# How do I calculate how much UREA and Sodium-MetaBisulfite I need?



## Aberu_ (Jan 14, 2018)

If I have x mL of AR and I have around y grams of gold in the AR solution, how much UREA would I need to neutralize the acid, and how much Sodium Meta-BiSulfite would I need to precipitate all the gold? Would I need to add any water to the solution? Sorry if this is common knowledge or doesn't make sense, I am new to gold recovery.


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## Lino1406 (Jan 14, 2018)

Urea - just to end fizzing. SMB 1:1 to expected gold


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## FrugalRefiner (Jan 14, 2018)

Aberu_ said:


> If I have x mL of AR and I have around y grams of gold in the AR solution, how much UREA would I need to neutralize the acid


That depends on how much excess nitric you used. The best technique is to use just enough nitric to get the job done. Then you don't have excess nitric to neutralize. When they do have to deNOx their solutions, most members use sulfamic acid instead of urea.



> and how much Sodium Meta-BiSulfite would I need to precipitate all the gold?


As Lino said, use about the same weight of SMB as the weight of gold in solution.



> Would I need to add any water to the solution?


That's hard to say. You didn't say how many "x ml" of solution you had to how many "y grams" of gold or how you got there. We try to dissolve gold in the minimum amount of acid. Then add a bit of sulfamic or sulfuric acid, dilute with about 3 times the volume of water, allow to cool, filter, and precipitate. If you used more solution than necessary, you may not need to dilute at all. Give us an idea of how much x and y were, and we may be able to help more.

Welcome to the forum.

Dave


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## Aberu_ (Jan 14, 2018)

First of all, thank you for the quick response! I was planning on using 120 mL of AR to dissolve 3 grams of gold, is this too much/too little?


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## jimdoc (Jan 14, 2018)

Aberu_ said:


> First of all, thank you for the quick response! I was planning on using 120 mL of AR to dissolve 3 grams of gold, is this too much/too little?




If you are planning to do this, then simply put it on hold until you study enough to know all you need to do, before you start. Don't rush into it, and things will go better.


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## anachronism (Jan 14, 2018)

I don't know why you guys are all saying 1:1 on SMB:Expected gold because in practice it simply doesn't work that way. If you had said "given a pure solution of AR" it might have been closer to being applicable but I very rarely work with pure AR so I guess most people don't either. 

It's not correct, it doesn't happen and it doesn't work that way so the myth needs debunking once and for all. 

The correct answer is "as much SMB as required to drop all the gold." 8) 8) 

Thank you and goodnight 8) 

Jon


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## FrugalRefiner (Jan 14, 2018)

Aberu_ said:


> First of all, thank you for the quick response! I was planning on using 120 mL of AR to dissolve 3 grams of gold, is this too much/too little?


That would be WAY too much acid. As jimdoc said, slow down and spend some time studying. When you say 120 ml of AR, I'm guessing you're planning to mix up the AR and pour it on the gold. It is far better to add a bit more HCl than you calculate you will need, then add the nitric in small increments to avoid using too much.

Dave


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## g_axelsson (Jan 14, 2018)

Aberu_ said:


> First of all, thank you for the quick response! I was planning on using 120 mL of AR to dissolve 3 grams of gold, is this too much/too little?


I would start with about 8 ml and see if that was enough...

But as Dave wrote, add enough HCl and the nitric as needed, I would probably cover the gold in HCl, not so worried about exact volume as long as it is more than four times the amount of nitric I'm going to use. Excess HCl doesn't hurt the following steps. Then I would add nitric in small portions until the gold is dissolved. Excess nitric is not so good to have so it is best to remove before precipitating pure gold. That's called denoxing.
http://goldrefiningwiki.com/mediawiki/index.php/Denoxing

But that's been described so many times already, so do some searches, read articles in the library, download Hoke's book and read, then read some more. 

By the way, I have never used urea and it isn't recommended on the forum. What is recommended though, is using stannous for testing, that way you can follow the gold even when it is in solution.

Göran


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## Lino1406 (Jan 14, 2018)

SMB, Na2S2O5=190, gives 4 electrons
Gold ion Au+++=197, takes 3 electrons
So, theoretically we need 0.7:1 (SMB:gold)
But some SO2 escapes without doing its job...


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## anachronism (Jan 15, 2018)

Aye Lino

That's the chemistry and reality is different hence my comments Sir. After all it's what really happens that matters in the end game not what theory says. 8) 

People tend to take instructions literally without thinking outside of the box, so saying it's gramme for gramme doesn't really provide substantive assistance for the process. I'll bet there are people out there putting 10g of SMB in and stopping at that point when it probably requires another 30g to drop the gold. 

Jon


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## cosmetal (Jan 15, 2018)

anachronism said:


> Aye Lino
> 
> That's the chemistry and reality is different hence my comments Sir. After all it's what really happens that matters in the end game not what theory says. 8)
> 
> ...



What physical clues do you see when too little SMB is used? Does the drop take longer? But, given extra time, (like overnight settling) a complete drop still occurs? Or. will the drop stall-out and stop and when any settling occurs, you still have an auric chloride solution but it is a more pale yellow?

James


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## galenrog (Jan 15, 2018)

The best way to determine if values are still in solution is to test the solution. 

Time for more coffee.


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## cosmetal (Jan 15, 2018)

galenrog said:


> The best way to determine if values are still in solution is to test the solution.
> 
> Time for more coffee.



Of course. SnCl2 is the standard.

But, I was wondering about any physical changes in appearance or reaction between too much SMB, just right SMB or too little SMB during the PM drop.

Looking for any visible, physical clues rather than measured formulas.

Thanks,

James


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## anachronism (Jan 15, 2018)

Hi James

Experience tends to be the best way to judge how your drop is progressing. Assuming you haven't used any Ferrous Sulphate (which provides a deep yellow tinge to the meniscus) you can look at the meniscus and see a yellow tinge in a pregnant solution. Also when you add SMB to a pregnant solution the foam produced can have a yellow tinge or a brown tinge as the gold precipitates. When you get close to having dropped all the gold the foam produced will change to being a true white colour. 

These are merely guides and as Galenrog quite rightly pointed out you need to test the solution to be sure. Do note though that Sulphur Dioxide in solution (the active by product of SMB in an acidic solution) can sometimes give a false positive when testing with Stannous Chloride.

If you use a bit too much SMB then you don't need to worry. After all, extra SMB is far cheaper than leaving gold in the solution. Your last bit of gold will drag down a bit of copper if it's present in your liquor. Again it's a tiny amount and it will go when you do your washes.


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## cosmetal (Jan 15, 2018)

anachronism said:


> Hi James
> 
> Experience tends to be the best way to judge how your drop is progressing. Assuming you haven't used any Ferrous Sulphate (which provides a deep yellow tinge to the meniscus) you can look at the meniscus and see a yellow tinge in a pregnant solution. Also when you add SMB to a pregnant solution the foam produced can have a yellow tinge or a brown tinge as the gold precipitates. When you get close to having dropped all the gold the foam produced will change to being a true white colour.
> 
> ...



Thanks for the clues! Never thought of viewing the meniscus. I will from now on.

The reason I was asking for visual clues is that I have only completed three drops in my refining career.

The first was a total nightmare that took a week of research and trial to finalize. 

The second was better but still a back and forth between HCl adds and too much nitric, sulfamic acid overdosing to go after the nitric and SMB clouds. I do remember seeing that the foam had a brown tinge and then finally white color foam.

The last one was a dream. Just right HCl - very little nitric needed - no visible reaction when I added some sulfamic/DH2O solution - very classic reaction when I added my SMB/DH20 solution. But the brown gold cloud took longer to start settling. Much longer. But, I waited overnight and got a complete drop. Checked clear solution with SnCl2 and got no reaction. Happy. But slightly confused by the color difference between the three drop's brown color. First - dirty dark brown. The second - medium brown. The last one - more a tan color. I now suspect that was due to the iron pollution I had with the first two drops. 

I am going to dry and weigh this drop and then add all three together for another refine. Then I'll finally melt and get to post a picture of my first baby!  

Thanks,

James


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## kadriver (Jan 20, 2018)

Here is a link to a video that I produced that shows all the techniques that I learned from this forum. It's long, but explains in great detail the entire process including demonstrations that may answer some of your questions:

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=26551

kadriver aka sreetips


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## kadriver (Jan 20, 2018)

Here's another link to a video that compares premixing Aqua regia vs incremental dosing with nitric acid so that just enough nitric is used to just dissolve all the gold. With incremental nitric dosing there is no need to add urea or anything else, if it's done correctly, because there is no excess nitric to remove. The results speak for themselves.

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=26328

kadriver


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## cosmetal (Jan 21, 2018)

kadriver said:


> Here is a link to a video that I produced that shows all the techniques that I learned from this forum. It's long, but explains in great detail the entire process including demonstrations that may answer some of your questions:
> 
> http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=26551
> 
> kadriver aka sreetips



Kadriver,

Great vids! All of them.  

I've always enjoyed watching them. I think yours was the first youtube vid I watched when I first became interested in PM recovery.

Inspirational - they got me moving.  

Peace,
James


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## youngling (Mar 11, 2018)

cosmetal said:


> galenrog said:
> 
> 
> > The best way to determine if values are still in solution is to test the solution.
> ...


we use Urea and SMB , smb and the urea is dissolved in distilled hot water. we add the smb in small batches and watch the reaction each time , using a spoon similar to a soup spoon i scoop some and do a little shaking back and forth, the green brown solution slowly starts clearing up and you'll find small bits of gold "clumping together" if its too fine you've added too much smb and you'll end up getting copper along with it . its all knowledge passed down. trial and error


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