Cubic β-Fe2O3 as the product of the thermal decomposition of Fe2(SO4)3

Hyperfine Interactions - The thermal decomposition of Fe2(SO4)3 in air has been investigated using transmission Mössbauer spectroscopy, CEMS and X-ray powder diffraction. The hexagonal...     

A test of the onsager reciprocal relations and a discussion of the ionic isothermal vector transport coefficientsI Ij for aqueous AgNO3 at 25°C

Values ofI _ij calculated from experimental data are given for AgNO₃ at 25°C. Experimental values of the ratioI ₁₂/I₂₁ are calculated to provide a sensitive direct test of the Onsager reciprocal relations,I ₁₂=I₂₁. This ratio is found to be unity within experimental error (ca. 2%). The general physical interpretation ofI _ij/N as mobilities is discussed. An approximate way of estimatingI _ij for dissociated salts is considered. A comparison is made between AgNO₃ I _ij data and corresponding data for NaCl and KCl. It is concluded that ion-pair formation (1) sharply increases the magnitude of the interaction mobility,I ₁₂/N; and (2) increases the intrinsic mobility of Ag⁺,I ₁₁/N, and decreases the intrinsic mobility of NO ₃ ^– ,I ₂₂/N.     

The Role of Intermediates in the Process of Red Ferric Pigment Manufacture from FeSO4⋅7H2O

One method of industrial manufacture of red ferric pigments is based on the thermal decomposition of FeSO₄7H₂O into -Fe₂O₃(copperas red). The difficult reproducibility of the color quality of the final pigment is the main problem of this process. One of the factors that can influence the pigment color is contamination by some of the intermediates formed during the transformation process. The identification of two groups of intermediates is the basic result of an extensive laboratory investigation carried out using ⁵⁷Fe Mössbauer spectroscopy and X-ray powder diffraction (XRD). The first group of intermediates includes sulfato-phases as FeSO₄H₂O, FeSO₄, Fe(OH)SO₄, Fe₂O(SO₄)₂, Fe₂O(SO₄)₂xH₂O x(0,1), and Fe₂(SO₄)₃. Thermally metastable polymorphs of iron(III) oxide, -Fe₂O₃, -Fe₂O₃ and -Fe₂O₃, represent the other group. Mössbauer characterization of all intermediate products is given. A significant influence of -Fe₂O₃ on the pigment color was found.