# Link between SMB quantity and gold quantity



## Uciocciu (Dec 20, 2018)

Hi, 

I just begin to take information on PM refining. I'd like to ask a simple question. 

Is there a link between the quantity of SMB that is poured (in gram) and the quantity of gold that we hope to obtain (in grams)? If so, is there a mathematical rule, such as 1 gram of SMB for 1 gram of expected gold?

Thank you in advance, 

U ciocciu


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## nickvc (Dec 20, 2018)

I must admit I have never used smb but with any precipitant if your testing your solution using stannous you always know if you have any gold left in solution. Getting used to regular testing is useful and will keep you informed as to where your gold is.


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## Uciocciu (Dec 20, 2018)

Thank you so much for your response !

Using stannous chloride is the best solution indeed.

But is the SMB quantity you drop based on your assessment of the gold quantity you expect ? 

Is there any link between SMB quantity and gold quantity ?


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## anachronism (Dec 20, 2018)

There is no link at all.

You use as much as is required to get a stannous reading that shows you have no gold.

Test - test - test.


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## FrugalRefiner (Dec 20, 2018)

If you do a search using the words SMB weight gold weight, you'll find plenty of links. The generally quoted ratio is to use about the same weight of SMB as the weight of gold you expect, but it's just a general guideline. It depends on many things. If there is excess nitric, some of the SMB will be consumed reducing the gold which immediately goes back into solution. Other metals in a dirty solution will use some. So it's just a general guideline. You can start by adding 80% of what you expect to need, then test. Add more as needed till the solution tests negative.

Dave


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## Lino1406 (Dec 20, 2018)

(Edited)
SMB:gold 1:1 w/w
Copperas:gold 6:1
here is citation from Amen "You will need about fifteen ounces of copperas to recover two and a half ounces of gold"


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## anachronism (Dec 20, 2018)

Lino1406 said:


> SMB:gold 1:1
> Copperas:gold 5:1



Absolute rubbish.


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## g_axelsson (Dec 20, 2018)

anachronism said:


> Lino1406 said:
> 
> 
> > SMB:gold 1:1
> ...



In what way is that rubbish? What are the correct numbers then?

Of course there is a link or a proportion between the amount of precipitant used and the amount of gold precipitated. For SMB I've also heard the 1:1 based on weight, but I don't recall I have ever seen a number for copperas before.
It should be easily calculated from the chemical equations if anyone is interested enough.

In real life various side-reactions will affect the result to a certain degree. Testing is the real way to be sure you have added enough.

Göran


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## anachronism (Dec 21, 2018)

If you are going to say SMB: Gold = 1:1 then you have to provide a set of circumstances where that equation prevails. 

So - go for it guys. Provide us with that complete set of conditions:

Temperature
Liquid volume
Shape of container
Liquid type
Liquid viscosity
Gold Chloride concentration 
Contaminants present

In reality 1:1 does not happen so stoichiometry plays absolutely no part. 

Since I first mentioned this on this forum and elsewhere I have been contracted by no less than five people who have taken this incorrect 1:1 link to mean that they calculate their gold return, add the corresponding amount of SMB, collect the gold that's dropped and that it- they throw the solution out. 

Now whilst it's easy to say they are misinterpreting things and not following correct process if five people have been doing that then I'd suggest it's as much in how the information is presented as in the way they are doing it. 

So I suggest, since people take things too literally that we break that link between SMB:gold and tell it how it really is - namely you use as much SMB as is required to drop all your gold and give a negative stannous test. <<< This IS the reality and I would challenge anyone out there to prove different. 8) 8) 

Jon


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## Shark (Dec 21, 2018)

According to Hoke, for copperas

﻿


> In another vessel, dissolve in warm water about a pound of green
> copperas for each 50 pennyweight of fine gold that you expect to
> recover. Use fresh green copperas, with about a quart of water to a
> pound. Add a little hydrochloric acid, enough to make the copperas
> solution a clear green.



I have used that exactly as she describes but I had to make small adjustments to get the negative test using it. While I know very little of the chemistry behind much of it, I do understand the importance of testing as I work through the processes.

A questions on the subject in hopes of learning a bit more about it: 
How does heat play into the factor of using the precipitant?


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## anachronism (Dec 21, 2018)

Shark said:


> A questions on the subject in hopes of learning a bit more about it:
> How does heat play into the factor of using the precipitant?



Hi shark

If you are using SMB the active ingredient is the S02 that is produced. The hotter the solution, the quicker the reaction happens and more of the S02 comes out of the solution into the air before it is used. As such the hotter the solution, the more you need to use because of wastage.


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## Shark (Dec 21, 2018)

The past few months I have been heating my solutions to make my drops and it seems to produce cleaner gold drops for me when using SMB. I have not tried the copperas with heat yet, but I want to see what difference it makes as well. Is there a point that raising the temperature higher offers no benefit? I have been doing pretty good at around 125*F for both the auric chloride and the SMB in solution.


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## anachronism (Dec 21, 2018)

I use caked SMB for my drops as per Deano's recommendation rather than pre-dissolving it. That's another procedural difference that has a bearing on claimed percentages. 

With Ferrous Sulphate I do drop warm because I agree it seems to make a positive difference. The only danger with that is when you don't quite denox properly and it boils over. Schoolboy mistake of course but it doesn't hurt to share. 8) 8)


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## g_axelsson (Dec 21, 2018)

I like to still push the 1:1 number for SMB, not that it is an exact ration but because newbies often dump huge amount of chemicals into their reactions without any thought of what's reasonable. If you expect 10g of gold then don't add half a kilo of SMB to your solution and then wonder if it was enough. The number is a reasonable amount to start with, if it doesn't produce gold then there is something wrong and you need to deal with it before just adding more SMB.

Remaining oxidizer, out-gassing and side reactions (Cu++ -> Cu+ for example) will throw the numbers off so there is no way you could just run blindly and skip testing and a stock pot will always be a good insurance for not loosing any values.

I don't have time right now but it would be fun to run a small test, dissolve some gold, filter and then add a small amount of SMB without precipitating all of it. Just to see how much gold actually dropped. It's an easy test and could probably be done with just a few hours work.
I'll try to remember this one and get back to it when time permits.

Refining reminds me a lot of the two foundation laws of astronomy :
1. One is close to ten.
2. One is a lot less than ten.

Göran


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## anachronism (Dec 22, 2018)

That's completely illogical Goran. 8) 8) 

I'd still like to push a patently incorrect figure even though I've shown you a clear reason not to do this, that has harmed peoples' refining? Interesting concept old friend. 

Next you'll be telling me it takes 1 cc of Nitric and 3 cc of HCl to dissolve a gramme of gold.....

:lol: :lol: 

Jon


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## Lino1406 (Dec 22, 2018)

Some parachronistic information. Comparing the data below with actual recommendations above show a safety factor of 1.4


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## Shark (Dec 22, 2018)

Lino1406 said:


> Some parachronistic information



I admit, I had to go look up that definition.


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## g_axelsson (Dec 22, 2018)

Wonderful! Tanks Lino!

Göran


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## Geo (Dec 22, 2018)

Just a side note. Overuse of SMB will cause several problems for the beginner. The main problem is gold powder that will not settle. The SMB is decomposed by the acid in the solution producing SO2. The small bubbles attract metallic gold on the outside of the bubble. The bubble is consumed in the conversion and the gold settles to the bottom. If the gold is depleted and there is still SO2 present in the solution, the remaining bubbles will attract whatever gold is left. The bubbles buoyancy tries to take it to the surface but the weight of the gold keeps it from rising to the surface. So now there are many small bubbles in the solution with tiny amounts of gold metal that neither rises or settles. The small gold "floaters" on the surface is bubbles that manage to make to the surface and burst depositing it's gold on the surface where surface tension keeps the gold from settling. The solution to this problem is to heat the solution. Warm to hot solutions expels gas faster than a cold solution. The excess SO2 is expelled and the suspended gold is allowed to settle. Be aware that warming the solution with the precipitated gold in the container can result in left over nitrates redissolving some of the precipitated gold. Hot reagents are more reactive than cold reagents. Always test after heating and cooling.


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## anachronism (Dec 23, 2018)

g_axelsson said:


> Wonderful! Tanks Lino!
> 
> Göran



For a table that shows "theoretical" data with no corroboration? Come on guys - is this the best rebuttal and chemistry you can give the theory I have posited?


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## nickvc (Dec 23, 2018)

I love these theoretical amounts as they are usually complete tosh unless you are working under strict laboratory conditions with very clean solutions ie no other metals no excess acids and at the correct temperature, they are good for a starting point but I wouldn’t bet any of my gold on them.
Theoretical chemistry and real world recovery and refining chemistry are almost two different subjects and a simple example is cleaning your gold powders in Hcl, theoretically Hcl cannot dissolve any of your gold but in reality it does, maybe not much but it still will hold some of your gold.
The answer to the how much precipitant you need is simple to determine you add it until a test using stannous shows there is no gold left in solution and the fact is your precipitant is a lot cheaper than the gold your after so if you use a little excess I think that’s still a bargain.


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## nickton (Oct 17, 2019)

Copperas is a bargain but I wouldn't say SMB is really. I believe one pound of Stump out by Bonide sells for $9.00 now, and it goes fast...Perhaps I am too cheap, but I'm not crazy about paying that much for it. :G :G :mrgreen:


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## g_axelsson (Oct 17, 2019)

Interesting thread that i had forgotten about.

Right now I'm split between copperas (make it myself from waste acid from the reverse plating cell) and SMB. When visiting Jon I had the opportunity to test several different precipitants. So today it's more a question about availability, whatever is closest to where I'm refining. It's more or less the same to me whatever I use and if I have a problem with contamination I'll just switch.

Göran


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## anachronism (Oct 17, 2019)

Goran

The biggest eye opener for me was watching Kurt use copper dust to precipitate. It instantly used up any free Nitric and frankly the gold cleaned up very nearly as well as using other precipitants. 

"Very nearly" is good enough for recoveries. 8) 8) 

Edit: I remember 4metals telling me one night that it's a darned good precipitant and he was right. This was the first opportunity to give it a go. 

Jon


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## rickzeien (Oct 17, 2019)

anachronism said:


> Goran
> 
> The biggest eye opener for me was watching Kurt use copper dust to precipitate. It instantly used up any free Nitric and frankly the gold cleaned up very nearly as well as using other precipitants.
> 
> ...


How fine was the copper dust. 

Sent from my SM-G950U using Tapatalk


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## anachronism (Oct 17, 2019)

I'll go look at the container Rick and let you know later.


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## g_axelsson (Oct 17, 2019)

Fine enough to not spot any grains in the copper powder. Like flour.





Göran


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## snoman701 (Oct 17, 2019)

It’s around 300 mesh. 

Called atomized copper. 


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## anachronism (Oct 17, 2019)

snoman701 said:


> It’s around 300 mesh.
> 
> Called atomized copper.
> 
> ...



It's dust. It works. What's not to like? 8) 8)


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## snoman701 (Oct 17, 2019)

For it to work it has to be oil free. A thinly spread layer should sink, not float. 

Probably easiest to put it in a spice like container so it can be sprinkled...if you put in a large dollop it tends to clump together as the noble metals precipitate, then form an insoluble layer. What’s worse is that clump will get HOT and melt in to the bottom of a bucket or barrel. 

I use it to drop out pgm’s from AR following gold drop. 


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## niks neims (Oct 18, 2019)

I have read it here that it is a good idea to alternate precipitants between recovery/refining drops... It seems like a very logical idea to me, also someone once mentioned that copperas handles dirty solutions better than SMB, so for what little recovery/refining I still do, I use Copperas for initial recovery drop and SMB for clean, refining drops, I don't know, SMB it just feels cleaner, the best would be SO2 gas of course;

The atomized copper powder - so it's basically quick cementation? Surely it would only be used for recovery drop, not refining, unless you plan to wash your refined powder with nitric afterwards?


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## anachronism (Oct 18, 2019)

niks neims said:


> The atomized copper powder - so it's basically quick cementation? Surely it would only be used for recovery drop, not refining, unless you plan to wash your refined powder with nitric afterwards?



Yes Nik. Absolutely correct - it's best for recovery. That given if you're on your game with cleaning it makes very little difference. You can still clean it using the 50/50 HCl/water method.


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## niks neims (Oct 18, 2019)

anachronism said:


> Yes Nik. Absolutely correct - it's best for recovery. That given if you're on your game with cleaning it makes very little difference. You can still clean it using the 50/50 HCl/water method.



I'd still prefer to cement with a solid bar, though... much slower, but less potential contamination... Also I can't get my head around how can you dissolve away copper with just HCL, It's not the first time someone mentions it, and I am at a loss how would HCL without an oxidizer take care of copper?


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## anachronism (Oct 18, 2019)

In theory it doesn't you're quite correct. 

That's why as Kurt pointed out we didn't get to three nines. If you're testing, and careful you can ensure that you don't add a lot of extra copper. 

The purpose is to get your gold here, and collate it for a proper refine. It's fast and effective and works best the premise that there's a fair amount to do in a limited time. 

If you don't have those time limitations then sure go for the bar. I only tried a copper bar a couple of times and wasn't overly happy with the gold I got- and on balance this was a lot better all round. 

If you think laterally- there's nothing to stop you starting with a spoon of copper and moving on to something else when the copper has used up any free Nitric that's lurking, which it all too often does no matter how well you think you've denoxxed with Sulphamic.


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## niks neims (Oct 18, 2019)

anachronism said:


> In theory it doesn't you're quite correct.
> 
> That's why as Kurt pointed out we didn't get to three nines. If you're testing, and careful you can ensure that you don't add a lot of extra copper.
> 
> The purpose is to get your gold here, and collate it for a proper refine. It's fast and effective and works best the premise that there's a fair amount to do in a limited time.


There was this quote here somewhere (I don't think it was you, though the humor of it was very similar) regarding brute force gold recovery from e-waste, something along the lines "quit playing Mr. Little Chemist, just drop your gold by cementing it with copper, no need for fancy precipitants if you are not shooting for 3N up at least", I found it very funny and worth remembering 




anachronism said:


> If you don't have those time limitations then sure go for the bar. I only tried a copper bar a couple of times and wasn't overly happy with the gold I got- and on balance this was a lot better all round.



To be honest, I gained a new respect for cementation when I did some silver in nitric- there is something very satisfying in the way copper bar cements out silver and it flakes of...



anachronism said:


> If you think laterally- there's nothing to stop you starting with a spoon of copper and moving on to something else when the copper has used up any free Nitric that's lurking, which it all too often does no matter how well you think you've denoxxed with Sulphamic.



I must say I would not feel comfortable mixing together denoxing and precipitation steps (there is no practical reason, I just like to filter pregnant AR to crystal clear right before precipitation, so I know that anything that comes down is "pure" gold) be it with copper, copperas or SMB; I must admit I cheat with urea (I know it is frowned upon, but cant understand why) for denoxing and found it works best for me (secound best, after not adding too much nitric of course)... I guess there is some preference of style in different techniques


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## anachronism (Oct 18, 2019)

I'm completely with you regarding the silver precipitation with a copper bar. Yes it looks great too. 

I used to be nervous about mixing precipitants. There's far too much water under the bridge now for that nervousness to remain because sometimes it just has to be done. Being logical about it, the approach that says if all else fails use a copper bar- is exactly that. 8) 8)


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## niks neims (Oct 18, 2019)

anachronism said:


> if all else fails use a copper bar



oh, jeah, it has saved my gold from a mess a few times 

It's right up there with "READ HOKES!" & "FORGET YOUTUBE" !


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## kadriver (Nov 24, 2019)

snoman701 said:


> For it to work it has to be oil free. A thinly spread layer should sink, not float.
> 
> Probably easiest to put it in a spice like container so it can be sprinkled...if you put in a large dollop it tends to clump together as the noble metals precipitate, then form an insoluble layer. What’s worse is that clump will get HOT and melt in to the bottom of a bucket or barrel.
> 
> ...



I tried cementing PGMs from a solution containing dissolved copper with zinc in my stock pot refining videos but the zinc dropped the copper with the PGMs. Using copper powder is a good suggestion. Will cement out the PGMs and leave the copper in solution. Wish I'd of thought of that back then. I've even got fine mesh copper powder in my cabinet. I must try this when I refine my stock pot next time. Someone said Rick recommended copper powder in the stock pot refining but it didn't click until just now.

Thank you,
kadriver


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## nickton (May 3, 2020)

Referring to the reactivity series: What if you put some gold in the stock pot, to cement only PGMs first, since they are the only thing below gold on that list. Your first batch of black slime should therefore be only PGMs, which would be separated from the start, then you could cement the remaining solution first with silver to get the gold (and thus recover what you deliberately put in as well), then with copper to recover the silver, then finally with zinc, iron or aluminum to clean out remaining base metals. 

This would be an ongoing series of cementations one could let sit in separate buckets-- and would require much less additional acid for the whole waste refining process. The only real problems would be the initial leap of faith and extra supply of gold required for adding to the stock pot to start with, and the extended soaking times needed. 

(I hope that made sense)... Or did I misunderstand how it works?

I guess the main question I would have about this method is: How much gold would one need to cement those PGMs?


Please excuse if this is slightly off topic by the way, but I've been looking for a thread to post it to.


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## butcher (May 3, 2020)

nickton,
You have theory correct, and understand how it works, but with silver, gold, and the platinum groups being so unreactive, or in the Nobel metal group, so close together in the series, it would be very difficult to cement the PGM's with gold...
It may be possible under some conditions, I do not believe it would work as well as copper or a more reactive metal...


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## nickton (May 3, 2020)

Yea I thought there might be an issue there. In watching sreetips' video it seemed a bit excessive (?) to use so much zinc to drop the PGMs, since it would include so many base metals too, so I started to think about possible better ways. 

thanks for the clarification, butcher.


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