Science, Tech, Math › Science Saponification Definition and Reaction Share Flipboard Email Print Saponification is the chemical reaction that makes soap. Zara Ronchi / Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated January 08, 2020 Saponification is a process by which triglycerides are reacted with sodium or potassium hydroxide (lye) to produce glycerol and a fatty acid salt called "soap." The triglycerides are most often animal fats or vegetable oils. When sodium hydroxide is used, a hard soap is produced. Using potassium hydroxide results in a soft soap. Saponification Example In saponification, a fat reacts with a base to form glycerol and soap. Todd Helmenstine Lipids that contain fatty acid ester linkages can undergo hydrolysis. This reaction is catalyzed by a strong acid or base. Saponification is the alkaline hydrolysis of the fatty acid esters. The mechanism of saponification is: Nucleophilic attack by the hydroxideLeaving group removalDeprotonation The chemical reaction between any fat and sodium hydroxide is a saponification reaction. triglyceride + sodium hydroxide (or potassium hydroxide) → glycerol + 3 soap molecules Key Takeaways: Saponification Saponification is the name of the chemical reaction that produces soap.In the process, animal or vegetable fat is converted into soap (a fatty acid) and alcohol. The reaction requires a solution of an alkali (e.g., sodium hydroxide or potassium hydroxide) in water and also heat.The reaction is used commercially to make soap, lubricants, and fire extinguishers. One Step Versus Two Step Process Saponification is the chemical reaction that makes soap. Zara Ronchi / Getty Images While the one-step triglyceride reaction with lye is most frequently used, there is also a two-step saponification reaction. In the two-step reaction, steam hydrolysis of the triglyceride yields carboxylic acid (rather than its salt) and glycerol. In the second step of the process, alkali neutralizes the fatty acid to produce soap. The two-step process is slower, but the advantage of the process is that it allows for purification of the fatty acids and thus produces a higher quality soap. Applications of the Saponification Reaction Saponification sometimes occurs in old oil paintings. Lonely Planet / Getty Images Saponification may result in both desirable and undesirable effects. The reactions sometimes damage oil paintings when heavy metals used in pigments react with free fatty acids (the "oil" in oil paint), forming soap. The reaction starts in the deep layers of a painting and works its way toward the surface. At present, there is no way to stop the process or identify what causes it to occur. The only effective restoration method is retouching. Wet chemical fire extinguishers use saponification to convert burning oils and fats into non-combustible soap. The chemical reaction further inhibits the fire because it is endothermic, absorbing heat from its surroundings and lowering the temperature of the flames. While sodium hydroxide hard soap and potassium hydroxide soft soap are used for everyday cleaning, there are soaps made using other metal hydroxides. Lithium soaps are used as lubricating greases. There are also "complex soaps" consisting of a mixture of metallic soaps. An example is a lithium and calcium soap. Source Silvia A. Centeno; Dorothy Mahon (Summer 2009). Macro Leona, ed. "The Chemistry of Aging in Oil Paintings: Metal Soaps and Visual Changes." The Metropolitan Museum of Art Bulletin. Metropolitan Museum of Art. 67 (1): 12–19.