}{\text{=−[(99.3±0.7)/45.76]10}}^4{T}^{\text{−1}}\text{+8.716±0.01;}$$ and for BaF₂ the equation is $$\log P_{\mathrm{atm}}{\text{=−[(85.1±0.9)/45.76]10}}^4{T}^{\text{−1}}\text{+7.659±0.01.}$$ The errors quoted are the standard deviations from the least‐squares fitted lines. The heat of sublimation of MgF₂ at 1366°K is 88.3±2.5 kcal mole^—1 while the heats of sublimation at 298°K are 103.7±2.5 kcal mole^—1 for SrF₂ and 92.3±2.0 kcal mole^—1 for BaF₂.