Hydrogen adsorption (physisorption) on the faujasite-type zeolite Mg-X was studied by means of variable-temperature (80-140 K) FT-IR spectroscopy. Perturbation of the adsorbed H-2 molecules by the cationic adsorbing centres of the zeolite renders the H-H stretching mode IR active, at 4065 cm(-1). Simultaneous measurement of IR absorbance and hydrogen equilibrium pressure, for a series of spectra recorded at the increasing temperature, allowed standard adsorption enthalpy and entropy to be determined. They resulted to be Delta H-0 = -13 kJ mol(-1) and Delta S-0 = -114 J mol(-1) K-1, respectively. Both, spectroscopic and thermodynamic results are discussed in the broader context of corresponding data for hydrogen adsorption on other alkali and alkaline-earth cation exchanged zeolites, showing that, while an approximate correlation exists between Delta H-0 and H-H stretching frequency, deviations can be expected for the case of zeolites containing small metal cations. (C) 2010 Elsevier B.V. All rights reserved.