Synthesis, characterization and thermal behavior for Tutton's salts K2M(SO4)2.6H2O (M = Mg, Co, Cu) are reported. These double salts crystallize in the monoclinic system, with the space group P21/a (Z = 2). The unit-cell parameters were affined with "affma" software. The IR spectrums reveal also the characteristic vibrational of water and sulfates. Thermogravimetry (TGA), differential thermal analysis (DTA) and XRD at high temperature investigations show that the dehydration of these salts occurs between 70 and 200°C. This indicates the removal of all water molecules around 200°C. Schemes of their decomposition are proposed. While K2M(SO4)2.6H2O (M = Mg, Co, Cu) salts are isostructural, they do not exhibit the same decomposition steps.
