Will it BLEND?

[SilverNitrate]

Yes, if you have dropped your gold from AR using copper ingot/foil/wires then you may only have have 95% gold by weight.
You can boil it in HNO3 or H2SO4, but you will have to agitate the mixture to a great degree.
My method to getting that other 9 is to take your gold precipitate and place in a blender (an old Osterizer with glass pitcher and SS chopper blade works perfect) pour in 50% mixture of HNO3 or H2SO4 make sure you have good seal on the bottom and top and let it churn for a couple minutes. After you take this out keep the acid for more refining, rinse it off, neutralize and dry it. Now your gold is atleast 99.5% and depending on what silver or other alloyed to gold content you could have 99.99% fine gold!

 

[Harold_V]

Yes, if you have dropped your gold from AR using copper ingot/foil/wires then you may only have have 95% gold by weight.
You can boil it in HNO3 or H2SO4, but you will have to agitate the mixture to a great degree.

I'm a bit confused about your post. Here's what troubles me. If a person is looking to recover gold from a solution that may contain other elements (platinum and palladium come to mind), the copper used for precipitation will not be selective. All of it will precipitate, assuming enough copper is introduced. HNO3 will remove the copper or the palladium, but platinum would remain. The process you recommend is very good for recovering the values, but not so good for refining. A selective precipitant would be preferred by far, many of which are not only more reasonably priced, but very convenient, minimizing contaminations in the bargain.

The other thing that troubles me is that H2SO4 will not dissolve copper. It is commonly used as a pickle for copper, to remove oxides, which readily dissolve in dilute H2SO4.

Is it possible you are making reference to something beyond refining, simple recovery of values with little concern for purity? Otherwise, one might be far better off to use a precipitant that is in keeping with the requirement at hand.

My method to getting that other 9 is to take your gold precipitate and place in a blender (an old Osterizer with glass pitcher and SS chopper blade works perfect) pour in 50% mixture of HNO3 or H2SO4 make sure you have good seal on the bottom and top and let it churn for a couple minutes. [/color]After you take this out keep the acid for more refining, rinse it off, neutralize and dry it. Now your gold is atleast 99.5% and depending on what silver or other alloyed to gold content you could have 99.99% fine gold!

Real mixed emotions here. HNO3 will attack the sintered bronze bushing that is characteristic of most blenders. Stainless is passivated by HNO3, so not much change would be expected from the stainless. H2SO4, on the other hand, will definitely dissolve stainless.

How are you dealing with the dissolved metals that are sure to lend contamination to your process instead of removing them?

Have you had your end product assayed to verify your claim of purity? Achieving 4 9's gold isn't easily accomplished chemically, and would be particularly difficult when you're introducing dissolved metals in the process. Just curious, mind you. I hope to learn something from your experience.

Harold

 

[SilverNitrate]

Method based on cleaning up the precipitated gold. When copper is used to plate out the gold over an extend period of time (I keeps it in a minimum of 1 week) the copper tend to flake off or adhere to some of the gold sponge. Using a blender to chop everything up in HNO3 gets the chunks smooth and improves the surface area for the acid to work on the metals.

An old Osterizer blender has served well for me. I use HNO3 because I have easy access to it, but H2SO4 is something I haven't used. The stainless blades are holds up well, then again think of this as a consumable for your lab, (the glass pitcher replacement can be found at some dollar stores and resale shops) make sure it has the rubber 'O' rings in it.

After this is blended for 1-2 minutes, I pour it all in a glass pot and heat it to a near boil to dissolve the traces of copper.
I suction rinse off the gold (make sure your used HNO3 is for another AR batch) with water then ammonium NH4OH to drive off trace ions.

when I have assayed this method I gets it up to at least 99.5 with 99.85 being my highest. then again this is from multiple batches of varying techniques.

I mention H2SO4 for when HNO3 may not be available... H2SO4 will dissolve copper when heated. The stainless steel (which is not hot) will only become matte looking from a polished surface, so the H2SO4 may only remove a micron of its layer.

 

[Harold_V]

when I have assayed this method I gets it up to at least 99.5 with 99.85 being my highest. then again this is from multiple batches of varying techniques.

Please accept my comments in the spirit in which they're offered. This thread is a rare opportunity for readers to see what's wrong with a process, so they can avoid using it. I'd like to have them see it as an opportunity to learn things NOT to do.

Personally, I wouldn't find the quality you mentioned, above, acceptable. I've re-refined gold of higher quality because I wasn't pleased with the purity.

Do you have a copy of Hoke's book? If you do, you'll understand what I'm about to say. If you do not, you certainly need one. If not, I recommend you invest in one at your earliest convenience, and read it well, until you understand what it has to offer, and why you shouldn't be using the procedure you outlined. Perhaps then you may wish to alter your techniques in keeping with acceptable procedures that yield quality gold. Yours do not.

Using copper for recovery is no stranger to me. I used it for years, and know all too well that there is little chance of high purity---blender be damned. Copper should be looked upon as a recovery process, not a purification process. You are creating far too much work trying to eliminate something that isn't necessary to be included when refining gold. Unless I don't understand something, perhaps having overlooked something of importance, you would be so much better off abandoning the use of copper in this case.

For the record----I used copper to recover silver. It's the fastest and easiest method to recover silver, and works well in that it will not precipitate any of the other base metals, all of which contaminate the electrolyte in a parting cell, drastically shortening its useful life.

When copper is used to recover silver from a nitrate solution, copper becomes the chief contaminant in the electrolyte, even after melting the cement silver with a generous flux cover, which, in theory, absorbs all the copper oxide. Clearly, too much copper is included, in spite of careful washing of the cement, and the melting procedure, which never included any soda ash. There would be no reason for it to behave differently with gold, so you are clearly introducing copper that will not be removed. If you'd use a different precipitant, you could expect gold that ran, easily, 999, and probably better. You're struggling to get there after washing and blending. Not good!

I mention H2SO4 for when HNO3 may not be available... H2SO4 will dissolve copper when heated.

No. it will NOT dissolve copper when heated. It is commonly used to pickle copper, and I've used it myself for that very purpose. You can boil copper for a prolonged period of time without dissolving it in the least, aside from the oxides that were present. My experience is related to heat treating beryllium copper springs after manufacturing. They were heat treated in a furnace without a controlled atmosphere, so were oxidized. Prolonged boiling to insure removal of all the oxides didn't alter them in the least.

It would be a kindness to not post information that is misleading----some of these folks hang their hat on words posted by folks that post as if they know what they're doing, even when they don't. Advising anyone to dissolve copper with H2SO4 is a disservice.

The stainless steel (which is not hot) will only become matte looking from a polished surface, so the H2SO4 may only remove a micron of its layer.

That's because you are dissolving miniscule traces of stainless, which ends up in the gold, albeit as a solution. As I've already stated, one does not introduce contaminants to eliminate contaminants. Metallic objects should not become a part of the refining process, not for any reason, especially when they are not necessary, and they aren't in this case.

In keeping with that thought, you also failed to address the fact that nitric acid, along with sulfuric, will have a profound effect on the Oilite bushing found in blenders. Not only will each of them dissolve some of the bushing, with the dissolved metals becoming a part of the slurry, the bushing is prone to premature failure because it is being dissolved. You risk an acid leak on the top of the blender unit.

I see the blender idea as one best never used, and I highly suggest readers avoid this method of processing. It is a sure recipe for low quality gold. Fact is, I firmly believe that gold of reasonable purity would be degraded by the process, not improved.

If you can provide us with evidence that I'm wrong, I'll gladly retract my comments, accompanied with an apology.

For those that may not understand refining, I've worked damned hard to provide information that is successful. I really don't like to see methods proposed that defeat not only my efforts, but are not acceptable as a process. Anyone that desires to refine should learn good, sound, basic processes and become familiar with the reactions and results before venturing beyond that which is proven by time. A person with no experience has no idea if a process is working in an acceptable fashion, or not. It is for that reason I promote Hoke's book. When you understand it, you will be able to make decisions that don't get you in trouble.

Please let me know if I've missed something.

Harold

 

[SilverNitrate]

I'll post a pic a bit later of the finished and dried gold powder. And it looks to be of good quality.
Though I never used H2SO4 in a blender, only HNO3, the blender pitcher I have used more than a dozen time for 3 years and have seen no diminished performance not even any leaks from holding the acid or products.
H2SO4 will along with heat dissolve copper, I have used to make CuSO4.5H2O all the time (blue crystals used for copper plating)
My OP was not meant for purifying the gold, but just rather cleaning it up because bits of solid copper will be in the gold precipitate. I like to use the blender because it makes the gold precip denser, (I can fit 20oz of it in a 4oz bottle) where as if not it would be half that.
Also I usually gets 1/2 oz of undissolved copper out of my 10 oz gold precip batch.

I'd like to see this Hoke book, is it avail electronically?

 

[Harold_V]

I'll post a pic a bit later of the finished and dried gold powder. And it looks to be of good quality.

The appearance means very little. It's the purity that matters, assuming you care. Many here do.

The real test is how it melts. If you can melt it without a flux cover, and have it remain shiny, with a broad crystal structure on the surface of the button, and a deep pipe where it last solidifies, you may have my attention. Right now, I still don't like what I'm being told.

Refining gold is no stranger to me, having done it for more than 20 years, many of them as my sole source of income. Not that I consider myself the sole authority, far from it. I simply know what it takes to get pure gold, and introducing contaminants to it isn't exactly the way to go. I do agree, copper is a great way to recover gold from solution if you aren't concerned with purity. It leaves behind many contaminants, but is NOT totally selective. If you have any of the platinum group in solution, they, too, are precipitated. That defeats the purpose of precipitation, with one exception. I have advised folks to use it when they've screwed up and have dissolved an abundance of base metal with the values, but otherwise I see little to recommend it.

Going a bit further, I'm NOT an advocate of washing precipitated gold with nitric. Once the gold has been precipitated, it's very easy to re-dissolve when nitric is re-introduced. One can do an admirable job of washing precipitated gold using HCl (having come from a chloride solution when it's precipitated, the introduction of more HCl isn't risky), but when precipitating with copper, that is no longer true. HCl has little effect on pure copper, certainly not enough to cleanse it properly.

Though I never used H2SO4 in a blender, only HNO3, the blender pitcher I have used more than a dozen time for 3 years and have seen no diminished performance not even any leaks from holding the acid or products.

That surprises me, I must say. I've used enough nitric acid to know that if it's presented to a copper alloy, the reaction is sure and swift. How you're avoiding damage I don't understand. One thing is sure, if it gets past the seal, it won't take long to destroy the bearing----otherwise it wouldn't have any effect on the gold, wouldn't you say? Personally, I wouldn't be willing to risk the loss, nor the danger of nitric acid entering the motor, which it can do if it leaks. None of this is sound chemistry, not in my book.

H2SO4 will along with heat dissolve copper, I have used to make CuSO4.5H2O all the time (blue crystals used for copper plating)

Absolutely. It dissolves the oxides----but you can boil copper for hours on end without dissolving the metal itself. Unless you are dealing with concentrated sulfuric, you are misinformed. Do you recall my telling you that sulfuric acid is used as a pickle for copper? Why do you suppose that is?

Next time you have the opportunity, place a solid piece of copper in some sulfuric and give it a prolonged boil. Inform all of us how much gets dissolved. As I said, I've boiled copper components to remove oxides. There's no way in hell they were dissolved. Physically, those that had been boiled were identical in every way aside from surface finish. Mind you, I'm looking at this from the perspective of a machinist, so I'm very capable of taking measurements to tenths of thousandths, and have the necessary instruments.

If sulfuric was the solution to dissolving copper, there would be almost no need for the work-arounds these guys have created, a result of the difficulty in obtaining nitric acid, at least here in the States. It doesn't work, so until you have done it successfully, it would be a kindness to quit telling folks it does.

My OP was not meant for purifying the gold, but just rather cleaning it up because bits of solid copper will be in the gold precipitate. I like to use the blender because it makes the gold precip denser, (I can fit 20oz of it in a 4oz bottle) where as if not it would be half that

Given the method of precipitation, I guess I can understand that. It still would be poor reason to use copper, however. There are precipitants that will yield quite dense gold -----one of which is SO2. It not only yields dense precipitate, it also yields gold without including a contamination, aside from drag-down of residual metals. The use of copper doesn't eliminate that problem either, so there is no advantage. I'm totally mystified by your insistence in its use. It makes no sense, not if you're trying to recover pure gold.

Also I usually gets 1/2 oz of undissolved copper out of my 10 oz gold precip batch.

Interesting.

Need I say more?

You can recover your gold without introducing metals. You'd be far ahead of the game. Can you explain it in terms that will have me understand your logic?

I'd like to see this Hoke book, is it avail electronically?

I know of no source aside from buying the book. It's not expensive-----not if you know of only your method of dealing with gold. You stand to learn so much, it would be a bargain at $300. You can purchase it for less----about $75. It's worth every dime----especially when you're using such bizarre procedures. You can be proud to have come so far without good guidance, but you really need to explore better procedures unless your intention is to fill those 4 ounce bottles with impure gold powder.

Here's a source for the book. Please do yourself a favor and invest in a copy. It will be very revealing.

http://www.gesswein.com/catalog/catalog.cfm?cat=12&sub=3&subsub=59&catalog=1&CFID=1471004&CFTOKEN=30985426

If you are not successful at Gesswein, there is another source. Let me know and I'll provide the information. A recent post indicates that Gesswein has a lower price. The title you are looking for is Refining Precious Metal Wastes, written by C.M. Hoke.

For the record----I have no personal interest in the book, or in Gesswein. I'm simply trying to give you some much needed guidance via Hoke's book. It's very good, especially for those that don't understand acceptable testing and refining procedures. You need not be a chemist to understand the book-----it's written in layman's terminology, and is a step by step instruction, unlike almost any other book I've seen on refining.

Harold

 

[Lou]

Only concentrated sulfuric acid dissolves copper, and that's only at high temperatures (150C+), and used in excess. You won't be getting much hydrate either (remember excess sulfuric), so it won't be that nice blue colour.

50% concentrations of warm H2SO4 are good for pickling Cu.



Harold is right, if you're dropping with copper, you'll have other things coming down too. Even if you use a proper reducing agent like sulfite, you can still have drag down and get crappy gold. While the nice blonde of your gold is indicative of good quality, that can be misleading. The true test is in the melt. If you see any oxide scum on the gold or your borax discolours then it is evident that you have impure gold.