Vapour pressures of anhydrous sulphates. Part I. Knudsen effusion results between 560 and 1000 °C for alkali-metal sulphates

Abstract

Knudsen weight loss results are reported for Li₂SO₄, Na₂SO₄, K₂SO₄, Rb₂SO₄, and Cs₂SO₄ between 560 and 1000 °C. At the higher end of the temperature range, absolute values of the vapour pressure are in fair agreement with those formerly obtained by effusion techniques but are significantly larger than those so far determined mass spectrometrically. At the lower end of the temperature range a sharp change is now observed in the slope of the log P vs 1/T plot in the case of Li₂SO₄ and Na₂SO₄, and this is tentatively interpreted in terms of the formation of Li₂O and Na₂O in the vapour phase, the dissociation of these oxides at the higher temperatures giving rise to vapours composed of Li (or Na), SO₂, and O₂.