(-16.4 °C), 8 (-3.4 °C), 6 (116.7 °C), 4 (181 °C), 2 (ca. 300 °C). [ 1 ] In the hexahydrate, the Mg 2+ remains octahedral , but is coordinated to six water ligands . [ 2 ] The thermal dehydration of the hydrates MgCl 2 (H 2 O) x (x