Created nano particles to fall out of AR

[MAB]

I took some gold foils from a mix of gold plated pins, washed the foils real good, then done AR with the foils, I added to much nitric and now I have gold particles in suspension, usually I can evaporate it down and redo and all is good, but this time I evaporated it down and the solution was like syrup - I added HCL, then 1mil drops on nitric, I felt like there could not have been more than 4g of gold, but anyways I did a stannous test after each 1ml increment of nitric up to the final increment of 4 mil of nitric, the gold refused to go into solution, is it possible that the colloidal gold particles is covered with another metal that is preventing the nitric acid to do the job, I tried some sulfuric also in the solution in case of any Metastannic acid, either way, nothing is working and still have colloidal gold particles in solution, any one have some ideas or advice ?

 

[Shark]

Do you have any quality pictures of it?

 

[4metals]

You are evaporating the solutions down into a concentrated thick syrup to eliminate the free nitric acid. Then you are adding more nitric? Have you tried adding more Hydrochloric Acid? Gold, being a noble metal, will not passivate so I suspect you boiled off all of the Hydrochloric Acid and now it won't dissolve because gold doesn't dissolve in nitric acid.

 

[Martijn]

I evaporated it down and the solution was like syrup - I added HCL, then 1mil drops on nitric,

Are you sure you added HCl to the syrup and not some other acid? It should dissolve in AR, if not, is it possible it's not gold, but maybe Platinum?

 

[Yggdrasil]

I took some gold foils from a mix of gold plated pins, washed the foils real good, then done AR with the foils, I added to much nitric and now I have gold particles in suspension, usually I can evaporate it down and redo and all is good, but this time I evaporated it down and the solution was like syrup - I added HCL, then 1mil drops on nitric, I felt like there could not have been more than 4g of gold, but anyways I did a stannous test after each 1ml increment of nitric up to the final increment of 4 mil of nitric, the gold refused to go into solution, is it possible that the colloidal gold particles is covered with another metal that is preventing the nitric acid to do the job, I tried some sulfuric also in the solution in case of any Metastannic acid, either way, nothing is working and still have colloidal gold particles in solution, any one have some ideas or advice ?

There should not be any Gold particles in AR.
They will dissolve in a flash, before any other Gold.
So if you have Gold particles in your solution, one of your acids are depleted.

 

[MAB]

Thanks for everyones input, I ended up cementing the gold out with copper
.

 

[Martijn]

I am really curious what exactly you did, as gold particles in suspension can not be cemented out, they are not in solution. And with an excess of nitric there should not be any gold particles as said before.

So you think you solved it, but have you actually? Because the chemistry makes no sense.

 

[Yggdrasil]

I am really curious what exactly you did, as gold particles in suspension can not be cemented out, they are not in solution. And with an excess of nitric there should not be any gold particles as said before.

So you think you solved it, but have you actually? Because the chemistry makes no sense.

As I said to him, he could not have Gold particles in there, as they would be the first to dissolve.
Probably caused by misunderstood observations.