Double Aqua Regia

[kiwisue202]

Hi

We have just commissioned a refinery using gear from Orostudios. We are pretty confident with the aqua regia but we arent getting rid of enough silver in the process so purity is only 99.94 ish. We want to do a second aqua regia process to see if this helps but some people in passing have said this is risky as it can lead to gold losses. We cant really think how and why it would but was hoping to check with you peps who have been doing this for years

Our starting gold is 96.5% gold and rest silver

Cheers

 

[Yggdrasil]

Hi

We have just commissioned a refinery using gear from Orostudios. We are pretty confident with the aqua regia but we arent getting rid of enough silver in the process so purity is only 99.94 ish. We want to do a second aqua regia process to see if this helps but some people in passing have said this is risky as it can lead to gold losses. We cant really think how and why it would but was hoping to check with you peps who have been doing this for years

Our starting gold is 96.5% gold and rest silver

Cheers

Aqua Regia will not dissolve much Silver at all.
Dilute and chill the AR and then filter it until it is crystal clear.
Then precipitate.
If you decide to do a second refine it is wise to use a different precipitant the second round.

 

[FrugalRefiner]

How are you washing your precipitated gold?

Dave

 

[kiwisue202]

500ml of water and 500ml nitric acid - mix and leave for 5mins
Then clean with Distilled water x 3
500ml sulfuric and 150ml hydrogen - stir and leave 5 mins
Clean with water x 3
then cover with Methylated spirits and leave for 5 mins

Thanks so much

 

[FrugalRefiner]

500ml of water and 500ml nitric acid - mix and leave for 5mins
Then clean with Distilled water x 3
500ml sulfuric and 150ml hydrogen - stir and leave 5 mins
Clean with water x 3
then cover with Methylated spirits and leave for 5 mins

Thanks so much

I've never seen that cleaning process before. Interesting.

Since you say you're not getting rid of enough silver, I'm guessing you're getting a bit of silver chloride in your precipitated gold.

The nitric won't touch it. Pirahna is unnecessarily dangerous. I don't know what the methylated spirits are for.

You can get rid of the silver chloride in two ways.

First, I would try using HCl washes.

If that doesn't get you where you want to be, you can do a wash with ammonia.

Either method should dissolve the silver chloride. If you use ammonia, be sure to promptly reacidify the wash solution to avoid the possibility of explosive compounds.

See Lou's washing procedure for details on the HCl washing technique.

Dave