Preparation and special application of potassium hydroxide

制備

Preparation

歷史上，氫氧化鉀是通過(guò)向氫氧化鈣（熟石灰）的濃溶液中加入碳酸鉀來(lái)制備的。鹽復(fù)分解反應(yīng)導(dǎo)致固體碳酸鈣沉淀，留下氫氧化鉀在溶液中:Ca(OH)2+K2CO3→CaCO3+2KOH。

Historically, potassium hydroxide was prepared by adding potassium carbonate to a concentrated solution of calcium hydroxide (hydrated lime). The salt double decomposition reaction leads to the precipitation of solid calcium carbonate, leaving potassium hydroxide in the solution: Ca (OH) 2+k2co3 → caco3+2koh.

過(guò)濾掉沉淀的碳酸鈣并將溶液煮沸，得到氫氧化鉀(“煅燒或苛性鉀”)。這種生產(chǎn)氫氧化鉀的方法一直占主導(dǎo)地位，直到19世紀(jì)后期，它才被目前一直使用的電解氯化鉀溶液的方法所取代。該方法類(lèi)似于氫氧化鈉的制造(見(jiàn)氯堿工藝):2KCl+2H2O→2KOH+Cl2+H2。

Filter the precipitated calcium carbonate and boil the solution to give potassium hydroxide ("calcined or caustic potassium"). This method of producing potassium hydroxide was dominant until the late 19th century, when it was replaced by the method of electrolyzing potassium chloride solution. This method is similar to the manufacturing of sodium hydroxide (see chlor alkali process): 2kcl+2h2o → 2koh+cl2+h2.

市售的氫氧化鉀通常是半透明顆粒狀，由于氫氧化鉀具有吸濕性，所以在空氣中會(huì)發(fā)黏。因此，氫氧化鉀通常含有不同量的水（和碳酸鹽一樣）。它在水中的溶解是強(qiáng)放熱的。濃縮的水溶液有時(shí)被稱(chēng)為鉀溶液。即使在高溫下，固體氫氧化鉀也不容易脫水。

The commercially available potassium hydroxide is usually translucent and granular. Due to its hygroscopicity, it will become sticky in the air. Therefore, potassium hydroxide usually contains different amounts of water (like carbonate). Its dissolution in water is strongly exothermic. Concentrated aqueous solutions are sometimes called potassium solutions. Even at high temperature, solid potassium hydroxide is not easy to dehydrate.

在較高溫度下，固體氫氧化鉀在氯化鈉晶體結(jié)構(gòu)中結(jié)晶。OH基團(tuán)要么是快速無(wú)序的，要么是隨機(jī)無(wú)序的，因此OH基團(tuán)實(shí)際上是半徑為1.53的球形陰離子(大小在Cl和F之間)。在室溫下，?OH基團(tuán)有序的，K中心周?chē)沫h(huán)境是無(wú)序的，根據(jù)OH基團(tuán)的取向，K-OH距離范圍為2.693.15?。氫氧化鉀形成一系列結(jié)晶水合物，即一水氫氧化鉀KOHH2O，二水氫氧化鉀KOH2H2O和四水氫氧化鉀KOH4H2O。

At higher temperature, solid potassium hydroxide crystallizes in the crystal structure of sodium chloride. OH groups are either rapidly disordered or randomly disordered, so oh groups are actually spherical anions with a radius of 1.53 (between Cl and F). At room temperature,? The OH groups are ordered, and the environment around the k center is disordered. According to the orientation of OH groups, the k-oh distance ranges from 2.69 to 3.15?. Potassium hydroxide forms a series of crystalline hydrates, namely potassium hydroxide monohydrate kohh2o, potassium hydroxide dihydrate koh2h2o and potassium hydroxide tetrahydrate koh4h2o.

像氫氧化鈉一樣，氫氧化鉀表現(xiàn)出很高的熱穩(wěn)定性。氣體狀態(tài)下是二聚體。由于其高穩(wěn)定性和相對(duì)低的熔點(diǎn)，它通常被熔融鑄造成小球或棒，具有低表面積和易攜帶的性質(zhì)。

Like sodium hydroxide, potassium hydroxide exhibits high thermal stability. It is dimer in gas state. Because of its high stability and relatively low melting point, it is usually melt cast into small balls or rods with low surface area and easy to carry.

特殊應(yīng)用

Special applications

像氫氧化鈉一樣，氫氧化鉀吸引了許多特殊的應(yīng)用，幾乎所有的應(yīng)用都依賴(lài)于它作為一種強(qiáng)化學(xué)堿的性質(zhì)，以及隨之而來(lái)的降解許多材料的能力。例如，在通常被稱(chēng)為“化學(xué)火化”或“再分解”的過(guò)程中，氫氧化鉀加速動(dòng)物和人類(lèi)軟組織的分解，只留下骨頭和其他硬組織。昆蟲(chóng)學(xué)家希望研究昆蟲(chóng)解剖的精細(xì)結(jié)構(gòu)，可以使用10%氫氧化鉀水溶液來(lái)應(yīng)用這一過(guò)程。

Like sodium hydroxide, potassium hydroxide has attracted many special applications, almost all of which depend on its properties as a strengthening alkali and its subsequent ability to degrade many materials. For example, in a process commonly referred to as "chemical cremation" or "re decomposition", potassium hydroxide accelerates the decomposition of soft tissues in animals and humans, leaving only bones and other hard tissues. Entomologists hope to study the fine structure of insect anatomy, and can use 10% potassium hydroxide aqueous solution to apply this process.

在化學(xué)合成中，氫氧化鉀和氫氧化鈉的選擇取決于所得鹽的溶解度或質(zhì)量。氫氧化鉀的腐蝕性使其成為清潔和表面的試劑和制劑中的一種有用成分，并且其本身可以抵抗氫氧化鉀的腐蝕。

In chemical synthesis, the choice of potassium hydroxide and sodium hydroxide depends on the solubility or quality of the salt. The corrosivity of potassium hydroxide makes it a useful ingredient in reagents and preparations for cleaning and disinfecting surfaces, and it itself can resist the corrosion of potassium hydroxide.

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