# aqua regia dropping gold without precipitant



## micronationcreation (Jan 29, 2011)

hi, i am a novice, i have read hokes book and i am using e-scrap and aqua regia, i was in the process of reducing the AR solution to get rid of the nitric, i added a little sulphuric and more hydrochloric and reduced again.

Now it appears the gold has dropped from the solution without the aid of a precipitant, is this possible? 

The sediment is brown and grainy and looks like gold. Do i filter then add the precipitant anyway?


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## nickvc (Jan 29, 2011)

Welcome to the forum.
I think it's highly unlikely that gold has precipitated from your solution.
Some more details of exactly how you reached this point might help us to help you. The use of Aqua Regia directly on e scrap is rarely a good idea as it will dissolve many troublesome metals along with the gold.


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## micronationcreation (Jan 29, 2011)

hi thanks for your reply, 

i processed the e-scrap with nitric first, and then i soaked the stripped boards in AR to dissolve the gold contacts. the AR turned a green/yellow colour, i assume there was copper left on the boards which turned it this colour.


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## Platdigger (Jan 29, 2011)

If there was enough copper, it may have cemented out your gold.
Do you have stanus?


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## Harold_V (Jan 30, 2011)

It is not unusual for gold to self precipitate---Hoke addressed the issue in her book. It occurs when you evaporate to a highly concentrated solution that is free of nitric. The solution often borders on being red/black when gold precipitates, and has begun baking out on the vessel. 

What Hoke suggests is for a few grains of sodium chlorate be introduced to the solution, which should re-dissolve the traces of gold. I never tried her method. 

When I'd experience that problem, I simply added a few drops of nitric, along with enough HCl to re-dissolve the self precipitated gold. Considering I generally had a button of gold included to consume the unused nitric, it was not a problem.

That you've had this experience speaks volumes about your proper use of nitric. You obviously used it sparingly, whether by choice, or by chance, but you've witnessed the benefit of using the proper amount. The problem is, you can't tell when you have, especially if you're dissolving values from dirty materials, such as polishing wastes, or filings from the jeweler's bench. It is for that reason I always chose to use a little more than was required, then to eliminate what little remained by the added button of pure gold in the evaporation process. That worked for me, but my procedures may have been very different from those that you use. 

Harold


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## donnybrook (Feb 28, 2011)

One of the things that can occur when you add sulfuric acid to your solutions is that you will drop any lead that might have been involved especially if the material under dissolution was a solder base. It drops rapidly rather than slowly.It is a dark color but can appear to be brown.
donnybrook


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