MadSci Network: Chemistry

Re: Why does my skin feel soapy if I get sodium hydroxide on it?

Date: Wed Dec 13 10:31:45 2000
Posted By: Sojo Luis E., Staff, Reseach and Development, Axelson Biopharma Research
Area of science: Chemistry
ID: 975449872.Ch


Sodium hydroxide will in fact soaponify (turn into soap) the fatty acid esters and oils on your fingertips & skin. This results in the formation of sufactants (soaps). In the case of the fatty acid esters, after reacting with sodium hydroxide, these molecules loose their ester ends and become free fatty acids. Due to their molecular structures (polar heads, (carboxylic acid ends) with non-polar end organic hydrocarbon chains) free fatty acids act as soaps surrounding grease with their non-polar ends, while their polar ends are pointed into the water. In this way grease is extracted from water or surfaces (clothes, etc). They also decrease friction between rubbing surfaces, i.e. your fingertips. This last effect is what you feel as you rub your fingertips together after soaking them in sodium hydroxide. You probably have noted that after doing the finger rubing experiment and after you washed your hands with lots of water (it takes lost of water to get rid of the soapy feeling), your fingertips feel a bit rough. This is due to the lose of grease and fatty acid ester from your fingertips.

Admin note: Please be cautioned that even dilute solutions of sodium hydroxide (NaOH) are caustic, and will easily burn skin, and cause severe damage should the solution come in contact with the eyes or other mucous membranes.
-L. Bry, MadSci Admin

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