Abstract <p>An approach proposed in this study, which is based on the hydrogen permeation method, has been used to determine the temperature dependence of the terminal solid solubility of hydrogen in iodide-refined hafnium GFI-1 in the temperature range from 350 to 550°C. The experiments were performed in the regime with maintaining a low constant saturation rate for a membrane sample, instead of the traditionally used regime with maintaining constant input pressure. This approach made it possible to obtain the values of terminal solid solubility under the conditions maximally close to equilibrium. It is shown that the obtained results are in good agreement with the few available data in the literature for the same temperature range.</p>