Thermal analysis of Na2CO3 · H2O crystals

Abstract Monohydrated sodium carbonate crystals have been grown by slow evaporation of its aqueous solution maintained at 40 ± 1°C. The thermal dehydration of this crystal has been studied by dynamic and isothermal TG measurements. It is observed from dynamic TG that the single molecule of water of crystallization is lost in two steps of 0.3 mole and 0.7 mole at temperatures 426 ± 5 and 454 ± 5 K, respectively. From isothermal and dynamic TG measurements, the kinetic parameters E and Z are calculated using different known forms of the function F(α). It is observed that consistency of E and Z values in isothermal and dynamic TG measurements for the two dehydration steps gives the correct function F(α) = −[log(1-α)] 0.5 . The activation energies for this function for the two dehydration steps are ≈6 and ≈9 kcal mole −1 , respectively.