Analysis of phases present in a plaster - by heating and weighing the plaster at fixed conditions of temp. and water vapour pressure

摘要

Analysis of different phases present in a plaster obtd. from a natural or artificial gypsum consists of heating the plaster to a temp. (TB) between the temp. (TA) defined by the intersection between the curve (G) of dehydration temp. against water vapour press. and the curve of isosteric press. of water vapour against temp. P (epsilon is 0.5), epsilon being the fraction of water contained in the soln. of soluble anhydrite, (and epsilon is 0-0.66) at a press. of water vapour greater than that defined by the intersection of the curves, and weighing under these conditions (wt. MB). Then while maintaining constant the press. of water vapour, the temp. of the mixt. is increased to bring it to the isostere P (epsilon is 0.5) and the mixt. is weighed again (Mo). Finally, under constant vapour. pres. of water, the mixt. is heated to a temp. corresp. to insol. gypsum for the mixt., which is weighed again (Mo). Then, knowing the molar masses of the different phases. The masses of gypsum are calculated. Process is much shorter than the prior art method which takes 48 hrs.