Thermochimica Acta, Vol.233, No.2, 243-256, 1994
Thermal-Decomposition of Calcium Citrate Tetrahydrate
The thermal decomposition of calcium citrate tetrahydrate in dynamic air or dry nitrogen has been studied thoroughly. Thermal events encountered throughout the decomposition range (room temperature to 1000-degrees-C) have been monitored by TG, DTA and DSC. The encountered events have been characterized by analysing the decomposition solid products using X-ray diffractometry, IR spectroscopy and scanning electron microscopy (SEM). Non-isothermal kinetic and thermodynamic parameters (A, k, DELTAE, DELTAH, C(p) and DELTAS) have been determined. The results show that Ca3(C6H5O7)2 . 4H2O dehydrates in two successive steps at 60-140-degrees-C and 140-190-degrees-C each involving release of two moles of water. The ultimate decomposition product has been found to be CaO which formed above 640-degrees-C in air or dry nitrogen flow. SEM examinations indicate the formation of fusion nuclei accompanying the second dehydration step. Decomposition pathways in air and nitrogen are proposed.