Inequalities $\Delta Gp > 0$ and $\Delta S > 0$ are the general conditions of fundamental realization of hydrogenation’ process in straight direction in the closed system. Using the Onsager’s principles of thermodynamics of the nonequilibrium (irreversible) processes, it is possible to distinguish some basic potentials, which promote the process or hinder it. Significance of these potentials at different stages of advancement of diffusion front through the surface layer of the sample is not identical. From the experimental data ($Р$, $Т$, $m_{H}$, $\tau$), the estimated effective factor of diffusion $D_{еf}$, and volume $\Delta V_{і}$ filled by gas during $\Delta \tau_{i}$, the module of compression of hydrogen gas, ${\partial \mu}/{\partial \rho}$ , is calculated. Reduction of this module increases the gradient of concentration, which is formed within the sample at specified internal stress. Strength of relaxation becomes higher. Dependences of ${\partial \mu}/{\partial \rho}$ on both the hydrogenation’ process duration $\tau$ and the hydrogen-penetration depth $h$ for various states of Ti are constructed. As a matter of fact, the values of ${\partial \mu}/{\partial \rho} = f(\tau, h)$ and gradient of elastic strength $\Delta \sigma(T)$ appear to be competitive during the process. The dependences of ${\partial \mu}/{\partial \rho} = kT/\rho$ against reciprocal temperature allow estimating the activation energy of elastic strength relaxation. The H concentrations in cast and as-annealed Ti reach about $C_{H} \leq 4%$ mass. that corresponds to atomic ratio ТіH$_{2-\delta}$ ($\delta \geq 0.05$).