[Jesper]

Hello Chemical Forums,

I have a few questions that I hope you may be able to help with ...

I'm considering using Natriumpersulphate (Na₂S₂O₈) for etching argentium which is a silver & germanium alloy (typically ~92.5% silver), however, do not know if this is "feasible" in terms of:

1. Contamination of the Natriumpersulphate so that it subsequently is less useful for etching copper PCBs. This is the most important question as I'd rather not spoil the natriumpersulphate's ability to etch copper 

2. Etching efficiency. Will the natriumpersulphate be efficient in etching the argentium? To my knowledge, the reason why argentium often is used by silversmiths as an alternative to pure silver is that argentium doesn't visually oxidize in air like silver does over time. As I understand it, the germanium part of the argentium migrates to the surface of the argentium where it is then oxidized by the air. This oxidation visually looks very silvery (which is the reason the argentium continues looking clean and non-oxidized), while at the same time sealing the argentium's surface so that air doesn't diffuse into the underlying silver. However, I don't know if the oxidized germanium/silver alloy on the outside of the germanium can be etched by the natriumpersulphate ... Might one of you know of this?

Insights are appreciated ... 

Greetings,

Jesper

[wolf_of_benjamin]

Yes possible; only nitrates, chlorides and chlorates must be stronger but no acid can dissove Argentum (Silver). Theoretically your acid could etch Argentum : Silver (Ag).

[Jesper]

Hi,

& thanks for replying ... when you write Argentum (silver) then I can't help wondering if you've seen that it's not argentum but argentium I'm hoping to etch? As I write, Argentium is a silver/germanium alloy which I guess makes it somewhat different than silver - not least because apparently a germanium oxide forms on the outside of the argentium...

Would you still say that etching is possible without damaging the Na2S2O8 bath?

Best regards,

Jesper

[Arkcon]

I find it hard to understand what you mean by "damaging" a bath, by definition, this is a oxidative compound, isn't it always eventually consumed by the etching process, not matter what is being etched?  Anyway, the previous response is wrong at least 2 different ways -- the poster clearly writes Argentum as in silver twice, then says no acid can dissolve it, which isn't true of silver.

[Jesper]

Hi & thank you also for replying.

isn't it always eventually consumed by the etching process, not matter what is being etched?

... this is what I don't know ... I have a vague remembrance from my chemistry teachings that there was something about "levels" and that if a substance had shifted to a certain level other lower level substances could not be oxidized - or something like that. Can you shed some light on this?

Also, if one of you here in the forum has some knowledge about the effect of the Germanium ... I can also just try to see what happens but would like to know if it damages the bath ... If that's possible ...

Regards,

Jesper

[Borek]

Sounds like you may be thinking about reactivity series. But it doesn't work this way - your solution should work till it is consumed.

[Jesper]

Thanks - clarification much appreciated 

Jesper