Dissolution rate of a gypsum (CaSO4·2H2O) sample rotating in pure water was measured by automatically detecting electric conductivity of the solution

in one-second time interval of data acquisition. Superficial shape (7 cm×4 cm×2 cm) and surface area (100 cm2) of the sample were maintained constant basically during measurement. Under surface reaction-controlled dissolution experiment condition

the kinetics model was used for regression of dissolution rate constant (ks) and reaction order (n). The values of ks were 1.91×10-8

3.46×10-8

4.92×10-8

7.07×10-8 mol·cm-2·s-1 respectively for temperatures 25

45

65

85℃

accommodated by a value of 1.27 for reaction order n. Consequently activation energy of dissolution reaction was correlated 19.07 kJ·mol-1 through the Arrhenius equation. Because of eliminating uncertainty of sample's surface area in dissolution experiment

the results calculated from the kinetics equation with the model parameters regressed in this paper were more consistent with experimental value and closer to theoretical expectation of dissolution rates in literature.