Alkaline lime is a mixture and there is no single chemical formula. It is often expressed by NaON+CaO. Alkaline lime is also called soda lime. Alkaline lime is white or beige powder, loose and porous, and it is a mixture of calcium oxide (CaO, about 75%), water (HO, about 20%), sodium hydroxide (NaOH, about 3%) and potassium hydroxide (KOH, about 1%).

Industrial soda lime is obtained by calcining alkali stone (namely Na2CO3 NaHCO3 2H2O, limestone rich in potassium and sodium), and then the clarified aqueous solution is concentrated to make caustic soda.

It plays different roles in different chemical reactions:

Carbonate can be decomposed by heating to produce CO2, and only (NH4)2CO3 or NH4HCO3 can be produced. After the mixed gas produced by decomposition passes through alkali lime, CO2 and H2O are absorbed, and pure NH3 is obtained. (used for drying).

Its drying function can be used to remove impurities in gas, such as NH(HO). Alkaline lime can alSO remove so, HS, HCl, co and other acidic gases. Desiccants commonly used in junior high schools can be divided into acidic, alkaline and neutral. Desiccant, as its name implies, is used for drying (drying gas is common in middle school, but it can also dry liquid, which is not common in middle school). Of course, depending on the nature of the desiccant, the types of substances to be dried are also different.