# Silver Recovery From Silver Solder Brazing Rod - VIDEO



## kadriver (Jan 10, 2018)

I recovered the silver from Stay-Silv 15 silver solder brazing rod:

https://youtu.be/Tu00RAHouQs

kadriver


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## g_axelsson (Jan 11, 2018)

I don't know for fact what the precipitate is but I'm certain it isn't silver chloride. If you had chloride in the water or nitric acid it would have formed a cloud of silver chloride whenever you added more water or nitric to the beaker.

According to http://www.harrisproductsgroup.com/en/Products/Alloys/Brazing/Phos-Copper/Stay-Silv-15.aspx the braze consists of :
Cu - 80%
P - 5%
Ag - 15%

Phosphorus in nitric acid apparently turns into phosphoric acid. That should react with the copper in solution and form Cu3(PO4)2, an insoluble phosphate salt. After some more reading I realize that it should form Cu2(PO4)OH, the green hydrated copper phosphate salt. Still, it's insoluble in water.

Let's see what happens with the silver in solution... Silver phosphate, Ag3PO4 is only slightly soluble in water (mg/liter) but more soluble than the copper phosphate. With a lot of copper nitrate in solution the reaction should move towards silver nitrate in solution and copper phosphate as a precipitate. How fast this reaction goes, I can't tell, but it can take significant time so I should expect some silver also precipitating with the copper.

This is just speculations on my side, backed up with some research online. Let me know if you think I'm wrong or if I have drawn some false conclusions.

https://en.wikipedia.org/wiki/Copper(II)_phosphate
https://en.wikipedia.org/wiki/Silver_phosphate

TLDR; The precipitation is probably mostly copper phosphate.

(TLDR = Too Long, Didn't Read.  )

Göran


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## anachronism (Jan 11, 2018)

Goran behave- don't use text speak 8) 8)


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## g_axelsson (Jan 11, 2018)

I better warn myself, one hour ban from the forum... Ouch! That hurts... see you in an hour. :wink: 

Göran


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## anachronism (Jan 11, 2018)

g_axelsson said:


> I better warn myself, one hour ban from the forum... Ouch! That hurts... see you in an hour. :wink:
> 
> Göran



Back now then? 8)


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## g_axelsson (Jan 11, 2018)

Awww, that was the worst hour since Butcher banned the whole world in one go. :mrgreen: 

Göran


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## kadriver (Jan 13, 2018)

I couldnt figure out why it was taking so much nitric. After I posted the video I realized, after reading some of the comments, that as the silver dissolved in the presence of 80% copper, that the silver was probably cementing out as soon as it went into solution, then cementing out and going back into solution, over and over.

This consumed much nitric acid as it went.

I beleive that this is why I had so little silver chloride precipitate the first time I added hydrochloric acid. Then once most everything dissolved, the silver stayed in solution because there was no copper left for the silver to precipitate out on. I'll bet that there may be some more silver in the last few bits of undissolved Stay Silv 15 that was left in the beaker.

Ive still got all the residue from this experiment, I may try to make a supplemental video and get the rest of the silver.

kadriver


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## g_axelsson (Jan 13, 2018)

You were practically running silver inquarted with copper, unless copper phosphate creates a protective surface (in the same manner that silver chloride does) it could easily cement back silver while dissolving copper.

Göran


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