Hydrofluoric acid (Hydrofluoric acid)

Japanese: フッ化水素酸(弗化水素酸) - ふっかすいそさん（英語表記）hydrofluoric acid

An aqueous solution of hydrogen fluoride (HF). Also called hydrofluoric acid. It is obtained by adding concentrated sulfuric acid to fluorite powder, heating it, and cooling the hydrogen fluoride that is produced. Its azeotropic mixture is 35.37%, with a maximum boiling point of 120°C. Known hydrates include HF･H ₂ O (melting point -35.2°C) and 4HF･H ₂ O (melting point -100.3°C). It is a colorless, irritating liquid that emits smoke in the air, is toxic, and severely attacks the skin and mucous membranes. Unlike other hydrohalic acids, it is weakly acidic in dilute aqueous solution. The following dissociation equilibrium exists:

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

フッ化水素HFの水溶液。フッ酸ともいう。蛍石の粉末に濃硫酸を加えて加熱し，発生するフッ化水素を冷却して得られる。共沸混合物は35.37％で，最高沸点は120℃。水和物としてはHF･H₂O(融点－35.2℃)，4HF･H₂O(融点－100.3℃)などが知られている。無色の刺激性液体で，空気中で発煙し，有毒で，皮膚や粘膜を強く侵す。他のハロゲン化水素酸と異なり，希薄水溶液で弱酸性を示す。次のような解離平衡がある。

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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