Preparation and characterization of a blue iron–titanium double sulphate

Abstract

The preparation of a blue iron–titanium double sulphate is described. Although its composition can approach a stoicheiometry of FeTi(SO₄)₃ preparations usually contain an excess of iron and it does not seem possible to prepare the accurately stoicheiometric compound. The analytical data and Mössbauer spectra indicate that there are substantial variations from the formal cation charges appropriate to an Fe^II–Ti^IV system even when the composition approaches FeTi(SO₃)₄ and appreciable concentrations of Fe^III occur. There is no evidence that the Fe^III occurs as an iron(III) oxide. The phase can be represented as [Fe²⁺_{1–x – y}Fe³⁺_{x + y}][Fe ³⁺_xTi³⁺_yTi⁴⁺_{1–x – y}](SO₄^2–)₃ which, in the limit of 1 : 1 stoicheiometry of iron and titanium becomes [Fe²⁺_1–yFe³⁺_y][Ti ³⁺_yTi⁴⁺_1–y](SO₄^2–)₃.