定义Definition
硝酸 HNO₃ 是无色液体，见光或受热分解而呈黄色。它是强酸，同时是强氧化剂，能溶解铜、银等不活泼金属。工业上由奥斯特瓦尔德法用氨催化氧化制得，主要用于制造化肥、炸药和硝基化合物。
Nitric acid, HNO₃, is a colourless liquid that turns yellow as light or heat decomposes it. It is a strong acid and a strong oxidising agent that dissolves unreactive metals such as copper and silver. It is made industrially by the catalytic oxidation of ammonia (the Ostwald process) and used mainly for fertilisers, explosives and nitro compounds.
奥斯特瓦尔德法The Ostwald process
氨在铂铑网上与空气反应：4NH₃ + 5O₂ → 4NO + 6H₂O；NO 被氧化：2NO + O₂ → 2NO₂；NO₂ 被水吸收：3NO₂ + H₂O → 2HNO₃ + NO，生成的 NO 循环使用。
Ammonia reacts with air over a platinum–rhodium gauze: 4NH₃ + 5O₂ → 4NO + 6H₂O; NO is oxidised, 2NO + O₂ → 2NO₂; and NO₂ is absorbed in water, 3NO₂ + H₂O → 2HNO₃ + NO, the NO being recycled.
氧化性Oxidising power
硝酸与金属反应一般不放出氢气，而是被还原为氮的氧化物。浓硝酸与铜：Cu + 4HNO₃ → Cu(NO₃)₂ + 2NO₂ + 2H₂O（红棕色气体）；稀硝酸与铜：3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O。冷的浓硝酸使铁、铝表面钝化。浓硝酸与浓硫酸的混合物（混酸）产生 NO₂⁺，用于苯的硝化。
With metals nitric acid usually gives nitrogen oxides rather than hydrogen. Concentrated acid with copper: Cu + 4HNO₃ → Cu(NO₃)₂ + 2NO₂ + 2H₂O (red-brown gas); dilute acid: 3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O. Cold concentrated nitric acid passivates iron and aluminium. Mixed with concentrated sulfuric acid it generates NO₂⁺, used to nitrate benzene.
安全Safety
浓硝酸有强腐蚀性，接触皮肤使蛋白质变黄（黄蛋白反应），其蒸气和分解产生的 NO₂ 有毒。应存放于棕色瓶中、置于阴凉处，远离有机物和还原剂。
Concentrated nitric acid is highly corrosive and stains skin yellow (the xanthoproteic reaction); its vapour and the NO₂ from its decomposition are toxic. Store it in brown bottles in a cool place, away from organic matter and reducing agents.
化学性质Chemical properties
见光分解：4HNO₃ → 4NO₂ + O₂ + 2H₂O
Decomposes in light: 4HNO₃ → 4NO₂ + O₂ + 2H₂O
与浓硫酸生成硝酰正离子：HNO₃ + 2H₂SO₄ → NO₂⁺ + H₃O⁺ + 2HSO₄⁻
Forms the nitronium ion with sulfuric acid: HNO₃ + 2H₂SO₄ → NO₂⁺ + H₃O⁺ + 2HSO₄⁻
与氨中和生成硝酸铵：NH₃ + HNO₃ → NH₄NO₃
Neutralised by ammonia to ammonium nitrate: NH₃ + HNO₃ → NH₄NO₃
年表Timeline
- 1776
拉瓦锡证明硝酸中含有氧
Lavoisier shows that nitric acid contains oxygen
- 1902
奥斯特瓦尔德取得氨催化氧化制硝酸的专利
Ostwald patents nitric acid production by catalytic oxidation of ammonia
- 1909
奥斯特瓦尔德获诺贝尔化学奖
Ostwald receives the Nobel Prize in Chemistry