Study of thermal preparation of iron (III) pigments by means of thermal analysis methods

Article abstract of DOI:10.1007/BF01913924

The decomposition of hydronium jarosite occurs in two temperature ranges: first a loss of 8 moles of H₂O from 2 moles of jarosite, and then in the second step one mole of H₂O and 4 moles of SO₃ are simultaneously evolved. Fe(OH)(SO₄)₂ are assumed to be intermediates. During the thermal treatment of Na or K jarosites, only Fe₂(SO₄)₃ appears as intermediate. The decomposition temperatures are significantly influenced by the type of crucible used (determination of partial pressure of gaseous decomposition products). The particle size distribution of the starting jarosite has no effect upon the temperaure of the decomposition steps and the reaction with ZnO. The results of TG measurements were evaluated via calculations of the steps of the experimental activation energies for these partial decomposition jarosites and for their reaction with ZnO.