# SMB or Backing Soda???



## joekbit (Oct 13, 2014)

from Joe

Hello all, I am new to this but as the topic says SMB or Backing soda? I can remember reading that SMB does not actually drop the gold, the sodium bicarbonate is dropping the gold. In other words, when you add SMB to a aqueous solution it changes to sodium bicarbonate and that is actually what drops the gold? Note the question mark.

If this is true why use SMB to start with? Why not just get some backing soda from the grocery store?

Like I said I am new to this. I had a small amount of scrap, just home left overs E Scrap. Long story short, I had been processing it a bit here and there. Reached the stage of gold(3), diluted it added some backing soda and in a very short time my liquid was clear and I now have what looks like it may be Max 1grm of precipitated gold sitting in the bottom of my jar.

Back to the question, is there a deeper reason why most everyone and everything I see on dropping gold they use SMB?

Thanks I look forward to the comments and feed back.

Oh 1 other question, how do I set this up to follow my own posts?


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## etack (Oct 13, 2014)

WHAT!!!!!!!!

SMB creates SO2 That is what drops your gold. Please read more then read it again. If you did this your ignorance on this subject is showing. You will not only reduce your gold but you will also reduce all the other base metals in your solution too.

You will have a powdered form of what you started with.

Eric


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## MarcoP (Oct 13, 2014)

Baking soda is erroneously used by beginners in waste treatment, or various PH adjustments, because it runs at high costs and creates hazardous risks as it will precipitate heavy metals' carbonates and hydroxides. I'm curious about the source.


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## mls26cwru (Oct 13, 2014)

Sounds like you have been getting your information from youtube and/or instructables.com.... forget anything you "know" and read Hoke's and/or Ammen's books. there should be some links to an electronic copy in the new users forum. 

The idea behind using SMB is to *selectivly* precipitate gold. The SO2 created by SMB is what does this. While sodium bicarbonate will precipitate gold out of solution, it will precipitate everything else as well and put you right back at your starting point. 

Oh, and it is "baking soda", just so you know


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## GotTheBug (Oct 13, 2014)

Find a local place that has home brewing supplies. You can pick up a huge bag of SMB (used for yeast control) for the lowest cost I've seen.


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## joekbit (Oct 13, 2014)

I have Hokes book and I am reading it, as for my ignorance, your right, but is it really appropriate to make such statements. My thought NO. In all my digging and it has been extensive, I have never found a definitive answer/ SMB is specific to precipitating gold and will not drop other contaminates.

Thank you for the answer.


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## jeneje (Oct 13, 2014)

If i may ask here. What type of solution did you use to refine your gold, and how did you recover it from the escrap? Just curious.
Ken


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## MarcoP (Oct 13, 2014)

joekbit said:


> I have Hokes book and I am reading it, as for my ignorance, your right, but is it really appropriate to make such statements. My thought NO. In all my digging and it has been extensive, I have never found a definitive answer/ SMB is specific to precipitating gold and will not drop other contaminates.
> 
> Thank you for the answer.



In a chloride solution it may create CuCl precipitate especially when over using it but easily removed by HCl washes.
As per your original doubt, it seems that you are over exaggerating by using digging and extensive in the same phrase, moreover it still doesn't give any justification to your baking soda question.


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## the iron dwarf (Oct 13, 2014)

from the cell phone boards there is no doubt Pb and Sn in the solution but due to the extensive digging that joe has done he must have dealt with them earlier.

I have just been preparing some gold plated boards by dissolving as much of the solder as possible before washing them and removing the solder mask, when done I will add them to the fingers I have and use AP to get the foils, I also have a few pins but have to sort them and some need treatment for solder before the AP


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## joekbit (Oct 13, 2014)

jeneje said:


> If i may ask here. What type of solution did you use to refine your gold, and how did you recover it from the escrap? Just curious.
> Ken


I started with hydrochloric and peroxide for the initial burn, did that a number of times until I had nothing in my filter but foils, flecks and specs that were quite obviously gold. I then incinerated my filter and flushed out the ash. After drying that out I used HCl and Cl, in very small amounts, 6ml to 2 ml, tested, poured the liquid into a jar and repeated with the sediment until my test for gold showed nothing. Took a number of washes, so to speak. I had about 3 or 4 ounces of gold 3 in a jar. I'm not going to do the math on how many times that adds up to.

At that point I diluted it 50% and added my "baking soda", a little at a time, and behold the mud started to drop. I left it over night. Looked today and the liquid was as clear as tap water with the grown mud on the bottom. I preformed another check on the clear liquid and it tested negative for gold.

I took my time doing this, a couple days actually. Its now in storage until I come up with some more things to process.


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## Geo (Oct 13, 2014)

Sodium metabisulfite (SMB) is pretty specific about what it will precipitate. Sulfur dioxide gas is created when you decompose SMB in an acid solution. It is this mechanism that precipitates the gold. Any other information you have regarding this fact and contradicts it is most likely false. To say that SMB does not precipitate gold goes against what is taught here on the forum. It is listed on the forum as an accepted precipitant for gold. Perhaps if you can show that sodium carbonate will selectively precipitate gold excluding other metal, and, you can make gold relatively pure (relative to gold precipitated with sodium metabisulfite) using it for refining, you will have center stage for quite some time.


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## joekbit (Oct 13, 2014)

Geo said:


> Sodium metabisulfite (SMB) is pretty specific about what it will precipitate. Sulfur dioxide gas is created when you decompose SMB in an acid solution. It is this mechanism that precipitates the gold. Any other information you have regarding this fact and contradicts it is most likely false. To say that SMB does not precipitate gold goes against what is taught here on the forum. It is listed on the forum as an accepted precipitant for gold. Perhaps if you can show that sodium carbonate will selectively precipitate gold excluding other metal, and, you can make gold relatively pure (relative to gold precipitated with sodium metabisulfite) using it for refining, you will have center stage for quite some time.


Geo and others.

I have no doubt that you are all correct. and given they can never put anything on the internet that is not true,,,,lol the information I found was likely not correct. That is why I asked the question.

As far as the comments about me reading, well I am new to the forum and just now getting a very basic idea on how and where to find questions that were already asked. Such as mine.


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## etack (Oct 13, 2014)

joekbit said:


> I have Hokes book and I am reading it, as for my ignorance, your right, but is it really appropriate to make such statements. My thought NO. In all my digging and it has been extensive, I have never found a definitive answer/ SMB is specific to precipitating gold and will not drop other contaminates.
> 
> Thank you for the answer.



My statement was not meant to be condescending it was statement of fact.

Saying "your ignorance on this subject is showing" is true; sorry if you have an issue with that.

I would suggest reading and listening to others on this.

Bad info should be and is swiftly voided on this forum.

Eric


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## solar_plasma (Oct 14, 2014)

Maybe the confusion comes from the fact, that SMB will form sodium hydrogensulfite in water and all alkali sulfite compounds will form the same SO2 with HCl. The question should have been, if the OP can use sodium hydrogensulfite instead of SMB,because SMB will give sodium hydrogensulfite in water anyway.

Na2S2O5 + H2O -> 2 NaHSO3

HSO3- +HCl -> SO2 + Cl- + H2O

SO3-- + 2 HCl -> 2 Cl- + SO2 +H2O

side reaction: SO2 + H2O <=> H2SO3

the reduction of gold by oxidation of S(IV) to S(VI):
SO3-- +H2O -> SO4-- + 2e- + 2H+
Au+++ + 3e- -> Au0

Baking soda NaHCO3, just as washing soda Na2CO3 is able to precipitate a lot of insoluble metal carbonates, so at a given pH you are precipitating nearly every metal dissolved. Carbonate and hydroxide precipitations are therefore mainly used for waste treatment.

Feel free to correct me.


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## Harold_V (Oct 14, 2014)

etack said:


> joekbit said:
> 
> 
> > I have Hokes book and I am reading it, as for my ignorance, your right, but is it really appropriate to make such statements. My thought NO. In all my digging and it has been extensive, I have never found a definitive answer/ SMB is specific to precipitating gold and will not drop other contaminates.
> ...


joekbit,
This board is not known for supporting less than factual information, and is quick to point out the error of one's way. To not do so would destroy any sense of credibility we have earned through our vigilance in not promoting misinformation. For that reason, you can expect a less than hoped for response when you post something that isn't true. We do not permit flaming of readers here, but we are quick to put to an end nonsense that is misleading. 

New readers are strongly advised to read, and not comment until they understand how the board functions, and to refrain from posting on processes that are not recognized, in particular, as in this case, where the information is totally misleading. If that was not the case, every nut case in the world would come here and try to explain to those of us who have experience in the world of refining how the processes should be carried out. That, of course, makes no sense, as the vast majority of those who come here have no clue, aside from having been exposed to presentations on the net, the bulk of which lack enough information to be helpful, and in some cases, are down right misleading. 

To help you understand, SMB is used by those who choose to precipitate with SO2, but do not have a bottle of the solution at their disposal. You must come to terms with the idea that it is the SO2 that causes the gold to precipitate. That is not open to discussion, as it would serve no practical purpose. 

The SO2 is not used in the fluid state, but, instead, the gasses are tapped from the bottle and introduced to the gold chloride solution via a glass tube, discharging at the bottom of the vessel. Properly introduced, none of the gas reaches the surface, as it is readily absorbed. 

Harold


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## solar_plasma (Oct 14, 2014)

solar_plasma said:


> Maybe the confusion comes from the fact, that SMB will form sodium hydrogensulfite in water and all alkali sulfite compounds will form the same SO2 with HCl. The question should have been, if the OP can use sodium hydrogensulfite instead of SMB,because SMB will give sodium hydrogensulfite in water anyway.
> 
> Na2S2O5 + H2O -> 2 NaHSO3
> 
> ...



For the completeness and inspired by Harold's post, I'd like to add, that even sulfites and hydrogensulfites are reductants, those equations are fine to calculate the stoichiometry, but practically it is the SO2 itself, which is the active reductant, because even in aqua almost all SO2 is dissolved, but not reacted to H2SO3. Further, practice shows, excess HCl is needed when using SMB to precipitate elemental gold. Also dry SO2 is able to reduce finely devided PbO2 to PbSO4. As an interesting side note, SO2 can also work as an oxidizer with strong reductants like SnCl2. In this case it gets reduced to H2S. One more reason for undesirable effects of tin(II) in solution (false positive stannous test with excess SO2 or maybe under circumstances precipitation of contaminants from gold solutions).

Mechanically it is even more complicated: SO2 (as a Lewis acid) will often build a compound with the oxidizing agent (as a Lewis base) and lead the last one to a lower oxidation state by adding electrons. (look also Hollemann/Wiberg, Inorganic chemistry, Chapters 2.4.1 and 2.5.2 about SO2 and H2SO3)

Please, tell me, if my broken English can be understood, otherwise I should refrain from trying to explain those more complicated subjects. In fact I learn a lot by doing so, to explain something in English as much as reflecting over, what I believe to have understood.


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## kurtak (Oct 14, 2014)

joekbit said:


> As far as the comments about me reading, well I am new to the forum and just now getting a very basic idea on how and where to find questions that were already asked. Such as mine.



Correct - you are NEW to the forum - & what you will find here is that this forum is like no other on the internet :!: --- Here you will find that the active members are in fact accomplished refiners --- meaning they have spent a "great" deal of time reading, studying, researching & applying that which was learned from the reading, studying, researching to have earned the right to call them selves refiners & thereby have also "earned" the right to be a part of this forum

You - just like the rest of us - must also earn this right - & that is done by "first" doing the "required" reading, studying, researching --- you wont get away with simply saying you have - because what you post will make it clearly evident to us as to whether you really have or have not

Example - you said - "I started with hydrochloric and peroxide for the initial burn" --- we do not use acids (with or with out an oxidizer added) to "burn" anything - we use them as solvents to "dissolve" &/or "leach"

Making comments like this (& other things you have said so far) is why Eric (eteck) said --- "If you did this your ignorance on this subject is showing" --- I am quit sure that Eric was not calling you an ignorant person --- rather he was simply pointing out to you that when it comes to the subject of refining you are ignorant about this subject & have "a lot" to learn

If this is something you really want to learn - then you have come to the right place - there is no better place anywhere in the world to learn about the art of refining then right here --- & that is the point --- you have to start by FIRST learning - that means you have start by first reading - & not just reading but rather studying it - which means you have to put the time in doing your own research

Then - once you get a grip on the terminology used & the how, what, why & when of things done - then you can start asking questions that make sense so we can give answers that also make sense

Start by first reading Hokes book (its a free down load here on the forum) & read it until you really understand what she is saying - her book will give you the "basics" of what you need to know & understand about refining

Then spend time searching & reading on this forum (2 to 4 hours a day for 6 to 8 weeks) this will give you a better understanding of the what, how, why & when we as refiners do what we do to call our selves refiners & be a part of this great forum --- it will also give you an understanding as to why we do not put up with "want to be" refiners that think they already know it all

Welcome to the forum - we are all very happy to help those that really want to learn about this - but it FIRST requires that you show enough real interest to do the required "home work" to learn & get on the same page as us so we can actually talk shop when we talk

Kurt


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## kurtak (Oct 14, 2014)

solar

I gotta say I really enjoy reading what you post & you say it very well in English 8) 

Kurt


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## rickbb (Oct 14, 2014)

kurtak said:


> solar
> 
> I gotta say I really enjoy reading what you post & you say it very well in English 8)
> 
> Kurt



Me too, I just wish I understood more of it.


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## solar_plasma (Oct 14, 2014)

rickbb said:


> kurtak said:
> 
> 
> > solar
> ...



My fault. I should elaborate my explanations more deeply, instead of believing everybody loves reading chemistry school books all the time.

When I am reading something that is beyond my capability of understanding, for example when the chemists, physicists and metallurgists are in their favorite element, I pick up some terms I don't know and search for them in wiki or other sources. Each time I come back to that thread, I understand a little more.


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## kurtak (Oct 14, 2014)

solar_plasma said:


> When I am reading something that is beyond my capability of understanding, for example when the chemists, physicists and metallurgists are in their favorite element, I pick up some terms I don't know and search for them in wiki or other sources. Each time I come back to that thread, I understand a little more.



And you do this to me often :!: :mrgreen: 

Kurt


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## joekbit (Oct 14, 2014)

kurtak said:


> joekbit said:
> 
> 
> > As far as the comments about me reading, well I am new to the forum and just now getting a very basic idea on how and where to find questions that were already asked. Such as mine.
> ...




Kurt, and others as well
Yes this is something I am very interested in for a number of reasons. I'm disabled and need something to do, something I can learn from and enjoy. This seems to be both with the potential to earn a little extra money while doing it. I did do an introductory post in the appropriate location. 

My apologies for taking statements that others have made incorrectly. One of the very first things I looked at before registering on the forum was the posting dates and how long the users have been members. Very impressive, so I joined. I will refrain from using terms such as "burn" unless I actually burn or incinerate. Hokes book is great, very informative. SO2 is spoken of on page 57.

All this being said, I believe we could call this a solved question, or answered question.


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## jungle_Dave (Jan 3, 2015)

Jokebit,

In sciences we deal with having a great idea and then immediately criticizing it either by ourselves or by our peers.
This is actually a really good thing . You should never take it personally. I did when I started my studies but it passes quickly. 
I got into this area of interest due to a back injury that left me bed ridden for the better part of 2 years. Reading, reading again, misunderstanding what I read is all part of the fun and has kept me relatively sane through the whole process.
I hope that the same can be true for you too.

Sodium metabisulfite (SMB) has many many uses both in organic/inorganic chemistry and industrial applications.

The cheapest source I have here is at the pool product store probably the same where you are. BTW also a good place to pick up hydrochloric acid if you are in the US or EU, I have to make my own HCL and nitric acid here.


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## joekbit (Jan 4, 2015)

Well I think I have grown a bit since I first asked this question


jungle_Dave said:


> Jokebit,
> 
> In sciences we deal with having a great idea and then immediately criticizing it either by ourselves or by our peers.
> This is actually a really good thing . You should never take it personally. I did when I started my studies but it passes quickly.
> ...



You are so right. I have seen statements about reinventing the wheel in many places on this forum. This goes to the (great idea) you mentioned. The truth is we should always try to reinvent the wheel. that's how we as a species have made it to where we are today. I look at it this way. a wheel is a wheel, but what its made of makes all the difference as to what it can accomplish. The historical fact is that all the minds we consider to have been great men (people) from the past were once ridiculed some even condemned. 
edited
In short there is always a better way if we dare to try and find it.


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## Geo (Jan 4, 2015)

Experimenting is good. Here on the forum, we encourage everyone to experiment and find what works for them, safely. When people come to the forum with a concept and unproven theories looking to find acceptance that what they envision will work, that's where the problems start. If someone has preconceived notions about what is right and wrong, it is easy to see. Every attempt to better educate is met with angst and hostility. That's what we try to avoid and sometimes it can be quite harsh. If a new member is putting themselves or their family at risk, we can't just say 'your gonna poke your eye out kid" and let it stay at that. Anything "new" (unless it's something nuclear) has most likely already been tried and proven. Anything that the normal refiner can obtain has been used for thousands of years. Yep, even that. Aside from modern glassware, there's nothing new about refining. It's a proven fact that the Egyptians was electroplating objects with gold nearly 5000 years ago. I don't know why they would want to but it just goes to reason that they could strip gold just as well. Fire assaying is one of the earliest forms of refining and is still the standard for quantitative analysis today. Necessity really is the mother of invention and we have many great and wonderful methods to do what we do. I feel the attitude is more of an air of a person should learn the tried and true methods before they decide to start tinkering with the unknown. Just my opinion.


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## joekbit (Jan 5, 2015)

well said Geo


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## Harold_V (Jan 5, 2015)

joekbit said:


> The truth is we should always try to reinvent the wheel.


Depends, doesn't it?
What is your objective?

Mine was to own pure gold when it was illegal to do so. To that end, I followed procedures that were known to work. For that, I was rewarded with success, and the founding of a refining business (unintentionally) which was sold when I retired at the relatively young age of 54. 

I could just as easily thought myself clever and spent the same amount of time trying to improve on the wheel, which was, for all practical purposes, sufficiently round as it was. YMMV.



> great men (people) from the past were once ridiculed some even condemned. Einstein was placed in a mental institution.



Cites, please. Quite frankly, I don't believe it, nor have I been able to uncover anything that would lead me to believe that to be true (I am making reference to your comment about Einstein being institutionalized). I consider that an attempt to disseminate misinformation (not a good idea on this board). If you can not provide cites, please remove that statement from your post. If you do not, it will be removed, along with the balance of your comments. 

Harold


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## artart47 (Jan 5, 2015)

Hi Joe!
Welcome to the forum. You're on the way with what you've learned so far as is evident by the jar of foils. As you continue to study and gain experience you'll get better and better results and become more efficient. If you aquire components that you haven't yet prosessed, be sure to learn everything you can find before attempting to recover from them. Unfamiliar objects could contain hazerdous material that could cause safety and environmental problems. Cadmium, Beryllium, etc...
As our other members have told you already, you may have dropped more than just the gold and your powder may be in need of a second refining. Something that I did when I first started gold recovery was to store my recovered gold in a jar containing weak HCl and a spoonfull of the copper chloride solution I used to for recovery of foils. The solution will change color as it dissolves contaminents from the gold. 
Good luck!
artart47


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## necromancer (Jan 5, 2015)

can the OP or a mod fix the spelling error in the title (if worth while) for ease of searching.

thank you


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## joekbit (Jan 5, 2015)

artart47 said:


> Hi Joe!
> Welcome to the forum. You're on the way with what you've learned so far as is evident by the jar of foils. As you continue to study and gain experience you'll get better and better results and become more efficient. If you aquire components that you haven't yet prosessed, be sure to learn everything you can find before attempting to recover from them. Unfamiliar objects could contain hazerdous material that could cause safety and environmental problems. Cadmium, Beryllium, etc...
> As our other members have told you already, you may have dropped more than just the gold and your powder may be in need of a second refining. Something that I did when I first started gold recovery was to store my recovered gold in a jar containing weak HCl and a spoonfull of the copper chloride solution I used to for recovery of foils. The solution will change color as it dissolves contaminents from the gold.
> Good luck!
> artart47


Thanks
I do a lot of micro testing with any new materials. Hokes calls them acquaintance experiments. I take small amounts of the material and try the different solutions to see what will work best. As of today I have about 6 grams of wet powder, under general chat I posted "example of contamination". Interesting. Take a look if you have the time and make some comments.

edit to add link
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=21695


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