# SMB mixing



## Chipr62 (Mar 14, 2008)

How many grams of SMB do I mix per pint of water?


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## lazersteve (Mar 14, 2008)

Chip,

The SMB can be used dry or wet it works either way.

The key is to use enough SMB to reduce all the gold to a metallic state. This usually requires 1 gram of SMB per gram of gold to be reduced as a general rule of thumb. If you don't get all the chlorine (HCl-Cl reaction) or nitrate (AR reaction) out of the solution the amount of SMB needed could increase, typically not more than double the amount of gold expected.

If you want to use water with your SMB, the solubility of SMB in water at 20C is 47 g per 100 mL, so a pint of 20 C water (473 mL) can hold enough SMB when saturated to reduce ( 47 x 4.73) 222.3 grams of gold at optimal conditions.


Steve


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## goldsilverpro (Mar 14, 2008)

I prefered dissolving the SMB in water before adding it to the gold solution. When I added it in clumps, the gold precipitated on the surface of the clump, preventing complete dissolution and usage of the SMB.


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## Chipr62 (Mar 15, 2008)

Thanks Steve I will give it a try tomorrow. I don't know exactly how many grams of gold in solution I have so I will let you know what happens. Thanks again.

Chip


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## Chipr62 (Mar 16, 2008)

Steve, once again you are right on target. I had diluted the HCL/CL soln to about 1:4 with water and got the gold to precipitate out. I have about 2 liters of HCL/CL to work with and I will let you know the grand total gold weight when done.

Thanks alot for your help.


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## Anonymous (Mar 21, 2008)

What is SMB?...as you can tell from my question I am completely new to this and I have no history in chemisrty but i think I found the right place to find out what I need to know. I have read and watched alot of the tutorial material from Steve and I think I have a pretty good grip on the process of stripping and disolving the gold fron pins and fingers but I am a little lost about the percipitation, what is SMB and where do I get it or do I make it myself. Any help would be greatly appreciated.

thanks


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## Chipr62 (Mar 21, 2008)

Hey Jowich, I too am just getting into this. SMB is short for Sodium MetaBisulfite. I got my from The Chemistry Store online, http://www.chemistrystore.com/sodium_metabisulfite.htm

I am still working the kinks out of my SMB solution. I tried 20 gms per 100 ml of tap water and got and found myself adding more in a dry state just to yeild some decent results. I would suggest buying the 10 lb. size of SMB and get yourself a good electronic scale. Hope all goes well for you.

Chip


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## Palladium (Nov 25, 2008)

8)


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## DNIndustry (Nov 26, 2008)

Make sure the water is hot. (Not boiling)35C - Guestimate
The formula in the manual says SMB+Water 28g/240mls I think.....
Saturated is 65g/100 mls.


Understanding the underlying chemistry may help.
The point of SMB (Na2S2O5) is actually to hydrolize to Sodium bisulfate (NaHSO3).
Na2S2O5 + H2O-> 2NaHSO3

The second part of the reaction is SO2 displacing your Au
So depending on what u are using I would always recommend balancing the equation stochimetricly...Im sure there are examples.

As a tip. I never had much luck with SMB, until I started running it hot, dilluted, and adding your solution to the SMB... The last part makes a huge difference. Infact i ran a precipitation, not much came out. had another run, i decided just to add into the previous to use up excess smb....Wow! i know ball park what was in each and what didnt come out the first time, did on the second...


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## lazersteve (Nov 26, 2008)

DNIndustry,

One small correction on your formula, NaHSO3 is Sodium Bisulfite, not sodium bisulfate.

As for adding SMB, I *always* add my SMB dry with lots of swirling of the beaker or stirring with a glass rod. Stannous tests afterward proves the gold is all precipitated.

Just two days ago the temperature outside was below 40F (~4C) at dusk. I precipitated a batch of gold from solution, outside in the cold, with solid SMB in less than 2 minutes. I added the SMB and swirled the flask, within one minute the solution turned dark brown. Within 1 hour all the gold had settled nicely. The solution had be filtered outside and was completely cooled. Expect a slight delay of less than 2 minutes before the solution changes to clear then brown.

I find that the removal of oxidizers from the gold solution to be the most important factor when using SMB. All the free chlorine or NOx should be removed before adding dry SMB. If you add a small amount of SMB and brown powder forms then redissolves, you have free oxidizers in the solution.

Add small amounts of dry SMB with stirring, let it all dissolve, then add more if necessary. Test with stannous once the brown cloud or sponge of gold settles.

Steve


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## SilverFox (Dec 9, 2008)

lazersteve said:


> The solution had be filtered outside and was completely cooled. Expect a slight delay of less than 2 minutes before the solution changes to clear then brown.


I thought filtering for gold precept could be awe full troublesome, Wasn't Siphoning the recommended process for getting your gold sponge out of solution?

if you invented yet another process please let me know


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## Lou (Dec 9, 2008)

I think the invention of filtering might be too big a claim for any of us here.


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## lazersteve (Dec 9, 2008)

Fox,

I filter all solutions *before* precipitating the gold, not after.

Steve


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## SilverFox (Dec 10, 2008)

LaserSteve said:


> Fox,
> 
> I filter all solutions before precipitating the gold, not after.
> 
> Steve



Sorry I got hung up on the order you presented your steps, and said Huh?

First Steve listed listed adding the SMB, then watching the color change. I didn't know if he was using something other then a coffee filter. I just wanted to keep the steps clear for me. I didn't mean to sound accusatory or correct you, no malice intended.

I get confused easy enough.. 


:?


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## patnor1011 (Dec 28, 2008)

I am bit confused...
I have one question. I have found out that in hotel where I am working they have swimming pool and lots of Sodium bisulfate in 25kg bags. Can I use this for dropping gold or it is complete diferent from SMB?


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## goldsilverpro (Dec 28, 2008)

Completely different stuff.


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## butcher (Dec 28, 2008)

that's ate not ite, sulfite is what we want, to Form SO2 gas in our solution's


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## patnor1011 (Dec 29, 2008)

yeah that was the point... I have read lots of posts and there was ate, ite and so... that is why I was a bit not sure if I am getting it right... Thanks for info... Still reading hoke, gathering stuff, and preparing for big day...


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## butcher (Dec 29, 2008)

we also use ferrous sulfate (FeSO4) {ATE}, 
it works differently as a precipitant than the Sulfites {ITE} that provide the SO2


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