This paper deals with the theory of a class of relaxation mechanisms which may in part account for the absorption of sound in certain solids. The basic postulates of Eyring's theory of absolute reaction rates are applied to the development of general differential equations describing structural‐chemical state changes. The macroscopic effects of transitions between the activated and unactivated states of complexes of atoms are discussed, and the results are applied to the problem of sound absorption and mechanical relaxation due to structural‐chemical changes in soda‐silica glasses. It appears that the transition of alkali ions from holes in the glass lattice into the interstitial space, as in electrolytic conduction, is associated with the acquisition of a certain activation energy, so that the transition probabilities are finite. The process is thus of the nature of a relaxation mechanism which is capable of causing sound absorption. The functional dependence of absorption on frequency predicted by the theory and the predicted functional dependence of the relaxation time on temperature are found to agree with experimental results.