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The other day, I tried to mix liquid castile soap and washing soda (sodium carbonate) to use in doing laundry. I mixed equal parts liquid soap and sodium carbonate by weight. To my surprise, an exothermic reation occured (my glass jar got warm), and then the substance became hard. Before it got hard, I touched the tip of my finger to it and didn't get any chemical burns.

The castile soap that I used was homemade. My soap contained: water, potassium soybeanate, and glycerin.

The soap was made of: water 172.36g potassium hydroxide 91.45g soybean oil 453.59g

for a total of 717.41g before boiling down which I then dilluted to a water to soap ratio of 4:1. The soap was well cooked (5-6hrs) and cured for a week.

Could a chemist help me understand what reaction occurred?

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  • $\begingroup$ I think the issue is that you had unreacted organic acids that were strong enough to be deprotinated by $\ce{NaCO3}$. So then it's just an acid-base reaction between $\ce{NaCO3}$ and the leftover organic acids in the soybean oil. Then the solids would be the Na salts of the organic conjugate bases, which are insoluble in oil. $\endgroup$ – airhuff Feb 7 '17 at 10:27

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