The dilatation caused by the sorption of H and D in amorphous samples of melt-spun Pd82Si18 and sputter-deposited Pd81Si19 has been measured at room temperature for ambient charging pressures P up to 760 torr. By comparison with the strength of the Gorsky relaxation, it is concluded that (a) the dilatations per hydrogen and deuterium atom are identical and independent of concentration and (b) the non-linearity of the dilatation vs. p1/2 isotherms is due solely to a deviation from Sieverts' law. The isotherms exhibit a distinct isotope-dependence, of a similar nature to that for crystalline Pd. A sputterdeposited film is found to dissolve more H or D than a melt-spun ribbon, due possibly to a less structurally-relaxed configuration.