Abstract
The metastability of α-CaSO4·1/2H2O in 2.62-14.83% H2SO4 solutions was studied by wet DTA method. On the basis of the measured values of reaction temperature and induction period for hydration of a-CaSO4·1/2H2O in 2.62-14.83% H2SO4 solutions in this study and previous results1) -3) , the relation between H2SO4 concentration Z (%) and reaction temperature Y (°C) in the case of 1 minute induction period was given as follows : Y= _38.75e-0.1344z+ 86.74 (where Z= 2.62-14.83) As a result of estimating the maximum point from above and previous similar relation in 20.20-40.48% H2SO4 solutions3) , the value of Z= 17.29% and Y= 82.94°C was obtained. The metastable zone for α-CaSO4·1/2H2O in 2.62-40.48% H2SO4 solutions was determined. The phase diagram for metastably of calcium sulfate in the CaSO4-H2SO4-H2O system was shown by the isochrones in the case of 1 minute induction period for dehydration of CaSO4.2H2O2) and hydration of CaSO4·1/2H2O in this and previous3) studies.
