Decomposition of powders of Groups IV?VI transition metal disilicides during their analysis

Abstract

1. When disilicides of the Groups IV–VI transition metals are decomposed by a process involving melting them together with sodium hydroxide, sodium carbonate, or sodium peroxide or by sintering them together with a mixture of sodium carbonate and zinc oxide (2∶1), the explosions and flareups observed are caused by the evolution of hydrogen and carbon monoxide gases. The most suitable method of decomposing the disilicides is to melt them together with undehydrated sodium hydroxide in nickel crucibles. 2. In their behavior toward acid and alkaline fluxes (solutions), disilicides of the Groups IV–VI transition metals are analogous to elemental silicon [4]. Thus, elemental silicon does not react with acid fluxes, such as acid potassium sulfate or potassium pyrosulfate, nor do the disilicides [2]. Both elemental silicon and Groups IV–VI transition metal disilicides react with sodium hydroxide (solutions or melts), with hydrogen evolution. The reaction of elemental silicon with carbonates of the alkali metals is accompanied by carbon monoxide evolution [5]; carbon monoxide is liberated also when the disilicides are melted or sintered together with sodium carbonate (see Table 2).