Available equilibrium pressure-temperature-composition relationships for body centred cubic (bcc)  (M = W or Ru) and  bcc  are analysed on the basis of statistical thermodynamics. In the systems under consideration, H solubility x under given condition of temperature T and hydrogen partial pressure  tends to diminish with increasing y. Extent of suppression of H absorption into the  alloy lattice per y rise represented by a decrease of the parameter q for number of available sites for occupation by H atoms per metal atom was greater with Ru than with W and correspondingly extent Q of stabilisation of H in the  alloy lattice was evaluated to be more negative (i.e.  H being more stable) with W  than with Ru  while Q in  was evaluated to be  In either Nb alloy under consideration, interaction E(H-H) between the nearest neighbour H atoms was evaluated to be attractive (negative). On the other hand, in spite of suppressed solubility of H into  q value for this alloy remained unchanged from that (0.55) for  and the evaluated Q for this alloy  remained virtually comparable to that for  while the entropy term R  for this alloy  changed appreciably from that for  where  refers to the partition function of H in the metal lattice at T.