Synthesis and thermal behaviour of Na2SO4·MgSO4·4H2O

Abstract

The thermal behaviour of astrakanite was investigated by conventional thermal analysis techniques in air and by constant rate thermal analysis (CRTA) under residual water vapour pressure above the sample P H 2 O ¼ 5 hPa. It has been shown that the pathway of the thermal dehydration depends strongly on the nature of atmosphere above the sample. A correlation between structure evolution and thermal behaviour was developed. The apparent activation energies corresponding to the two dehydration steps of Na 2 Mg(SO 4 ) 2 Á4H 2 O were also measured experimentally by means of two CRTA curves and were found equal to 83 ± 7 and 111 ± 8 kJ mol -1 , respectively.