Selenium dioxide - Nisanka selenium

Japanese: 二酸化セレン - ニサンカセレン

The chemical formula is _SeO2 . It is produced by dissolving selenium in 6N nitric acid _to produce selenious acid, _H2SeO3 , which is then thermally decomposed, or by burning selenium in air or oxygen. It is a colorless, volatile solid. Its specific gravity is 3.95 (16°C), its melting point is 340°C, and it begins to sublime at 317°C. In its gaseous form, it has a symmetrical folded linear structure with a bond distance of 1.61 Å. In its crystals, Se and O form an infinite chain structure in which they are alternately linked in a shape resembling a regular tetrahedron (Figure). It dissolves in water to become selenious acid. It is easily reduced to selenium by ammonia gas or by sulfuric acid in a sulfuric acid solution.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

化学式SeO₂。セレンを6規定硝酸に溶解して亜セレン酸H₂SeO₃をつくり，これを熱分解するか，セレンを空気または酸素気流中で燃焼させると生ずる。無色揮発性の固体。比重3.95(16℃)，融点340℃，317℃で昇華しはじめる。気体では対称折線形構造をとり，結合間隔は1.61Å。結晶中ではSeとOが正四面体に似た状態で交互に連なる無限鎖構造である(図)。水に溶けて亜セレン酸になる。還元されやすく，アンモニアガスや，硫酸溶液中では二酸化硫黄によって還元されてセレンになる。

出典　株式会社平凡社世界大百科事典第２版について　情報

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