# Method for Ultra High Purity Gold



## Lou

A discussion with a friend via gmail chat earlier today sparked my mind about high purity precious metals. Sprinkled throughout the literature are methods for obtaining metals and compounds of exceptional purity. 

Here is one such method that reliably produces 6N+ pure gold.

As I find methods, I will continue to post them. At the very least, some of us here may have academic interests.

Method for UHP gold:

*All acids and reagents used must be of trace metal grade. Recommended is the Trace Metal line of products from J.T. Baker. Under no circumstances should any metal containing object or apparatus contact the gold or solution; only aqua regia boiled quartz and PTFE apparatus should be used.*
_
Gold of 99,995% purity (20 g.) well rinsed in ether and then in HCl is dissolved in aqua regia in an 800-ml. acid washed quartz jointed flask, and the solution is concentrated to a thick syrup at 80 degrees Centigrade, removing the most part of the nitric acid. It is then boiled 5 times further and periodically 20 ml. of hydrochloric acid (4:1) is added to expel nitrogen oxides. The residue is taken up in 650 ml. of hot 18.2 MΩ water and digested until all soluble material is dissolved. It is then allowed to settle for eight days in a dust-free atmosphere, preferably in a closed system. The precipitate consists of AgCl containing small amounts of Au, Pd, SiO2, etc. The gold solution is vacuum filtered through a micron quartz frit via decanting (do not disturb the precipitate). This and all later precipitates are *not* worked up further to obtain gold.

Gold refined by use of SO2 still contains some Pd, while that precipitated with oxalic acid contains Cu, Pb and other metals. Therefore both of these procedures must be used to obtain gold of the desired purity. Ultra high purity sulfur dioxide is passed through the warm gold solution (80°C) obtained above; the gold precipitates quantitatively on careful neutralization with ammonia (1:1). The product is allowed to settle overnight and the deposit of spongy gold is washed by decantation (7 times) with 200 ml hot 18.2 MΩ water; it is then heated for four hours on a steam bath with concentrated hydrochloric acid and washed free of acid with hot 18.2 MΩ water. Then it is redissolved in aqua regia in a quartz flask, the nitrogen oxides removed, filtered, and reduced. The entire procedure above is repeated seven times in order to remove all Ag, Cu, Ni, Zn and Pb. It is no longer necessary for the gold solution to sit. The precipitated gold product is then digested for 12 hours with ammonia (1:1), washed free of ammonia with 18.2 MΩ water, heated for four hours on a steam bath with hot concentrated nitric acid, and decanted. Ammonia (1:1) is again added and later removed by washing with 18.2 MΩ water . The gold sponge is dissolved in dilute aqua regia; after addition of HCl, the solution is concentrated by evaporation, diluted with UHP H2O, decanted and filtered.

The gold is precipitated by careful addition (there is a danger of foaming over) of small portions of powdered, UHP crystalline oxalic acid (ACS grade may be resublimed twice). If the solution retains a yellow colour, it is carefully neutralized with ammonia and more oxalic acid is added; the addition of the acid is continued until the solution remains colorless. The resultant gold sponge is again dissolved and reprecipitated with oxalic acid. It is then Pd-free. Finally the gold is redissolved, precipitated with sulfur dioxide and heated with concentrated hydrochloric acid, and washed with 18.2 MΩ water. The residual traces of HCl are removed with ammonia and it is again washed with UHP water. The product is transferred to a quartz dish and dried at 110°C. Yield 75-80%. The gold prepared in this manner is spectroscopically and analytically pure (free of metallic Cu, Ag, Ni, Pd, Fe, Zn and Pt) and is above 99,9999% in quality._


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## Anonymous

Dang - Thanks for the info, but for a novice backyard operation like I have, Lazer Steve, here I come.

Seriously, that is real good information for the professional and novice, I even learned a couple of things from reading that (this old dog can learn a few new tricks.)

But, what is 18.2 M Ohm water?

Luck....Jack


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## Noxx

Very useful information, thanks a lot.

I suppose it's millipore water ?


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## goldsilverpro

Good info, Lou. I can see a few of those things that I could incorporate into my procedure.


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## lazersteve

Lou, 

Great post, it reads like it came right from the Organic Synthesis site that I love so much!

18 Mega Ohm water is water that has a resistance of 18 Million Ohms on your ohm meter. Pure water free of dissolved solids has a very high electrical resistance.

Steve


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## Lou

Water of that quality is very hard to make. It is really friggen pure water . The machine to make that water costs (or used to) about $8k, oh and did I mention that it likes to break down and that you need to replace cartridges on it. Water that pure is a pain in the butt to make--multiply distilled deionized water that's been passed over all sorts of ion exchange resins, activated carbon, assorted membranes, and then repeated. Unfortunately, if you left such water in an untreated glass bottle or out in the open air, it would be ruined! It would be basic from reacting with terminal hydroxys on the glass surface, and if exposed long enough to the atmosphere, it will become acidic from absorbing CO2. Now you see why analytical chemistry is somewhat challenging--variables, and lots of them!

I love the uncanny resemblance this technique's rinse procedure has to that advocated by Harold, Chris, Steve, and used by many, many more on this site!

I recently purchased some gold and platinum of 6N5 quality at spot price. Some of you may be thinking that it's a rip off, but gold from a supply house refined by a chemist to that level of purity would command three times the market value per ounces _in bulk_. For small amounts like 5-20g it would be 8 or more times market value. 


As you may have noticed, the starting material was already purer than the quality of commercially pure gold (as Chris and Harold have corrected me) at 99,995 so you can see the trouble that is required just to make a couple orders of magnitude purer. This procedure is one I typed by hand (I had it loose leaf) onto the forum and it's fairly old (20 years at the least). I'm willing to bet that the procedure will give gold of even higher purity than 6N, which was probably the limit of the most complicated analysis back then.

I also had/have procedures for rhodium, palladium, platinum, rhenium, osmium, ruthenium, and iridium. I suppose they're not useful from the aspect of _recovery_, but they are highly useful as far as refining goes. 
I think these procedures are enlightening just from the standpoint of it being the pinnacle of refining let alone from practical value it has for us as refiners in improving our technique. 

As I find them, I will post them. Moderators willing, perhaps we can move them into another thread and sticky it for future reference.



Lou


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## Noxx

I suppose another moderator stickied this post, it's not me this time 

You're right Lou. The distilled/filtered water we use at our school lab has a pH aroud 5.5 if I remember correctly. This is due to dissolve CO2 of course.

I'm glad you posted the process. In my never ending goal to reach to purest gold possible, this is very useful.

Cheers


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## lazersteve

Lou,

I stickied the post for you. :wink: 

Steve


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## Rag and Bone

It would be cool if somone was setup for the ultra purity process. Everyone could send in their gold and do one big batch of it. Unfortunately, it's beyond my technical ability.


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## Lou

I'm setup for it. It's just expensive for reagents, very, very expensive.


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## Anonymous

Lou,

Great post! but what if I'm happy with 4n's plus only. Is there any way I could refine scrape gold without costing me too much money and time? Can I cut some corner with your procedure above? Can you post a procedure to get 4n's plus. thanks


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## Lou

Absolutely. Really, a good investment is dibutyl carbitol, a polyether that solvates gold. Diethyl ether also works, but you'll get one hell of a buzz working with it in an unventilated environment. Its flammability also makes gasoline look benign. 

If you just want to precipitate the gold once and get 4N, extract with dibutyl carbitol (nicknamed diglyme). Wash the extract well with 3M HCl until it the acid is colorless. Then precipitate with the reductant of your choice. Filter and collect the gold, washing well with solvent. Take the gold powder and (if rinsed right, it's chloride free) boil it with 4M nitric acid for an hour. If the nitric is colorless (no green, no blue) then chances are good that you're doing well. Filter again (saving the nitric to use for some other purpose) and add the gold to concentrated ammonia and stir for an hour or so. Any blue will indicated copper. You don't really need to rinse the gold after this, any ammonia or ammonium nitrate will be lost to the melting process. The gold will assay 4N and it should take less than 6 hours from dissolution of crude material to casting the pure metal.


Lou


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## Noxx

Lou said:


> Wash the extract well with 3M HCl until it is *colorless.*
> 
> Lou



:?:

If you extracted gold, won't your solution be yellow ?

I know for sure that your solution will be «cloudy» this happens to me all the time. Slow vacuum filtration plus 3 times HCl scrubbing is what is needed.


Anyway, I really like how DBG works. It's clean and efficient, and it's reusable !


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## Platdigger

That last post was excellent Lou! I am saving that one for sure....
Randy


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## Lou

Of course Noxx! I miscommunicated--I've edited it so it reads better.

I meant wash with HCl until the HCl rinse no longer has any color. If the HCl isn't picking up any color, then it's not solvating (m)any base metals. 

The cloudiness is due to the solubility of water in the ether. As an aside, don't use anything other than HCl or quite dilute sulfuric--ethers can be cleaved by strong acids (i.e. HBr or HI).

Hope this clears it up for you, no pun intended!

Lou


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## Catxyoli

hi everyone , i was searching the forum and found an excelent article betwen HaroldV and GoldsilverPro is astonishing and will shore clear many minds on refining gold to 9.999

Please read especialy Goldsilverpro method 

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=325&postdays=0&postorder=asc&highlight=refine+jewelry&start=15

good reading...


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## ppoowweerr

So if someone were actually able to produce 6n or better gold, where or how would you sell it? I have not made any but I might pursue it in the future if it became a practical option, although very unlikely.


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## Lou

Semiconductors and specialty research purposes. It's not a commodity at that point by any measure.


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## Noxx

I'd say for medical grade applications...


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## Chumbawamba

Holy wow, this is like the Olympic Gold Medal of refining. Has anyone here ever performed the process?

Who came up with it? Does it really require all those steps? I'm sure the answer is, "Yes, if you want 6N fine gold". What I'm interested in knowing is the WHY for each step. For you experienced refiners each step probably makes sense, but for newbs like me I'm interested in knowing what the chemical reasons are for each step. If some has the time to summarize I'd appreciate that. Otherwise, I guess I'll learn in time.


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## Lou

You want to know why?

Why quartz?

Pure transparent quartz is usually metals free and comes in a high grade. It's leached with the acids you're working with before hand to remove any surface metal cations that may be present in the quartz. Most anions like chloride and sulfate are not problematic in the refining of gold because they are thermally labile (go off when the gold is melted) but they are to be avoided because they usually contain a base metal counter ion (the cation, a positive ion that is a oxidized metal species in this particular case). Trace metal acids are very pure acids that are very expensive (they have part-per-trillion levels of base metals). The conductivity water is used for the same reason--no conduction means no metal ions acting as electrolytes.


Who? It's a German procedure, I don't know who, but it's quite similar to that in Georg Brauer's collection but it must be a newer modification because the technology to analyze gold to that purity (which is practically at detection limits) didn't really exist til ICP-MS came into its own. 

Sulfur dioxide by itself gives a high quality precipitate, but is prone to reduce copper (II) to copper (I) which we see as a white-gray chloride. Any silver is removed by the decantation procedure and by filtering. In this case, the gold is already very pure, so any copper that is inadvertently reduced will remain in the acidic solution as a chloro complex. Doing it over multiple times will ensure that all the copper is removed. Any palladium present will be a ''rider'' with the gold that comes down. To remove that, oxalic acid is used. The ammonia is used to adjust the pH to get complete precipitation.


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## Chumbawamba

Hey Lou.

I still can't say I understand all of it, but your explanatory paragraphs certainly help in bringing me closer. Thanks for taking the time.


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## HAuCl4

Ferro in page 10 of their BDG document claim 6N gold purity can be achieved with a certain oxalic acid mole concentration in the reduction phase. I don't know if that claim is true, but that may help cutting some corners and some costs to obtain UHP gold.

I'd love to read Lou's comments regarding that claim on page 10 of Ferro's document.

I imagine very specific extractants are also available for UHP Pt and Pd, and probably every other metal in the periodic table.


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## BGT

So I have gold precipitate from a gold drop using SMB (sodium meta bisulfite) 75 grams smb to a 500ml AU cloride filtered solution.

How do you get﻿ it to a dry powder after this? (steps to dry powder) Also, I have tried to torch the precipitate directly after it settles for 24 hours and while still wet and it just turns into black beads. (borax and argoflux were added) Should there not be any flux or borax in the melting dish? Which Step is missing?

Thanks.


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## Harold_V

BGT said:


> How do you get﻿ it to a dry powder after this? (steps to dry powder) Also, I have tried to torch the precipitate directly after it settles for 24 hours and while still wet and it just turns into black beads. (borax and argoflux were added) Should there not be any flux or borax in the melting dish? Which Step is missing?
> 
> Thanks.


Read Hoke.
I saw no mention of any attempt to wash the recovered gold. 
Why is that?

Harold


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## lazersteve

BGT said:


> So I have gold precipitate from a gold drop using SMB (sodium meta bisulfite) 75 grams smb to a 500ml AU cloride filtered solution.
> 
> How do you get﻿ it to a dry powder after this? (steps to dry powder) Also, I have tried to torch the precipitate directly after it settles for 24 hours and while still wet and it just turns into black beads. (borax and argoflux were added) Should there not be any flux or borax in the melting dish? Which Step is missing?
> 
> Thanks.



Did you confirm you had gold in solution with stannous chloride befroe adding all that SMB? 


That's a lot of SMB unless you had several ounces of gold in the 500mL. Copper I chloride will precipitate with SMB if a lot of copper is present in the solution when the SMB is added. Copper will turn black when the torch flame is removed.

It's likely you precipitated a combination of gold and copper I chloride, melted it and now have dirty gold beads. Try sanding the black coating off of one of the beads with an emery board to see if it has a golden core. If not, it may all be copper and or base metals.

Steve

Steve


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## BGT

I started using a separatory funnel with BDG. Tested with Stannous Chloride from beginning to end. Gold was there. Followed and separated 3 times with 32% hcl wash. Used oxalic in a magnetic stirrer for 5 hours at 85C. Placed contents in Buchner Funnel and got 3 filters worth of brown powder. Torched the powder/filter with a MAPP torch and got black rocks. Sanded the surface and saw shiny gold underneath, but it is so embedded within the rock like substance that my question is what is the best way to free it up again? Should I place the rocks in sulphuric? Should I AR it all over again?

Thanks.

Mark


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## lazersteve

The black is oxides from the base metals you pulled over from not following the proper process. Your HCl wash was way too strong and your pregnant solution was not diluted first.

Here's a step by step process that works for me:

** Process using BDG 

Here's the general procedure:

 Dilute the pregnant solution to 25% concentration (1 part solution to 3 parts water).

Filter/Settle & Siphon out any sediments that form.

 Add a portion of the diluted pregnant solution to your clean funnel (500mL). 

 Add enough BDG to hold the expected gold in the pregnant solution (BDG holds ~50 gm/L max). 250 mL of BDG will can strip out 12.5 gm of gold maximum. 

 Stopper the funnel and vigorously shake for several minutes.

 Let funnel sit to until the two layers completely separate. The top layer should not be cloudy. The patent mentions a centrifuge, this would speed the separation greatly.

 Funnel off the lower layer into a separate glass vessel.

 Repeat with each portion of the solution until all the solution has been processed using the same batch of BDG (Up to the 12.5 gm limit).

 In a separate beaker mix a solution of HCl (Muriatic 31.5%= 10 Molar) with distilled water 20 parts water: 1 Part HCl.( 19 mL H2O per 1mL HCl). You will need a total of 3 times the amount of BDG you used of this diluted acid. If you used 250mL of BDG you need to mix up 750 mL of this rinse acid (712.5 mL H2O to 37.5 mL HCl). You will be running three rinses of equal volume to the BDG (250 mL). I only used one rinse when I did my experiments. The better you rinse the cleaner your gold. The patent states three to five rinses.

 Add an amount of the diluted acid from the step above equal to the volume of BDG used to the funnel. If you used 250 mL BDG then add 250 mL of the diluted acid.

 Stopper and shake vigorously for several minutes.
 Let separate as before and drain off the acid wash into a separate vessel ( not the same one as before ).

 Repeat steps 9-11 two more times. You can combine the rinses in the same vessel.

 Dissolve 90 gm Oxalic acid per 100 mL of distilled H2O. Use the formula Lou has posted here to determine how much you will need. Place 250 mL (equal volume to BDG) of this solution in a 1L pyrex beaker with a magnetic stirring rod (not required). Put the beaker on a hotplate. Heat to 80C and turn on the stirrer (if available) to a very slow speed. Oxalic acid is hazardous READ THE MSDS!! Here is a link to some follow up on Oxalic acid use.

 Carefully filter the BDG from the funnel into the 1L Pyrex beaker with the Oxalic acid warm.

 Heat (with stirring) for 2-3 hours. The gold will drop as beautiful gold flakes or a fine brownish mud. The BDG will be clear when it is depleted of gold.

 Filter the gold out and wash with full strength hot muriatic acid.

 The gold should be 99.9%+.
The above is a method I formulated and tested from the BDC patent.

Steve


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## BGT

Thank you so much for the detailed BDG information! Already starting it right now.

Just a few quick questions. How do you rinse the filter paper with the hot muriatic acid? Do you leave the round filter paper in the buchner funnel with the brown powder sediment on the paper and pour in hot muriatic acid into the buchner funnel, wait for it to drain and then remove the filter paper out? After removing the filter out of the buchner funnel, Is it better to let the paper air dry or just torch it right away, or scrape off the powder from the filter when it is dry?

Mark


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## lazersteve

Mark,

You could do it the way you suggest or you can wash the gold into a beaker with a spray bottle and add the HCl then heat. Pour off the acid after the color of the acid no longer changes any darker.

Steve


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## HAuCl4

Thanks for posting the BDC detailed process Steve. Do you use the process regularly?. The drop is faster using ammonium oxalate in slightly acid solution and shaking it. I never did more than a few ounces at a time though.  And have no idea how to scale it up. :roll:


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## lazersteve

I used the process quite a bit several years ago when I was learning how to properly use Dibutyl carbitol (BDG). Lately, I turned my attention to it again as a means of quick stripping gold plating when mixed with a selective solvent for gold. The real issue when using it like I'm trying to do now is that the gold has to be fully stripped from the parts without any water in the reaction for the reagents to be selective and extracted into the ethereal upper layer. 

I'm still working on this process, so I will not disclose any details about the process until I have more experimental data on it's usefulness. It involves an easy to make reagent that looks to be easily recycled so it's well suited for use with BDG.

Once I have enough experimental evidence to back up my ideas for the selective stripper and a complete process, I will post more about it.

I have used potassium oxalate to reduce the gold from BDG as well as straight oxalic acid.

Steve


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## HAuCl4

Interesting Steve. Thanks. The DBC process felt lengthy and cumbersome to me. Almost prefer to dissolve twice, and precipitate once with SMB and once with oxalate, to obtain a very pure product but maybe not as good as with DBC. If it could be made simpler and faster, I'd like to learn about it.


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## Lou

Liquids to liquids. 

http://www.chemglass.com/images_product_1/CG-1375-01.jpg


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## HAuCl4

Interesting gadget Lou!. 8)


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## HAuCl4

Is there some type of additive, like corn starch or egg white or something, that will help cleaning the AgCl faster than waiting for days to settle completely, before dropping the gold?. :?:


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## BGT

Is there a better way to torch the filter paper in the melting dish?

I am using a MAPP torch and treating the the dish with heat from the torch then sprinkling on some anhydrous borax on the melting dish then place the filter paper on the dish and then torch the paper. Is there anything that can be better within these steps. The residue gold is from a bdg/oxalic method so I have ultra pure going into the dish already.

Thanks,

Mark


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## Barren Realms 007

BGT said:


> Is there a better way to torch the filter paper in the melting dish?
> 
> I am using a MAPP torch and treating the the dish with heat from the torch then sprinkling on some anhydrous borax on the melting dish then place the filter paper on the dish and then torch the paper. Is there anything that can be better within these steps. The residue gold is from a bdg/oxalic method so I have ultra pure going into the dish already.
> 
> Thanks,
> 
> Mark



Pour some alcohol on the filter paper and light it and let it burn and then tourch it.


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## joem

HAuCl4 said:


> Is there some type of additive, like corn starch or egg white or something, that will help cleaning the AgCl faster than waiting for days to settle completely, before dropping the gold?. :?:


 :shock: 
I'm not eating an omlette at your house


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## Harold_V

BGT said:


> Is there a better way to torch the filter paper in the melting dish?
> 
> I am using a MAPP torch and treating the the dish with heat from the torch then sprinkling on some anhydrous borax on the melting dish then place the filter paper on the dish and then torch the paper. Is there anything that can be better within these steps. The residue gold is from a bdg/oxalic method so I have ultra pure going into the dish already.
> 
> Thanks,
> 
> Mark


I'm at a loss to understand why you got the gold on or in a filter in the first place. That is an unneccessary operation that leads to problems. Problems about which you are asking for a solution. 

What am I missing?

Harold


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## HAuCl4

joem said:


> HAuCl4 said:
> 
> 
> 
> Is there some type of additive, like corn starch or egg white or something, that will help cleaning the AgCl faster than waiting for days to settle completely, before dropping the gold?. :?:
> 
> 
> 
> :shock:
> I'm not eating an omlette at your house
Click to expand...


I met a winemaker that told me he uses egg white to clear fine sediments and turbidity in his wine...so I inmediately thought about silver chloride... Call me nuts!.


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## BGT

Hello. I was ending up with the material in the filter after pouring it in there from the Oxalic/BDG Drop. In order to get it all out of the beaker, and be able to re-use the BDG, pouring it all in a buchner funnel with a filter(s) was how I got it out of the beaker. 

Is there another way to get it all out of the beaker? (and still keep the BDG)

Thanks.

Mark


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## lasereyes

If I remember correctly, they used minute quantities of gold of this purity in the experiments at the Brookhaven national laboratory with the relativistic heavy ion collider. I got to take a look around the place a couple of years ago. They are defiantly on the bleeding edge of experimental physics. Here is a picture of gold ions colliding at extreme temperatures:


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## jpnuke33

totaly new to the refining process, and want to learn HOW TO; refine my,
rings to their purest state. easiest way, refining 101 if you will

Thank You,jpnuke33


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## jimdoc

jpnuke33 said:


> totaly new to the refining process, and want to learn HOW TO; refine my,
> rings to their purest state. easiest way, refining 101 if you will
> 
> Thank You,jpnuke33



Just start reading. You found the right place.
Now you need to do some homework.

Jim


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## Harold_V

jpnuke33 said:


> totaly new to the refining process, and want to learn HOW TO; refine my,
> rings to their purest state. easiest way, refining 101 if you will
> 
> Thank You,jpnuke33


Yes, I understand. 

Here, refining 101 begins with you reading Hoke. 

Harold


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## Militoy

HAuCl4 said:


> joem said:
> 
> 
> 
> 
> 
> HAuCl4 said:
> 
> 
> 
> Is there some type of additive, like corn starch or egg white or something, that will help cleaning the AgCl faster than waiting for days to settle completely, before dropping the gold?. :?:
> 
> 
> 
> :shock:
> I'm not eating an omlette at your house
> 
> Click to expand...
> 
> 
> I met a winemaker that told me he uses egg white to clear fine sediments and turbidity in his wine...so I inmediately thought about silver chloride... Call me nuts!.
Click to expand...


One of my "side interests" is winemaking - though since I moved to the High Desert many years ago, I have pretty much switched over from grapes to local fruits like prickley pears - or to blends of local fruits with grapes. The use of albumen from egg whites to clear turbidity caused by tannin in wine "must" is a time-honored method. Works like a charm.


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## Lou

Too bad in the hyper acidic and often oxidizing solutions we use, the albumin would at the least denature (uncoil) and more probably just hydrolyze the peptide/amide bond.

They make flocculants for getting troublesome fine precipitates out of solution.


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## HAuCl4

Found a cheap and expedite way to "hydrolyze the crap out" instead. To be released in the Kitchen Warrior pamphlet when it is finished... :lol: 
I suspect Republic does something similar for their 5N in one pass process.

I doubt there is anything "new", but anyways... :shock:


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## Python

Hi Lou.

Im sorry to bother, but im from south africa and dont know anyone who can help me.
Im new in the refining process, but i dissolved some gold in AR, and want to precipitate it, using Ferrous Sulphate, but nothing happens. can you please help.

Thank you for your time.


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## Harold_V

Python said:


> Hi Lou.
> 
> Im sorry to bother, but im from south africa and dont know anyone who can help me.
> Im new in the refining process, but i dissolved some gold in AR, and want to precipitate it, using Ferrous Sulphate, but nothing happens. can you please help.
> 
> Thank you for your time.


We have a policy against double posting. Readers tend to read all posts, regardless of where they are posted on the board---so duplicating can lead to confusion, plus it wastes time of those of us that moderate. It also makes it difficult to find information, due to responses having the potential to be in more than one place. 

I have already responded to your inquiry on another thread. Please go there to read what I have to say.

Harold


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## vichem

millipore water is full of surfactants, I make my pure water by dubble distilation thru KMnO3 in basic conditions and K2Cr2O7 in acidic conditions, then i have 18,2Mohm


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## Lou

You mean KMnO4. Thanks for the thread clutter.


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## gold4mike

Resurrecting an old thread...

LazerSteve mentioned earlier in this thread, on 1/24/11, that he was working on a process with a selective gold stripper but would wait to post further about in until he had more data.

Steve, did you ever get the process to where you wanted it? If so, can you share that with us? It seems like I'm doing more and more pins and other plated objects lately and I it would be great to see a better process than the two I'm currently using - poorman's nitric and acid peroxide.

Thanks!


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## lazersteve

The experimental method is a back burner project and I have not gotten around to testing it. I did manage to make my reagents for the reaction several months ago, but that is where it stands right now.

Steve


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## 10wt_Percent

Perhaps Zone Refining as employed in the semiconductor industry is of utility in achieving super-high purity numbers. Just thinkin "outside the flask". :idea:


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## butcher

I believe Lou has done something similar to zone refining in a tube furnace, which sounds lab equipment extensive, and complicated to me (the uneducated in that process).

I know nothing about the process, but I assume the gold, or other metals would have to be in a fairly pure state to begin with, just a uneducated guess.

He has discussed that process on the forum.


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## Lou

That is gas phase crystal growth from already pure (5N+ material) to get material that is about as pure as it could get to limits of detection on glow discharge mass spectrometry. The process given here has a bad yield, but will give the purest gold in quantity (6N) and the rest of the gold can be recovered and sold. I do not advocate re-using that gold over and over, for the buildup of impurities. Even making 5N gold is difficult--most refiners struggle to achieve that *consistently* without solvent extraction and/or oxalic acid.

Zone refining can also be done on pretty much any metal. It works better if the metal is less conductive of heat (so gold and silver are very hard to do). One can use a small, high power density coil for the lower melting point metals (i.e. Pt/Ti and below); higher temperatures and it is much more efficient to use a focused electron beam. Zone refining is done in passes wherein a rod of the feedstock material moves through a hot zone that melts. Essentially, the metal recrystallizes and pushes the impurities to the edge of the molten zone. Done many times over, very high purity materials can be achieved. This is often used on silicon crystals that are first grown as boules and pulled with a oriented seed crystal--they are then zone refined for additional purity. Zone refining sometimes is very cost effective for PGM refining when the material is contaminated with elements that are a drag to remove hydrometallurgically and have the appropriate partition coefficient. 

One can always recognize zone refined bars by their appearance:








For additional reading:

http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=54&t=8910

I'm going to try and be more involved in the ASTM subcommittee for precious metals products and standards, so it'll be interesting to look at application/industry-specific standards development.

Lou


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## solar_plasma

Since there has been asked for how to purify up to 999,999, I would like to make everyone who hasn't seen it yet aware of this thread.


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## jimdoc

I have some Alfa Aesar Premion 99.9975+% gold.
https://www.alfa.com/en/catalog/11390 

They don't list 99.9999 gold.


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## Geo

I remember when I first joined the forum, four 9's was the rage and there was a lot of talk about it. Then the high purity discussion died down after someone showed pure gold crystals grown in a plasma furnace (can't remember the exact post) and that was the holy grail of refining at the time. It takes high tolerance equipment to purify gold to the chemically pure state of six 9's. I would be too embarrassed to state that I can purify gold to acceptable bullion grade and I have practiced quite a bit. I'm not being modest but just truthful. If I try my hardest, I'm sure I can get 99.5 but I'm not stretching it any farther. That's already stretching a little bitty thing a long way.


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## solar_plasma

Obviously it is just a question of expense. When four 9's can be obtained at first refining simply using diglyme, more than this seems not to be so hard - if expense is no object.


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## Lou

I should emphasize that this method produces gold sponge that serves as the feedstock for chemical vapor transport into the single crystal clusters that I posted about (that was me Geo). Gold of that purity is sold to other refiners as reference standard. Sometimes the product is better than existing standards.


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## Anonymous

Nickvc has made a good point on many occasions, and it does go some way to validate at least one of Mod's assertions.

That is, you only get paid for the gold content of a button. If it's 99% gold then you get still get 100% of the gold value by weight. There's an argument for refining to 99% or below purity if you have a steady out turn for your gold at those levels of purity. 

The point where it becomes cost prohibitive to keep increasing purity is something that does need to be kept in clear perspective if you're selling your gold. Obviously if you're keeping it and making it pretty then it's a completely different story.

Jon


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## 4metals

Years ago, before the jewelry manufacturers in the US started to leave, there was an excellent market for a small to medium sized refiner to make high purity metals. As that market has dwindled considerably, there is still industrial needs for high purity metals but nowhere the quantity or need there once was. 

If you are selling to a refiner or even to a major, you will have your refined metals discounted when you sell. Whomever you sell to assumes they will have to re-refine it and it will likely be assayed and thrown in with the high grade feed. For gold that is likely >99% gold content. 

For this reason I tell my clients who sell karat bars to refiners and only refine the material requiring stone removal that a single drop of the gold without getting carried away will give you the purity needed to sell at the best price. No sense putting time energy and chemicals into an unprofitable situation. 

However to be well versed in the art of refining it pays to know how to make high grade gold and for that reason a thread like this is valuable to help you figure out steps you can easily do to increase your purity and keep costs down. 

Who knows, maybe one of the national labs will call you and want .9999 gold and you'll have a market. If they want .999999 gold, call Lou!


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## JohnBB

I may have made an error..I wonder if anyone can help me..

I used Dibutyl Carbitol for the first time...I mixed together my completed Aqua Regia solution containing my gold and PGRMs.. the total 750 mls went completely into the (140F degrees) DBC solution and a color change took place after 24 hrs. I then filtered out any solids and remaining AR solution... then made up Oxalic Acid 1000g/1L and made 2 L, which I heated to 80 C. I added the DBC pregnant solution heated to 80C to the Oxalic and stirred for 24 hrs at 80C...I received no gold Chloride drop.

Prior to the Ox/DBC mixing I also washed the pregnant DBC solution with (337 ml 37% HCL with 2663 Mls DI water 4 times). The wash water was yellow and last wash was pretty clear. 

1.) Can I still recover the gold from the DBC or the acid wash or the Oxalic acid layer(which is now yellow), and if so, where exactly is the gold now? I have saved all solutions separately.

2.) My DBC was from TCI chemical company of Japan.

PLUS..some posts mention Ammonia...?

I am not sure what to do next...Please send rescue service..;-)

Thank you,

john


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## MarcoP

Hi John, I can only help by finding out where your gold is. Prepare some Stannous Chloride and test your solution.

Marco


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## Geo

To my understanding, solvent extraction is a messy business. The two solutions, AR and DiButyl Carbitol (DBC) will not mix. Think in terms of oil and water. After the two has been mixed together to allow the DiButyl Carbitol to touch all of the AR solution, you should allow the two solutions to separate. The AR solution should be depleted of precious metals and can be removed with a separatory funnel. Of coarse it should be tested with stannous chloride to be sure. Now you have the DiButyl Carbitol to deal with. 

If this did not happen, you did something wrong. If you did do all of this, you should have explained in your post exactly what you did and how you did it. Did you heat the pregnant solvent when adding the oxalic acid? Were you constantly stirring while you added the oxalic acid?


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## Lou

John,

DBC will load about 130-150 g/L of gold and do it in a few hours tops. You want to use good stirring (preferably overhead) and then allow the phases to settle.
You can then wash the extract like you've done with HCl to scrub out any iron or other crap.

You heat the oxalic solution to boiling with the DBC with good stirring and you get high purity gold. The washes should have not much of anything in it, perhaps Fe/Pd. You can recycle those to another digest.

Lou


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## Research135

Lou said:


> *I also had/have procedures for rhodium, palladium, platinum, rhenium, osmium, ruthenium, and iridium.* I suppose they're not useful from the aspect of _recovery_, but they are highly useful as far as refining goes.
> I think these procedures are enlightening just from the standpoint of it being the pinnacle of refining let alone from practical value it has for us as refiners in improving our technique.
> 
> As I find them, I will post them. Moderators willing, perhaps we can move them into another thread and sticky it for future reference.
> 
> 
> 
> Lou


That would be an interesting read, for sure.


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## colt45gto

wow, Thanks Lou but i think i need to be able to crawl before i can walk with this.

this isn't gold refining its chemistry at a super level. to me anyway.

i feel cleverer already!


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## Tndavid

Very interesting read on the ultra high purity gold. I would love to see some videos of the process. Or pictures from beginning to end product. That would be awesome. Thanks Lou and all the rest of you guys.


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## RaAt2

From karat gold.
1-Inquart with silver. Granulate and part in nitric acid. Decant. Boil residue in sulfuric acid. Decant.
2-Dissolve residue in HCl and sodium chlorate. Add a few drop of sulfuric acid. Let it stand. Decant and filter clear solution.
3-Add 5% zinc chloride `to clear solution. Add sodium hydroxide dropwise till PH is near 7. Let it stand. Decant clear solution.
4-Add HCl till pH is 4. Add Butyl Diglyme. Shake. Decant organic phase. Rinse organic phase with HCl twice.
5-Add hot sodium oxalate/ HCl mix at pH 4. Keep heat on.
6-Wash several times with pure HCl and distilled water.
7-Melt in zirconia crucible with oxyhydrogen torch. Product is 6N + .


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## Tndavid

RaAt2 said:


> From karat gold.
> 1-Inquart with silver. Granulate and part in nitric acid. Decant. Boil residue in sulfuric acid. Decant.
> 2-Dissolve residue in HCl and sodium chlorate. Add a few drop of sulfuric acid. Let it stand. Decant and filter clear solution.
> 3-Add 5% zinc chloride `to clear solution. Add sodium hydroxide dropwise till PH is near 7. Let it stand. Decant clear solution.
> 4-Add HCl till pH is 4. Add Butyl Diglyme. Shake. Decant organic phase. Rinse organic phase with HCl twice.
> 5-Add hot sodium oxalate/ HCl mix at pH 4. Keep heat on.
> 6-Wash several times with pure HCl and distilled water.
> 7-Melt in zirconia crucible with oxyhydrogen torch. Product is 6N + .


Pics???


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## 4metals

He has been banned. Although very clever!


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## Ravn

Hi 

In the Journal Hydrometallurgy there is an interesting paper on how to make gold with purity >99,9998 % (>5N) using a relative simple process. 

Hydrometallurgy 95 (2009) 262-266 
"Processing of high purity gold from scraps using diethylene glycol di-N-butyl ether
(dibutyl carbitol)" Byoung Hi Jung a, Yi Yong Park a, Jeon Woong An c, Seong Jun Kim c, Tam Tran b, Myong Jun Kim


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## FrugalRefiner

Dibutyl carbitol is also know as butyl diglyme, or BDG. You'll find many posts about the process if you search for BDG.

Dave


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## Ravn

> Dibutyl carbitol is also know as butyl diglyme, or BDG. You'll find many posts about the process if you search for BDG.


I am well aware of the different names for Dibutyl Carbitol. I was only trying to inform about a new simple process for producing high purity gold :wink:


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## nickton

I may have made an error..I wonder if anyone can help me..

"I used Dibutyl Carbitol for the first time...I mixed together my completed Aqua Regia solution containing my gold and PGRMs.. the total 750 mls went completely into the (140F degrees) DBC solution and a color change took place after 24 hrs. I then filtered out any solids and remaining AR solution... then made up Oxalic Acid 1000g/1L and made 2 L, which I heated to 80 C. I added the DBC pregnant solution heated to 80C to the Oxalic and stirred for 24 hrs at 80C...I received no gold Chloride drop.

Prior to the Ox/DBC mixing I also washed the pregnant DBC solution with (337 ml 37% HCL with 2663 Mls DI water 4 times). The wash water was yellow and last wash was pretty clear. 

1.) Can I still recover the gold from the DBC or the acid wash or the Oxalic acid layer(which is now yellow), and if so, where exactly is the gold now? I have saved all solutions separately.

2.) My DBC was from TCI chemical company of Japan.

PLUS..some posts mention Ammonia...?

I am not sure what to do next...Please send rescue service..;-)

Thank you,

John"


I am not an expert but I do know you should add ammonia before precipitating with oxalic acid in order to get a neutral ph level (I think it should be 7), but perhaps you already did that.


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## nickton

nickton said:


> I may have made an error..I wonder if anyone can help me..
> 
> "I used Dibutyl Carbitol for the first time...I mixed together my completed Aqua Regia solution containing my gold and PGRMs.. the total 750 mls went completely into the (140F degrees) DBC solution and a color change took place after 24 hrs. I then filtered out any solids and remaining AR solution... then made up Oxalic Acid 1000g/1L and made 2 L, which I heated to 80 C. I added the DBC pregnant solution heated to 80C to the Oxalic and stirred for 24 hrs at 80C...I received no gold Chloride drop.
> 
> Prior to the Ox/DBC mixing I also washed the pregnant DBC solution with (337 ml 37% HCL with 2663 Mls DI water 4 times). The wash water was yellow and last wash was pretty clear.
> 
> 1.) Can I still recover the gold from the DBC or the acid wash or the Oxalic acid layer(which is now yellow), and if so, where exactly is the gold now? I have saved all solutions separately.
> 
> 2.) My DBC was from TCI chemical company of Japan.
> 
> PLUS..some posts mention Ammonia...?
> 
> I am not sure what to do next...Please send rescue service..;-)
> 
> Thank you,
> 
> John"
> 
> 
> I am not an expert but I do know you should add ammonia before precipitating with oxalic acid in order to get a neutral ph level (I think it should be 7), but perhaps you already did something that does the same thing. Just my 2 cents.
> 
> PLEASE excuse the crude copy and paste quote technique. :mrgreen:


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## Lou

Sounds like you extracted iron, not gold.

Have you stannous chloride tested any of your raffinates?


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