Strange thing happened

[sayf]

A friend of mine faced a strange thing
He smashed ceramic processors and directly added them to 1:3 aqua regia , during that he noticed that not all wires have dissolved in aqua regia so he decided to filter the processors and he put the aqua regia in a different container , then he made a new 1:3 aqua regia to dissolve the remaining metals in the processors he said , then after the process is done he filtered the new aqua regia and added it to the old aqua regia , then he went out to have a smoke , but when he came back he found precipitation of gold started and it was 22 k gold !!
so guys what the hell has happened here ?
How gold started precipitating without neutralizing nitric and without adding any precipitants
Was there any metal in those processors caused the precipitation to start automatically ?!

 

[Rotz]

I am new but as I read that, I thought, firstly AR dissolves the gold because gold on surface, than other metals dissolve, mainly copper, so solution will saturate the copper, than gold will turn to solid form by the means of cementation. I am not sure but experience can do this two process together. But according to me it is risky. Solder or other base metals can make a suprise.

 

[jarlowski1]

He should not be making the AR with 3:1 ratio, instead he should cover the material with HCl and add a small amount of nitric (with experience you learn how much too add at first). Let that react to the point where the brown fumes and small bubbles slow down, then add a small amount of nitric and repeat until no more fumes evolve when more nitric is added. Keep in mind that there also has to be enough water present to allow the metal salts to dissolve into. Which is what most likely happened. The solution was super saturated and when it was allowed to cool down (the time you friend went to have a cigarrette) the solution precipitated the gold. The hotter the solution is the more metal salts it can hold, when allowed to cool the saturation point of the solution goes down, so a super saturated solution can be fully liquid at 100c but mostly crystals at 20c.

 

[Rotz]

Yes, as a result if you manage a process like that you need to make a calculation. it is hard to calculate substrate amount from nitric amount adjustment. Last month I tried some of gold finger to directly AR, about the finishing of the process I saw pure fine gold(nice brown) on the surface of the solution. I think the base metals help to the gold while gold turn to solid form.

 

[nickton]

that method is a waste of nitric and complicates the refining process. Before even thinking of using AR, one should first dissolve base metals with a bubbler and HCI and peroxide. Much more economical and keeps base metals out of gold in solution.