Abstract: Normal methods of impregnating silicalite with noble metals leads either to metal loadings under 8% at high (greater than 60%) dispersion or loading of over 8% noble metal at low dispersion. To obtain silicalite impregnated with a noble metal at more than 8 weight percent loading and with at least 60% dispersion it has been found necessary to pretreat the silicalite with a base and to impregnate the base treated silicalite with a noble metal compound in two stages separated by calcination. Platinized silicalite so prepared may be dispersed in a poly(tetrafluoroethylene) matrix and used as a fixed bed to catalyze isotopic exchange gaseous hydrogen and water vapor arising from a mass of liquid water flowing over the fixed catalyst bed.