Germanium: Refining issues?

[upcyclist]

The problem: I have some Argentium, the proprietary Sterling silver alloy that contains 1.2% germanium, that I'm considering using for inquartation. Basically, I've used & reused it to where it's failing during casting, so it's time to purify it, or at least use it to learn inquartation and save off the silver for later.

It sounds like it'll dissolve in concentrated HCL, forming germanium chloride. So, if I use an HCL soak to get rid of impurities, it'll likely end up there. Perhaps also in nitric if I use that?

Theoretically I could fractionally distill the GeCl₄ off, get it to GeO₂, blah blah blah. Current price is at $2k/kg, and each ounce of Argentium would contain about a third of a gram of Ge. I don't think it would be worth 70¢ per troy ounce of Argentium at my scale. And like Silicon, who's going to buy it if I can't get it 6-nines pure?

My main question: presumably it would dissolve during a hot HCl soak to remove impurities--which is cool, cuz it's an impurity now. But, where do metalloids fall on the reactivity series [of metals]? Will it cement out with copper when I'm processing my stock pot?

 

[upcyclist]

...or would it cement out with iron during the waste processing steps?

Part of the point, of course, is to keep my PMs pure, but it sounds like germanium chloride ain't the prettiest thing in the world and I'd like to make sure it either cements out or at least drops when I bring the pH of my waste acid up to 7.

 

[butcher]

As far as I know germanium does not dissolve easily in dilute acids. But can be dissolved in concentrated nitric or sulfuric acids.

If this holds true, as far as in-quartering gold with the silver that has a small amount of germanium, I would think the silver would dissolve in the dilute nitric acid, and possibly leaving the more insoluble the germanium (or germanium oxide) behind.

In aqua regia germanium would most likely be difficult to dissolve,you may be able to dissolve the fine gold powder without heat, this may leave the germanium behind, and if it did follow the gold, I am guessing it would form the more volatile germanium tetrachloride which could be distilled of with heat.
gemanium tetrachloride has a boiling point around 90 Deg.C

But then again I am just guessing here, with this guess in mind, I would further study the reactions to see what may actually happen..

 

[g_axelsson]

I'm with Butcher and guessing... germanium oxidizes slowly in air so it shouldn't be too hard to oxidize it in nitric acid either, forming germanium dioxide. In HCl GeO₂ reacts fast forming GeCl₄ and H₂O. GeCl₄ boils off at 86 C.

According to Gilchrist in this paper germanium doesn't form any hydroxide at least below pH7.

This is just a speculation after reading up on the subject, I have no real experience with germanium chemistry. I would recommend taking the question onto the sciencemadness board, lits of competent chemists there.

Edit : read this thread http://www.sciencemadness.org/talk/viewthread.php?tid=15572
Seems like germanium is quite inert after all, really hard to dissolve and basically non toxic if in metallic or oxide state.

Göran

 

[Lou]

It passivates easily and makes a self healing GeO2 layer.

Ge itself is actually at this time over twice as valuable as silver.

 

[upcyclist]

It passivates easily and makes a self healing GeO2 layer.

Ge itself is actually at this time over twice as valuable as silver.

The passivation is of course exactly why they use it in Argentium.

It may be more valuable than silver, but the silver is much more plentiful in the alloy. Among my local fellow silversmiths, I'm the only one that consistently works with Argentium, so I'm the only one generating the material for refining. Even the silver is going to get stashed as AgCl once I precipitate it out.

I can experiment with it, but since I don't know the color of germanium in solution, and don't know how to test for it, it'll be more like "this thing went poorly/wrong, I wonder if it was the germanium?"

It sounds like it should be okay--any that dissolves in hydrochloric or nitric will likely end up in the stockpot or waste (any that forms GeCl₄ might boil away with the fumes). Any that doesn't dissolve will end up in the AR. If it doesn't dissolve in the AR, it can be filtered out before I drop the gold (and possibly saved). Any that does dissolve in AR hopefully won't drop with the gold.

I think the most likely contamination would be if the gold carries it down. I guess I'll know when the purity is tested. I can always not use the Argentium for inquartation right away, and use fine/sterling silver and/or copper the first few runs, so I'll know when significant gold impurities are possibly Ge and not just noob technique.

As always, thanks for your big brains!