The bulk electric conductivity and the static dielectric constant of acid polyhydrates, having a clathrate structure, were determined between 4 and 300 K. The effect of isotopic (D versus H) was investigated in the same temperature range. Protonated and deuterated acids show virtually identical Arrhenius plots of the conductivity between room temperature and 125 K, below that temperature they differ. The deuterated compound exhibits a smaller conductivity and a smaller dielectric constant as compared with the protonated one.