Abstract
On the basis of the measured values of reaction temperature and induction period for dehydration of calcium sulfate dihydrate in 20-55% sulfuric acid solutions obtained by means of a wet DTA in previous investigation', the method to set up an empirical equation that expresses the relation among the three factors of sulfuric acid concentration Z (%), reaction temperature y (°C) and induction period x (min) was studied. In analyzing data the following equations of approximational function were used;
y=Yx-m
Y=-a1eb1z+C1
m=a2Zbz+c2
These equations were linearized, and tested by regression analysis.
The relation among the three factors of Z, y and x was represented as follows:
y=(-4. 886e0.04897Z+111.33)x-(1. 362x10-10Z5. 093+0. 01410)
It was confirmed comparing with the measured values that above empirical equation is applicable to the region of Z-=-20-55% and x=1-30 minute. From the above results, it became possible to show the phase diagram for metastability of calcium sulfate dihydrate in sulfuric acid solution by isochrones of induction period, and the phase diagram thus expressed was considered to be useful in practical use.
