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June 1, 2011 7:05 PM   Subscribe

Calling all chemistry minded people! Wha' happen to mah soap??

I have some problemed skin (hello heartbreak of psoriasis), so I tend to make my own skin care concoctions at home. Among these are a sea salt/Epsom salt scrub, a castile based liquid soap, and I tend to use apple cider vinegar as a rinse.
One day, I was in a hurry, and experimented with combining the liquid soap with the salt scrub. Within a few minutes I was covered in a gummy, waxy substance that was next to impossible to wash off. Clearly I had stumbled upon some interesting chemical reaction, but not really being all that knowledgeable about such things, I am DYING to know (in relatively plain English) what exactly happened. I assume it was some kind of "reverse saponification", but what could have triggered it? The salt? The vitamin e oil in the soap? The vinegar?
posted by evilcupcakes to Science & Nature (3 answers total) 1 user marked this as a favorite
 
"Salting out"
(from Wikipedia)
In the traditional one-step process, the triglyceride is treated with a strong base (e.g. lye), which accelerates cleavage of the ester bond and releases the fatty acid salt and glycerol. This process is the main industrial method for producing glycerol. If necessary, soaps may be precipitated by salting it out with saturated sodium chloride.

Basically, the Castille Soap is only made by the one-step process. You did step two.
posted by Green Eyed Monster at 7:13 PM on June 1, 2011 [3 favorites]


(That's the Wikipedia article on saponification, btw)
posted by Green Eyed Monster at 7:30 PM on June 1, 2011


Interesting. I read that article, but since the waxy substance didn't seem to at all resemble "soap", I thought it didn't apply. Thanks!
posted by evilcupcakes at 3:44 PM on June 2, 2011


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