For pt. I see ibid., vol.7, no.12, 2126 (1974). A temperature wave method has been used to measure the specific heat of the PdH system through the critical-point region. The specific heat at constant hydrogen concentration displays a simple discontinuity at the critical point, corresponding to the critical-point exponent, alpha , being equal to zero. In combination with other critical-point exponent data obtained from PdH this result leads to the conclusion that mean-field theory describes the critical-point behaviour of PdH.