The thermodynamics of hydrogen-metal systems may be determined from measured absorption-desorption isotherms using either Sievert's (volumetric) or the gravimetric method. These methods are rather complementary and their relative advantages and disadvantages have been fully discussed///. One of the most important differences is that the former method involves multiple dosing, with an associated error that accumulates with each pressure step, whereas the latter directly measures the mass uptake for each pressure point. In practice the use of small pressure steps is quite