By evaporation of an aqueous mixture of M(III) sulfate and ethanolammonium sulfate (a) in the presence of sulfuric acid and (b) without sulfuric acid, double acid, double sulfates of AI(III) and Fe(III) were obtained. The stoichiometries of the compounds were obtained by means of elemental and TG analyses. From the X-ray powder diffraction patterns it was concluded that, depending on the presence or otherwise of sulfuric acid, two different structures of the Al double sulfate with the same empirical formula HOCH2CH2NH3Al(SO)4)2 . 6H2O were obtained. It was also established from the TG curve that the HOCH2CH2NH3Fe(SO4)2 . 2H2O obtained dehydrates at a higher temperature and is more stable that the AI(III) double sulfates.