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I live in a small town where Potassium hydroxide is not readily available. (I need above for preparing liquid soap.) But Potassium chloride ($\ce{KCl}$) and Quick Lime ($\ce{CaO}$) are available as fertilizer and White-wash ingredients respectively. Can $\ce{KOH}$ be prepared from above ingredients? What will be reaction conditions?

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    $\begingroup$ Any crudely prepared KOH will pose a lot of problems. Calcium forms scum. $\endgroup$
    – AChem
    Jan 11, 2021 at 1:59

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Mixing $\ce{KCl + CaO}$, or $\ce{KCl + Ca(OH)2}$, will never produce pure $\ce{KOH}$ without $\ce{Ca(OH)2}$. And this Ca(OH)2 will prevent soap from being synthesized out of oil, as $\ce{(Ca(OH)2}$s destroy soap in case a little bit of soap has been synthesized. The only way of producing $\ce{KOH}$ out of $\ce{CaO}$ or $\ce{Ca(OH)2}$ is to mix it with potassium carbonate $\ce{K2CO3}$. Of course $\ce{Ca(OH)2}$ is not very soluble in water. But $\ce{CaCO3}$ is still more insoluble. So the following reaction is possible :$$\ce{Ca(OH)2 + K2CO3 -> 2 KOH + CaCO3(s)}$$ And the insoluble $\ce{CaCO3}$ can be filtrated to produce a KOH solution

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Isn't potassium carbonate available as fertilizer? It's a lot more common. Then it would be a simple matter of mixing $\ce{CaO}$ with water and adding $\ce{K2CO3}$. Eventually you'd be left with solid $\ce{CaCO3}$ and $\ce{KOH}$ in solution.

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    $\begingroup$ A big limitation with this method is calcium hydroxide is not readily soluble in water. You might get a gram or a few grams per liter into solution at thd start, but if you allow hydroxide ions to accumulate in the water then the solubility equilibrium shifts and the calcium hydroxide dissolution is choked off. $\endgroup$
    – Oscar Lanzi
    Jan 11, 2021 at 2:43
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    $\begingroup$ historically potash lye was made by leaching the ash containing these two reactants, continously collecting the koh solution. Perhaps this works by preventing the equillibrium shift as hydroxide ions don't accumulate $\endgroup$
    – Francis L.
    Jan 11, 2021 at 2:58

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