Silver+Selenide


 * Silver selenide** (Ag2Se) is a clear, [|hexagonal] compound. It 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-sulfer silver ores from mines in Nevada.

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

[|Naumannite] ||
 * ~ Silver(I) selenide ||
 * [[image:http://upload.wikimedia.org/wikipedia/commons/thumb/4/4f/Ag2Sestructure.png/200px-Ag2Sestructure.png width="200" height="187" link="http://en.wikipedia.org/wiki/File:Ag2Sestructure.png"]] ||
 * Other names
 * ~ Identifiers ||
 * [|CAS number] || [|1302-09-6] ||
 * [|PubChem] || [|6914520] ||
 * ~ Properties ||
 * [|Molecular formula] || Ag2Se ||
 * [|Molar mass] || 294.7 g/mol ||
 * [|Density] || 8.216 g/cm3, solid ||
 * [|Melting point] || 896.85 °C ||
 * [|Solubility] in [|water] || insoluble ||
 * [|Band gap] || 0.15 eV [|[][|1][|]] ||
 * ~ Structure ||
 * [|Crystal structure] || [|orthorhombic], [|//oP12//] ||
 * [|Space group] || P212121, No. 19 ||