The thermal decomposition of sulfatic phases takes place in accordance with (1), in which Me can represent the metals beryllium, magnesium or calcium. No hydrate phases occur with the sulfates of strontium, barium and radium so reaction 1a does not apply and only 1b takes place.
MeSO4 · nH2O → MeSO4 + nH2O↑ ⇥(1a)
MeSO4 → MeO + SO2↑ + ½O2↑ ⇥(1b)
The dewatering/dehydration takes place typically at temperatures above about 80 ºC and is complete at about 300 ºC. The water-free phase, anhydrite, remains but with further heating it also decomposes with the release of SO2. Knowledge of the...