GB812945A - Process for purifying alkaline earth metal hydrides - Google Patents

Abstract

An alkaline earth metal hydride, e.g. calcium hydride, is purified by successively heating equal portions of the hydride in a single vessel under such conditions that hydrogen is evolved from each portion and is mixed with alkaline earth metal vapour which is evolved from the preceding portion in substantially stoichiometric proportions, and condensing the hydride from said mixture. Hydrogen may be finally added to combine with the metal evolved from the last portion. Hydrogen may also be passed through the hydride being decomposed. The portions may be added in succession to the decomposition vessel, or the portions may be present in a single body of the hydride and a decomposition zone allowed to progress discontinuously or continuously through the body. In the latter case a cylindrical vessel having a plurality of external electrical heating rings may be employed. Alternatively the hydride may be passed continuously through a furnace. Using an electrically-heated metal resistance wire for heating the decomposition vessel a temperature of 900 DEG C. may be attained, with which may be used a pressure of 0.1 mm. of mercury; using induction heating a temperature of 1200 DEG C. may be attained, with which may be used a pressure of 100 mm. of mercury; using radiation heating, electrical resistance heating or induction heating in a carbon apparatus a temperature of 1800 DEG C. may be attained, with which may be used atmospheric pressure. The hydride may be condensed in less than 0.01 sec. A mechanically-movable condensation surface which is freed from condensate by a stripper when the layer of condensate has reached 3 mm. may be used. Specification 803,767, [Group II], is referred to.