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These days I'm working on a school project and I need to make soap without using sodium hydroxide.

If I really need to use it and there is no alternative, how can I obtain it from chemical reactions?

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closed as too broad by Mithoron, Todd Minehardt, airhuff, Gaurang Tandon, aventurin Mar 23 '18 at 16:57

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    $\begingroup$ Use potassium hydroxide? $\endgroup$ – DHMO Sep 28 '16 at 15:07
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    $\begingroup$ If you can't buy it from a chemical vendor I don't know if you'd be any better off making it yourself. Do you happen to have a lot of sodium metal laying around? If not do you have the means to make a molten salt electrolytic cell? And all this just for some soap? $\endgroup$ – ringo Sep 28 '16 at 15:17
  • $\begingroup$ I think that i can make a molten dalt electrolytic cell...and it's not question of just some soap but question of something that i really want to do...i love challenges $\endgroup$ – Dou Aeza Taf Sep 28 '16 at 15:22
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    $\begingroup$ Many hardware stores sell it as drain cleaner. I know ACE does. However, beware: NaOH is a nasty chemical and on top of that there is no guarantee of purity on something sold for drain cleaning, so it could contain even worse. You might be able to find higher quality lye at craft stores. It'll still melt your skin off, though. $\endgroup$ – user7652 Sep 28 '16 at 16:01
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    $\begingroup$ wikihow.com/Make-Your-Own-Soap I would advise you not to try to make NaOH.It can be extremely dangerous.Use the link I gave. $\endgroup$ – user14857 Sep 29 '16 at 2:23
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In short: Yes, you can make soap without buying sodium hydroxide and the method adds a historical touch to the school project.

Back in the days when food was cooked on open fireplaces or in ovens fired with wood, the remaining ashes (of the burnt wood) were collected for good reason.

Leach the ashes with water and filter out the insoluble residue. Measure the pH of the solution and you'll recognize that it is alkaline. This is due to the formation of soluble carbonates when the wood was burned.

You can now either try to use the solution for the saponification of vegetable oils or animal fat, or evaporate the solution to dryness in order to obtain a solid material which will mostly consist of potassium carbonate.

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You can heat a small amount of baking soda ($\ce{NaHCO3}$) to ~9000C (a reddish-orange glow) to decompose to first washing soda ($\ce{Na2CO3}$) and then to sodium oxide ($\ce{Na2O}$). When it cools, slowly and carefully add the $\ce{Na2O}$ to water to get $\ce{NaOH}$ solution.

N.B. $\ce{NaOH}$ is caustic: it will damage skin and eyes, and can even dissolve a glass container.

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