Measurements of the electrical resistivity under hydrostatic pressure have been made and an x-ray analysis has been performed for the interstitial alloy . The results have been compared with specific heat and thermal expansion results for the same sample. An anomaly in the specific heat observed at 388-394 K was attributed to a phase transition due to the ordering of H atoms. The trapezoidal shape of the anomaly was explained in terms of the equilibrium phase separation occurring within the two-phase region, as in the case of the liquid-solution-vapour transition. At lower temperatures a series of specific heat anomalies at (small), (medium) and (large) was observed and assigned to the subsequent orderings of the H atoms. The smallest anomaly coincides with the change of the Nb-sublattice symmetry which is cubic below and orthorhombic above the temperature at which this anomaly is found and also, with a bend in the curve representing the temperature dependence of the resistivity. The temperature location of this bend has been found to be insensitive to the applied pressure (up to 19.5 kbar). The biggest low-temperature specific heat anomaly coincides with a jump in the relative elongation.