Uranium Silicide, USi₂

Uranium Silicide, USi₂, is obtained from a mixture of urano-uranic oxide (56 parts), silica (180 parts), aluminium filings and flowers of sulphur (each 250 parts), by the aluminothermic method. The product after ignition is treated successively with dilute hydrochloric acid, sodium hydroxide, aqua regia, dilute hydrochloric acid, sodium hydroxide, and finally with water. The silicide remains as lustrous, grey, cubic crystals, of density 8.0. It is stable towards acids, except hydrofluoric acid. It burns slowly in oxygen at 800° C. Chlorine reacts at 500° C., giving a mixture of uranous and silicon chlorides. Fused alkalies oxidise it completely at red heat to uranate and silicate.