Oils are fats in liquid form. Oils are large organic compounds formed by the reaction between fatty acids and glycerol and can also be described as large ester molecule..
Fatty acids + Glycerol —————> Fats and water.
The fatty acids are acids with long hydrocarbon chains and may be saturated or unsaturated. Examples of fatty acids are oleic acid, palmitic acid and stearic acid.
Soaps are produced by boiling concentrated alkalis such as sodium hydroxide (lye) with various fats. The fatty acid in fat will react with sodium hydroxide to produce an ‘organic salt’ which is soap.
Lye (Sodium Hydroxide) + Fat ( Fatty acid + Glycerol ) ———–> Soap (salt) + Glycerol
Lye is a corrosive alkaline substance, commonly sodium hydroxide (NaOH, also known as ‘caustic soda’)
Soap is the result of a chemical reaction between oil or fat and lye called the saponification process. The saponification process is defined as the reaction of combining a base (fat) with an alkali (sodium hydroxide) to produce a salt (soap) and a free alcohol (glycerin). The goal of the process is to create soap with no leftover fat or lye.
The oil or fat used in the soap making process may be either animal or vegetable. Animal fats that are used include tallow and lard. Vegetable oils used either alone or in combination include avocado oil, coconut oil, castor oil, olive oil, palm oil, soybean oil, vegetable oil and numerous others. Each type of fat has its own saponification value. The saponification value determines the amount of lye needed to turn the fat to soap.
As boiling of fat and sodium hydroxide takes place, common salt (sodium chloride) is added to make the soap solidify and float on the surface of of the solution. The soap can be added with dyes and perfumes to make the soap look and smell better. The soap can then be separated from the solution through filtration. The type of soap produced depends on the type of oil and alkali used.