Cultivation of Metal Crystals by Separation from the Gaseous State

Abstract

F.KOREF describes experiments on the deposition of crystalline tungsten on a wire consisting of a single tungsten crystal, which is heated electrically in a mixture of hydrogen and tungsten hexachloride vapour in an electric oven.1 When the oven is fairly cool (about 110° C.) and the pressure is kept down to 12 mm. of mercury, the wire being raised to 1000° C., the metal deposits in crystalline form, growing from the unit crystal, so that the dividing line between the two is scarcely visible in a magnified section, which, when etched, shows the characteristic structure of a tungsten crystal. The external form shows more or less distinct crystalline surfaces and edges, though the surfaces are not perfectly plane, being sometimes concave cylindrical, while the edges are not always sharp. It is concluded, however, that the whole mass forms one crystal, which has grown from the original crystal Wire. The number of bounding surfaces seems to depend on the direction of the crystal axis in the original wire, the prism being four-, six-, or eight-sided. The diameter can be increased from 0.05 to 0.15 mm., the temperature being kept constant during the deposition by regulating the heating current.