What does soap contain?

Answer 1

Ordinary soap contains fatty acids (triglycerides) that have been treated with a strong base (e.g. sodium hydroxide or potassium hydroxide) to form a salt. These salts can emulsify other fats and oils, enabling them to be removed by water.

Typical soap compounds include sodium tallowate and sodium cocoate.

Modern detergents use similar chemical compounds including sodium laureth sulfate and sodium sulfonates.

As soaps are made by mixing melted fats (a source of fatty acids) and lye (the source of the alkali metal) this permits some small amounts of unreacted lye as a contaminate in the final product. Soaps also often contain some glycerin, which is released from the fat when the lye reacts with and separates the fatty acids from it.

Commercial manufacturers can incorporate many additives in the soaps they sell: fragrances, lotion, antibacterials, deodorants, pumice rock, etc.