# Precipitating gold with sodium nitrite



## Shark (Apr 3, 2018)

While Hoke and Ammen both mention using sodium nitrite as a precipitant I am curious if anyone has or still uses it. While using different precipitants for the second refine is pretty standard for me, I would like to know the thoughts on when the sodium nitrite could be the preferred choice over SMB or copperas, which are my two go to choices as they are the most commonly mentioned. While anachronism mentions he uses ascorbic acid, I don't think he has ever mentioned why he prefers it over the others and these thought/ideas from any and everyone are what I am curious about. 

Thoughts or ideas, how and or why?


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## Owltech (Apr 3, 2018)

The process is shown here:
https://www.youtube.com/watch?v=c9MRmSXRmgo

It's in Russian but you can auto-translate the subtitles in English

https://www.youtube.com/watch?v=DtmrYkloHAU

In this video the guy uses NaNO2 to precipitate Au from solution containing Au, Pd, Pt and Cu


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## Shark (Apr 3, 2018)

Owltech said:


> The process is shown here:
> https://www.youtube.com/watch?v=c9MRmSXRmgo
> 
> It's in Russian but you can auto-translate the subtitles in English
> ...


 
Translation looses something it seems. Can you tell if he explains why he used the NaNO2 rather than some other precipitant?


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## Owltech (Apr 3, 2018)

at 7:10 in the video he says that with NaNO2 the gold will precipitate (together with some Cu(OH)2), leaving behind Pd, Pt and Cu in solution. He uses NaNO2 to part Au and Pt/Pd


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## Shark (Apr 4, 2018)

Owltech said:


> at 7:10 in the video he says that with NaNO2 the gold will precipitate (together with some Cu(OH)2), leaving behind Pd, Pt and Cu in solution. He uses NaNO2 to part Au and Pt/Pd



Thanks.


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## anachronism (Apr 5, 2018)

Hi Shark

Regarding Ascorbic acid. 

I use it for a number of reasons and in particular situations. Firstly it doesn't "gas off" Sulphur Dioxide making it more user friendly than SMB. Secondly it's fast and it's also really easy to see when your solution has given up all its gold by the colour change. It's also very good at taking out the last small piece of gold from a solution that you've already dropped with "green stuff" and instead of having to make up a new batch you can put a teaspoon of this in and leave it. You get no false positives from this like you can do with SMB.

It's also extremely good for small concentrated solutions where "green stuff" doesn't work so well without increasing the volume dramatically. 

The only downside is that it does require more settling in some cases as the precipitant (especially on weak solutions) can be very fine indeed. That given I do tend to pour off the majority of the gold and clean it from my drops whilst leaving the small amount that requires settling to do its thing overnight so it doesn't make too much of a difference to me.


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## Shark (Apr 5, 2018)

Thanks Jon, I might have to check into that. While my wife dosen't normally hang around my refining space, she does come out and watch once in a while, especially the drops. She is allergic to sulfur in most any form and can't be around when I am using SMB on the larger drops. This is often the factor when I chose a precipitate such as copperas.


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## g_axelsson (Apr 5, 2018)

anachronism said:


> Regarding Ascorbic acid.
> 
> I use it for a number of reasons and in particular situations. Firstly it doesn't "gas off" Sulphur Dioxide making it more user friendly than SMB. Secondly it's fast and it's also really easy to see when your solution has given up all its gold by the colour change. It's also very good at taking out the last small piece of gold from a solution that you've already dropped with "green stuff" and instead of having to make up a new batch you can put a teaspoon of this in and leave it. You get no false positives from this like you can do with SMB.
> 
> ...


It's been discussed before on the forum about the selectivity of ascorbic acid. According to Lou, ascorbic acid will precipitate silver, palladium and copper from solutions, at least when boiling.

Any experience with that? Any problem with selectivity? Do you heat the solution when precipitating gold?

I did some digging on the forum (over 90 posts about ascorbic acid) and tried to put together a short article about ascorbic acid.
http://goldrefiningwiki.com/mediawiki/index.php/Ascorbic_acid

Göran


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## ARMCO (Apr 5, 2018)

g_axelsson said:


> anachronism said:
> 
> 
> > Regarding Ascorbic acid.
> ...


Thank you for that. 


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## Shark (Apr 5, 2018)

g_axelsson said:


> anachronism said:
> 
> 
> > Regarding Ascorbic acid.
> ...



Thank you very much for that. How I missed one of Sreetips videos is beyond me as I always go there for most things first.


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## nickvc (Apr 6, 2018)

I have used ascorbic for many years and find it excellent as a precipitant especially when used after using copperas, it was myself who introduced its use to anachronism and I nor Jon have had problems with co precipitation, as the advice is to cool gold solutions prior to dropping the heat needed to cause problems is absent. My advice to anyone is to try it and make sure to remove any oxidizer before using it and still use a good acId and water boil on the powders to fully clean them before melting.


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## anachronism (Apr 6, 2018)

To be frank I don't precipitate when boiling Goran 8) 8) 

I can confirm that I have no more problems with co-precipitation than with any other precipitant. I've got some processing to do over the next few days and I'll put a pic or two up on this thread. If I knew how to even make a video I'd do that but sadly I don't.

Edit: Also I believe I recall Lou telling me that it's incredibly useful for dropping Pd from Nitric solutions, although I am sure he can clarify.


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## Lou (Apr 6, 2018)

Yes it will reduce Pd from nitric acid solutions.


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## g_axelsson (Apr 6, 2018)

The reason I talked about precipitating from a hot solution is because that was what Kadriver / Sreetips did in his video.
https://www.youtube.com/watch?v=CAhh6p4E6-I&feature=youtu.be&t=165

If it doesn't need heat to work well for gold then we should recommend using it cold to minimize co-precipitation of other metals.

Göran


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## anachronism (Apr 6, 2018)

Hi Goran

I made the comment about "not boiling" merely because I couldn't see the justification of dropping from a boiling solution. Hot yes, but boiling- no. 

I'm not entirely sure why he was doing it hot, however maybe it's simply because he followed straight on from getting rid of his Chlorine. No matter either way. I don't use HCl/Cl or derivatives so I don't need to use use heat to drive off Chlorine. Solutions can sometimes be hot from de-noxxing with Sulphamic if I'm working fast so yes there's a similarity between the two situations even if the chemistry differs. 

That given I've precipitated using Ascorbic both in hot solutions and cold and it really doesn't make any difference to the operation. You're good either way.


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## butcher (Apr 6, 2018)

Using sodium nitrite as a precipitant for gold.
Sodium nitrite and hydrochloric acid = nitrous acid and sodium chloride (table salt)
HCl + NaNO2 --> HNO2 + NaCl

Gold chloride reduced with sodium nitrite = elemental gold sodium chloride (salt) and nitrogen dioxide gas.

AuCl3 + 3NaNO2 --> Au + 3NaCl + NO2
Chloroauric acid (acidic gold solution).


Gold is reduced to elemental gold metal powder, sodium chloride, nitrous acid, and nitrogen dioxide gas.
HAuCl4 + 4NaNO2 --> Au + 4NaCl + HNO2 + 3NO2


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## Owltech (Apr 7, 2018)

g_axelsson said:


> The reason I talked about precipitating from a hot solution is because that was what Kadriver / Sreetips did in his video.
> https://www.youtube.com/watch?v=CAhh6p4E6-I&feature=youtu.be&t=165
> 
> If it doesn't need heat to work well for gold then we should recommend using it cold to minimize co-precipitation of other metals.
> ...



Gold reduction with ascorbic acid (vitamin C)
https://www.youtube.com/watch?v=25hhaysYM8o


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## ARMCO (Aug 4, 2018)

Owltech said:


> g_axelsson said:
> 
> 
> > The reason I talked about precipitating from a hot solution is because that was what Kadriver / Sreetips did in his video.
> ...



In the video he mentioned bringing down The pH with baking soda (I see that being called bringing the pH “down” frequently when really bringing it “up” would be the correct term nevertheless…). I’m assuming and think I’ve experienced that when the pH is too low (acidic), It inhibits the drop of gold. What is the best range for the pH to facilitate the drop. If you’ve got a pH meter or other testing that means, what pH range should you bring it to? 

Thank you in advance


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