# Using ferrous sulfate vs SMB as a precipitant details?



## Bloomglassworks (Feb 18, 2013)

What s up y'all, just getting into this whole precious metal extraction thing, and I had a few questions about the AR process. First of all, is there any difference in the way you use ferrous sulfate vs SMB, or any pros or cons for one or the other? Is the anything I need to know about potential reactions? Is there a ratio of ferrous sulfate to use for an expected yield ? Any help on how to use the stuff would be helpful, I have a big bag of it and was not able to find SMB locally, so If I can use it just the same ill be quite happy! 

Also what are y'all using to neutralize the AR, I have urea, and baking soda, would one of those suffice? I had my sister tell me nitric acid and urea might not be a good combo... 


Sorry for the noob questions, I did a couple hours of searching with no results asking my exact query. Any help is much appreciated! Thanks again ! -Dcp


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## jeneje (Feb 18, 2013)

Bloomglassworks said:


> What s up y'all, just getting into this whole precious metal extraction thing, and I had a few questions about the AR process. First of all, is there any difference in the way you use ferrous sulfate vs SMB, or any pros or cons for one or the other? Is the anything I need to know about potential reactions? Is there a ratio of ferrous sulfate to use for an expected yield ? Any help on how to use the stuff would be helpful, I have a big bag of it and was not able to find SMB locally, so If I can use it just the same ill be quite happy!
> 
> Also what are y'all using to neutralize the AR, I have urea, and baking soda, would one of those suffice? I had my sister tell me nitric acid and urea might not be a good combo...
> 
> ...



Hello, the prefered method for dropping gold out of solution is SMB, CM Hoke talks about using ferrous sulfate and it will work great to. To expell the HNO3(nitric) from your solution, you should use a methord called denoxing, by evapotating(DO NOT BOIL) the solution down to a thick syrup and then adding HCL to remove the brown nitric fumes. Repeat this several times to make sure all the HNO3(nitric) has been removed. Urea will work but not recommended. Then double your solution with H2O(water) and add the ferrous sulfate and stir. It should turn brown and your gold drop to the bottom.

Hope this helps.
Ken

ps. download CM Hokes book found here on the forum and read, read and read. Good bedtime stories :lol:


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## butcher (Feb 18, 2013)

Bloomglassworks,

There are many things you will need to learn here, fist you should study Hokes book.

Aqua regia should be used to dissolve gold, not base metals or gold and base metals.

You need Listen to your sister, she is correct urea and nitric can make dangerous compounds especially with metals and processes we use, many will suggest urea to de-NOx a solution, I never do, not only because of possible danger, but you add another impurity, urea will not destroy nitric acid, as most people who recommend its use believe, it will destroy nitrous acid or NO2 in solution, actually urea is often added to fuming nitric acid, for this reason when they want pure nitric acid free from NO2, the urea does not destroy the pure nitric acid, but removes the NO2 gas from the pure HNO3.

Learn to make your Aqua regia when dissolving gold with limiting the amount of nitric acid using only the amount of nitric acid needed and no more, this way you do not have nitric acid (oxidizer) to eliminate, when you do have some free nitric acid to remove use the evaporation process, evaporation and an added gold button, or sulfamic acid, to remove free nitric from your solution.

Aqua regia is a difficult to master, and needs understanding and practice to be able to use it, reading about it seems like a simple thing to use, but in reality can have many difficulty's for a beginner, solutions can be boiled over easy from the reactions, or during evaporation process when nitric in solution is concentrated, people will say you can dissolve any metals with your gold and make it sound simple to get your gold back, the internet is full of miss-information or missing facts, and either mislead you in your thinking or do not tell you the whole story or are just plain bunk, there are other methods to dissolve gold, especially when gold is in flakes, powders or foils or finely divided state, like HCl/NaClO (bleach), or HCl/32% H2O2, there are other solutions but these are the one you will want to learn about.

Copperas (ferrous sulfate) (FeSO4) has probably been used more throughout history than sodium metabisulfite (SMB) to precipitate gold, and works just as well sometimes better depending on circumstance, ferrous sulfate can be made at home easily (I have many post on how),if you buy your ferrous sulfate as a garden supplement it could be oxidized (brown), if it is brown do not use it will not work, the crystal salts of ferrous sulfate should be a pretty green color salt, the brown is oxidized iron salts and no longer copperas good to use to precipitate gold, using any precipitant to recover your gold is best used with testing, using your stannous chloride to help you determine the end point or if the reagent is needed or would even work, most of the reagents as a general rule use about as much in weight of reagents as gold in solution, copperas and SMB are not the only reagent that will precipitate gold from solution, each reagent will normally reduce other metals besides gold from solution (although most are fairly selective), here is were you will read in Hoke why she may choose one over the other depending what other metals may be in solution or where she will use a different reagent on the second refining to purify the gold as the different reagent used on the second refining would nor precipitate the same base metal the reagent in the first refining did.

You need much more than a few hundreds of hours of study before you beginning to use any chemical, and much more than this before you use aqua regia.

Begin your study with Hokes book.
Forget about trying to recover or refine at this point, all you would do is make dangerous messes lose your gold and other precious metals and put yourself and others in danger.
Your Lab work at first should be the getting acquainted experiments, you will be shown in Hoke's book, these are some of the most important things to learn in the beginning, how metals react in solution, which ones cause troubles, and how to recognize the reactions.

Study how to deal with the toxic waste, another most important task, this will keep you from not only going to jail when the authority's come to check you, and on what you are doing with the chemicals you have been buying, but also will help you to be able to treat the toxic hazardous waste so that you are not poisoning yourself or other people with these deadly solutions.

Study the safety section and other material so you do not poison your self with the fumes from these reactions many of which may not be detectable to your nose, some of which would only take a few lungs full to kill you or others that will damage your lungs to the point they will no longer work several years down the road, study also all of the acids and chemicals you use, many of which by themselves may not be that dangerous but when reacted with a metal or an ore can kill, some of which a few drops in the eyes could blind you for life burning the eyeballs out of your head, some acids and organics can create such flammable substances they could self ignite in your lab, many solutions and metals make explosives, This is not meant to frighten you but to emphasis the true dangers involved, study and understanding is your best protection, what you do not learn CAN KILL YOU...

your gold or other precious metals will not go anywhere while you study (if you just jump in head first you might just as well say bye bye to them),and while you study you can collect and prepare your material for when you have studied and have a good understanding of the process from beginning to end, including how to deal with waste, this way you will collect enough values, and have a good understanding of how to recover and refine those values.


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## Bloomglassworks (Feb 19, 2013)

Hey, thanks for all the great info! I will certainly look for a download of that book. I should have perhaps explain I am not a complete newcomer to organic chemistry, the safety aspect is something I do not take lightly, believe me! Before looking into gold refining i have done a little dabbling outside of my college courses at the time. I am a lampworker, and scientific glass artist, so when my client told me what his apparatus was for, i figured id try my hand. I dont plan on stepping beyond the boundaries of the more simple processes, and now that i have done a bit More research, ill probably stick to processors and other items with minimal base metals to contend with. As far as toxic disposal goes, I have a uncle who is a paint chemist who typically has a lot of waste to deal with, so I will run thing by him before I dispose of anything, some of it I may be able to drop off at his building. It's been a few years since college, but its all starting to come back to me! Thanks again for the help y'all! Great advice!


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## Bloomglassworks (Feb 19, 2013)

Oh and also after looking more into it, I think I may shelve the nitric acid all together, and find another source perhaps nano3,. The more I think about it, without a lab spec fume hood/chamber It is too volatile to warrant its benefits...


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## butcher (Feb 19, 2013)

paint (can be dried) it is dealt with a little different than the toxic metal solutions, reading dealing with waste in the safety section will give you a way to deal with it safely.

If you use NaNO3 and an acid you make nitric acid, it can have the same dangers as store bought HNO3, We use 70% HNO3, in aqua regia, and we dilute it 50:50 with water to remove base metal or dissolve silver, we also make our own nitric acid, it can be used safely once you understand its dangers and take precautions, the forum has tons of information on how to make and use it safely, as far as base metals there are other chemicals we sometimes use to remove it, if thin metal the Copper II Chloride leach (also known as acid peroxide or HCl/3%H2O2, works wonders).

There is a lot to learn, and your background will help in making that easier.

P.S. this is inorganic chemistry, from what I have seen of organic chemistry this should be a lot easier to learn, but there is more to this than just the chemistry which is only a small part of recovery and refining of metals.


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## Bloomglassworks (Feb 20, 2013)

Great advice! Thanks! So far I have about 5 grams of gold recovered with just the hydrochloric leech from processor pins, im probably going to wait until I build a hood to do the AR


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## Bloomglassworks (Feb 20, 2013)

I am trying to find a free ebook version of hokes book with no success, can someone please post a link to where I can download it? Thanks!


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## butcher (Feb 20, 2013)

http://www.scribd.com/doc/2815953/Refining-Precious-Metal-Wastes-C-M-Hoke
C.M. Hoke http://tinyurl.com/mfnyhs
Waste treatment for the small refiner http://tinyurl.com/78z9v5a
http://tinyurl.com/82ynbxb
http://www.goldrecovery.us
http://www.goldnscrap.com


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## FrugalRefiner (Feb 20, 2013)

If you don't want to go through scribd, here is a direct download of Hoke's book from the forum _Refining Precious Metal Wastes_.

I also recommend the 2 forum handbooks compiled by aflacglobal, Forum Handbook Vol 1 and Forum Handbook Vol 2.

Dave


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## Alentia (Mar 13, 2013)

While keep going to the source... the Hoke. I remember seeing someone posted to use the same amount of Copperas for the amount of gold to be recovered.

Here is what Hoke states:
_
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._

It should be 6/1 = Copperas/Gold ratio to recover gold. While SMB is 1/1


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## solar_plasma (Mar 13, 2013)

> Is there a ratio of ferrous sulfate to use for an expected yield ?




get familar with *molar concentration* http://en.wikipedia.org/wiki/Molar_concentration
*atomic weights* and the *periodic system*, then you can easily calculate it, if you know the complete reaction formula and the masses you are dealing with. Normally it will be an educated guess to get the parametres. Mention, this is only easy done in reactions that runs completely, fx. HNO3 + H2O * ->* H3O+ + NO3- (strong acids). Often it will be a *chemical equilibrium* reaction,fx. CH3COOH + H2O * <->* CH3COOH- + H3O+ (weak acids). 'Calculating this is quite ugly in more or less complex blends of ions , then you need sourcebooks and cryptic formulars. But since we allways try to get a quantitative (more or less) precipitation (all gold precipitates), the last one should not be necessary in the most cases. Surely,you didnt understand most of it, but maybe it helps to get some words for further study.

in order to confuse you totally: H3O+ is still simplified since water builds ion clusters, but those are only interesting if you fx. want to understand how an photoionisation detector or a ionmobilitydetector works....so forget this again and let us remain in concious of that we are working with simplified theoretical models and let us remain in respect of the complexity of reality.


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## Alentia (Mar 17, 2013)

Guys, my apologies, it is Sunday and I had my wine already, but I have interesting observations:

While precipitating gold from AR solution with SBM, solution instantly darken and gold drops.

I have made test #4 today with HCl/Cl, while I was 100 positive, my solution has gold in it, I have added SMB and nothing happened, except solution became clear.

The gold started precipitate only after about 1 hours, solution darken and while swirling the flask, I have started to get some solids in the middle. I have left it overnight as solution was full of dark precipitation from bottom to top.

And another observation: When precipitating gold with SMB solution clears to normal water color, if no other metals (or very low) present, while with Copperas solution actually getting darker green color with tints of yellow. Even stannous tests solution negative, there is big contemplation not to move it to Copper/Iron waste drum.


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## xenxis (Jul 18, 2015)

i am wondering if ferrous sulfate we buy at pharmacy which is red in color when dissolved, will work as good as green ones?? thanks :roll:


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## solar_plasma (Jul 18, 2015)

In the case of doubt, I say no. There are obviously other ingrediants in that stuff, which we don't know, what it is. Or, depending on what kind of red you have in mind, it might just be degenerated/oxidized and is of course useless then.


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## Anonymous (Jul 18, 2015)

Google this term Xenxis. 

"Ferrous Sulphate Heptahydrate." 

Then look at images. This is the stuff you want. It's freely available on most shopping sites including eBay and you want it green. You don't have to use the Heptahydrate- that's personal choice however the pictures will give you a great idea of how to know what you are looking for on eBay or Amazon or anywhere else.

Use the images as a reference for when you search "Ferrous Sulphate" on any of the shopping sites you use. Hope that helps.

Jon


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## Geo (Jul 18, 2015)

When ferrous sulfate turns brown,rusty,red, it means the the iron has oxidized and will not precipitate gold.


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## xenxis (Jul 18, 2015)

thank you very much for your response  so i have to find the moss killer type then


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## Xydoman (Nov 1, 2021)

butcher said:


> Bloomglassworks,
> 
> There are many things you will need to learn here, fist you should study Hokes book.
> 
> ...


Man, you ain't lyin. I took the dive iin head first approach . It worked out EXACTLY as you have put it. My first Metric ton (guessing) of material produced about a 10th of what it should've, due to mistake after stupid mistake. I've had to have a friend who has taken a few years of chemistry, literally step in and take over due to several botched batches that were just buckets of hazardous material sitting around that I had no idea what to do with (learned later that after processing these buckets, he recovered over half an ounce of gold, several ounces of silver, along with platinum and palladium that I had no idea were even in there..) for him to step in I agreed beforehand that the buckets were now his and he got whatever came ouf of them. Good or bad. Everything I own is covered in rust, and yes, I'm still very much concerned about possible health problems that I'm unaware of at the moment, after having to replace my guitar strings twice a month due to corrosion and a constant scratchy throat and heavy breathing. I've been at it for a year now and have learned which processes I can handle with my severely limited knowledge, and lessons learned. Here is the truth of it.. THERE IS NO COMMON SENSE THAT CAN BE UTILIZED AS AN UNTRAINED PERSON USING THESE CHEMICALS. make no assumptions. The processes involved here are done with knowledge that you have to Learn. A skilled chemist might be able to get away with trial and error , but even HE or SHE is only trying things based on knowledge possessed by extensive study and supervised practice. No one just KNOWS how all this stuff reacts together. You HAVE to learn. I wish I had. Now I've got 3 basic procedures that I can do effectively, and I never deviate from the steps. I always wear my approved safety gear and never get in a hurry. I really hope that becoming responsible hasn't gone too late and that I haven't screwed up my lungs. I've watched too many loved ones due of lung cancer or emphazyma to know that it's a hard way to go. Thanks for this post, sbd I really hope that all who read it heed your advice.


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## pawnshop (Nov 1, 2021)

Bloomglassworks said:


> What s up y'all, just getting into this whole precious metal extraction thing, and I had a few questions about the AR process. First of all, is there any difference in the way you use ferrous sulfate vs SMB, or any pros or cons for one or the other? Is the anything I need to know about potential reactions? Is there a ratio of ferrous sulfate to use for an expected yield ? Any help on how to use the stuff would be helpful, I have a big bag of it and was not able to find SMB locally, so If I can use it just the same ill be quite happy!
> 
> Also what are y'all using to neutralize the AR, I have urea, and baking soda, would one of those suffice? I had my sister tell me nitric acid and urea might not be a good combo...
> 
> ...


Advice is worth what you pay for it. But I use AR and SMB. 

And these processes give off NOx (the brown gas coming off the reaction) which can cause permanent lung damage, thus a chemical fume hood is necessary. 

My Nitric is 67-70% technical grade. Some say put in the HCL and add the Nitric slowly. That is not what I do, and at this point, I have refined over 100oz of Au to 99.9%. The first step is to inquartation where you lower the Au concentration by adding silver. Pour that into the shot and dissolve in dilute (35%) Nitric acid. This yields a brown powder/solid. From experience and XFR analysis the gold is 97-98% pure. 

AR dissolves low carat or high carat gold. More than 10k and less than 18k doesn't work well.

But once you have the brown powder, I rinse it and dissolve it in AR. My Aqua Regia AR formula is 4 parts HCl to 1 part NHO3 (67-70%). To go further the amount of AR is normally 150ml max per 31.1gr of Au. This breaks down to 4.82ml/gr.

I refine 3oz at a time in a 5000ml beaker. I will start by adding 100ml of HCL and 25ml of NHO3. And go up from there. I also heat it to approx 380 degrees C. But this takes hours... in the process, I add 4-5ml of Sulfuric Acid to drop out the lead.
When the gold is completely dissolved the liquid will be yellow and there is normally a powder in the bottom. (Lead and other base metals). From here I rinse and filter through a Buckner funnel until the liquid is completely clear. Here is the purpose behind a 5000ml beaker for 3toz of gold. By my formula, it only requires 450ml of AR. But in the rinse process, 1500 to 2000ml of H2O gets added. 

Some will disagree with this, but I add Urea a pitch at a time to the liquid until it stops reacting to burn off the unused Nitric. If done properly it takes 1gr of Sodium Meta Bisulfite for every gr of gold in solution. I hate to have too much SMB personally. I filter and rinse.

This gold is 98-99% pure. I repeat the AR process and the difference is that the liquid has little to no solids precipitate and it is a beautiful color of orange. The gold that precipitates on the second go-round is 99.9 - 100% pure.

Another good point of reference is that it takes roughly 1.22ml of 70% Nitric acid combined with 1.22ml of H20 per gram of metal to dissolve the base metals from inquarted gold.


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## orvi (Nov 17, 2021)

pawnshop said:


> Advice is worth what you pay for it. But I use AR and SMB.
> 
> And these processes give off NOx (the brown gas coming off the reaction) which can cause permanent lung damage, thus a chemical fume hood is necessary.
> 
> ...



well written. caution and patience is sometimes better than losing just a few % of the yield, when you are working with multiple oz  in early days i experienced some runaway AR dissolutions  but luckily I was able to quickly place the beaker in the bucket, so no big damage was done... from then, I fill the beaker just to the 30-40 % of volume and start with only half of nitric required for the rxn.
i just add, from my experience, that rose and pink 18k gold dissolves fairly well in AR (warm/hot), due to low silver content (generally when silver is kept below 10%). it produce white AgCl ppt, but AR slowly eat the gold trough this, leaving AgCl "corpses" of granules or flakes dissolved. i found out that this process is speeded up extraordinarily when using ultrasound bath to disintegrate the AgCl layer  

personally, im used to recover mostly electro-scrapp (pins, fingers-platings, etc.), so i go straightly to AR (nitric acid is determining reagent for me from point of obtaining here, HCl is easy-obtainable), dissolve everything, then reduce remains of nitric using sulphamic acid while solution is still warm (nice chemistry behind - decomposition is quick and practically quantitative, forming nitrous oxide. from my point of wiew, urea dont perform anywhere as well as sulphamic acid). adding until it stop fizzing, then cool it down to ambient temperature, filter through Buchner and precipitate with sodium sulfite or SMB. most of the times, i have no idea how much gold i should expect, so generally i add it spoon at a time with stirring, until i can smell the SO2 gas from distance, and than add just half spoonful "for sure"  
without adding deNOxing agent, its very common you find no ppt in the morning, because residual nitric kill all the SO2 and gold goes back into the solution 
gold mud is settled overnight, most of the liquid decanted. gold is then washed 2-3 times with hot HCl (sometimes i encounter minute dissolution of gold back into the solution, so i always keep all acid washings, use it as starting acid for next batch) until the washings lose color, and next with water, than dryied in a beaker... and thats it  if small quantity is produced (under half-gram), after washing i sweep the beaker with paper towel and directly burn it in a crucible and melt it  XRF assays are in range of 99.7 to 99.94 % Au, rest being solely Ag. done numerous times over years 

i never trusted the purity of technical ferrous sulfate (which i could access here), so i never used it in larger scale. SMB or sodium sulfite are abundant chemicals for me, so i stick to this route, its efficient, no waste metal is added...


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