Activated bleaching clay

Finely-divided clay, e.g. bentonite, is mixed with concentrated sulphuric acid, which is substantially free of water, usually of a quantity enough to activate the clay and to produce a free-flowing mixture, e.g. 5-40 per cent by weight of acid, and subsequently contacting this mixture with steam. Preferably the clay/acid mixture is heated to 100 DEG C. before the steam treatment, e.g. by fluidizing with heated air.