What causes old dynamite to “sweat” and why is that so dangerous?
In: Chemistry
Dynamite is nitroglycerin, an explosive liquid, which is absorbed into some solid powder. Over time, it’s not going to stay perfectly in the sorbent, so the nitroglycerin will start to leak out. This is particularly dangerous because nitroglycerin is a pressure-sensitive explosive, so being just out and about like that it’s prone to exploding if bumped too hard.
Liquid nitroglycerin, the explosive part of dynamite, is very very sensitive. It’s easy to set it off with little more than a slap. Dynamite mixes special dirt into it to keep it from blowing up too easily.
Just like any wet dirt, the liquid will soak out, and once the liquid is free again it is super easy to set off.
Nitroglycerin is an explosive liquid first discovered in 1847 which was the first explosive to really supersede black powder. However, it’s very unstable and can even be detonated by physical shock (e.g. dropping some on the ground) and degrades over time into even more unstable forms.
There were several major industrial accidents related to the use, transport, and manufacture of nitroglycerin; in 1864 Alfred Nobel’s brother Emil was killed in an explosion at the family’s nitroglycerin factory outside Stockholm. A few years later, Alfred Nobel managed to successfully stabilize nitroglycerin by mixing it with diatomaceous earth (a naturally occurring mineral which is composed of the fossilized remains of algae), inventing dynamite.
While dynamite was stable enough to be used as a practical industrial explosive, it does not remain stable indefinitely. Over time, the nitroglycerin will start to leach out, which is called “sweating” and in its pure form will become extremely unstable again. Generally speaking the “shelf life” of dynamite is considered to be one year if it is stored properly.
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