Use of water-insoluble aluminosilicates in tanning process for the production of leather

In the process of defatting and pretanning of pickled dehaired hides comprising subjecting pickled dehaired hides to the action of an aqueous liquor containing

• (1) surface-active compounds selected from the group consisting of anionic surface-active compounds and nonionic surface-active compounds,
• (2) electrolytes, and
• (3) sequestering agents, rinsing and recovering defatted and pretanned hides, the improvement consisting essentially of employing a water-insoluble aluminosilicate, containing bound water, of the formula
• (Cat.sub.2/n O).sub.x.Al.sub.2 O.sub.3.(SiO.sub.2).sub.y
• wherein Cat represents a cation selected from the group consisting of alkali metals and mixtures of bivalent metal ions with at least 5 mol % of the mixture of alkali metal ions, n represents an integer from 1 to 3 of the valence of the cation, x is an integer from 0.5 to 1.8 and y is an integer from 0.8 to 50, said aluminosilicates having an average particle size in the range of 0.1.mu. to 5 mm and a calcium binding power of from 0 to 200 mg CaO/gm of anhydrous active substance measured at 22.degree. C., as partial replacement of said surface-active compounds, electrolytes and sequestering agents.