  Recent observations have shown that at a certain composition of solid
solutions AgCl$_x$Br$_{1-x}$, AgCl-CdCl$_2$, AgBr-CdBr$_2$, of ionic crystals,
the electrical conductivity exhibits a value appreciably larger than that of
the end constituents. Here, we investigate the electrical conductivity $\sigma$
of LiH$_x$D$_{1-x}$ solid solutions -which are of prominent importance in fuel
hydrogen storage applications- and find that in the whole composition range no
maximum is likely to occur in the $\sigma$ versus x dependence.
