Came across the following paper in the Journal of Chemical Health and Safety, which inspired me to look into the many interesting ways that potassium can get you injured, killed or jailed – or just trash your research laboratory. It’s quite interesting subject.
Potassium’s name suggests its caustic nature. The english term comes from potash (literally ashes mixed in a pot with water), while the neo-Latin Kalium is based on the Arabic al qaliy, “from ashes”. Both are references to the caustic ash which used to be used to make soap (the U.S. Army Survival Manual still lists the recipe if you want to give it a try).
You remember the scene in Fight Club with lye? That’s this stuff:
Potassium’s oxides range from oxidized to VERY oxidized (K2O, K2O2, and KO2), each stage more anti-social than the previous. All oxides are highly corrosive and have the nasty habit of forming potassium hydroxide when mixed with water (again, the Fight Club stuff). Potassium superoxide (KO2) will actually explode on contact with water organics – or even when cut or bashed.
However, that is not even the worst of it. Potassium on its own will quickly convert to the nastier versions, simply from contact with the air. There was one case (can’t find it at the moment) where a student stole a small piece of potassium from a laboratory. It converted to potassium superoxide in the air, and then his body’s sweat set it off.
What happens is that potassium and its oxides will quickly set free oxygen and hydrogen from water, along with enough heat to cause it to detonate. Just as though this wasn’t enough, fumes of potassium bicarbonate, hydrogen peroxide and other fumes that are not the best to inhale.
All of this makes storing potassium a pain. It needs to be kept away from oxygen and water both.
One way to do this is to store the metal in petroleum (and it says something that storing this stuff in petroleum is the less explosive option). The problem is that petroleum tends to evaporate and then expose the metal to the air, so you are right back where you started.
There are heavier oils you can use, but the problem is that lithium is one of the lightest metals in existence. If the oil is to heavy, the lithium will float to the surface and be exposed to the air.
The best option is to keep lithium in petroleum and check the level of petroleum very regularly (at least once a week, if not more – if anyone has any details on this, please write).
Oxidation of lithium leads to the above mentioned states. You either get a white surface:
…if it’s just a little oxidized, or a yellow surface:
…if it is very oxidized. This is the stuff that can explode just by being cut or broken.
How do you deal with this?
[Disclaimer: I don’t suggest you try any of this. If you are stuck with this kind of potassium, please have it dealt with by a trained professional, the risks being what they are. Please make damn sure you read the paper itself to get the full protocol]
- Dumping the metal into water (no more than one 15 gram slug at a time). You need a large receiving drum (about 20 liter capacity, at least), a way of dropping the lithium into the water without being near it, and lot’s of space (you want to be at least 20 meters distant from every structure). Make sure you are at least 3 meters away from the apparatus and drop the slug. It will make a big bang, but should render the lithium harmless (eventually). This is a favourite of the army.
- Slow burning the metal on a coke fire. This one I am filing under ‘What could possibly go wrong?’ The full method is apparently described in the 1985 Handbook of Laboratory Waste Disposal
- Slow dripping of alcohol onto scraps. Another ‘what could go wrong?’ one. The method described involves slow dripping of alcohols onto the scraps of the material. This one is even worse – how do you define a scrap? Which alcohol? I haven’t found any answers to this stuff, but it suggests how things could go very wrong.
Just as though all of the foregoing wasn’t enough of a headache, potassium compounds are explosive precursors and tend to be highly regulated. In Singapore, improper handling of an explosive precursor can get you two years in jail and a fifty thousand dollar fine. I’m not sure what the law is elsewhere, but I doubt they are much more lenient, when compounds like potassium chlorate and potassium nitrate are recommended by the Mujahideen Explosives Handbook (the link goes to a Naval Postgraduate School document on terrorism, so don’t worry about ending up on some watchlist).
Here’s a classic story about how sodium nitrate can explode. Money quote:
Clawson told students he had performed the experiment “three or four” times that morning. Junior Courtney Fillmore was in one of those classes.
“It sparked, but it did not blow up in my class,” she said.
…there’s a line for the ages. The ration between incidents and injuries is six hundred to one. Those sparks were a helpful warning, not a guarantee that nothing bad could happen.
‘Potassium’ should be one of those words that causes you to freak out when it shows up on a lab inventory. Anyone who is making use of it should explain – in great detail – how he plans to dispose of it, if and when it goes bad. If necessary, call in outside consultation – and, yes, that may mean army or the police force.