SMB or Baking Soda???

[joekbit]

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?

 

[etack]

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

 

[MarcoP]

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.

 

[mls26cwru]

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

 

[GotTheBug]

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.

 

[joekbit]

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.

 

[jeneje]

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

 

[MarcoP]

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.

 

[the iron dwarf]

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

 

[joekbit]

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.

 

[Geo]

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.

 

[joekbit]

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.

 

[etack]

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

 

[solar_plasma]

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.

 

[Harold_V]

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

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

 

[solar_plasma]

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.

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.

 

[kurtak]

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

 

[kurtak]

solar

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

Kurt

 

[rickbb]

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.

 

[solar_plasma]

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.

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.