The authors studied the diffusion of silver in the superionic conductor Ag//8HgS//2I//6 for the first time. The results obtained confirms the existence of significant differences in the numerical values of Haven's ratio for structurally similar solid electrolytes of the alpha -AgI type. The aquisition of reliable results on diffusion in superionic conductors, such as alpha -Ag//2HgI//4, Ag//6I//4WO//4, and Ag//1//6I//1//2P//2O//4, and the establishment of the relationship between these data and the features of the crystal structure of the solid electrolytes studied will make it possible to quantitatively examine the theory of superionic conduction in this class of compounds.