[Bane]

Hey everyone,

So here's an interesting discussion topic.  What I'm doing is making jewelry from bits of iron meteorite.  I'm putting a quantity of small, sub-BB size fragments of meteorite into tiny glass bottles for use as pendants, earrings, etc.  Stardust jewelry! The thing is, the meteorite fragments are mostly iron (not sure of the alloy quantities, but certainly almost 100% iron), and thus will rust over time if not properly protected.  Some of the fragments were already slightly rusted when I received them. 

So what I need to know is - how should I protect these small bits of stardust? I want to make certain that once sealed inside the tiny bottle (with a cork, glued in place), the fragments will not rust. 

So far, I can think of two possible solutions, but I'm not certain how well either will work. 

The first solution I can think of is to coat the fragments with a small amount of oil or other rust preventative, although I'm not sure what kind to use.  Whatever oil I use, it must not create a film on the inside of the glass, which might obscure the bottle's contents. It also must be colorless, and preferably odorless, or low-odor.  I've been toying with the idea of coating the fragments with WD-40, then cleaning most of it off before putting the fragments into the bottle.  However, WD-40 has a rather strong odor, which may or may not penetrate the cork over time.  Thoughts?

The second solution involves replacing the oxygen inside the bottle with some other gas, or vacuum, since oxidization requires the presence of oxygen.  Anyone know how I might accomplish this? Perhaps create a semi-vacuum inside the bottle? We're talking really small bottles here, as in 25mm tall.  What might happen if I put a drop of 99% rubbing alcohol inside the bottle and ignite it, then put the cork in (with glue to seal it in place)?

Any thoughts or suggestions would be welcome.

Thanks!

[fledarmus]

Many people use exactly the opposite approach - use a very clear oil, and just fill the bottle with oil, leaving the meteorite to be viewed through the oil.

Another possibility would be to coat the meteorite fragments with a clear acrylic or lacquer before putting them in the bottle.

Depending on how deeply you want to get involved, you could use ampules instead of bottles, sealed in a nitrogen or argon environment. It isn't that difficult - many chemicals, especially NMR solvents, are delivered that way. An open ampule is prepared and attached to a hose hooked to a vacuum/inert gas manifold. The air inside is purged by successive applications of vacuum and inert gas, and then the glass wall is melted with a pinpoint torch to seal the top of the ampule. http://www.sigmaaldrich.com/catalog/product/aldrich/z184950?lang=en&region=US

[Bane]

I have tried filling the entire bottle with mineral oil, although I seem to be having problems with bubbles forming inside the bottle afterward.  with this method though, there's really no way to secure the cork in the bottle, as the oil overflows when putting in the cork.  It still stays put, but it seems like air must still be getting in somehow, thus the bubble.  Anyway, is mineral oil even suitable for this?  Or is there something that might be better suited?  Thanks

[Jasim]

You could use an acid to reduce the rust back into iron and coat the iron in a layer of iron-acid salt. For instance, using phosphoric acid will coat in a layer of ferric phosphate.

The coating of ferric phosphate would slow down the rusting process. Rust only occurs in the presence of oxygen and it's catalyzed by moisture. Removing as mush moisture from the container as possible would help slow rusting. You could fill the container with a non-reactive, dry gas such as dry nitrogen - as long as you could be sure to seal it well. That would prevent rusting indefinitely so long as the container stays sealed.

A note: The ferric phosphate may have a slightly different color, a kind of dark gun-metal grey.


I think your best bet would be to fill the bottle with dry nitrogen. The biggest issue would be sealing the bottle. Carbon dioxide would also work (which is basically your idea behind burning away all the oxygen, but that would not work). You can get nitrogen and carbon dioxide tanks from beer supply stores. Try a Google search, can get a tank for under $100.

[Bane]

I didn't think about using carbon dioxide gas.  Would it work as well as the nitrogen, in theory?  It would certainly be easier to get hold of, since I can just get a pack of those small CO2 tanks that are used for BB guns.  Although getting the gas out of those little tanks might prove problematic...

What about nitrous oxide from whipped cream cans?  Is that stuff pure enough? Maybe a dumb idea, lol.

How should I introduce the carbon dioxide into the bottle though?  From what I've been able to gather online, CO2 gas is about 1.5 times heavier than air, so might I be able to "pour" it into the bottles?  Any ideas on how I could accomplish this consistently?  Thanks

[Bane]

And just out of curiosity, why won't burning out the oxygen work? Would the flame not consume it completely?

[Bane]

*Ignore me, I am impatient*.  Also, anyone know where I might buy dry nitrogen?  Google's not turning up much so far.  I had someone on another forum tell me that it's sometimes sold in a can for displacing air in containers of wood finish, but I haven't been able to turn up anything there either.  Thanks

[fledarmus]

You can buy cylinders of nitrogen at any welding supply store - it is used for inert gas welding. If you need it dryer than that, feed it through a cylinder containing a drying agent. Indicator Drierite is a good choice.

[Borek]

Liquid nitrogen is very dry, removing water is an important part of the manufacturing process. Just putting a drop in the bottle.

I wonder if sealing the samples in glass ampules as fledarmus suggested won't solve the problem. Amount of oxygen left inside would be quite small, amount of water an additional order of magnitude lower. They are not going to produce substantial amount of rust.