Prevent magnesium powder from reacting

[Spatula Tzar]

I may soon be embarking on a metal grinding task. The process is fairly straightforward, but I need to know how to prevent magnesium powder from reacting with water. The only source I can find says to use potassium dichromate, but this is rather toxic. Will boric acid suffice as it will for aluminium? Some other chemical?

[Trayvon Martin]

catch it in oil?

[Aperson444]

Mineral oil is typically used for alkli metals. You may have difficulty getting the stuff off though. Perhaps use pentane or hexane?

[Spatula Tzar]

Magnesium is not an alkali metal...

Low molecular mass alkanes are far too volatile and dangerous to catch magnesium when grinding. One errant spark, and it goes up in flames. Mineral oil might work though.

[Hydroponichronic]

Originally Posted by Spatula Tzar

Magnesium is not an alkali metal...

Alkaline earth metal. Close enough. Similar in its reactivity.

Originally Posted by Spatula Tzar

Low molecular mass alkanes are far too volatile and dangerous to catch magnesium when grinding. One errant spark, and it goes up in flames. Mineral oil might work though.

This. To get mineral oil off, just let the Mg powder settle, then pour off the excess mineral oil. Once the Mg powder has only a little oil around it, scoop it into a filter (or some paper towel if no filter), and drip VM&P naphtha to take the oil off. The VM&P will solvate the oil and then it will evap off the metal powder quickly and under light heat.

['Ed Rush]

I don't know, did you try google?

[Spence_tron]

I've ground down Mg bars into a collection tray with a layer of water without any problems, I just made sure to dry the filtered Mg powder/flakes well and store it with a pack of desiccant in an air tight glass jar. The Mg collected worked fine for my pyrotechnic purposes. Adding 1% boric acid will help to stabilize it, it doesn't just work on aluminum (but it's typically used in nitrate/aluminum compositions). For the record, I do add a pinch of boric acid when I grind Mg bars nowadays just for some peace of mind. It seems to work fine.

If you're really paranoid about it you could follow Hydro's advice, but I think it may be a waste of solvent given the application.

[Sentinel owl]

From an archived version of the "metal grinding machine" web page that I have stored on my computer:

Magnesium
Magnesium is somewhat problematic because of its reactivity with water. A spoonful of potassium dichromate added to the bath greatly suppresses the amount of bubbling that takes place. I've also used mineral spirits instead of water when grinding magnesium with very fine sandpapers, but this is less convenient.

Mineral spirits would have a nasty tenancy to evaporate away and cause noxious fumes (plus aforementioned flammability issues). I would definitely think about using mineral OIL though. Gloppy, and also would make a mess but in a different way, but no evaporation problems. Just make sure it's not getting inside your motor or whatever you are using to grind the grinder.

[nuclearrabbit]

Magnalium is amazingly easy to powder in a ball mill. Would the combination suffice for your purpose?

And hi Spatch.

[Anders Hoveland]

must you use water? What about just using kerosene? Get some dry ice to create an insulating layer of carbon dioxide so the kersone does not catch fire from the sparks.

[InspiredByMe]

Originally Posted by Anders Hoveland

must you use water? What about just using kerosene? Get some dry ice to create an insulating layer of carbon dioxide so the kersone does not catch fire from the sparks.

That's utterly retarded. If it does spark and catch fire you are fucked. CO2 cannot be used to extinguish magnesium fires, it reacts greatly with lit Mg. Adding kerosene, hell any hydrocarbon fuel, to the mix is just asking for trouble.

Mineral oil should work. I have no doubt Tzar already found a solution though.

[Irukanji]

If you can do it all inside of a glove box full of argon(or MIG/TIG welding gas, which should do the job) you can use whatever tool you want.

If you can get some gas tight piping into your ball mill, just rig the argon line straight into it, fill it up, then seal the whole unit. Should be ok if it is gas tight(teflon on the threads will assist)