Chlorine-containing liquid phase compounds of germanium or silicon containing a chloride of boron or phosphorus or both as contaminant, are purified by contacting them with charcoal, a hydrous oxide or a hydrous silicate. The material may be passed down a column packed with the absorbent. The germanium or silicon compound first may be refluxed with copper (to remove any sulphur compounds), or contacted with aluminium chloride and liquid chlorine as in Specification 798,073. The purified material may be reduced to elemental germanium or silicon by passing the material in vapour form mixed with hydrogen up a tube in which is supported vertically a filament of germanium or silicon heated by an induction coil surrounding the tube; after deposition of germanium or silicon on the filament it may be zone melted by moving the coil and filament relative to one another. The material also may be reduced to the element by hydrogen reduction over tantalum. In examples silicon tetrachloride, silicon chloroform and germanium tetrachloride, are purified by contact with alumina, silica gel, charcoal, titanium dioxide gel, ferric oxide, fuller's earth, tungstic acid, magnesium hydroxide, diatomaceous earth and sodium aluminium silicate, and elemental silicon and germanium obtained from the purified material. Titanium dioxide absorbent is obtained by hydrolysis of tetraisopropyl titanate with ammonium hydroxide, followed by drying and heating in air. Ferric oxide absorbent is obtained by dissolving ferric hydroxide in hydrochloric acid, adding ammonium hydroxide, and drying and heating the precipitate. Silica absorbent is obtained by adding silicon tetrachloride to water to form a gel, and then washing, drying and heating the gel.