Best method of precipitating gold from aquaregia?

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Shark

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This won’t be exact science….
I often heat AR to around 100F* while creating around 200ml of a saturated solution of sulfamic acid in water at the same temperature. Once both are at temperature I gently and carefully add the sulfamic to the AR. Often the first few drops are added being less than 1/2 a plastic spoon and often around 1/4 plastic spoon as a test to check the reaction. I only use this method when I know the remaining nitric will be minimal. The watered down version will delay the reaction but will not reduce how aggressive it can be. It also seems to affect how the lead may react in AR. If I know larger amounts of lead are involved I prefer to use the sulfamic directly. Not being science educated it seems logical to me that two liquids would combine better to form an expected reaction. At least in the situation of AR and sulfamic acid.
 

dpgold

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If all material is dissolved & potassium nitrate (or nitric acid) is still strong in solution, just add water to dilute. I have never neutralized solution.
It may have worked in this case because there was no excess nitric. Theoretically if there is excess nitric the drop will re dissolve the gold after it starts to precipitate unless there is some reaction in the solution that neutralize the nitric. I was having emotion seeing that big beaker close to the edge of the wall.
 
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It may have worked in this case because there was no excess nitric. Theoretically if there is excess nitric the drop will re dissolve the gold after it starts to precipitate unless there is some reaction in the solution that neutralize the nitric. I was having emotion seeing that big beaker close to the edge of the wall.
I see what you are saying about the beaker 😅

I'm still a novice, but now thinking, adding vitamin c to solution is somehow neutralising the excess nitric acid. I just tested the theory with a small amount (sorry, I should of filmed it) I made sure I used too much potassium nitrate in solution. After dissolving a small amount of gold, I didn't dilute with water just added vitamin c ascorbic acid. An instant fizz and small cloud of brown gas, (in fume hood) then the small amount of gold precipitated straight out of the solution. I can't test with higher concentrations of nitric acid due to accessibility of chemicals.
 
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Found this possible explanation for the reaction I'm observing using ascorbic acid to precipitate gold in poor mans AR (using meat curing salt 99.8% pure potassium nitrate).

Reaction of nitrite with ascorbic acid and its significant role in nitrite-cured food​

Heating of the reaction solution at less than 100°C resulted in a loss of nitrite from the solution, which was greater with increasing concentration of ascorbic acid. The reaction product formed between nitrite and ascorbic acid is probably responsible not only for nitrosation reactions, but also for the loss of nitrite observed during curing of meat.
 
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Yggdrasil

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Found this possible explanation for the reaction I'm observing using ascorbic acid to precipitate gold in poor mans AR (using meat curing salt 99.8% pure potassium nitrate).

Reaction of nitrite with ascorbic acid and its significant role in nitrite-cured food​

Heating of the reaction solution at less than 100°C resulted in a loss of nitrite from the solution, which was greater with increasing concentration of ascorbic acid. The reaction product formed between nitrite and ascorbic acid is probably responsible not only for nitrosation reactions, but also for the loss of nitrite observed during curing of meat.
Are you using Nitrite or Nitrate?
 

Yggdrasil

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I'm using nitrate. Uneducated in this, I can only presume it is a similar reaction whether nitrite or nitrate as from my experience, it works.
I do not know for sure, but I do not think nitrite NO2 can't be used as poormans AR.
And since its composition and formula differs from Nitrate it's likely to behave different.
But maybe someone has tried it and can explain closer??
 

Shark

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Nitrate is used in HCl to make AR. Sodium nitrite is used as a precipitant in AR. Adding the nitrite to a gold bearing AR will make the gold come out of solution. Adding a nitrate to hydrochloric acid will make a solution of AR. The two are not interchangeable where AR and gold are concerned.
 

Alondro

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I prefer using vitamin C. It's safe enough to eat :) & no horrible toxic smell like SMB. I read so many posts regarding gold not dropping, I always refine twice as in vids, dirty then clean solution, & up to now🤞have not had that problem.
Hydroquinone also works, but it's more pH sensitive. It won't work in exceedingly low pH solutions. In my tests, the best result came from adding urea first until no more bubbles were produced (the pH will be raised to roughly 2 when this is done), then add the hydroquinone.

The one issue I found is that it will tend to produce nanogold in very dilute solutions, which is actually what it's used for in biological applications for making 'gold bullets' for DNA administration to cells, or for making ultra-fine gold powder for electron microscopic examination.
 
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