In addition to our previously reported study of physisorption of hydrogen to Na+ sites on the (100) faces of NaCl crystallites [Dai and Ewing, J. Chem. Phys. 98, : 5050 (1993)], there is a second site (the Cl- ion) available for adsorption. Here, we report the induced infrared absorption of HD adsorbed on this second site. The infrared transition of these adsorbed HD molecules is blue shifted by 10 cm(-1) from the absorption of the first adsorption site molecules. Isotherms of HD on the second site yield an isosteric heat of adsorption of -1.7+/-0.5 kJ/mol, or approximately half that for the first site.