Preparation and special application of potassium hydroxide
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.
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.
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.
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.
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.
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.
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.
That's all for the preparation and special application of potassium hydroxide. If you want to know more, you should pay attention to our website www.jinhao360 Com consulting!