# Gold powder wont settle down properly on Nitric Acid?



## autumnwillow (Jul 14, 2014)

I went to my local refiner today where they inquarted my karat gold to 25% gold using silver.
Then when they started to use nitric acid on it. We got a muddy solution, as if the gold wont settle down where we used to have just a greenish/bluish solution and gold powder settling down.

What could have been the problem here? They say palladium and/or platinum could have been present in my karat gold. Which I am not sure of.

They then tried to rinse it (gold powders pouring off in the process) where it is contained in a bucket (for re-refining tomorrow). When they tried to melt the rinsed gold, it wouldn't melt at all. They then tried to add silver. It melted, then they repeated the process of using nitric acid again to dissolve the other metals, we still got the same solution (dark brown muddy solution). They repeated the process of rinsing, with some gold powders again being poured off with the rinse.

Now this time they added only small amounts of silver and more on copper for the inquartation. And for the nitric part we now have a greenish/bluish solution with gold powder settling down. They were able to properly rinse this one. When melted it looked as if its not 23-24k gold. Where we usually get about 23-24k gold.

I understand that my refiner is not that knowledgeable in the AR process of refining. Its the reason I am in this forums. I've been researching a lot and want to start my own refinery. Only budget and location of the refinery have been stopping me. Its the chemical fume hood for AR process that I am having trouble to build. (I want a PTFE or PPR based hood)


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## FrugalRefiner (Jul 14, 2014)

autumnwillow said:


> I went to my local refiner today where they inquarted my karat gold to 25% gold using silver.
> Then when they started to use nitric acid on it. We got a muddy solution, as if the gold wont settle down where we used to have just a greenish/bluish solution and gold powder settling down.
> 
> What could have been the problem here? They say palladium and/or platinum could have been present in my karat gold. Which I am not sure of.
> ...


So many possibilities... so many questions. I'll ask for some more details that may allow others to make a better assessment.

You say the gold was inquarted to 25%. What was the original material? Jewelry, dental gold, gold filled?

Are you sure the inquarted material was 25% gold? Might it have ended up less than 25%? If too much silver was added, the gold might not stay together, but instead become finely divided.

You say the solution was muddy instead of green/blue. But what color was the solution? After the solution was poured off, it should eventually settle and allow you to see the color.

Did your "refiner" ever test any of the solutions with stannous? That could answer what PMs are in which solutions.

I agree, your "refiner" needs to study some more. I see mis-steps throughout the process you've described.

Dave


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## resabed01 (Jul 14, 2014)

In my limited experience I may be wrong but to me it sounds like you encountered Tin.
It's possible karat gold may have tin as part of solder that was used for a repair.


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## autumnwillow (Jul 14, 2014)

It was karat jewelry -- scrap jewelry. The solution was greenish/bluish when they filtered it using a strainer filled with cotton. The gold was like floating in the solution or something. It was flowing with the nitric acid when they were slowly pouring it off. I think it would take days for it settle down. I didn't have that much time since I needed to go back to work.

My problem is the loss. In my assay (using touchstone) the return was supposed to be at least 220 grams. We only had 194 grams left and it was not even that pure. My returns are usually +/- 5%.

No stannous testing was performed. 

We are a small jewelry manufacturing shop. I use tin for my solders in jewelry. And I have been using it for years and have been refining with them for almost a year now. So I don't think its the Tin.

What was the cause of the gold powder not melting in the first try (silver inquartation)? 
Why did the use of copper in inquartation allowed the gold to settle down in seconds after the addition of water in the nitric acid solution?
Why did this method allowed the gold to be melted?

I don't think their excuse for palladium/platinum content was the reason for it. Since palladium should dissolve in nitric acid.


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## necromancer (Jul 14, 2014)

the loss may be from ""using a strainer filled with cotton""

just my 2 cents


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## autumnwillow (Feb 11, 2017)

Okay let me revive this topic. I'd like to solve it.

It happened yesterday when I was refining a karat scrap, there was already an estimated yield and the lot needs to be refined asap so I did not perform an assay.

Now the problem is, this same thing happened. I added 700g of silver, estimate is about 218g of 24k, the lot weight is 400g.



This is the inquarted gold being digested in the nitric, notice the gold as powder moving around the entire solution, they were too fine.
So fine that some of them bypasses a #1 filter paper.

I guess the estimate was wrong? I added too much silver? I will know today as I have already performed an AR digest. In the AR digest when I added HCL no white precipitates but the solution was dark, same as in picture, as soon as I added nitric it started to turn in an orange color.

Edit to add:
This happened after crushing the flakes and re-digesting in nitric. I always do this and never had a problem like this.
And forget my initial posts here I was a noob back then.


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## nickvc (Feb 12, 2017)

You are using far too much silver, inquart means to make the gold content to be around one quarter of the whole metal weight you have made it one fifth, you only needed to add 480 grams of silver, by having the gold to finely divided you are having the problems you are posting about.


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## autumnwillow (Feb 12, 2017)

I do not inquart. I bring down the content to 20% not 25%. This results in faster nitric digestion and lesser contaminants for AR due to more surface area that the nitric can attack. 

Sent from my SM-G920F using Tapatalk


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## g_axelsson (Feb 12, 2017)

If the gold breaks down into fine particles then you have the amount of silver and base metals too high. If this was a carat lot then maybe some of the jewellery was fake or gold plated. Your 20% gold is already on the border of breaking down so it doesn't take a lot extra base metal to make it break down into separate particles.

If adding the HCl turned the liquid black I guess that it came from the fine particles getting suspended in the acid. When you added the nitric it dissolved the fine particles first and turned it into the familiar orange color of gold chloride.

Göran


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## autumnwillow (Feb 16, 2017)

195g was refined out of the lot. Estimate was wrong as there was a typo. It's down to 17% content. I do not think this is the cause. My proof would be simply for you to try yourself. Go alloy gold until you get a 15% content. You won't experience what I experienced.


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