Saponification is a chemical process that involves the cleavage of esters into carboxylate salts and alcohols by the action of aqueous alkali, typically aqueous sodium hydroxide solutions. When the carboxylate is long chain, its salt is called a soap. The process of saponification is used to make soap, which is an essential everyday item used for bathing, cleaning, washing, and in other household chores. The process of saponification involves the hydrolysis of an ester with NaOH or KOH to give alcohol and sodium or potassium salt of the acid. The saponification value is the amount of base required to saponify a fat sample. Soap makers formulate their recipes with a small deficit of lye to account for the unknown deviation of saponification value between their oil batch and laboratory averages.

The mechanism of basic hydrolysis involves the hydroxide anion adding to the carbonyl group of the ester. The immediate product is called an orthoester. Expulsion of the alkoxide generates a carboxylic acid.

Saponification is an exothermic chemical reaction that occurs when fats or oils (fatty acids) come into contact with lye, a base. In this reaction, the triglyceride units of fats react with sodium hydroxide or potassium hydroxide and are converted to soap and glycerol. The products of the saponification reaction are glycerin and soap, which is a fatty acid salt.

In summary, saponification is a chemical process that involves the hydrolysis of esters to form carboxylate salts and alcohols by the action of aqueous alkali. The process is used to make soap, which is an essential everyday item used for various household chores.