A reactor, a plant, and a continuous, industrial process carried out therein for preparing high-purity silicon tetrachloride or high-purity germanium tetrachloride by treating the silicon tetrachloride or germanium tetrachloride to be purified, which is contaminated by at least one hydrogen-containing compound, by a cold plasma and isolating purified high-purity silicon tetrachloride or germanium tetrachloride from the resulting treated phase by fractional distillation. The treatment is carried out in a plasma reactor in which longitudinal axes of a dielectric, of a high-voltage electrode, and of a grounded, metallic heat exchanger are oriented parallel to one another and at the same time parallel to the force vector of gravity.