# SMB Residue Remains



## Akureyi (Jul 19, 2022)

My batch of "not-quite" Aqua Regia (4:1 HCL to Nitric ~200ml of Nitric used) came out very green, looking a bit like a forbidden flavor of Mountain Dew. At the bottom was a lot of white residue which I am currently working under the impression that it is residue from all the SMB added when trying to drop the gold. I am pretty sure this is from excess Nitric acid still in the solution so I filtered my mixture into my E. Beaker and slowly boiled the solution down over night and re-filled it will HCL. Now I have a very urine-colored mixture, much closer to what I know it should look like but the white residue remains at the bottom of my beaker.

Here are a few pictures of it as it currently sits and how it appeared before boiling down to reduce Nitric Acid.

Stannous Chloride gave me a good reaction so now I just need to know if there is a way to remove the white residue or if I should strain off as much of the clear liquid as I can and call whatever stays behind a loss? Am I correct in thinking this residue is just left over SMB or another by product? Maybe its the remnants of the coffee filters?


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## Shark (Jul 19, 2022)

Looks like a weak and dirty solution of AR. Filter until it is completely clear with no sediment. Check for left over nitric using a small bit of sulfamic acid. If no fizzing reaction add a small amount of smb to drop the gold. If there is a reaction add small amounts of sulfamic acid until the reaction stops. Sulfamic works best hot, around 125*F. It takes roughly one gram of smb to drop one gram gold so go easy on it. I would start with 5grams and test with stannous until it came out negative for gold.


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## Akureyi (Jul 20, 2022)

Custom Building Products Aqua Mix 1 lb. Sulfamic Acid Crystals 050231 - The Home Depot






www.homedepot.com





Would this work?


Shark said:


> Looks like a weak and dirty solution of AR. Filter until it is completely clear with no sediment. Check for left over nitric using a small bit of sulfamic acid. If no fizzing reaction add a small amount of smb to drop the gold. If there is a reaction add small amounts of sulfamic acid until the reaction stops. Sulfamic works best hot, around 125*F. It takes roughly one gram of smb to drop one gram gold so go easy on it. I would start with 5grams and test with stannous until it came out negative for gold.


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## Shark (Jul 20, 2022)

Yes. It is the exact same as I use.


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## Akureyi (Jul 20, 2022)

Shark said:


> Yes. It is the exact same as I use.


So should I add heat to my clear solution and then add a little bit of this to it or add it to it first then heat it up?

Clarifying: should I add some crystals first and watch for the reaction or will it work better to heat it up first then add the crystals and wait for a reaction?


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## Shark (Jul 20, 2022)

Heat works best for me.

I heat to around 125*F. About the same as a coffee maker will get. Add a pinch of sulfamic and watch the reaction. If a light reaction occurs give it a vigorous stir while watching it. If no reaction then you can add your smb. The sulfamic will also cause lead to drop out of solution so before adding smb, make sure you have nothing settling out. If it does settle or become unclear then filter it until clear again before the smb additions.


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## Akureyi (Jul 20, 2022)

Shark said:


> Heat works best for me.
> 
> I heat to around 125*F. About the same as a coffee maker will get. Add a pinch of sulfamic and watch the reaction. If a light reaction occurs give it a vigorous stir while watching it. If no reaction then you can add your smb. The sulfamic will also cause lead to drop out of solution so before adding smb, make sure you have nothing settling out. If it does settle it become unclear then filter it until clear again before the smb additions.


You're awesome, thanks


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## popslab (Jul 22, 2022)

Akureyi said:


> You're awesome, thanks


I do the same, except I add the sulfamic acid before I filter. This way lead is gone and so is any left over Nitric.


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## dpgold (Aug 19, 2022)

Shark said:


> Looks like a weak and dirty solution of AR. Filter until it is completely clear with no sediment. Check for left over nitric using a small bit of sulfamic acid. If no fizzing reaction add a small amount of smb to drop the gold. If there is a reaction add small amounts of sulfamic acid until the reaction stops. Sulfamic works best hot, around 125*F. It takes roughly one gram of smb to drop one gram gold so go easy on it. I would start with 5grams and test with stannous until it came out negative for gold.


I had a similar problem with somewhat dirty AR, I added nitric to AR bit by bit, in the end when I tried to denox with urea there was no reaction whatsoever but SMB kept making a strong reaction every time I added a little. Is it possible for the gold to drop but still have a reaction to SMB?


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## Yggdrasil (Aug 19, 2022)

dpgold said:


> I had a similar problem with somewhat dirty AR, I added nitric to AR bit by bit, in the end when I tried to denox with urea there was no reaction whatsoever but SMB kept making a strong reaction every time I added a little. Is it possible for the gold to drop but still have a reaction to SMB?


Do not use Urea. Use Sulfamic, it will take care of both the Nitric and NOx.


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## dpgold (Aug 19, 2022)

Yggdrasil said:


> Do not use Urea. Use Sulfamic, it will take care of both the Nitric and NOx.


I can't find Sulfamic over here, I will look further. To this batch I already tried to denox (if this is the correct term) but there was no reaction at all , then I have added SMB little by little and it was fizzing every time I added a bit. I was worried I might add too much and stopped. Heated the solution, added a bit of sulfuric . Is it possible to still have a reaction to SMB but at the same time to have gold precipitation?


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## 4metals (Aug 19, 2022)

Akureyi,

I have been going through old posts for the library and some members used an outside photo program as you did in your first post. The trouble is, in time, these photos are either removed from the external source or are no longer available on the forum. 

Please use the attach files option here on the forum to attach all of your future photos as they will then remain on the forum for future readers of these threads. 

Thanks, and welcome.


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## Shark (Aug 19, 2022)

dpgold said:


> I had a similar problem with somewhat dirty AR, I added nitric to AR bit by bit, in the end when I tried to denox with urea there was no reaction whatsoever but SMB kept making a strong reaction every time I added a little. Is it possible for the gold to drop but still have a reaction to SMB?





dpgold said:


> I can't find Sulfamic over here, I will look further. To this batch I already tried to denox (if this is the correct term) but there was no reaction at all , then I have added SMB little by little and it was fizzing every time I added a bit. I was worried I might add too much and stopped. Heated the solution, added a bit of sulfuric . Is it possible to still have a reaction to SMB but at the same time to have gold precipitation?


Can you find copperas (ferrous sulfate)?
If you can get it…
Follow the advice from Hoke’s book on preparing copperas and using it.


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## Shark (Aug 19, 2022)

If no sulfamic or copperas, try warming the solution to about 125F for an hour, while mixing 10 grams of smb in 50ml of water and 50 ml of HCl. Heat it to around 125F also. Stirring vigorously, slowly add the smb to the AR.


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## dpgold (Aug 19, 2022)

Shark said:


> If no sulfamic or copperas, try warming the solution to about 125F for an hour, while mixing 10 grams of smb in 50ml of water and 50 ml of HCl. Heat it to around 125F also. Stirring vigorously, slowly add the smb to the AR.


Would this work even if I already added the SMB initially?


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## Shark (Aug 19, 2022)

How much gold do figure is in the solution.


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## dpgold (Aug 19, 2022)

Shark said:


> How much gold do figure is in the solution.


2 to 4 grams I guess, I had a plastic jara about 1l full of gold plated contacts and anything that seemed to be plated


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## Shark (Aug 19, 2022)

If the jar is almost full, add it a container twice it’s size. Heat it at 125F at least an hour. Add the 10 grams of smb to 50ml water. Heat it to the same temperature, it can be hotter but more heat can produce a more violent reaction. Measure out 50ml of hydrochloric acid. One everything is heated add the HCl to the solution. Stir. Slowly add the liquid SMB stopping if it becomes violent, we don’t want a run away reaction here. Maintain the heat, allowing it to settle.


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## Shark (Aug 19, 2022)

dpgold said:


> 2 to 4 grams I guess, I had a plastic jara about 1l full of gold plated contacts and anything that seemed to be plated


I would not heat it in plastic. Old glass coffee pot would be better. Good beakers would be a plus to measure liquids in. 

A 1L jar and plated parts will be a very small amount of gold. It could take quite a while for it to settle, and even be hard to see in a liter of dirty or dark solution. It can be done but it reacts a lot differently than larger quantities will. Even allowing it to settle over night to a day or two would not be unusual.


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## dpgold (Aug 19, 2022)

I kept the contacts in the plastic jar about 6"Hight x 4" diameter. I had crushed them in a high speed mill and added HCL and small increments of nitric. They were divided in two coffee pots made of glass with catch pans. After the reaction was done I have added water filtered all the crushed parts and washed a couple of times added water and filtered. I have then added a bit of sulfuric and cotton filtered. Added a bit of urea to see if there was a reaction but none was seen. 
Then when I added urea bit by bit a lot off fizzing happened and the fizzing did not stop. Then per some advice I have received earlier, I heated it until simmer and added a bit of sulfuric. Now the solution is very dark and I let it settle. Anyway there seem to be signs of too much SMB. 
Next I will follow your suggestion. I appreciate it. Is it possible to have had a precipitation without the urea ( I did not ad any after I saw that there was no reaction at all even after some time)
View attachment 20220819_153357.mp4


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## dpgold (Aug 19, 2022)

View attachment 20220819_122702.mp4


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## Shark (Aug 19, 2022)

The last video is after adding the smb???


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## dpgold (Aug 19, 2022)

Shark said:


> The last video is after adding the smb???


no, that was before filtration, very dirty, the stannous test was first positive and the last after boiling and smb does not look positive,


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## Shark (Aug 19, 2022)

That looks like a filtering nightmare!
This is a great example of why to not add things directly to AR. 

Give time to settle. My guess is it will be a very light dust on the bottom of the pot. Once it is recovered, or not, it seems time to cement it on copper.


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## Shark (Aug 19, 2022)

I don’t know how to copy paste links on my phone, so search for a post from FrugalRefiner called “When in doubt cement it out”. It will help you later as well to clean up excess waste’s. It can often be the easiest way to fix a problem in refining and recover valuable metals from it.


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## FrugalRefiner (Aug 19, 2022)

When In Doubt, Cement It Out


When In Doubt, Cement It Out This is advice I often give to new members who find they've created a bit of a mess, and they're wondering how to recover their values (gold, silver, PGMs, etc.). Perhaps they've followed a process they've seen on YouTube that left out some important details...




goldrefiningforum.com





Dave


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## Shark (Aug 19, 2022)

Thanks again Dave.


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## cejohnsonsr1 (Aug 20, 2022)

dpgold said:


> I had a similar problem with somewhat dirty AR, I added nitric to AR bit by bit, in the end when I tried to denox with urea there was no reaction whatsoever but SMB kept making a strong reaction every time I added a little. Is it possible for the gold to drop but still have a reaction to SMB?


Urea won’t denox. As long as you don’t have too much excess nitric just use SMB. The gold will precipitate and be instantly redissolved which will consume the nitric. That’s only if you have a little excess nitric. If you have a lot then you’re using way too much nitric and it’s better to denox with sulphamic.


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## Shark (Aug 20, 2022)

Actually urea will kill the NOx from solution. What it doesn’t do is destroy the nitric acid. This leave the potential for more NOx to be generated if the gold is not separated from the solution fairly quick, allowing for risk of the gold going back into solution. Sulfamic acid will kill the nitric acid itself, allowing excess generation of NOx to be stopped as well. Urea will do the job of allowing to recover the gold. But needs a bit different method and care versus sulfamic.

Edit: sulfamic has the added benefit of dropping any potential lead. Effectively doing two steps at once.


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## dpgold (Aug 20, 2022)

today I separated what was decanted, whatever gold was there at the bottom was mixed with too much SMB as I was afraid. I don't know why the solution had no reaction to the urea but I think either there was not enough nitric (although the stannous test was initially positive) . I did not get a chance to do anything today but I plan to follow your suggestion and try to get rid of the smb decanted at the bottom. 
Some time ago it happen to somebody and as I was reading I thought how could he have put so much SMB  and now I did it myself. So I have learned something.


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## Shark (Aug 20, 2022)

Learning with out hurting someone is always a plus. The excess smb should rinse out on the water rinse if the water is hot.


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## dpgold (Aug 20, 2022)

Shark said:


> Learning with out hurting someone is always a plus. The excess smb should rinse out on the water rinse if the water is hot.


heating the solution and filtering will make smb go through the filter and the rest should stay in the filter?


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## Shark (Aug 20, 2022)

Yes. Should work that way. Or decant the majority of the solution from the powders and refilling with water and heat again. Doing this several times will accomplish the same basic results.


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## dpgold (Aug 21, 2022)

I was just looking to Jeff doing a drop with SMB and the gold wouldn't drop apparently due to the PH being too high. The colour of the solution seemed the same with mine at the point when I wanted to drop. I was wondering if that is what happened with mine. Meanwhile I had put the filtered part with a piece of copper in it and leave it for about two weeks stirring. Would that be ok? Is cementation like a drop only it takes longer?


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## Shark (Aug 21, 2022)

I think ph plays a part in it. I don’t know the chemistry behind it but, often, on stubborn drops, adding a little hydrochloric acid seems to be the big factor. When using heat to denox the way Hoke explains never seems to be problematic. This is where I learned to add some hydrochloric at times when a drop became a problem. Often when working with dirty solutions we introduce other factors as well sometimes they help, sometimes they can be a real pain to figure out. I like FrugleRefiner’s method of cementation with a real stubborn drop. It saves time and pm’s can be recovered fairly quick versus just placing some copper in it. But then learning the real cause behind a problem can be beneficial down the road as well.


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## cejohnsonsr1 (Aug 21, 2022)

Shark said:


> Actually urea will kill the NOx from solution. What it doesn’t do is destroy the nitric acid. This leave the potential for more NOx to be generated if the gold is not separated from the solution fairly quick, allowing for risk of the gold going back into solution. Sulfamic acid will kill the nitric acid itself, allowing excess generation of NOx to be stopped as well. Urea will do the job of allowing to recover the gold. But needs a bit different method and care versus sulfamic.
> 
> Edit: sulfamic has the added benefit of dropping any potential lead. Effectively doing two steps at once.


The whole point is to consume the excess nitric. It’s not a risk. As long as nitric is present gold cannot be precipitated without immediately being redissolved. That’s why urea is not suitable for the purpose. It won’t remove the nitric.


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## Shark (Aug 21, 2022)

In some situations the hydrochloric may be consumed before the nitric. Especially when using poorman’s AR and a dirty solution. When using urea you can remove the NOx, drop the gold and filter it out with little to no problems. The gold is removed before enough NOx is generated to go back into solution. If, as I prefer, the gold is allowed to settle out, maybe over night or longer, it then changes and gold can go back into solution. Maybe not that night, but later in the next day. You can add more material and use up the nitric if your sure to have enough hydrochloric. But without the hydrochloric things begin to change, sometimes in very strange ways. When we keep dropping the gold and allowing the nitric to dissolve repeatedly it also allows other metals to drag down that may not go back into solution with the weakened AR. This at times leaves a light, fluffy powder that takes a while to settle and then our washing skills come into play.

Both can be used with good results but require a different approach. If we use urea and have lead involved the use of sulfuric may be needed to remove the lead. But if we use sulfamic we remove the nitric and the lead and need one less chemical. I opt for the less chemical approach, as most who have been at this for a while do, even though some old timers did and still do use urea.

I don’t think we disagree on which chemical to use so much as why we use a specific one. It’s just using a different approach to reach the same goal. The approach I know better is the sulfamic approach.


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## dpgold (Aug 21, 2022)

Shark said:


> I think ph plays a part in it. I don’t know the chemistry behind it but, often, on stubborn drops, adding a little hydrochloric acid seems to be the big factor. When using heat to denox the way Hoke explains never seems to be problematic. This is where I learned to add some hydrochloric at times when a drop became a problem. Often when working with dirty solutions we introduce other factors as well sometimes they help, sometimes they can be a real pain to figure out. I like FrugleRefiner’s method of cementation with a real stubborn drop. It saves time and pm’s can be recovered fairly quick versus just placing some copper in it. But then learning the real cause behind a problem can be beneficial down the road as well.


what is his cementation method?


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## Shark (Aug 21, 2022)

FrugalRefiner said:


> When In Doubt, Cement It Out
> 
> 
> When In Doubt, Cement It Out This is advice I often give to new members who find they've created a bit of a mess, and they're wondering how to recover their values (gold, silver, PGMs, etc.). Perhaps they've followed a process they've seen on YouTube that left out some important details...
> ...


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## dpgold (Aug 21, 2022)

Cementation is a very interesting thing, I have seen open aluminum or zinc being recommended for cementation and it would make sense to use only copper which would only cement out the metals below in the reactivity series which are PM . I wonder if there is a reason why aluminum or zinc could be recommended in this type of situations.
I see in the instructions above copper being advised for that specific reason.


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## Shark (Aug 21, 2022)

Choosing one over another could be based on the metal being recovered. It also can be determined based on our skills at cleaning our precipitate as well. For many we are only looking to recover the gold now and recover the rest from our stockpot later. Some metals are just easier to access than others as well. For the majority with a stubborn solution of mixed metals we can cement the pm’s for further refining and eliminate many of the excess base metals making for an easier second refine. At times other metals may be used on solutions we know only contain the majority of a known pgm. Much of this gets back to knowing what metals have been eliminated before starting the AR process. Clean AR is easier to work with. It is also getting into the realm of pgm’s which I know very little about.

For most of our needs we can run a successful gold recovery, move to the cementation process collecting any left over valuable metals, and move our remaining solution into the clean up stage. This helps keep from storing larger amounts of waste solution in a relatively confined area for many. Many larger operations used to cement in two or even three different areas to be sure of collecting every bit of values possible. Reading some of the older books, many found on google or archive.org, goes into depths of explanation that can never be reached in videos or short posts on forums. Many well worth reading although in harder to understand language than Hoke made it.


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