'The main active ingredient in “thunder-clappers” was a mercury salt.'

This doesn't seem particularly safe or good for the environment.

I doubt if the product is sold now.

Edit: https://en.m.wikipedia.org/wiki/Calomel

Ah mercury, sweetest of the transition metals.

https://m.youtube.com/watch?v=zfde7SHM6Dk

Forget about the environment, that thing will poison you.