Can you denox AR too much?

[chrundle_the_great]

Im probably one of the smallest hobby refiners here, my average recovery is around 2-4g. My process for refining is roughly 200-300ml of HCI, 1-2ml HNO3 again around an hour maybe again in another hour (on heat around 140-180°c). Before bed i turn it off by the next day usually all gold is in solution. Denox (I'm pretty slow) will give it all day, add SMB keep on low heat all night(I'm in minnesota would take days for the gold to settle in the cold). My normal process usually don't have too many issues.
Financially I'm struggling, close to being homeless although currently i have been able to keep a batch of AR and have just been adding more gold to it so I don't have to waste acids. My last batch is added around 8g. Total gold in AR should be around 20g. Denoxed, stannous positive, filtered to a new beaker, spoonful of SMB. Black, settled fast, 2 more spoons, foam forms lasted around 20 seconds stayed black continued to settle. Low heat 100°c (with outside temp AR is maybe 90°c). Checked after 2 hrs everything that settled is gone now AR is green(clear). Stannous still positive turned up heat evaporated about 20 ml, let cool, added SMB disappeared. Added 30ml H2O waited few hours, no change. Added 30ml of HCI no change cooked down 10ml. Now I'm writing this. I know I should have posted after my usual trouble shooting didn't work but ADHD didn't think about it until after. Could I have cooked it down too much and raised the acidity? Or could it still just have too much HNO3?

 

[Yggdrasil]

Im probably one of the smallest hobby refiners here, my average recovery is around 2-4g. My process for refining is roughly 200-300ml of HCI, 1-2ml HNO3 again around an hour maybe again in another hour (on heat around 140-180°c). Before bed i turn it off by the next day usually all gold is in solution. Denox (I'm pretty slow) will give it all day, add SMB keep on low heat all night(I'm in minnesota would take days for the gold to settle in the cold). My normal process usually don't have too many issues.
Financially I'm struggling, close to being homeless although currently i have been able to keep a batch of AR and have just been adding more gold to it so I don't have to waste acids. My last batch is added around 8g. Total gold in AR should be around 20g. Denoxed, stannous positive, filtered to a new beaker, spoonful of SMB. Black, settled fast, 2 more spoons, foam forms lasted around 20 seconds stayed black continued to settle. Low heat 100°c (with outside temp AR is maybe 90°c). Checked after 2 hrs everything that settled is gone now AR is green(clear). Stannous still positive turned up heat evaporated about 20 ml, let cool, added SMB disappeared. Added 30ml H2O waited few hours, no change. Added 30ml of HCI no change cooked down 10ml. Now I'm writing this. I know I should have posted after my usual trouble shooting didn't work but ADHD didn't think about it until after. Could I have cooked it down too much and raised the acidity? Or could it still just have too much HNO3?

How do you deNOx?
Too much acidity is no problem, too little acidity may pose a problem.

 

[Shark]

Do you have any other precipitant such as Ferrous Sulfate, etc. if not, it may be time for cementing in a piece of copper. As Yaggdrail ask, how did you denox your solution?

 

[chrundle_the_great]

How do you deNOx?
Too much acidity is no problem, too little acidity may pose a problem.

Denox by cooking, could I be using too low of heat?

 

[chrundle_the_great]

Do you have any other precipitant such as Ferrous Sulfate, etc. if not, it may be time for cementing in a piece of copper. As Yaggdrail ask, how did you denox your solution?

I do not, and denox by cooking off HNO3

 

[Yggdrasil]

Denox by cooking, could I be using too low of heat?

Heat will not denox much.
You need to evaporate to a syrup.
Much easier to cement on Copper.
It will not need denoxing.

 

[FrugalRefiner]

Denox by cooking, could I be using too low of heat?

Chrundle, "cooking" is a very inexact term, and not really suited to what we do. There are times we boil a solution, with a suitable cover or condenser, to speed the digestion of metals. There are other times that we evaporate a solution, to reduce its volume, and at times to deNO_X a solution. I know that seems very picky, but using the terminology we use in refining lets us know more precisely what you've done.

In order to deNO_X a solution, you want to heat it to hot, but below boiling. You want to reduce the volume of the solution till it is like a thin syrup. You then add HCl, at which point you will probably see the reddish brown fumes of NO_X evolve from the solution. You should repeat this procedure till no more NO_X evolve.

Dave

 

[chrundle_the_great]

Heat will not denox much.
You need to evaporate to a syrup.
Much easier to cement on Copper.
It will not need denoxing.

So with the process I explained above, once the gold precipitates out. When stannous comes back negative is there much of a chance it's a false negative? I've never brought it down to a syrup. Once I get precipitation I don't evaporate much after that usually

 

[Yggdrasil]

So with the process I explained above, once the gold precipitates out. When stannous comes back negative is there much of a chance it's a false negative? I've never brought it down to a syrup. Once I get precipitation I don't evaporate much after that usually

I have never heard about false negative.
Anyway we usually collect the barren solutions in a stck pot for later cementing and waste processing.

 

[Yggdrasil]

So with the process I explained above, once the gold precipitates out. When stannous comes back negative is there much of a chance it's a false negative? I've never brought it down to a syrup. Once I get precipitation I don't evaporate much after that usually

You did not say what your material is, did you?

 

[chrundle_the_great]

Chrundle, "cooking" is a very inexact term, and not really suited to what we do. There are times we boil a solution, with a suitable cover or condenser, to speed the digestion of metals. There are other times that we evaporate a solution, to reduce its volume, and at times to deNO_X a solution. I know that seems very picky, but using the terminology we use in refining lets us know more precisely what you've done.

In order to deNO_X a solution, you want to heat it to hot, but below boiling. You want to reduce the volume of the solution till it is like a thin syrup. You then add HCl, at which point you will probably see the reddish brown fumes of NO_X evolve from the solution. You should repeat this procedure till no more NO_X evolve.

Dave

Chrundle, "cooking" is a very inexact term, and not really suited to what we do. There are times we boil a solution, with a suitable cover or condenser, to speed the digestion of metals. There are other times that we evaporate a solution, to reduce its volume, and at times to deNO_X a solution. I know that seems very picky, but using the terminology we use in refining lets us know more precisely what you've done.

In order to deNO_X a solution, you want to heat it to hot, but below boiling. You want to reduce the volume of the solution till it is like a thin syrup. You then add HCl, at which point you will probably see the reddish brown fumes of NO_X evolve from the solution. You should repeat this procedure till no more NO_X evolve.

Dave

Its not picky, correct terminology is important specially when dealing hazardous material. I'm familiar with most but struggle with remembering it when it comes to explaining. I should keep a cheat sheet on hand to help when asking questions. When I first started and joined the forum I was unaware of denoxing AR. After having the proper steps explained and reading hokes I started the reduction process. First time I already had SMB in AR so before reaching a syrup the gold precipitated and I've stuck to that process with no real issues. Besides purity are there more negatives to not following the process through the other steps, if I have successful precipitate? (I'm aware that's contradicting since I'm having an issue now lol)

 

[chrundle_the_great]

I have never heard about false negative.
Anyway we usually collect the barren solutions in a stck pot for later cementing and waste processing.

I didn't think so, but wasn't sure. I do have a stock pot for AR just haven't made it to doing anything with it yet. Don't know if I should make a new post for this question but I've been curious about (do not know the proper terms im sure) pulling the copper out of AP solution with electroplating/reverse EP? Using carbon rods so solution can continue to be used I've found some research online but not for AP solution. Is that possible or has it been tried? Should I ask that question in a different thread?

 

[chrundle_the_great]

You did not say what your material is, did you?

So this batch of AR I've been adding to it. Mostly gold foils from Escrap. The most recent gold i added to it was mostly gold fill and some 10k-14k jewelry. Before I added to AR i did go through the process to remove (most) base metals

 

[FrugalRefiner]

I have never heard about false negative.
Anyway we usually collect the barren solutions in a stck pot for later cementing and waste processing.

A false negative is possible if there is excess oxidizer in a solution. As soon as the stannous chloride reduces the gold to the Purple of Cassius we all hope to see, the excess oxidizer can reoxidize the colloid back into solution. The purple may appear briefly, then disappear, or it can be so quick that you never see the purple.

Dave

 

[FrugalRefiner]

Don't know if I should make a new post for this question but I've been curious about (do not know the proper terms im sure) pulling the copper out of AP solution with electroplating/reverse EP? Using carbon rods so solution can continue to be used I've found some research online but not for AP solution. Is that possible or has it been tried? Should I ask that question in a different thread?

What you're talking about is electro-winning. It has its uses, but in the case of AP, it may be false economy. HCl is cheap and readily available for most, so it may be more economical to simply treat an exhausted AP solution as waste and start a new solution.

Dave

 

[chrundle_the_great]

What you're talking about is electro-winning. It has its uses, but in the case of AP, it may be false economy. HCl is cheap and readily available for most, so it may be more economical to simply treat an exhausted AP solution as waste and start a new solution.

Dave

So I'm in guess a full-time artist and use mostly natural material as a media (rocks, driftwood, metal). Interested in electro-winning because if done properly the process could form stable copper crystals or dendritic formations I'm assuming? Which for me would be far more valuable than just basic recovery. I think I made it make sense lol

 

[Yggdrasil]

A false negative is possible if there is excess oxidizer in a solution. As soon as the stannous chloride reduces the gold to the Purple of Cassius we all hope to see, the excess oxidizer can reoxidize the colloid back into solution. The purple may appear briefly, then disappear, or it can be so quick that you never see the purple.

Dave

Yes I'm aware of that, but it will show purple for a while and unless you have a massive excess it will be visible at least a few seconds.

 

[Shark]

Copper from a chloride based cell is often thin and powdery. It is easier to form solid pieces from a cell based on a sulfuric cell. You can form a cell and remove a large part of the copper then reuse the AP again for a little longer. But as Dave mentioned, Hydrochloric is relatively cheap. Just use it up, and start a fresh batch from a few ounces of your old solution.