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Extracting silver from a quaternary alloy of Ag-Cu-Ni-Zn

June 7, 2011

I recently came across some cheap 1946-1947 Australian Florins. I collect mainly pre-1965 US silver coins, but these florin were the right price at the right time. They're made of a q-metal in the following ratios:

Ag - 50%
Cu - 40%
Ni - 5%
Zn - 5%

These coins have very little numismatic value to me. I don't think the seller realized they are 50% silver (5 g per coin). Each coin weighs approximately 10.8 g-11 g. Now to my question. I'm having a bit of a challenge extracting the silver out of these coins. The presence of the copper and zinc, I think, are giving me difficulty using a HNO3-only solution. What is the best way to overcome this q-metal and extract just the silver? I have the following tools for making nitric acid:

Hydrochloric acid (32%)
Sulfuric Acid (98%)
Sodium Nitrate
Potassium Nitrate
Sodium Chloride
Copper Metal

Normally, I would create silver nitrate from scrap silver and precipitate silver from solution using copper metal. However, the HNO3 I'm producing and using on this q-metal alloy coin reacts for a short period of time and then stops. I'm left with an almost white coin and about one gram of precipitate. The precipitate does not visibly react HCI although solution does turn a light yellow over time.

I fear this mixture of metals is going to make it rather difficult to retrieve the silver from these coins... any suggestions would be much appreciated!

Seth Leonard
Hobbyist - Marietta, Georgia, USA

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June 9, 2011

Washed, dried, and weighed the precipitate -- 1 g. Color and texture was mainly a fine dark grey powder with small granular pieces of a white substance. The precipitate did not react at all in an HCI (32% v/v) bath. I expected any zinc in the substance to react and dissolve in HCI solution.

I washed the precipitate from the HCI bath and heated it. A very small amount turned a metallic-yellow color indicating to me that zinc may exist in some form. It melted very easily and formed a very brittle dark grey metal weighing about 0.4 g total. I assume the loss of weight was due to salts present in the precipitate and/or the zinc being volatilized during the melting.

I recently ordered a distillation apparatus for concentrating my HCI solution and for producing a stronger concentrated nitric acid. I have a feeling my solutions are not strong enough to dissolve the Ag-Cu-Ni-Zn q-metal. Any thoughts?

Seth Leonard
- Marietta, Georgia, USA

With "real" 67%-70% nitric acid, diluted 50/50 with distilled water, you should have no problems, since all 4 metals are soluble. Quite possibly, your method of making so-called "poorman's nitric" from sodium nitrate ⇦ this on Amazon [affil link] and sulfuric acid is faulty. I would suggest that you go to goldrefiningforum.com and search for "poorman's nitric." There you will find many articles on this subject plus information on safety and responsible waste disposal.

Chris Owen
- Nevada, Missouri, USA
June 8, 2011

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June 13, 2011

Thanks, Chris O for the input. As I said, I will be receiving a distillation apparatus this week for producing a more pure HNO3.

With some further research, I believe I've determined what the white substance is on the coin and why the reaction stopped. The solution I was using I believe contained excessive hydrochloric acid cause the solution to be more like AR than anything else. The white substance that resulted and I believe ultimately halted the reaction was silver chloride.

Once I can distill stronger acid's (sulfuric, hydrochloric, and nitric) I believe I will have better luck with these interesting q-metal coins.

BTW, I neutralize all my acids & wastes before disposing of them.

Seth Leonard
- Marietta, Georgia, USA