Abstract: Natural or synthetic gypsum is reacted with quicklime in any desired proportions, the heat needed for the complete conversion of gypsum in plaster being supplied, on the one hand, by the exothermic reaction of hydration of the quicklime and, on the other hand, by an external supply of calories obtained by indirect heating of the reaction mixture. This indirect heating may be effected by convection and conduction or by radiation from a metallic wall.

Abstract: In a process and apparatus for measuring qualitatively and quantitatively at least one volatile fraction contained in a solid, a sample of a given weight of the solid is introduced in a first enclosure having a known internal capacity, the sample is then brought up to a temperature beyond the temperature at which said volatile fraction becomes gaseous in the first enclosure, the gasified volatile fraction is allowed to become distributed both in said first enclosure and in a second enclosure connected to the first enclosure, the second closed enclosure having previously been brought to a constant temperature having a known value which is higher than the temperature at which the gasified volatile fraction becomes liquid, and the pressure increase which occurs in the whole system due to the gasification of said volatile fraction is measured.