Preparation and characterization of a blue iron–titanium double sulphate

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 Mossbauer spectra indicate that there are substantial variations from the formal cation charges appropriate to an FeII–TiIV system even when the composition approaches FeTi(SO3)4 and appreciable concentrations of FeIII occur. There is no evidence that the FeIII occurs as an iron(III) oxide. The phase can be represented as [Fe2+1–x – yFe3+x + y][Fe 3+xTi3+yTi4+1–x – y](SO42–)3 which, in the limit of 1 : 1 stoicheiometry of iron and titanium becomes [Fe2+1–yFe3+y][Ti 3+yTi4+1–y](SO42–)3.