Dispelling the dirty, historical lies about soap

My mother always told me that cleanliness was next to Godliness. It was one of my motivations for reading the entire Bible while I was still quite young. I wanted to find the place where it said that. Of course, the Bible doesn’t, and that led me to a crisis of faith in my mother. I discovered a long time ago that one shouldn’t blame God for human frailty. 

I eventually forgave my mother. She meant well. My wife agrees with my mother about cleanliness, in spades, regardless of the lack of scriptural validity. So, in retrospect, my mother prepared me well for my future. 

Though there are religious connotations attached to cleanliness, there is also a science involved. Of course, people were clean before there was science. It’s just that science likes to horn in and ruin all the pleasing, beautiful, and human activities celebrated since the beginning of time before science. People enjoyed bathing, eating, drinking, exercise, rest and a host of other activities long before science got hold of any of them. 

It turns out that SOAP is also an acronym for a messaging protocol that allows programs that run on disparate operating systems (such as Windows and Linux) to communicate using Hypertext Transfer Protocol (HTTP) and its Extensible Markup Language (XML). It stands for Simple Object Access Protocol (SOAP). 

SOAP sounds more interesting than plain soap! However, I’ve never quite figured out what HTTP is. I vaguely recall my chemistry teacher going on about triglycerides, glycerol, sodium hydroxide, balanced equations and saponification years ago. I just didn’t know he was talking about religion. But all that was before I lost my faith in chemistry. 

So “soaps” are water-soluble sodium or potassium salts of fatty acids, whatever those are. They make oils and adhering dirt water-soluble, so they can be carried away by water. The first soaps were probably made from the sap of certain plants, such as the Soap Plant (Chlorogalum pomeridianum), Soapbark (Quillaja saponaria), Soapberry (Sapindus mukorossi), and Soapwort (Saponaria officinalis) whose roots and stems can be crushed in water to be used as shampoo. 

These plants all contain a compound called saponin which forms the foamy lather. However, they also contain a toxin that can be used to stupefy fish in streams making them easy to catch. Don’t get excited. Stupefying fish with Soap Plant is now illegal.  In literature it isn’t clear if saponin had a stupefying effect on those who used it for shampoo. 

Maybe that is why we don’t use saponin from these plants anymore to make soap. Instead, we mix leftover fats and oils from food with alkali ashes left over from fire to saponify compounds. The Latin word for soap is sapo, so saponification is simply a complicated way of saying “making soap” without saponin. Isn’t that just like chemists to use big words for simple things? 

Most lipids, the polite word for fats, include natural oils that are made of some combination of molecules of glycerol and molecules called fatty acids. This latter term seems a little insensitive, but it was a different day. Since glycerol has three carbons with a fatty acid attached to each one, it is called a triglyceride.

When we mix triglycerides with lye, usually sodium or potassium hydroxide, the molecules come apart to make glycerin and soap. It can be a little tricky to get the exact same amount of fat and lye. If you don’t get it right, you either have oil or glycerin left over. Either way, you don’t want any lye left over as it is pretty caustic.

It is rumored that soap was once used as a punishment for children who told lies or used a swear word. A parent is said to wash their mouths out with soap! I guess the lye was supposed to dispel the lies and dirty words. It was a different day. I suppose my mother meant well.

Gary McCallister, .(JavaScript must be enabled to view this email address), is a professor emeritus of biological sciences at Colorado Mesa University.


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