# Went against my gut! Grrr...



## cnbarr (Jul 15, 2012)

Hi All,
I normally don't ask for help because I can usually find the answer on my own with the search function, but after a few days of searching I can't quite find what I'm looking for. With that being said, here is my issue, I have about five pounds of pins from backplane boards like this,




I processed them in 50/50 nitric in a stainless steel chaffing dish I received from glondor (first time I had a chance to use it, Thanks Mike worked great!). Anyway, after it had cooled I had a very prominent white precipitate which is virtually impossible to filter. But here is where I went against my gut, I was pulling all the pins with pliers, after three boards my hands were blister all to hell, (there is over 1600 pins per board) I had the bright idea to run the boards through my tile saw, (which I now immediately regret) since the pins were pressed in and not soldered. So I cut them as close as I could without touching the pins and through the section of board with pins into the nitric bath without paying attention to what material was under the solder mask. As you can see in the upper left corner of the first couple of pics, the silver layer under the solder mask, which I believe to be tin over copper, my first thought was silver but that didn't make sense in my head.


I now have over five liters of solution, that won't filter with foils in it, that I can't figure out what to do with. I have never dealt with this volume of solution before, every time time I encountered something like this I just dealt with the slow filtering and moved on with no issues.

Any input you guys can give me would be greatly appreciated.

Thank you,
Chris


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## butcher (Jul 15, 2012)

I would screen out what I could, I have a cheap plastic screen with a handle, I bought from the dollar store, the plastic holds up well to the acids, I put the screen into a plastic funnel and this funnels solution into a collection jar, after screening out the larger pieces, I would put a little wad of fiberglass insulation in the funnel (something like Laser Steve's Charmin plug, and filter out more of the finer stuff, then the liquid from this would go to my distilling rig (I may even add some gold plated pins to this with elemental copper that needed to be dissolved, this would give me some copper in the mix which would help drive off the nitric acid when distilled), a little sulfuric acid added, and I would distill off the nitric solution (which could then be reused), the results would end up copper sulfate, which the gold is not soluble in, and I could separate gold from, the copper sulfate solution can also be reused.


http://goldrefiningforum.com/phpBB3/viewtopic.php?f=38&t=6199&hilit=killing+two+birds+one+rock


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## NobleMetalWorks (Jul 15, 2012)

It's hard to tell what you might have in solution. It could be a lot of things. There may be some polymers, and the white may be silver nitrate. It could also be other things.

The silver nitrate will precipitate when your solution cools down. I feel that the white precipitant is Silver Nitrate, all you really have to do is put heat to the solution so that the silver nitrate dissolves back into solution, then filter it right away when the solution is warm, before the silver nitrate precipitates again.

After you figure out what is going on and how you resolved it, I would be interested to know what the problem was, and how you fixed it.

Scott


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## ericrm (Jul 15, 2012)

i dont know how much help this is gonna be..................... so do not do anything until you get a real answer ,not just my guess..........................

from yahoo answer:
What is the word equation for the chemical reaction of tin metal and nitric acid?
Tin metal and nitric acid...produtcs are a solid, a tin oxide and a brown gas, nitrogen oxide

Gervald F Gervald F
A Top Contributor is someone who is knowledgeable in a particular category.
Best Answer - Chosen by Asker
Tin + nitric acid ----> tin(II) nitrate + hydrogen

followed by

Tin(II) nitrate -----> tin(II) oxide + nitrogen dioxide + oxygen


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## philddreamer (Jul 15, 2012)

Eric, wether it's right or wrong, that's what I do. When I get a mix of old material that contains gold & solder, I run the material thru 50/50 nitric. The white gunk forms. After no more reaction, I let the solution settle overnite. I decant the solution, rinse the material with hot water & proceed to dissolve in HCl/Cl. Then proceed as usual.

Phil


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## Palladium (Jul 15, 2012)

I think i would put it in something taller than wider and let settle for a day. Take a piece of hose and draw off as much solution as i could. Wash with water, let settle, decant, then put the residue in a pyroceram dish and evaporate slowly until dry. Then incentrate in a pyroceram dish. Pre wash with hcl to remove any tin, copper, or oxides and process with hcl/cl.


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## ericrm (Jul 15, 2012)

philddreamer said:


> Eric, wether it's right or wrong, that's what I do. When I get a mix of old material that contains gold & solder, I run the material thru 50/50 nitric. The white gunk forms. After no more reaction, I let the solution settle overnite. I decant the solution, rinse the material with hot water & proceed to dissolve in HCl/Cl. Then proceed as usual.
> 
> Phil


i have never tryed it myself that why i was very caucious in my answer. im realy happy to read that it work for you and that i will be able to use it myself. thank you


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## Geo (Jul 16, 2012)

dealing with stannic acid is a pain no matter how you deal with it. if you incinerate it, it will lose an oxygen atom and turn back into elemental tin which then can be removed with hcl bath or you can dissolve the gold out of the material and spend time filtering solutions. in my opinion, if you dont remove the tin first, it will show up later.when you dissolve with hcl/Cl and let the solution sit undisturbed, does any white precipitate form? the tin will carry over and you may have to refine more than twice to clean it up.


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## cnbarr (Jul 16, 2012)

Thank you all for the replies, 



butcher said:


> I would screen out what I could, I have a cheap plastic screen with a handle, I bought from the dollar store, the plastic holds up well to the acids, I put the screen into a plastic funnel and this funnels solution into a collection jar, after screening out the larger pieces, I would put a little wad of fiberglass insulation in the funnel (something like Laser Steve's Charmin plug, and filter out more of the finer stuff,



Butcher, I always use fiberglass to filter out the finer stuff (I started using fiberglass after reading one of your posts about 7 months ago), but this solution clogs it instantly. I like plastic screen idea, I'll give that a try.



SBrown said:


> It's hard to tell what you might have in solution. It could be a lot of things. There may be some polymers, and the white may be silver nitrate. It could also be other things.
> 
> The silver nitrate will precipitate when your solution cools down. I feel that the white precipitant is Silver Nitrate, all you really have to do is put heat to the solution so that the silver nitrate dissolves back into solution, then filter it right away when the solution is warm, before the silver nitrate precipitates again.
> 
> ...



Scott, I have tried heating it and it doesn't change anything. I don't feel it is silver of any form in the solution, the precipitant is a very very fine off white powder that settles quite slowly, i believe to be tin. I pulled out a couple dip samples just to be sure and tested one with salt and one with Hcl, there was no reaction in either.

Geo, Palladium, ericrm, Phil, I will try a combination of your responses and transfer everything into three large beakers and try to get everything to settle and filter out, and see what might work best. But, I may have to agree with Palladium and Geo that incineration may be the best route due do the amount of solids I have. The hard part is getting everything to settle and filter so I can proceed forward.

Thank you all again for the suggestions, I will report back later when I have some results.

Chris


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## cnbarr (Jul 16, 2012)

Geo said:


> dealing with stannic acid is a pain no matter how you deal with it. if you incinerate it, it will lose an oxygen atom and turn back into elemental tin which then can be removed with hcl bath or you can dissolve the gold out of the material and spend time filtering solutions. in my opinion, if you dont remove the tin first, it will show up later.*when you dissolve with hcl/Cl and let the solution sit undisturbed, does any white precipitate form?* the tin will carry over and you may have to refine more than twice to clean it up.



Sorry Geo, I missed you question in there. I haven't been able to decant the nitric and get to the foils and solids yet, so I have not made it that far just yet.


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## glondor (Jul 16, 2012)

Hey Cnbarr. It's a small world. I am doing the exact same thing right now for a client from the forum. I had several large boards with press fit pins. They were wire wrapped on the back side so I had to pull them all by hand. About 12 thousand of them. 5 1/2 pounds. I used shop towel and electrical tape to mitigate the blisters. Made little finger jackets for the right places. Have nice hard callouses now. 

Normally i would have soaked the pins in HCL to get rid of the tin but there seems to be a shortage of HCL in the local stores. It's swimming pool weather for sure and all I could find locally was 2 one liter bottles. Not enough. Sooooo I did what you did. I have done material with tin before so here is what I am doing. 

I have a small stainless steel coffee filter that I set up as a sump in the pan. I tilt the pan a bit to drain the liquid to one end and draw from the sump with a little peristaltic pump i have. It is slow but it keeps the foils in the pan. I pump it to a paper coffee filter set up just to catch any fines for inspection, I will next wash the foils in the pan and let the lil pump do its thing again.

Next I will filter the foils thru the stainless coffee filter like so... Spoon the foils and dreck into the filter, not too much....and agitate the filter in a clean pan of water. The white dreck washes out and the foils remain. 

Take the coffee filter and tip it sideways in a clean bucket of water, filling it up. Invert it and pull out quickly. The suction will pull out all the foils. 

Reload the filter and ....

Run your solution (wash water) back through the coffee filter to catch any foils that may have got on the out side of the filter when you dumped to your "clean wash"

With practice you can get the foils fairly clean and it goes pretty fast. Incinerate and wash with HCL. Proceed as usual.

You can dry and incinerate the tin for hcl wash if you believe there is gold powder trapped in the tin. If you see dark bands or layers in the tin, It may be gold so proceed accordingly. Photos below for reference.


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## cnbarr (Jul 17, 2012)

Hey glondor,
That looks like it does trick nicely, your ingenuity always amazes me, I'll print this one off for future reference. I already poured off the pan into separate 4000ml beakers to let them settle out, I do find it easier when you can see into a solution.

What still perplexes me is where the tin came from? The pins came from Ericcson backplane boards, some of mine were wire wrapped as well but I removed all the wires, there was not an ounce of solder on any of them, they were all pressed in. The only thing I can figure is the silver colored layer under the solder mask was a tin/nickle plating, which was my bad for trying to take a short cut and cut the sections of board away that housed the pins, when I knew I shouldn't have I knew I should have just pulled all the pins.

But that raises another question, where you ran all pins with no pieces of board, where did the tin come from in your batch? Unless the pins themselves have tin in them?


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## philddreamer (Jul 17, 2012)

I too wonder where the tin sometimes comes from! :roll: These pins are pressed, too!
I bought a couple boards to run a test. there's over 500# available. The seller told me that there are 2 other persons that have bought the same material & both said they are recovering 1g of gold & 1g of Pd per pound of pins. Now, there's another, where is the Pd coming from? Are some pins also Pd plated? I let the solution settle overnite, will do a stannous test for Pd. Then I'll add fresh 50/50 in order to finish dissolution. I use nitric when running test to speed things. 
Question, can Pd be de-plated in the sulphuric cell?

Thanks!
Phil


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## goldsilverpro (Jul 17, 2012)

Yes, the original patent on the sulfuric stripper included Pd. Getting it out could be a problem though.


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## maynman1751 (Jul 17, 2012)

Phil, what is the silver colored material on the bottom half of the pins (second pic)? Are they possibly tin plated? It appears the holes they plug into are tin (solder) sockets.


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## philddreamer (Jul 17, 2012)

Thank you, Chris!
That been the case, I hope I can drop the gold & save the Pd solution for the stock pot or, just set aside for further processing later.

May, That silver material is what I was told contains Pd. I don't know about tin, because they are not soldered, they are pressed into the sockets. I do know I have a white sediment at the botom of the solution that does resemble tin or Ag-Cl. As I continue the process today I hope to find out. I'll keep you all posted.

Thanks!
Phil


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## qst42know (Jul 17, 2012)

glondor 

Are you aware you can get heavy metal poisoning through your skin?

Many metal salts can cause permanent life altering health effects.

Please put some gloves on friend.


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## Geo (Jul 17, 2012)

the tin comes from the pins. if the pins are springy, they could be bronze. bronze is copper and tin. if when you digest these pins in nitric acid or AP, you will have tin in your solution.


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## glondor (Jul 17, 2012)

Thanks for the warning Quest. I just took the gloves off to take the pictures. Did a good wash up afterward and back to the gloves.


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## cnbarr (Jul 17, 2012)

Geo said:


> the tin comes from the pins. if the pins are springy, they could be bronze. bronze is copper and tin. if when you digest these pins in nitric acid or AP, you will have tin in your solution.



The pins are a bit springy, I didn't think they made pins from bronze, but that makes a lot more sense at this point. Thanks geo!

Hey glondor, I was looking at the pictures of the shape of some of the foils from your pins and looks like we're processing very similar if not the same type of pins? After reading Phil's comment on Pd, I tested mine as soon as I got home from work this evening and got a positive stannous and a positive DMG test for Pd. I guess just something to look into. 

Just an update, I was able to decant and wash the solids once I transferred the solution to beakers (very slow to settle by the way, about 6-8hrs between each decant). I am know in the process of drying so I can proceed forward with incineration. If there was less tin I probably would have gone straight to AR or Hcl/Cl, but the tin is about 1 1/2in thick in the bottom of a 4000ml beaker, and I have fine particles of foils locked up in it. So I think incineration then an Hcl wash is going to be the most appropriate route at this point, If this sounds wrong or there is a better method for this please correct me in my intent to do so? 

Thanks,
Chris


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## qst42know (Jul 17, 2012)

See the Olin alloy at the end of this page. Quite a blend. 

http://en.wikipedia.org/wiki/Phosphor_bronze


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## glondor (Jul 17, 2012)

Hey Chris....We need more schooling.  Here's why. I follow the teachings of Harold on this tin thing. If I recall correctly, Harold has posted that the incineration and HCL wash was not a cure for tin. It just made it much more filterable. ( If I am misquoting you on this Harold Please correct me). This is my findings using this method. 

After incineration and the HCL wash, the solution always tests positive for gold. Everytime I have done it any way. This time I looked at what Geo posted about the tin becoming elemental with incineration so I doubled the incineration time to see if I could effect a change of the tin chloride to metal. Torched it with a mapp gas torch for 20 minutes, Even concentrated on selected areas for an extended time to see if I could make it elemental. Did not happen. Crushed the skin of material to a powder and tried to torch again but it was too fine and I was going to loose some to blowing out with even the lowest flame I had. 

Questions....Torching to red hot and keeping it there for 20 minutes and I still get A/R during the HCL wash. How can this happen? Shouldn't the nitrates be long gone? 

Does it require more heat or a longer duration to knock off the extra oxygen molecule? 

Thats all I can think of for the moment.


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## Geo (Jul 17, 2012)

this is from wiki.

When heated in an inert atmosphere initially disproportionation occurs giving Sn metal and Sn3O4 which further reacts to give SnO2 and Sn metal.[3]
4SnO → Sn3O4 + Sn
Sn3O4 → 2SnO2 + Sn

if you are heating it in an oxygen rich flame, it may not work. in theory, your trying to remove an oxygen atom, so you may have to use a retort or at least deprive it of oxygen.


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## ericrm (Jul 17, 2012)

information remove due to eroneous content :lol:


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## ericrm (Jul 17, 2012)

geo are you sure it is 4 SnO and not Sno2? or am i lost and i dont know it?


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## Geo (Jul 17, 2012)

http://en.wikipedia.org/wiki/Tin(II)_oxide

i cant make it link the whole address.


Tin(II) oxide
From Wikipedia, the free encyclopedia
Tin(II) oxide



IUPAC name[hide]
Tin(II) oxide
Other names[hide]
Stannous oxide, tin monoxide
Identifiers
CAS number	21651-19-4 
PubChem	88989
EC number	244-499-5
RTECS number	XQ3700000
Jmol-3D images	Image 1
SMILES
[show]
InChI
[show]
Properties
Molecular formula	SnO
Molar mass	134.709 g/mol
Appearance	black or red powder when anhydrous, white when hydrated
Density	6.45 g/cm3
Melting point	
1080 °C (decomp)[1]
Solubility in water	insoluble
Structure
Crystal structure	tetragonal
Thermochemistry
Std enthalpy of
formation ΔfHo298	−285 kJ·mol−1[2]
Standard molar
entropy So298	56 J·mol−1·K−1[2]
Hazards
MSDS	ICSC 0956
EU Index	Not listed
Flash point	Non-flammable
Related compounds
Other anions	Tin sulfide
Tin selenide
Tin telluride
Other cations	Carbon monoxide
Silicon monoxide
Germanium(II) oxide
Lead(II) oxide
Related tin oxides	Tin dioxide
(verify) (what is: /?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references
Tin(II) oxide (stannous oxide) is a compound of tin and oxygen where tin has the oxidation state of +2. There are two forms, a stable blue-black form and a metastable red form.
Contents [hide] 
1 Preparation and reactions
2 Structure
3 Uses
4 References
[edit]Preparation and reactions



Tin(II) oxide burning
Blue-black SnO can be prepared by heating the tin(II) oxide hydrate, SnO.xH2O (x<1) precipitated when a tin(II) salt is reacted with an alkali hydroxide such as NaOH.[3] Metastable, red SnO can be prepared by gentle heating of the precipitate produced by the action of aqueous ammonia on a tin(II) salt.[3] SnO may be prepared as a pure substance in the laboratory, by controlled heating of tin(II) oxalate (stannous oxalate) in the absence of air.[4]
SnC2O4 → SnO + CO2 + CO
Tin(II) oxide burns in air with a dim green flame to form SnO2.[3]
2 SnO + O2 → 2 SnO2
When heated in an inert atmosphere initially disproportionation occurs giving Sn metal and Sn3O4 which further reacts to give SnO2 and Sn metal.[3]
4SnO → Sn3O4 + Sn
Sn3O4 → 2SnO2 + Sn
SnO is amphoteric, dissolving in strong acid to give tin(II) salts and in strong base to give stannites containing Sn(OH)3−.[3] It also dissolves in strong acid solutions to give the ionic complexes Sn(OH2)32+ and Sn(OH)(OH2)2+, and in less acid solutions to give Sn3(OH)42+.[3] Note that anhydrous stannites, e.g. K2Sn2O3, K2SnO2 are also known.[5][6][7] SnO is a reducing agent and this appears to its role in the manufacture of so-called "copper ruby glass".[8]
[edit]Structure

Black, α-SnO adopts the tetragonal PbO layer structure containing four coordinate square pyramidal tin atoms.[9] This form is found in nature as the rare mineral romarchite.[10] The asymmetry is usually simply ascribed to a sterically active lone pair; however, electron density calculations show that the asymmetry is caused by an antibonding interaction of the Sn(5s) and the O(2p) orbitals.[11]
Non-stoichiometry has been observed in SnO.[12]
The electronic band gap has been measured between 2.5eV and 3eV.[13]
[edit]Uses

The dominant use of stannous oxide is as a precursor in manufacturing of other, typically divalent, tin compounds or salts. Stannous oxide may also be employed as a reducing agent and in the creation of ruby glass. It has a minor use as an esterification catalyst.
Cerium(III) oxide in ceramic form, together with Tin(II) oxide (SnO) is used for illumination with UV light.[14]
[edit]References

^ Tin and Inorganic Tin Compounds: Concise International Chemical Assessment Document 65, (2005), World Health Organization
^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed.. Houghton Mifflin Company. p. A23. ISBN 0-618-94690-X.
^ a b c d e f Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5
^ Satya Prakash (2000),Advanced Inorganic Chemistry: V. 1, S. Chand, ISBN 81-219-0263-0
^ The First Oxostannate(II): K2Sn2O3, M Braun, R. Hoppe, Angewandte Chemie International Edition in English, 17, 6, 449 - 450, doi:10.1002/anie.197804491
^ Über Oxostannate(II). III. K2Sn2O3, Rb2Sn2O3 und Cs2Sn2O3 - ein Vergleich, R. M. Braun, R. Hoppe, Zeitschrift für anorganische und allgemeine Chemie, 485, 1, 15 - 22, doi:10.1002/zaac.19824850103
^ R M Braun R Hoppe Z. Naturforsch. (1982), 37B, 688-694
^ Colour development in copper ruby alkali silicate glasses. Part I: The impact of tin oxide, time and temperature ,Bring, T., Jonson, B., Kloo, L. Rosdahl, J , Wallenberg, R., Glass Technology, Eur. J. Glass Science & Technology, Part A, 48 , 2 , 101-108 ( 2007)
^ Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
^ On type romarchite and hydroromarchite from Boundary Falls, Ontario, and notes on other occurrences, Robert A. Ramik,, Robert M. Organ, Joseph A. Mandarino, The Canadian Mineralogist; June 2003; v. 41; no. 3;. 649-657; doi:10.2113/gscanmin.41.3.649
^ Electronic structures of rocksalt, litharge, and herzenbergite SnO by density functional theory, A. Walsh, G.W. Watson, Phys. Rev. B 70, 235114 (2004)doi:10.1103/PhysRevB.70.235114
^ Cation nonstoichiometry in tin-monoxide-phase Sn1-δO with tweed microstructure, Moreno, M. S.; Varela, A.; Otero-Díaz, L. C., Physical Review B (Condensed Matter),56, 9,(1997), 5186-5192, doi:10.1103/PhysRevB.56.5186
^ Science and Technology of Chemiresistor Gas Sensors By Dinesh K. Aswal, Shiv K. Gupta (2006), Nova Publishers, ISBN 1-60021-514-9
^ "Spectral Studies of New Luminophors for Dental Porcelain". Jdr.iadrjournals.org. DOI:10.1177/00220345800590090801. Retrieved 2012-04-05.


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## ericrm (Jul 17, 2012)

sorry ,my mistake


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## cnbarr (Jul 17, 2012)

Geo, that made my brain melt, I will have to read it a couple more times!!!


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## ericrm (Jul 17, 2012)

Geo said:


> When heated in an inert atmosphere initially disproportionation occurs giving Sn metal and Sn3O4 which further reacts to give SnO2 and Sn metal.[3]
> 4SnO → Sn3O4 + Sn
> Sn3O4 → 2SnO2 + Sn
> SnO is amphoteric, dissolving in strong acid to give tin(II) salts and in strong base to give stannites containing Sn(OH)3−.[3] It also dissolves in strong acid solutions to give the ionic complexes Sn(OH2)32+ and Sn(OH)(OH2)2+, and in less acid solutions to give Sn3(OH)42+.[3] Note that anhydrous stannites, e.g. K2Sn2O3, K2SnO2 are also known.[5][6][7] SnO is a reducing agent and this appears to its role in the manufacture of so-called "copper ruby glass".[8]
> [edit]Structure


geo incinerating as we do it is not made in an inert atmosphere ... also SnO is supose to be soluble in strong acid and strong base
im totally lost...............


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## Geo (Jul 18, 2012)

inert is a simple way of saying oxygen free. when we incinerate things of organic nature or carbon based, we want oxygen to reach the material to convert the carbon to carbon dioxide.when you want to remove an atom of oxygen the opposite is true. if you heat tin oxide to its boiling point, it will release the extra oxygen atom.what i used as a retort was a 6" threaded steel nipple with a cap on one end and a reducing cap on the other so i could reduce the size down to a manageable size and connect a copper tube to it with a compression fitting.any closed container that can withstand the heat will work, of coarse it has to have a vent so the gases can escape.

also, metastannic acid is a form of tin oxide. when you dissolve tin in nitric acid, metastannic acid is what you get. if i knew of an acid that would break it down, i would be using it.


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## Harold_V (Jul 18, 2012)

glondor said:


> Hey Chris....We need more schooling.  Here's why. I follow the teachings of Harold on this tin thing. If I recall correctly, Harold has posted that the incineration and HCL wash was not a cure for tin. It just made it much more filterable. ( If I am misquoting you on this Harold Please correct me). This is my findings using this method.


Not being a chemist, I don't know that the tin has been removed. All I know is incineration, followed by a wash in hot HCl resulted in easier filtration, which was my goal. I do not recall even one instance where that wasn't a cure for bad filtration, so it is definitely a viable way to improve one's process.

Harold


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## cnbarr (Jul 18, 2012)

glondor said:


> Hey Chris....We need more schooling.  Here's why. I follow the teachings of Harold on this tin thing. If I recall correctly, Harold has posted that the incineration and HCL wash was not a cure for tin. It just made it much more filterable. ( If I am misquoting you on this Harold Please correct me). This is my findings using this method.
> 
> *After incineration and the HCL wash, the solution always tests positive for gold. Everytime I have done it any way.* This time I looked at what Geo posted about the tin becoming elemental with incineration so I doubled the incineration time to see if I could effect a change of the tin chloride to metal. Torched it with a mapp gas torch for 20 minutes, Even concentrated on selected areas for an extended time to see if I could make it elemental. Did not happen. Crushed the skin of material to a powder and tried to torch again but it was too fine and I was going to loose some to blowing out with even the lowest flame I had.
> 
> ...



The same thing has happened to me as well testing positive for gold after incineration. 

So if my understanding is correct, from what Geo has posted above, is the conversion of tin chloride to elemental tin, through incineration has to be done in a low or no oxygen environment? 

But as glondor said, How is the Hcl wash, after incineration still creating a weak AR? Unless a mapp gas torch doesn't keep it consistently hot enough too burn off the nitrates?


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## Palladium (Jul 18, 2012)

I'm with Harold on this one. I don't know how things work chemistry wise sometimes i just know they work. I've often wondered if it acts as a catalysis of some sort. I know that when you add one metal to another it changes the properties of both metals. Like when you add one metal to another and it lowers the melting point of both metals. Another example is when you add one metal to another so you can get it dissolve into solution like pure palladium or platinum that don't want to dissolve sometimes. Don't know what's happening i just know it happens! Read my thread called " I got robbed but i got pictures " to see what kind of lesson i had to learn the hard way and how expensive that lesson can be.


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## Geo (Jul 18, 2012)

cnbarr said:


> So if my understanding is correct, from what Geo has posted above, is the conversion of tin chloride to elemental tin, through incineration has to be done in a low or no oxygen environment?



actually, i was talking about tin oxide. tin chloride can be dealt with in a different way. when tin(II)chloride is formed in AP for instance, and is mixed with your foils, you can incinerate in the normal fashion and then hcl will dissolve it. tin(II)chloride is insoluble in hcl but when you incinerate it, it converts it to tin(I)chloride which is readily soluble in hcl.


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## cnbarr (Jul 18, 2012)

Palladium, I read your got robbed post it was a good read. I actually just dealt with something similar, I was refining the cemented values form my stock pot and had the same thing happen (minus the tin), but it would only dissolve a small portion of values in between incineration's, I ended up taking the last 1/4cup of powder to a friends house and had him smelt it with a flux mixture in his kiln. Then ran the resulting 78g nugget through my junk silver cell and collected the slimes for later processing.



Geo said:


> actually, i was talking about tin oxide. tin chloride can be dealt with in a different way. when tin(II)chloride is formed in AP for instance, and is mixed with your foils, you can incinerate in the normal fashion and then hcl will dissolve it. tin(II)chloride is insoluble in hcl but when you incinerate it, it converts it to tin(I)chloride which is readily soluble in hcl.



Geo, That makes more sense know, cause I didn't think you could reduce a chloride to an elemental. So just to double check, you can reduce tin oxide to elemental tin through incinerating in an inert (no oxygen) environment? And without the need of a flux mixture as well?


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## butcher (Jul 18, 2012)

I am not positive on all of the chemistry involved in the incineration process to deal with tin.

Here are some of my thoughts on it, tin metal is a base metal, above hydrogen in the reactivity series of metals, the metal I believe would oxidize fairly easily with red heat especially in air or with oxygen, I think carbon in a melt (not an incineration), may reduce tin to metal because it is below carbon in the reactivity series of metals this is if enough carbon was used in a melt and the furnace was deprived of oxygen.

so I do not think we reduce tin to metal in incineration but we do oxidize it making it easier to dissolve in the boiling hot concentrated HCl (which forms SnCL2 in solution, which is just soluble enough to filter), if we dilute this wash with too much water I believe we form Sn(OH)2 in solution and again the solution becomes a bear to filter, or if we dilute with a peroxide we form hydroxides and oxides of tin in solution (same problem with filtering).

Lowering the acidity of tin chloride SnCl2 (stannous chloride in solution can also give us oxides or hydroxides of tin making the filtering problem worse.

I also believe the tin in solution is a good reagent for reducing other metals in solution to elemental metal, like reducing dissolved gold in solution to colloids of gold, or reducing copper in solution to copper metal, the tin seems to hold these reduced metals in solution not letting them precipitate, almost impossible to filter out of solution and the more metals in the mess the worse the problem, the more diluted or less acidic the worse the troubles in dealing with them.

Tin chloride will also reduce silver in solution or reduce some of the silver chloride powder in the bottom of your solution to metal silver, although normally you would not have much silver dissolved in a chloride solution unless it is highly acidic and concentrated (like aqua regia may hold some silver in solution), the silver can be reduced to metal (similar to how they made some types of mirrors).

Tin in the highly acidic and oxidizing environment of nitric acid becomes metastannic acid (acid tin oxide) H2SnO3, this forms a gelatinous solution impossible to filter as the tin acid oxide is not that soluble, but also it will not settle out of solution (and here again I believe reducing some other metals in solution),

Tin metal will dissolve in copper sulfate reducing the copper to metal powder making a water-soluble tin sulfate solution. 
CuSO4 (aq) + Sn (s) à Cu (s) + SnSO4 (aq)

Yes you can use copper sulfate to dissolve tin from your scrap (instead of using you new jug of HCl).

If you have volumes of nitric solution with fine gold floating in solution and it will not settle or filter (at least for what would seem like forever), you could try what I proposed earlier in this thread (adding a little copper and some sulfuric acid) and distill off the nitric acid from this mix and leaving the gold in a solution of copper sulfate (and water soluble tin sulfate) the gold foil will separate easily from the copper and tin sulfate solution, the nitric distilled of would be less in volume than the original nitric used but can be reused, you also form some copper sulfates to use for other projects like to dissolve tin from gold plated pins.

Of course there are several other ways to try and deal with tin in solution besides screening or filtering evaporating to powder and incineration, then HCl boil wash method.

However you look at it or choose to deal with it tin can be a major pain.

Although I do not understand all of the chemistry of tin, I do understand it is a monster to deal with and will steal your gold from you if you are not careful.

But then again tin chloride can also be very useful it allows us to see where our gold is at when used properly in the stannous chloride test.

How can this metal be an angel at times and a devil in others?


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## cnbarr (Jul 19, 2012)

Just an update, I dried and crushed all the solids, then incinerated for a good 30 minutes, then crushed again and screen out any garbage. Then washed in hot water for 15 minutes, let settle and decanted. Then went to a boiling Hcl wash, let settle and decanted while warm. At this point I realized I am dealing with more then tin chloride, after decanting the Hcl wash I gave two more water washes, and still had a fair amount of chloride powders in my beaker but it settled quite quickly. It's look and texture and how quickly it settle leads me to think it is silver chloride but I could be wrong, any thoughts on if it is silver chloride and where it might have came from???





So after washing I ran it through AR, let settle filtered and dropped gold with ferrous sulfate, this wasn't too difficult after incinerating. I don't have yield data yet, I still need to wash and refine one more time. If I get some positive yes's that my powders might be silver chloride, I'll convert it with NaOH and sugar, then run the resulting button through my silver cell to see if any gold got locked up in it. If this sounds like a bad idea, please tell me???

Thanks again,
Chris


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## Geo (Jul 19, 2012)

if you incinerated and hcl didnt dissolve it, chances are its silver chloride. take a small sample and add to it some ammonium hydroxide (household ammonia) and see if it dissolves.heat it to be sure. filter out any solids and then add to the solution enough hcl to make it acidic. any silver will precipitate out as silver chloride. dont breath the smoke that comes off as you add the hcl.

this way you will know if it is silver chloride or something else.


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## butcher (Jul 19, 2012)

White powders (metal chloride salts) what are they and how to seperate them? 

HCl will convert copper I chloride insoluble powders to a solution of copper II chloride (brown if lots of copper green if less copper), silver or lead is insoluble in HCl,

To dissolve lead add water and boil, then lower heat and keep solution hot but let powders settle before decanting, (silver chloride will take a little time to settle), the boiling hot water will dissolve lead chloride, leaving silver chloride insoluble, when the lead chloride solution cools the lead will precipitate back out of the water, 

Silver chloride when dilute will turn almost purple to black in the sunlight (it can be dissolved in ammonia but must not be dried because can form a thermal or shock sensitive compound, acidify the solution to precipitate the silver and make the solution safe),

Then there is salt NaCl normally more of a clear, salt of course is also water soluble. 

There are a couple of more metals that make insoluble chloride salts but these are the ones we will deal with most of the time.


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## cnbarr (Jul 19, 2012)

Okay Geo, I took your advise and a took a small 30ml sample of the unknown chlorides and added ammonium hydroxide to it and this is what happened instantaneously,


Then I added heat and a touch more ammonium hydroxide, I then let it cool a bit and filter out the solids, here is a picture of the solids,


Then I added Hcl to bring the solution back to acidic, Ph of 0.1,


after bring the solution back to acidic with Hcl, there was no precipitation of silver chloride,


So I believe we can rule out silver chloride, and lead chloride, unless it is tin chloride (but it didn't cause settling or filtering issues in my AR last night) I am absolutely befuddled as to what it is and I think it is locking up gold, cause I just washed my powders from what I precipitated last night, and I don't think I have more then 2g from 4 1/2+lbs of these pins. My estimation was a bit higher then that.

This round has definitely been more then a learning experience, thanks you all so much for a wealth of knowledge and more still yet to be gained!!!

Chris

Edit: I just realized my phone takes better pictures then my real camera!!! :shock: :shock: :shock:


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## Geo (Jul 19, 2012)

i wouldnt let that sludge dry out without acidifying. ammonia can make some nasty stuff when dried with dissolved metals.


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## cnbarr (Jul 19, 2012)

Well noted I'll wash it back into the beaker!


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## glondor (Jul 22, 2012)

I got just shy of 15 grams from the 5 pounds 6 ounces of pins. Tell us what is going on with yours Cnbarr. Maybe we can help. What do you have and what did you do last?


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## steyr223 (Jul 24, 2012)

Awesome stuff guys
I'm on the edge of my chair.... waiting! !
O wait I'll get the popcorn. :lol: 

Steyr223 rob


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## cnbarr (Jul 24, 2012)

Sorry for the slow update, I had a very busy weekend with my kids, but hey that's what it's about right!    

So the resulting button form the first drop with AR was just under -1.5g, a lot less then I estimated. After running the tests with ammonium, on the previous page in this thread, I washed everything real good, then dried and re-incinerated again, washed in hot Hcl (solution would turn a clear rusty orange with a negative stannous test) and water washes, then ran through AR, again with no success. During the AR process I would get positive stannous test, not a strong positive but still positive, in clean yellow solution, but by the time it had cooled down I would only get a faint purple stain with stannous and no purple stain at all by the time it was filtered and ready to drop. 

So this makes me think a few things, 1. something is cause the gold to cement out 2. the unknown chlorides are locking up the gold and not allowing them to dissolve, 3. I possibly vaporized the gold during incineration. or 4. an obscure combination of all of the above.

So after all that I dried, re-incinerated, and hit the books reading everything I could find on tin compounds. I found out a lot about tin, a couple of things I found in common with the chemistry books I read, it didn't matter how old or new, is none of them really discussed how to convert tin(II) and tin(4) compounds back to elemental tin (if it's even possible) and they all stated how difficult it is to work with tin compounds in a solution. 

So after I incinerated for the third time the remaining powder is now a light tan to off white in color, I washed it with water and ran a few test, all the proceeding tests were done with a small sample in a test tube. 
1. added a 3ml of ammonium hydroxide, mixed, then heated thoroughly. poured off solution in to clean test tube, then added hcl one drop at a time: no reaction
2. re-acidified the powders in test tube 1 with Hcl, heated, then tested with stannous: negative stannous test
3. still test tube 1, added 8 drops of Hcl and 2 drops of HNo3, heated, cooled, then tested with stannous: positive stannous test
4. took a fresh sample and added 8 drops of Hcl and 2 drops HNo3, heated, tested with stannous: positive stannous test

So at this point I figured the last incineration was all it needed, so I put it all back into AR, and got the same results as the second time I ran it through AR, it would test negative for gold by the time it was ready to filter. I thought maybe my stannous was getting a little weak, I tested it against my standard solution many times just to make sure.

Back to the test tubes I took a fresh clean sample,
1. added a 3ml of water and a pinch of NaOH, heated gently: no reaction and no color change

The way I understood when I was ready about tin compounds, is that most stannic compounds are readily soluble in a concentrated alkali solution, which in theroy is what we deal with when we introduce tin into nitric acid. This creates a stannic/metastannic acid, then through incineration of the residue then creates stannic oxide, which should be soluble in concentrated sodium hydroxide. I am really trying to make an effort to better understand these chemical compounds/processes, so please correct me if my understanding is wrong.

At this point I am completely stumped, and have run out of ideas, so any thoughts any one else has are more then welcomed???

I had one of the same boards left that the pins came from, so I pulled just over a 1/2lb of them and ran through nitric. I used glondor's SS coffee filter basket technique he described in this thread to recover the foils from the chlorides. It worked perfectly, thanks glondor, I recovered and processed 2.18g from 0.65lbs of pins. I did this just make sure I wasn't going crazy.

I'll stop rambling now, thanks in advance for any input,
Chris


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## Palladium (Jul 24, 2012)

Palladium said:


> Don't know what's happening i just know it happens! Read my thread called "* I got robbed but i got pictures " *to see what kind of lesson i had to learn the hard way and how expensive that lesson can be.



http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=11596&hilit=i+got+robbed


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## Geo (Jul 24, 2012)

there is an instance of getting a negative result when gold is present. if you are testing a solution with free oxidizer, it can redissolve the purple test color almost as fast as it appears. Harold pointed this out to me. watch the test carefully and see if it turns purple and instantly clears, like a flash of color. if not, there may not be any gold there.


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## maynman1751 (Jul 24, 2012)

Without going back through the whole post, have you tried cementing out the values?
Have you tried evaporating the solution down to a syrup and acidifying with strong H2SO4?


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## cnbarr (Jul 24, 2012)

Hey Geo, I've had the disappearing stannous stain before, I always try to watch for it when I feel there is an excess of oxidizers.

Palladium, I've read your thread what feels like a hundred times,I tried to follow the procedure you used and I can't see anything you've done that I haven't. I forgot to mention in my previous post that I have tried Hcl/Cl with no positive results.

Maynman, H2so4 is one of the few things I hadn't tried at this point, so I said what the. Heck and added a 100 MLS of H2So4 and a little heat, this is what the solution looks like now,


And this is after diluting and filtering,


The addition of sulfuric also reduced the amount of poewders by about half. I think I mayjust have to donate this one to science, and accept the fact that the gold is gone or just not in the powders anymore. Any experiments you guys have wanted to try let me know I'll give anything a shot at this point?
thanks,
Chris


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## maynman1751 (Jul 24, 2012)

It definitely looks colloidal.....doesn't it?!!!!!
Ask Butcher. He has some ideas on colloidal gold recovery.
Did you evaporate it down before adding the H2SO4?


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## qst42know (Jul 24, 2012)

There are a couple possibilities in this thread.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=12496&p=123991&hilit=colloidal#p123991

Was that concentrated sulfuric you added, and did you bring it to a boil?


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## cnbarr (Jul 24, 2012)

maynman1751 said:


> It definitely looks colloidal.....doesn't it?!!!!!
> Ask Butcher. He has some ideas on colloidal gold recovery.
> Did you evaporate it down before adding the H2SO4?



It does look colloidal and that was my first reaction, but here is there thing, I did not add the sulfuric to a solution. I have not been able to keep any gold in a solution, so I added the concentrated sulfuric acid to the solid powders. It instantly turned that purple color and reduced the powders by half as well as changed the powders color from a light tan to an off grey.



qst42know said:


> There are a couple possibilities in this thread.
> 
> http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=12496&p=123991&hilit=colloidal#p123991
> 
> Was that concentrated sulfuric you added, and did you bring it to a boil?



Yes it was concentrated sulfuric and I brought just short of a boil then backed off the heat and let it cool down. I also took a small sample in a test tube and added eight drops of Hcl and one drop of nitric. There was no reaction at first, so I added a little heat and it turned a nice crystal yellow and tested with stannous and got a negative. So I added a little ferrous sulfate to see what would happen, about 8-10 crystals of ferrous and a little dusty brown swirl would form above it and disappear. So I added more ferrous sulfate and it wouldn't produce the same swirl anymore, the solution in the test tube just turned orange. I am NOT all that confident the brown swirl was gold due to a negative stannous test, I know excess oxidizer may have redissolved it. So I added a prill of urea then ferrous and there was still no reaction. So I'm not sure what the reaction was in the test tube was or what the purple sulfuric solution is but I have set the "purple drink" aside for now just in case. And I still have a beaker with unknown powders and chlorides.

This situation is an anomaly wrapped in an enigma rolled in a conundrum, :shock: :shock: :shock: 

Chris


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## maynman1751 (Jul 24, 2012)

> This situation is an anomaly wrapped in an enigma rolled in a conundrum, :shock: :shock: :shock:
> 
> Chris


WOW! Far out man! I've been there! :mrgreen:


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## Palladium (Jul 24, 2012)

Got to love it! But hey, it's how we learn. I never did really figure mine out. I've still got the solids though in a container for further research in the future if i ever have that Ahhhh Haaaa moment from learning.


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## butcher (Jul 25, 2012)

I am a little lost of where your at with this, it does look like gold colloids, and if this was from adding H2SO4 to the white powders, here is my thinking, the solution looks very dilute and to be a large volume, (it also looks like some salts formed of sulfates or chlorides?) with possibly some gold in solution, but gold will not dissolve in H2SO4, and would not form colloids from adding the sulfuric acid to a powder that contained gold.

But if the powders contained chloride salts like NaCl (table salt) and you added H2SO4 you could make HCl gas in solution and if you had tin also in the powders You could have stannous chloride in solution, now if there was some gold in solution you could get the color of purple, 

I do not know this is what you have, but it does seem possible, 

You may try taking a reasonable size very small sample of this solution, and evaporate it down to a thick syrup, add a little H2SO4, and continue heating (this should drive off any HCl as gas if the solution contains it), it can also help to break the colloids (if this is what the color is from), you may need to repeat the evaporation and sulfuric additions (or you may see black powders form), take care, as the concentrated hot sulfuric is very dangerous (do not boil) do not have heat so high that it boils and splashes hot sulfuric on you and burns you, wear battery gloves and use a face shield, an apron will also be helpful, this is dangerous, so take precautions, once you get the hcl driven off you may see black powders or a black solution in the sulfuric (if gold), let cool and pour the small amount of black solution into a vessel of water to dilute it. 

Do not pour water into concentrated sulfuric acid, the water will steam and can splash out acid onto you.
Pour concentrated sulfuric acid into water to dilute it safely.

You may see a black powder of gold form, (if gold was involved), if so decant liquid (if tin was involved it should be soluble as tin sulfate), the black powder (if any) can then be dissolved in HCl with a little bleach (heat to drive off chlorine) and tested with stannous chloride on paper filter or Q-tip or you could use a ferrous sulfate crystal in spot plate to test the solution for gold.

Or the color in the solution in your picture could have come from something else I really do not know.


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## beav3r316 (Jan 7, 2016)

I know this is incredibly old, but, I have to know...

Did you ever recover the gold?

And, if so, was it colloidal? 

I did have a question too. You said the HCL mix was orange. Iron? Did you check the crushed incinerates with a magnet? (I may have missed that, if so. It's 4 am...but I HAVE to read before bed...)

Again, sorry to bump, but, I found this thread full of good things, had I saw it 5 months ago, it would have saved me some heartache.


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## cnbarr (Jan 15, 2016)

beav3r316 said:


> I know this is incredibly old, but, I have to know...
> 
> Did you ever recover the gold?
> 
> ...



The test was left inconclusive and the powders were added to my flux refining drum for pyrorefining in the future. Sorry I couldn't have been of more help. The test was four years ago so my memory is bit fuzzy on it!


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## nickvc (Jan 16, 2016)

cnbarr said:


> beav3r316 said:
> 
> 
> > I know this is incredibly old, but, I have to know...
> ...




Knowing you I bet you were hoping to forget this, we have all been there at some point but the thing to remember is that if it isn't a customers material it isn't that much of a worry, you will get that missing gold at some point and look what's happened to its price over time 8)


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## beav3r316 (Jan 16, 2016)

cnbarr said:


> The test was left inconclusive and the powders were added to my flux refining drum for pyrorefining in the future. Sorry I couldn't have been of more help. The test was four years ago so my memory is bit fuzzy on it!



No worries!

I just saw this thread and was reading through it (as i am trying to do with EVERY thread on grf) and it had some relevant information pertaining to the first batch of pins i tried to do (and failed, as my school of youtube was far from the correct way of doing things). 

Great stuff in this thread though, a true wealth of information. 

Hope you got the majority of the gold in the end, your persistence is admirable.

Thanks again for sharing


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