Coconut lye sub product of artesanal coconut soap

DilfreDilfre Member
edited September 2016 in Advanced Questions
I have received at the lab a sample of "coconut lye" is a dark brown liquid with water consistensy coming as subproduct of coconut oil saponification. I mixed it with common salt and produces a precipitated soap. What it is the in progress reaction there?


  • You need to test the saponification number. I think it is crude glycerine instead of coconut lye. Taste it to see whether it is sweet or not.
  • BelassiBelassi Member, PCF student
    Normal reaction for a soap solution.
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  • BobzchemistBobzchemist Member, PCF student
    I'm guessing that you were sent the dark, bottom "niger" layer that occurs in the kettle soap-making process step known as "pitching". This happens after the salting-out step that removes the glycerin, so I don't think you'll find much glycerin, but I think it's about 20% soap.
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  • johnbjohnb Member, Professional Chemist
    The soap that bobz mentions is of very low quality and is mainly soaps of shorter chain fatty acids. The soap manufacturers I worked for had good "green" credentials even though it was several decades before the green movement became de rigueur or even known in manufacturing.

    That being the case and not wishing to contaminate the environment with tonnes of waste, the nigre waste was treated with ferric chloride to form short chain ferric soaps which separated as an unpleasant orange coloured, sticky, smelly paste. This stuff had a relatively high value in being sold to steel manufacturers as an additive to the mix in making high quality specialist industrial steels.

    The residual water after this process comprised sodium chloride and a small amount of glycerin which was recycled into the brine used in the soap making.
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