Abstract
A nuclear magnetic resonance study of xenon adsorbed on Pt-NaY zeolites, with or without pre-chemisorbed hydrogen, has made it possible, first, to prove that chemisorption of hydrogen occurs homogeneously on all particles of similar size, and, secondly, to determine the number of platinum particules and therefore their mean size. This technique seems highly useful when particles contain very few atoms and cannot be detected by electron microscopy.