Abstract: The invention relates to a zirconium phosphate in particles having sizes comprised within the range of from 1 to 100 .mu.m, a lamellar structure with interlayer distance, in the anhydrous state, comprised within the range of from 7.9 to 8.2 .ANG. and a surface area comprised within the range of from 9 to 20 m.sup.2 /g.The method consists in altering the lamellar structure of a zirconium phosphate with layer structure of alpha type by intercalating into it an organic substance containing a proton-acceptor group and water and by a treatment with ultrasounds, in regenerating the hydrogen form of said zirconium phosphate by an acid and in washing the same with diluted acids and/or water.

Abstract: Mixed phosphorous or arsenic salts of tetravalent metals are provided having the general formula M(HAO.sub.4).sub.2-x (HAO.sub.3).sub.x.nH.sub.2 O, where M is Zr, Ti or Hf, A is phosphorus or arsenic, x is between 0.05 and 1.95, and n is 0 to 6. The salts are highly stable and have wide potential application in the fields of ion exchange, catalysis, intercalation of molecules, solid electrolytes, and chromatography. The salts are prepared by reacting a halide, oxyhalide, nitrate, sulphate, phosphate or oxide of the tetravalent metal, preferably in an aqueous medium, with at least two oxygenated acids of phosphorus and/or arsenic.

Abstract: A prochiral or racemic substrate such as a prochiral ketone is converted into an optically active product through a process wherein said substrate is subjected to an asymmetric hydrogen transfer reaction by means of an optically active amino-alane or polyimino-alane represented by the formulaH.sub.2 AlNR.sub.1 R.sub.2, H Al(NR.sub.1 R.sub.2).sub.2 or (H AlNR).sub.nwherein R, R.sub.1 and R.sub.2 are alkyl, aryl or cycloalkyl radicals, n is an integer higher than 4, and which contains an Al -- N direct bond and an Al -- H bond per aluminum atom, and the third substituent bound to aluminum is halogen, --H, ##STR1## or --OR wherein R has the aforesaid meaning, and wherein the asymmetry center is constituted by a primary or secondary amine group containing an optically active alkyl radical.