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The polymodal microporosity and mesoporosity of porous glasses prepared by through leaching of phase-separated alkali borosilicate glasses in hydrochloric acid solutions of different concentrations are investigated by two new methods based on an analysis of the kinetic and equilibrium isotherms of gas desorption at a temperature of 77.5 K under low partial pressures, as well as by a modified classical adsorption method under medium and high pressures. It is established that an increase in the concentration of hydrochloric acid in the leaching solution brings about transformations in the microporous and mesoporous structures of the porous glasses. The structural transformations can be summarized as follows: (i) a considerable decrease in the specific surface of mesopores and the corresponding increase in the diameter of secondary silica globules, (ii) a decrease in the mesopore volume and the corresponding increase in the coordination number of the packing of secondary silica globules in channels formed upon phase separation, (iii) an increase in the diameter of mesopores arising from gaps between secondary silica globules in channels formed upon phase separation, (iv) an increase in the diameter of regions in these channels that are partially or completely free from secondary silica globules, and (v) the formation of ultramicropores with a molecular size of 0.4-0.5 nm.

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