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Comment by ISL | Hacker News Reader

It seems to be an unfortunate property of nature that some of the most-useful chemical and physical systems are also some of the least-friendly.

NaOH, in large quantities, is an unforgiving material. As I've read my way into carbon-capture technology, I was saddened to find it there, too. HF also comes to mind in this direction (but is in another league). There's a correlation between those properties that make them useful and those that make them dangerous.

The most powerful counterexample to this notion that comes to mind, though, is water. What a spectacular chemical, one that is so useful we have built ourselves from it, yet we can also swim in it for hours without concern for any adverse effect beyond temporarily-wrinkly skin. (While it's less-relevant for thermal solar, it's darn good at heat-capacity, too! :) )

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I mean, water is also aggressively hostile. We're just really well adapted to it. Even pure water will turn metal into rust unless you're using special alloys. Salt water is so bad that even alloys won't save you, you have to depend on sacrificial anodes and exotic surface coatings. Steam takes everything bad about water and jams the fast-forward button until the tape catches fire. There's a reason the first hundred years of steam power is basically just a timeline of scientific metallurgy and gasket technology.

Let's not forget about how dangerous oxygen can be. The oxygen we enjoy now first caused an extinction event: https://en.wikipedia.org/wiki/Great_Oxidation_Event

NaOH is merely "ordinarily dangerous", i.e. safe enough to be sold to households with a warning sticker on. As long as you don't get it on your skin in large quantities you're fine. You can fairly easily dilute it into harmlessness, although you then have to be careful not to kill a river. If you leave it for long enough it will slowly react with CO2 out of the air via carbonic acid, precipitating out as harmless sodium carbonate.

It doesn't have any enduring toxicity. It won't get into your bones or your genetics. It's not bioaccumulative.

Isn't NaOH part of the soap?

It's a precursor but there's barely any left of it in the final product.

Separate from it's use in the production of soap, it's used as a cleaner (often at very low concentrations).

In the production of soap, it is used to break down the fats used rather than being part of the soap.

https://en.wikipedia.org/wiki/Saponification

NaOH turns fat into soap.

It’s dangerous because you’re also partially made of significant amounts of fats (and other things), which gets very very painful and can make it somewhat difficult to continue living when they get turned to soap while still part of you.

Yes - kinda like (horribly poisonous) chlorine gas is part of table salt.

NaOH is mostly dangerous because it is so alkaline. When reacted with fat to create soap the alkaline OH- is reacts with the fat and is 'used up', leaving a mostly neutral product

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