“Soap is Manufactures from Fats”

Soap is a very common household product used every day for hygiene purposes. Soap used to be a commercial invention during the Middle Ages, used by the Romans. However, the way in which they made soap was very corrosive to the skin as it contained some of the unreacted base. The soap used during these days was created from natural minerals which include animal fat, consisting of glycerol with three fatty acid molecules. The glycerol and the three fatty acids can be split by using high temperatures, high pressure or by reacting it with a basic substance. 1 The base is made up from a mixture of sodium and potassium carbonate which can also be formed by mixing water with wood ashes. The base therefore converts the free fatty acid into a sodium or potassium salt which is known to be salt. The basic reaction produced is:
Fat + Base → Glycerol + Fatty Acid
Fatty Acid + Base → Soap
Salt is then added to the product created which allows the soap and glycerol to separate from the basic, alkaline solution. The soap then separates further from the glycerol solution and begins to sink to the bottom. The glycerol made from this reaction is also used as a by-product of the soap-making process.1
The same process is used in today’s society using saponification, yet the base used is very pure so that it does not damage people’s skin. Also, before the product is sold, most of the glycerol is removed. Most of the soaps sold are sodium salts of specific fatty acid mixtures. 1 The soaps used in shaving lather and liquid soaps are called soft (semisolid) soaps and they are generally made from potassium salts. Most of the soaps have other substances added to them, such as perfumes, creams, oils and dyes allowing the manufacturers to have a better retail product.
However, water contains magnesium and calcium ions caused by limestone rock found in rivers, lakes and wells which is consisted of calcium carbonate or a mixture of calcium carbonate and magnesium carbonate. So, as water flows through the limestone rocks, calcium and magnesium carbonate ions dissolve in the water resulting in hard water. When the magnesium and calcium ions react with soap, it forms an insoluble compound that is separated from the solution which causes a dilemma on both a domestic and industrial scale. Consequently, most people prefer to wash their hair or dishes in soft water as no residues from the soap remains. This is why people from the Middle Ages used to collect rain water to wash their hair and clothes because it is soft water.
I think that it is very clever that without the knowledge of science, people from the middle ages were able to create such valuable things that we still use today in our society, without realizing what they have created. Many of the products we use today come from some sort of creation that were used during the days when technology was not about.


Saponification – the production of soap by treating fats (triglycerides) with heat and a base to form soap and glycerol.
Soap – the sodium and potassium salt of a long-fatty acid.



1 Braid. Chemistry in Your Life. 2nd ed. New York, USA: W.H.Freeman and Company; 2006. pp 505-506.