Dental plate

[4metals]

I have never had to use poor mans AR but I would assume it will be limited if the material being digested is too thick. Copper can be used in lieu of silver but recycling it as 99% pure copper, as we can do with silver in nitric, is not so easy.

I know this will work with aqua regia and I'm assuming it will work with poor mans AR if you get small enough shot while pouring your inquarted alloy (in quarters with copper).

Things to watch out for are dropping of the gold out of solution by not using enough acid and saturating with copper. It may be tough to tell if everything is dissolved because the silver will be forming an insoluble chloride. One technique could be to add excess copper to drop the gold. Then you would test with stannous chloride until it doesn't test positive for gold, meaning it has all been displaced by copper. Then you will have essentially gold and silver chloride on the bottom. Filter it, rinse it, then dissolve the silver in ammonia to leave gold behind. This gold can be refined as normal and it should be pretty clean. Don't get into a habit of leaving alkaline silver in solution, acidify it and recover the silver.

This will definitely work with aqua regia, any experience or opinions from the poor mans AR users?

 

[lazersteve]

.. but copper will form a water-soluble copper chloride that will wash away and allow the AR to act on the gold. I understand that this process would have to continue until all of the metals reacted. If the process was stopped too soon, then the values would be cemented out of the solution by any unreacted copper.
Am I nuts?

This method should work fine with Poor Man's AR. As 4Metals mentions, as long as the silver content is not too high, even then his suggestions of using an excess of copper would give you a work around for the silver content as well.

The real trick when using Poor Man's AR to recover gold from low karat scrap is to control the amount of nitrate you add. Secondly, be sure to pour off the AR solution as it becomes satured with copper, adding more to continue the process.

I cover this Modified Poor Man's AR process in a step by step fashion here:

Modified Poor Man's AR

This method is really good for recovering gold from low karat scrap. The resulting gold will be very dirty and requires a good hot acid wash and finally the gold should be redissolved in AR and precipitated a second time.

Steve

 

[Lou]

Randy,

The saturated KCl is an old chemist's trick. It does work.

and Chemist, you form AgCl, not AgCl2 (which would have a minus charge, and is soluble...it is slightly yellow; almost like the faint yellow green of really saturated silver nitrate and nitrite).


Lou

 

[4metals]

Platdigger

I recently tried the Aqua regia saturated with KCl to dissolve some high silver karat gold. I made up the alloy to test the PDF we probably both read on this forum. I made an alloy of 75% gold and 25% silver and rolled it thin in a rolling mill. Sure enough it digested in the high salt acid but not in straight aqua regia where it froze pretty quickly. I can see this as a tool analytically where the sample can be prepared or is small and thin to begin with.

I then ran samples of the same alloy without rolling them, the metal was essentially the same thickness found in jewelery. (about 3/16") Both froze up rather quickly. I was hoping the salt trick could aid in digesting karat jewelry with stones. Often a percentage of these lots freeze up because they cannot be alloyed to control the silver before refining and some of it assays high for silver.

Unfortunately the thickness of the metal adversely effects the use of this technique for refining metal any thicker than thin rolled samples.

 

[Platdigger]

Good info 4metals, thanks for sharing the results of your testing.