Perchloric Acid - Perchloric Acid

HClO ₄ (100.46). It is obtained by adding concentrated sulfuric acid to potassium perchlorate and distilling it under vacuum. It is the only oxyacid of chlorine that can be isolated in anhydrous form, and is a colorless, mobile, fuming liquid. Its density is 1.768 g cm ^-3 (22 °C). Its melting point is -112 °C, and its boiling point is 39 °C at 7.5 kPa (56 Torr). Distillation at 1 atm causes decomposition. The anhydrous form decomposes easily and is dangerous. It has a strong oxidizing power and reacts explosively with organic substances. It is also corrosive to the skin. When added to water, it generates heat and forms many hydrates, HClO ₄ ･ n H ₂ O ( n = 1, 2, 2.5, 3, 3.5). It is commercially available as a 60-70% aqueous solution. Its oxidizing power is very strong in a concentrated aqueous solution when hot, but is weak and stable in a dilute aqueous solution when cold. The aqueous solution is a strong acid and reacts with many metals to generate hydrogen, producing perchlorates. It is used in electrolytic baths, electrolytic polishing, the manufacture of perchlorates, and as an oxidizing agent, as well as in analytical chemistry to dissolve samples and as a reagent for separating and quantifying potassium. Perchloric acid monohydrate is called oxonium perchlorate, and its crystal structure is [H ₃ O] ⁺ [ClO ₄ ^- ]. It is a hygroscopic solid. Melting point: 50 °C, boiling point: 110 °C. [CAS 7601-90-3]

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

HClO₄(100.46)．過塩素酸カリウムに濃硫酸を加えて真空蒸留すると得られる．無水状態で単離できる唯一の塩素の酸素酸で，無色の流動発煙性の液体．密度1.768 g cm^－3(22 ℃)．融点－112 ℃，沸点7.5 kPa(56 Torr)で39 ℃．1 atm 下での蒸留では分解を伴う．無水物はきわめて分解しやすく，危険である．強い酸化力をもち有機物質とは爆発的に反応する．また，皮膚を腐食する．水に加えると発熱し，多くの水和物HClO₄･nH₂O(n ＝ 1，2，2.5，3，3.5)をつくる．市販品は60～70％ 水溶液である．熱時濃厚水溶液では酸化力が非常に強いが，冷時希薄水溶液では弱く安定である．水溶液は強い酸で多くの金属と水素を発生して反応し，過塩素酸塩を生じる．電解浴，電解研磨，過塩素酸塩の製造，酸化剤として用いられるほか，分析化学で試料の溶解，カリウムの分離定量試薬として用いられる．過塩素酸一水和物を過塩素酸オキソニウムといい，その結晶は[H₃O]^＋[ClO₄^－]の構造となっている．吸湿性固体．融点50 ℃，沸点110 ℃．[CAS 7601-90-3]

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