Vapor Pressures of Scandium, Yttrium, and Lanthanum

Abstract

The vapor pressures of scandium, yttrium, and lanthanum were measured by the effusion method with a vacuum balance, and the heats of vaporization were measured with a mass spectrometer. The data are represented by $$\begin{array}{cc}\mathrm{Scandium}:& \log \mathrm{p\hspace{0.17em}(}\mathrm{atm}\text{)=(5.44±0.07)−(17020±90)/T,}\\ \mathrm{Yttrium}:& \log \mathrm{p\hspace{0.17em}(}\mathrm{atm}\text{)=(5.59±0.07)−(19950±90)/T,}\\ \mathrm{Lanthanum}:& \log \mathrm{p\hspace{0.17em}(}\mathrm{atm}\text{)=(6.08±0.09)−(21940±150)/T.}\end{array}$$ The errors quoted are standard deviations. The heats of vaporization at temperature are 77.9±0.4, 91.3±0.4, and 100.4±0.7 kcal mole^—1 for scandium, yttrium, and lanthanum, respectively, and the corresponding entropy changes are 24.9±0.3, 25.6±0.3, and 27.8±0.4 eu.