📚 Uses of the Halogens and Their Compounds | 卤素及其化合物的用途
The halogens – fluorine, chlorine, bromine and iodine – are among the most reactive non-metals in the Periodic Table. Their high electronegativity and ability to accept one electron to form halide ions give their compounds a wide range of industrial, medical and domestic applications. This article reviews the main uses of the halogens and their compounds, linking each use to the chemical properties that make it possible.
卤素——氟、氯、溴和碘——是元素周期表中反应性最强的非金属元素之一。它们具有高电负性，容易接受一个电子形成卤离子，因此它们的化合物在工业、医疗和日常生活中有着广泛的应用。本文梳理卤素及其化合物的主要用途，并将每种用途与使其成为可能的化学性质联系起来。
1. Overview of Halogen Uses and Key Properties | 卤素用途概述与关键性质
The uses of halogens follow a clear trend down the group. Fluorine is the most oxidising and the most difficult to store, so it is often used in the form of fluoride compounds or fluoropolymers. Chlorine is cheaper and easier to handle, making it the most widely used halogen for water treatment and bulk chemicals.
卤素的用途沿族向下呈现明显的规律。氟的氧化性最强，也最难储存，因此常以氟化物或含氟聚合物的形式使用。氯更便宜、更易处理，因此成为水处理和基础化学品中应用最广泛的卤素。
Bromine is a volatile liquid at room temperature and is mainly used in flame retardants and light-sensitive materials. Iodine is a solid that sublimes readily and is valued for its antiseptic and nutritional roles. Astatine is radioactive and has no significant commercial use.
溴在室温下是易挥发的液体，主要用于阻燃剂和感光材料。碘是易升华的固体，因其消毒和营养作用而受到重视。砹具有放射性，没有重要的商业用途。
2. Chlorine in Drinking Water and Swimming Pools | 氯在饮用水和游泳池中的应用
Chlorine is widely used to disinfect drinking water and swimming pool water. When chlorine dissolves in water, it undergoes a reversible disproportionation reaction to form hydrochloric acid and chloric(I) acid, also called hypochlorous acid.
氯广泛用于饮用水和游泳池水的消毒。氯溶于水后发生可逆的歧化反应，生成盐酸和次氯酸。
Cl₂ + H₂O ⇌ HCl + HOCl
The chloric(I) acid, HOCl, is the main antimicrobial agent. It is a small neutral molecule that can penetrate bacterial cell walls and oxidise enzymes and DNA, killing harmful microorganisms. In alkaline solution, hypochlorite ions ClO⁻ are the active species, which is why chlorine is also effective in swimming pools.
次氯酸 HOCl 是主要的抗菌成分。它是一种中性小分子，能够穿透细菌细胞壁并氧化酶和 DNA，从而杀死有害微生物。在碱性溶液中，次氯酸根离子 ClO⁻ 是活性成分，因此氯在游泳池中同样有效。
A disadvantage of chlorination is that chlorine can react with natural organic matter to form disinfection by-products such as trihalomethanes, which are suspected carcinogens. Water suppliers must balance effective disinfection against the formation of these by-products.
氯化消毒的一个缺点是氯会与天然有机物反应生成三卤甲烷等消毒副产物，这些副产物被怀疑具有致癌性。供水部门必须权衡有效消毒与副产物生成之间的关系。
3. Bleaches: Sodium and Calcium Hypochlorite | 漂白剂：次氯酸钠和次氯酸钙
Household bleach is usually a dilute solution of sodium chlorate(I), NaClO, made by passing chlorine into cold aqueous sodium hydroxide. This is another disproportionation reaction: chlorine is simultaneously oxidised to +1 and reduced to -1.
家用漂白剂通常是次氯酸钠 NaClO 的稀溶液，由氯气通入冷的氢氧化钠水溶液制得。这是另一个歧化反应：氯同时被氧化到 +1 价和还原到 -1 价。
Cl₂ + 2NaOH → NaCl + NaClO + H₂O
The hypochlorite ion ClO⁻ is a strong oxidising agent. It removes coloured stains by oxidising organic dyes to colourless products, and it disinfects surfaces by damaging microbial cell components. Calcium chlorate(I), Ca(ClO)₂, is used in bleaching powder for industrial and swimming-pool disinfection because it is more stable as a solid.
次氯酸根离子 ClO⁻ 是强氧化剂。它能将有机染料氧化成无色产物，从而去除有色污渍，并通过破坏微生物细胞成分对表面进行消毒。次氯酸钙 Ca(ClO)₂ 用于漂白粉的工业和游泳池消毒，因为它作为固体更稳定。
4. Fluoride in Dental Care | 氟化物在牙齿护理中的应用
Fluoride ions are added to toothpaste, often as sodium fluoride NaF or tin(II) fluoride SnF₂, and are used in some water fluoridation programmes. Fluoride helps prevent tooth decay by converting the mineral hydroxyapatite, Ca₅(PO₄)₃OH, in tooth enamel into fluorapatite, Ca₅(PO₄)₃F.
氟离子常以氟化钠 NaF 或氟化亚锡 SnF₂ 的形式添加到牙膏中，并用于一些饮水加氟项目。氟化物将牙釉质中的矿物质羟基磷灰石 Ca₅(PO₄)₃OH 转化为氟磷灰石 Ca₅(PO₄)₃F，从而帮助预防龋齿。
Fluorapatite is less soluble in acid than hydroxyapatite, so enamel becomes more resistant to acid attack from bacteria in the mouth. This is a good example of how a simple ionic substitution changes a material property enough to have a major health benefit.
氟磷灰石在酸中的溶解度低于羟基磷灰石，因此牙釉质对口腔细菌产生的酸侵蚀更具抵抗力。这是一个很好的例子，说明简单的离子取代足以改变材料性能，从而带来重要的健康益处。
5. Fluoropolymers: PTFE and Non-Stick Coatings | 含氟聚合物：聚四氟乙烯与不粘涂层
Polytetrafluoroethene, PTFE, is a fluoropolymer made by the addition polymerisation of tetrafluoroethene, CF₂=CF₂. The polymer has a very strong carbon-fluorine bond, which gives it exceptional chemical resistance and thermal stability.
聚四氟乙烯 PTFE 是由四氟乙烯 CF₂=CF₂ 加成聚合而成的含氟聚合物。该聚合物具有非常强的碳-氟键，因此具有优异的耐化学性和热稳定性。
PTFE is best known as the non-stick coating on cookware, sold under trade names such as Teflon. Its low coefficient of friction means that food does not stick to the surface. It is also used to make gaskets, seals, pipe linings and laboratory equipment that must resist corrosive chemicals.
PTFE 最著名的用途是作为炊具的不粘涂层，商品名为特氟龙。它的摩擦系数很低，因此食物不会粘在表面。它还用于制造必须耐受腐蚀性化学品的垫圈、密封件、管道内衬和实验室设备。
Because the C-F bond is so strong, PTFE does not degrade easily and can withstand temperatures up to about 260 °C in normal use. However, overheating PTFE-coated pans can release toxic fumes, so they should not be heated strongly when empty.
由于 C-F 键非常强，PTFE 不易降解，在正常使用中可耐受约 260 °C 的温度。但过度加热 PTFE 涂层锅会释放有毒烟雾，因此空锅不应干烧。
6. Bromine Compounds as Flame Retardants | 溴化合物作为阻燃剂
Many bromine-containing organic compounds are used as flame retardants in plastics, textiles and electronic equipment. When heated in a fire, these compounds decompose and release bromine radicals, which interfere with the free-radical chain reactions of combustion.
许多含溴有机化合物被用作塑料、纺织品和电子设备中的阻燃剂。在火灾中受热时，这些化合物分解释放出溴自由基，从而干扰燃烧的自由基链式反应。
By interrupting the combustion cycle, brominated flame retardants slow down the spread of fire and reduce the release of heat. This gives occupants more time to escape and reduces damage to property. Common examples include tetrabromobisphenol A and certain polybrominated diphenyl ethers.
通过中断燃烧循环，溴化阻燃剂减缓了火势蔓延并减少热量释放。这为人员逃生争取了更多时间，也减少了财产损失。常见的例子包括四溴双酚 A 和某些多溴联苯醚。
However, some brominated flame retardants are persistent in the environment and can accumulate in living organisms. Restrictions have been introduced for several of these compounds, encouraging the development of safer alternatives.
然而，一些溴化阻燃剂在环境中具有持久性，并能在生物体内蓄积。其中几种化合物已被限制使用，这推动了更安全替代品的开发。
7. Silver Halides in Traditional Photography | 银卤化物在传统摄影中的应用
Silver halides, especially silver bromide AgBr, are light-sensitive and have been used in photographic film and paper. When light strikes the film, silver ions are reduced to metallic silver in a photochemical reaction.
银卤化物，尤其是溴化银 AgBr，具有感光性，已被用于照相胶片和相纸。当光照射到胶片上时，银离子在光化学反应中被还原为金属银。
2AgBr → 2Ag + Br₂
The tiny silver particles formed by light form a latent image, which is then developed using reducing agents. Unexposed silver halide is removed by a fixing agent such as sodium thiosulfate. The result is a black-and-white image made of finely divided metallic silver.
光照射形成的微小银颗粒构成潜影，随后用还原剂显影。未曝光的卤化银被硫代硫酸钠等定影剂去除。最终得到由细小的金属银组成的黑白图像。
Although digital photography has largely replaced film, the photochemistry of silver halides is still a classic A-level example linking redox chemistry with a practical application.
尽管数码摄影已在很大程度上取代了胶片，但卤化银的光化学仍然是 A-Level 中将氧化还原化学与实际应用联系起来的经典例子。
8. Iodine as Antiseptic and in Thyroid Function | 碘作为消毒剂及在甲状腺功能中的作用
Iodine is used as an antiseptic in the form of iodine tincture, an alcoholic solution of iodine, or as an iodophor such as povidone-iodine. It works by oxidising microbial proteins and damaging cell membranes, making it effective against bacteria, fungi and viruses.
碘以碘酊（碘的酒精溶液）或碘伏（如聚维酮碘）的形式用作消毒剂。它通过氧化微生物蛋白质和破坏细胞膜发挥作用，对细菌、真菌和病毒均有效。
Iodine is also an essential element for human health because it is needed to synthesise thyroid hormones. Thyroxine, known as T4, contains four iodine atoms per molecule, and triiodothyronine, T3, contains three. A lack of iodine can lead to goitre and other thyroid disorders.
碘也是人体健康必需的微量元素，因为合成甲状腺激素需要碘。甲状腺素 T4 每个分子含有四个碘原子，三碘甲状腺原氨酸 T3 含有三个。缺碘会导致甲状腺肿和其他甲状腺疾病。
In medicine, the radioactive isotope iodine-131 is used to treat some thyroid conditions. It is taken up by the thyroid gland, where its beta radiation destroys overactive or cancerous thyroid tissue with relatively little damage to surrounding cells.
在医学上，放射性同位素碘-131 被用于治疗某些甲状腺疾病。它被甲状腺吸收后，其 β 辐射会破坏过度活跃或癌变的甲状腺组织，而对周围细胞的损伤相对较小。
9. Hydrogen Halides: HCl, HF and Their Industrial Roles | 氢卤酸：氯化氢、氟化氢及其工业作用
Hydrogen chloride, HCl, is produced on a large scale and dissolved in water to make hydrochloric acid. Hydrochloric acid is used to clean steel before galvanising, to manufacture chlorides, and to control pH in chemical processes. It is also produced in the stomach, where it aids digestion and kills pathogens.
氯化氢 HCl 被大规模生产并溶于水制成盐酸。盐酸用于镀锌前的钢材清洗、氯化物的制造以及化学过程中的 pH 调节。胃中也会产生盐酸，帮助消化并杀灭病原体。
Hydrogen fluoride, HF, is particularly useful because it reacts with silicon dioxide, the main component of glass. This reaction is used to etch glass and to remove sand from metal castings.
氟化氢 HF 特别有用，因为它能与玻璃的主要成分二氧化硅反应。该反应用于蚀刻玻璃以及清除金属铸件上的砂粒。
SiO₂ + 4HF → SiF₄ + 2H₂O
HF is highly toxic and must be stored in plastic containers rather than glass. Hydrogen bromide and hydrogen iodide are less widely used, but they serve as sources of bromide and iodide ions in organic synthesis.
HF 剧毒，必须储存在塑料容器中而不能使用玻璃容器。溴化氢和碘化氢的用途较少，但在有机合成中可作为溴离子和碘离子的来源。
10. Halide Salts, PVC and Refrigerants | 卤化物盐、聚氯乙烯与制冷剂
Sodium chloride, NaCl, is by far the most important halide salt. It is used as table salt, as a food preservative, and as a de-icing agent for roads because it lowers the freezing point of water. Industrially, electrolysis of concentrated sodium chloride solution produces chlorine, hydrogen and sodium hydroxide, all of which are essential feedstocks.
氯化钠 NaCl 是目前最重要的卤化物盐。它用作食盐、食品防腐剂，并因能降低水的冰点而用作道路除冰剂。工业上，电解浓氯化钠溶液可生产氯气、氢气和氢氧化钠，这些都是重要的基础原料。
Organohalogen compounds also have enormous importance. Polyvinyl chloride, PVC, is made by polymerising chloroethene and is used for pipes, window frames and electrical insulation. Halogenated hydrocarbons have been used as refrigerants, although chlorofluorocarbons CFCs were phased out because they deplete the ozone layer.
有机卤化物也非常重要。聚氯乙烯 PVC 由氯乙烯聚合而成，用于管道、窗框和电气绝缘。卤代烃曾被用作制冷剂，但氯氟烃 CFCs 因破坏臭氧层而被逐步淘汰。
The uses of halogen compounds therefore depend on a balance among reactivity, cost, stability and environmental impact. Understanding these factors helps explain why each halogen and its compounds occupy a specific niche in modern chemistry.
因此，卤素化合物的用途取决于反应性、成本、稳定性和环境影响之间的平衡。理解这些因素有助于解释为什么每种卤素及其化合物在现代化学中占据着特定的位置。
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