A thermal gravimetric method was employed to explore the course of dehydration of Na2CO3 . 10 H2O and Na2CO3 . H2O particles. Experimental data were amassed both in the temperature-increasing and constant temperature mode. Very small sample masses were used in an effort to eliminate an effect of heat and mass transfer processes on the rate of reaction. Kinetic equations of Arrhenius type were proposed for two stages of the dehydration and tested against the results collected by experiment.