After writing a blog post about how soap can kill viruses and how it can remove viruses from the skin, I started to examine how soap is produced, as each soap molecule contains two completely different chemical properties in its two ends (one end is "water loving" while the other end is "water hating" or grease loving). I learned about the function of soap molecules when I was in high school studying chemistry, but at that time, I was not thinking about how soap is made. So a few days ago, I started searching for the answer.
There are a few websites that I found interesting, and I would like to share with you some information from these sources. In general, the basic ingredients of a soap are oil (vegetable oil or animal fat), water, and lye. Lye is an alkaline salt which can be either sodium hydroxide or potassium hydroxide. Sodium hydroxide is used to make a hard soap while potassium hydroxide is used to make a soft soap. A combination of the two is used to make a cream soap.1,2
When oil and lye are mixed together, soap molecules (fatty acid salts) are formed in a chemical reaction called saponification.3 During the reaction, oil that contains fatty acid ester linkages undergoes alkaline hydrolysis with the metal hydroxide.
Triglyceride + 3 sodium hydroxide (or potassium hydroxide)>>>> glycerol + 3 soap molecules
Although water molecules are not involved in the saponification, water is an important mediator to mix the oil and the alkaline salt together. This is used to create the lye solution that is mixed into the oil. The correct proportion of water for saponification is crucial, as too much of it results in too soft a bar of soap. The majority of the water evaporates out of the soap as it cures and ages.
Soap has been made for thousands of years, and the basic recipe has not very much changed. Nowadays, with the help of the highly developed chemical industry, it is easy to get all the three ingredients to make soap. However, we may wonder how and where did the ancient people get the alkaline salt. The most ancient recipe for soap which was found on Babylonian clay containers dated at 2800 B.C. gives us a clue.4 Inscriptions on the containers showed that they used wood ashes as a source of alkaline salts.4,5 Lye is formed when wood ash (mainly potassium carbonate) is mixed with water.
You may like to make an organic, purely natural handcrafted soap by yourself once you know the basic ingredients. However, it is extremely important to remember that lye is a corrosive strong alkaline of pH 13. You can get serious burns if you don't handle the lye solution carefully. If you start by mixing wood ash with water, the mixture can turn your skin into soap once it comes in contact with your skin and absorbs the oil in your skin. Moreover, inhalation of the lye vapour will cause serious damage to your respiratory system and can be fatal.
References
1. "Soap ingredients" https://www.soapguild.org/consumers/soap-ingredients.php
2. "Why do we use soap?" Live Science, 5th March, 2020. https://www.livescience.com/57044-science-of-soap.html
3. "Saponification definition and reaction" ThoughtCo. https://www.thoughtco.com/definition-of-saponification-605959
4. "Who invented soap?-About soap inventors" http://www.soaphistory.net/soap-history/who-invented-soap/
5. "How to Make Homemade Lye Using Two Ingredients" ThoughtCo. https://www.thoughtco.com/make-homemade-lye-using-two-ingredients-608276
No comments:
Post a Comment