neutralize AQUA REGIA

[g_axelsson]

The past few days after my AR solution dissolve all the gold foils i diluted with water equal 3 times more than the AR solution and after i add a few mls of Sodium Hydroxide there was no reaction (that happen to all of my AR solutions) and then i add SMB diluted with water and the drop of gold was a successes i test my solution after for gold with SC and it was negative . I think the water diluted the nitric acid and didn't need for Sodium Hydroxide.

As Dave told you, using sodium hydroxide is not working really. If you get the pH too high you start precipitating various metal hydroxides, including gold I think. And it doesn't remove the nitrates from the solution. If you then acidify your solution again the nitrates will form nitric acid again and could dissolve gold.
What you want to do is to remove the nitrates as well as any nitric acid while keeping the solution acidic so metals doesn't fall out. Look up denoxing, it can be done in many ways. And it's all explained in Hokes as well time after time on the forum.

If you used sodium hydroxide some of the gold could have precipitated before you added SMB.
You should also filter the solution after you diluted it three times to get rid of any silver chloride that could have precipitated. Only solutions that are crystal clear should be used for precipitate gold unless you are only recovering gold and doesn't care about the purity.

Göran

 

[butcher]

Using heat can be important when using the added gold button to remove the free nitric and any nitrates.