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?
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?
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.
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.