Abstract: A process for tanning hides for soles or insoles with ammonium titanyl sulphate. The hides, subjected to soaking, liming, fleshing, and deliming, are first treated with ammonium sulphate. Successively, ammonium titanyl sulphate as well as citric acid or an alkali metal citrate are gradually added to the bath, while maintaining the temperature of the bath at a value not exceeding 37.degree. C. and a pH at values ranging from 1.7 to 2.5. After each addition, the hides are treated until they have absorbed at least 90% of the soluble Ti (IV). Sodium sulphite and hexamethylenetetramine are then gradually added: this addition is such as to bring the final pH of the bath to 3.8-4.5 and to exhaust the bath in soluble Ti (IV). NaHCO.sub.3 is successively added until a pH value of the bath ranging from 4.0 to 5.0 is reached, such pH being maintained for at least 2 hours.

Abstract: This invention concerns a new product consisting of TiO.sub.2 particles having pigmentary granulometric and morphological characteristics. It includes a chemically reactive coating consisting of a mixture of oxides and oxychlorides selected from the group consisting of Al.sub.2 O.sub.3 and AlOCl; SiO.sub.2 and SiOCl.sub.2 ; and ZrO.sub.2 and ZrOCl.sub.2.The particles of reactive TiO.sub.2 product are prepared as follows: the surface of the TiO.sub.2 particles is activated by thermally treating the particles in a moving bed with an anhydrous gas at 400.degree.-600.degree. C. The particles are then made to react in a moving bed at 350.degree. C. to 600.degree. C., in the presence of a carrier gas, with an inorganic chloride selected from the group consisting of AlCl.sub.3, SiCl.sub.4 and ZrCl.sub.4.This new product is useful, for instance, in TiO.sub.2 pigments coated with organic molecules which provide an affinity for the vehicles of paints.