New gold precipitating tecnique?

[Mida]

Hi People.
I have heard about a tecnique to reduce gold into metallic state using potassium nitrate and sulfuric acid.It is possible?.I have found no reference on books,about this system.I have heard that an amount of nitrate is dissolved in a concentrated solution of auric chloride;sulfuric acid is added,and the solution is evaporated until dry,and the gold will come out as metallic.Can anyone explain me the process in detail,also chemically speaking?.Thank you......

 

[Noxx]

Potassium Nitrate with Sulfuric acid will produce Nitric acid and Potassium Sulfate. None of these can precipitate gold.

What makes gold return to metallic state is the heating. If you are heating HAuCl4 up to dryness, it decomposes into Cl2 and Au (metal). This method is not recommended due to its hazard but also because it does not purify gold. If you have other Chlorides present as well, they will be reduced too !

It's not a selective «precipitation» method.

 

[goldsilverpro]

It's a twist on the old sulfuric fuming method for analyzing gold in certain solutions - primarily in 5 ml samples of gold bearing cyanide solutions. I used to use very hot concentrated sulfuric and an occasional drop of nitric acid to decompose the cyanide complex. Eventually, the gold precipitates as a sponge. The sulfuric never evaporates to dryness. Have you ever tried to evaporate sulfuric acid to dryness?

This is an extremely dangerous process, for many reasons. It requires very high temperatures, it produces large volumes of choking toxic fumes, and it tends to spit. I can't imagine using it for volumes over 100 ml.

Forget about this. You'll surely get burned badly. There are far, far, better, easier, and safer ways to recover gold from solutions.

 

[Mida]

Does HAuCl4 begin to decompose itself to which temperature?.Often I forgot my solutions on the hotplate.....

 

[goldsilverpro]

If you evaporate a gold bearing aqua regia solution down to complete dryness, you will see some gold flakes forming. That is why you only evaporate to a syrup.