Linde 4A zeolite was converted to Ni, Co, Zn and Cd forms by replacing sodium ions with divalent cations. The replacement was from 82 % (Ni) up to 100 % (Cd). Chemical, T.G.A., D.T.A. and X-ray analysis of the divalent metal zeolites have been made and data on the composition of the unit cells and the thermal stability of the lattices were obtained. Ni-zeolite is unstable, its crystal lattice being completely destroyed above 70"C, whereas Co-, Zn-and Cd-zeolites are stable up to 750-850°C. The adsorption of water on the latter zeolites is reversible. Ion-exchange isotherms for Co2+, Zn2+ and Cd2+ at three temperatures were obtained and the thermodynamic functions, AGO, AHo and AS", of the ion-exchange equilibria calculated. The thermodynamic data are discussed with respect to hydration and size of the cations. A possible explanation of the instability of Ni-zeolite is suggested.* samples stored over saturated NH4Cl solution at 22-23°C.?calculations based on the weight % assuming that the silica content corresponds exactly to 12 SiOz groups per unit cell.

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