The making of soap is can be used for teaching the nature and structure of lipids in Anatomy & Physiology

• Compounds can be classified as ionic, polar and non-polar
• Water is a polar compound that dissolves polar and ionic (charged) molecules
• Fatty acids are have a polar head and a non-polar tail
• Three fatty acids combined with a glycerol (alcohol) to form a non-polar triglyceride
• Fats are also called lipids
• Lard is a saturated fat and solid at room temperature
• Polymers are decomposed by hydrolysis

To make soap we have to break the triglyceride into its fatty acid and glycerol components. By using a strong base, such as lye, the lipid is hydrolyzed, the free fatty acids (FFA) will be solution as large cations (+ ions). This process is called saponification.

When soap meets grease, the non-polar FFA tail dissolves in the non-polar grease, while the polar FFA head dissolves in water. In this matter, grease particles become surrounding by water as an emulsion and can be rinsed out. This is what happens when you wash.

When working with lye DON"T breath fumes. If you do, you will notice a strange taste in your mouth. The lye is reacting with the lipids forming cell membranes on your tongue, and your tongue surface is turning into soap. Yuck!! In the same manner, your skin will feel slimy if you get lye on it!!

Always wear rubber glove and safety glasses when handling lye. Wash off immediately if you get careless. If you get lye in your eyes, you should wash them immediately with cold water and call a hospital. If you are careless enough to ingest (eat) lye, go straight to an emergency room!!

We will use glassware. Lye in an aluminum container will react violently !!!

Bring to the lab on soap day: A two-liter bottle and a plastic container to use as a mold (about 250 ml size)

I will have ready for you enough materials for each two-person team to have the following:

• 250 ml of melted lard
• 250 of lye solution (38.3 gr in 250 ml H₂O)

Stock beakers of each will be in a 50 degree Celsius water bath (122 Fahrenheit). This is HOT!

1. Bring your 2-liter bottle to me and I will pour in 250 ml of lye. Then, you will add 250 ml of lard.
2. The lye and lard will separate into two layers like salad dressing.
3. Put the cap on the bottle and gently shake the contents.
4. Stop shaking and see if the layers still separate. If they do, then continue shaking gently.

Note: When the mixture is ready it will coat the inside of the bottle like milk as it runs down to the bottom of the

bottle when you stop shaking)

5. When the layers no longer separate, pour the contents into your mold.
6. Throw your 2-liter bottle in the recycle bin. Clean up your mess.
7. Wait two weeks for the soap to cure