Formula Ag2Se Molar mass 294.7 g/mol | Melting point 880 °C Density 8.22 g/cm³ | |
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Silver selenide (Ag2Se) is the reaction product formed when selenium toning analog silver gelatine photo papers in photographic print toning. The selenium toner contains sodium selenite (Na2SeO3) as one of its active ingredients, which is the source of the selenide (Se2−) anion combining with the silver in the toning process.
It is found in nature as the mineral naumannite, a comparatively rare silver mineral which has nevertheless become recognized as important silver compound in some low-sulfur silver ores from mines in Nevada.
Structure
Silver selenide normally exists in the orthorhombic β-phase but at temperatures above 130 °C transforms into the cubic α-Ag2Se (Space group Im-3m, No. 229, Pearson symbol cI20). The phase transition increases ionic conductivity by 10,000 times to about 2 S/cm