I was thinking maybe have those chemicals sitting in a glass or temperature sensitive container inside the tank. So when there's too much pressure or heat, the container containing the neutralizing chemical is broken like a fuse and the chemical is automatically released.

Having the chemical in one location doesn't make it active all over, you need to disperse it. Like you need to shake glow-in-the-dark bracelets.

Well then... make a matrix of such fuse-containers? (say every 20cm or whatever) I guess manufacturing such a matrix would be pretty expensive though, you'd need to carefully automate its production I think. It would also definitely interfere with flow of fluid in the tank.

Easy to imagine protective mechanisms in hindsight, now imagine you have to build a system for every tank of every chemical in the world

I am imagining some sort of regulations that enforce the creation and installation of appropriate safety systems upon all similar sites in the affected jurisdiction.

And a standard to prevent similar danger elsewhere in the world.

Or is that too fantastic? Perhaps I should stick with the distopian fiction I so love. Why haven't flying cars taken off yet?

I was thinking multiple long skinny tubes with etchings that make them more likely to split lengthwise. Maybe with a spring loaded/powered agitator so when the tube breaks there's some mechanical flinging/mixing of the inner chemical.

But I'm not a chemical processes engineer, so I don't know how much mixing is needed. But the existing emergency plan was to inject the the chemical through a single valve, so it seems like the dispersion and mixing requirements in this case seems to be low.

That is active.

Something passive could be submerging the tank in a pool of water (also good for proving spill containment won't leak).

Typically you don't have enough surface area for that. The walls are thick enough that thermal conductivity into an ambient-temperature liquid alone is not going to be sufficient.

Uh, you can't just disconnect a pressurized 35,000 gallon tank and drop it into a an enormous pool you just keep full under it at all times.

Riiight. That is exactly what I was thinking.

It's really unclear what you were thinking

I think the passive version is the tank stays in a pool all the time.