Lead Selenide, PbSe

Lead Selenide, PbSe, occurs in nature as the rare mineral clausthalite, and may be prepared by fusing the two elements together, or by precipitating a lead salt with hydrogen selenide. It may be obtained in a crystalline state by melting selenium with excess of lead, and dissolving away uncombined lead with nitric acid; also by reducing lead selenate with carbon, by the interaction of hydrogen selenide and lead chloride vapour, or by fusing the precipitated sulphide in an electric furnace. Crystalline lead selenide is lustrous and bluish grey, and has a density of 8.10 at 15° C. It is slowly attacked by fuming hydrochloric acid, and more readily by nitric acid. The molecular heat of formation of amorphous lead selenide is 13,000 calories, and of the crystalline compound 15,800 calories.

When lead is fused with excess of selenium, two layers are formed, the lower one of which contains nearly twice as much selenium as corresponds with the monoselenide, while the upper layer is nearly pure selenium. The monoselenide, however, is the only compound present in the lower layer, the excess of selenium being due to the solubility of the element in the fused monoselenide.