Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: valeg96 on 23/03/2014 15:38:55
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I found some cheap commercial softener that was very liquid -like water- but still pink, and had floaty bubbles of yellow stuff (fat I suppose, like the one you see in frozen meat broth). Some bottles had black mold, apparently confirming the fat theory (what else could host bacterial growth in an industrial-made detergent?). The question is, How could that happen? Is saponification reversible? Could it be some failed product forgery, for example diluting the soap? I have yet to test its pH, but I'm pretty sure it's fat and the alkali solution, and the process somehow reversed. I'll put some pics if needed.
Update: The solution is slightly acidic (universal indicator shows 5-6) and the bubbles do feel like fat on touch.
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While all reactions are reversible in principle, I think it is highly unlikely that soap would spontaneously un-saponify (enthalpy positive and entropy negative reaction).
But Fabric softener is not soap. Actually some formulations are emulsions of vegetable oil and water! (http://en.wikipedia.org/wiki/Fabric_softener#Composition) Most are made with synthetic hydrophobic compounds, but the effect is the same. If the emulsion degrades, you will see phase separation into water and "oil."
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And why would the emulsion return to its original compounds? Can a temperature shock be the cause? Or maybe the expiration date effectively has a purpose on commercial detergents?
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An emulsion is just a semi-stable mixture of immiscible liquids. Some of them separate very quickly (like salad dressing) and some are longer lived (like homogenized milk), but they will all separate eventually. Temperature shock can definitely play a role.