Superconducting transition temperatures of the system V1−xTixHy

T_c measurements for V_1?xTi_xH_y show that a decrease in T_c always occurs upon hydrogenation, but with slopes ($\text{?T}{}_{\mathrm{c}}\text{?y}\text{)}{}_{\mathrm{x}}$ that change with x. A phenomenological model is suggested, associating the T_c decrease in most of the range of x to changes in nominal number of conducting electrons and in the volume induced by the hydrogenation. The model roughly accounts for the variations in T_c in the V-rich alloys. It fails to explain the T_c variation at the Ti end.