Abstract: Soil modifiers comprising from 80 to 95% by weight of a mixture of ferric oxide and ferric sulphate in an oxide/sulphate weight ratio of from 0.2:1 to 2:1 are prepared by calcining at 500.degree.-600.degree. C in the presence of an oxidizing gas a material consisting essentially of ferrous sulphate with an average number of molecules of crystallization of from 1 to 5 obtained by partial dehydration of the waste materials, consisting essentially of ferrous sulphate heptahydrate, obtained in the manufacture of titanium dioxide from ilmenites or ilmenite slags by the sulphate process. These modifiers are particularly suitable for clay soils.

Abstract: A process for the joint production of titanium dioxide and sodium tripolyphosphate from ores of titanium and phosphorus, and from sulphuric acid, in which the titanium dioxide is produced by the "sulphate process" and the impure dilute aqueous solution of sulphuric acid resulting therefrom is concentrated and used in the initial attack of phosphatic ones to provide a solution containing vanadium and chromium which can be removed without requiring any preventive conversion. The resulting sodium phosphate is then converted to sodium tripolyphosphate in a known way.