Back to square 1. Can't you heat it even a little? Maybe, run your heat gun over it a little? Maybe a little more strong nitric will help.
Aqua Regia refining of karat gold scrap
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I heated the beaker until it was warm to the touch. No signs of a reaction, no bubbles, no vapors, nada. I added 10 mL more of 70% Nitric, nothing. The total solution size is about 100 mL.
The remaining pieces look silvery red with a moss of brown powder clinging to them. They are about the size of BBs. I see four of five of them amongst a 1/4" deep mossy brown mass. When swirled you can barely make out the BBs.
What next?
Steve
The remaining pieces look silvery red with a moss of brown powder clinging to them. They are about the size of BBs. I see four of five of them amongst a 1/4" deep mossy brown mass. When swirled you can barely make out the BBs.
What next?
Steve
Noxx
Well-known member
Maybe you could try to break the gold «crust» covering the pieces with a glass rod...
It's not so much a crust as a loose moss. When I swirl the beaker it floats off of the BBs freely revealing the silvery red metal underneath.
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lazersteve said:
Red flag!
Check the item with a magnet. It sounds like you may have a piece of iron that's precipitating copper----but that's a long shot. If it is copper, adding new acid should dissolve it-----but you say it doesn't dissolve.
When you inquart properly, the gold left behind, unless it breaks down to fine powder, which is often black, will be a dark reddish brown color, and will usually be the perfect image of what it was prior to dissolution of base metals, although it might be slightly smaller. There would be no reason for globules to grow (if they're not copper)------unless they are gold globules, being precipitated by some unknown element. None of your gold should have gone into solution with this process, so my money is still riding on the thing being magnetic. This is a strange one, Steve.
Harold
Harold,
Thank you for the reply, the material is not magnetic, I just checked it with a very powerful magnet and it didn't budge.
Here's a closeup of the stuff:
It's hard to see so I circled some of them in the photo.
Steve
Thank you for the reply, the material is not magnetic, I just checked it with a very powerful magnet and it didn't budge.
Here's a closeup of the stuff:
It's hard to see so I circled some of them in the photo.
Steve
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Long shot, Steve. Could you have possibly included some aluminum in the lot? Something has to be responsible for the growth of which you speak, and it should be soluble in nitric. After all, what it grows from came from nitric solution. Aluminum would be a likely candidate at it is not soluble in nitric, but would easily precipitate copper (and silver).
I'm baffled!
If it was up to me, I'd boil it hard in nitric, then go to AR----and let the chips fall where they may. Once in a while you come across something that seemingly has no solution. I'm not suggesting this is one of them, but without being able to do to it what I would do to it, and make observations that may mean something to me, based on my past experiences, I'm afraid I'm out of guesses. Keep posting your results, and maybe we can get this thing resolved.
Were it not for growing nodules, I'd suggest all you need to do is re-melt with more silver, but this thing bothers me-----the growth does, anyway.
Can you tell me what you started with? If so, can you describe each piece to the best of your ability? There may be something in what you used that's key to this thing. Some newer jewelry, for example, has no precious metal content. Class rings are amongst them as I recall. Sure could be wrong, though. I've been away too long.
Harold
I'm baffled!
If it was up to me, I'd boil it hard in nitric, then go to AR----and let the chips fall where they may. Once in a while you come across something that seemingly has no solution. I'm not suggesting this is one of them, but without being able to do to it what I would do to it, and make observations that may mean something to me, based on my past experiences, I'm afraid I'm out of guesses. Keep posting your results, and maybe we can get this thing resolved.
Were it not for growing nodules, I'd suggest all you need to do is re-melt with more silver, but this thing bothers me-----the growth does, anyway.
Can you tell me what you started with? If so, can you describe each piece to the best of your ability? There may be something in what you used that's key to this thing. Some newer jewelry, for example, has no precious metal content. Class rings are amongst them as I recall. Sure could be wrong, though. I've been away too long.
Harold
The source material came form the stripping cell.
I'm sure you've seen the pictures of it along the way here and there on the forum. I melted it without flux and it appeared to be mostly gold with a hazy or milky (hard to describe) whitish red surface coloration weighing 11.5 grams. I was shocked at how impure the cell gold came out this time exactly the opposite of what I expected :?:
From here I parted the gold with the silver I showed you earlier :
I melted the silver and gold together in a brand new clean melting dish and cornflaked:
I put the cornflaked material in a beaker with diluted nitric acid. The results are as you saw in my previous post.
Steve
I'm sure you've seen the pictures of it along the way here and there on the forum. I melted it without flux and it appeared to be mostly gold with a hazy or milky (hard to describe) whitish red surface coloration weighing 11.5 grams. I was shocked at how impure the cell gold came out this time exactly the opposite of what I expected :?:
From here I parted the gold with the silver I showed you earlier :
I melted the silver and gold together in a brand new clean melting dish and cornflaked:
I put the cornflaked material in a beaker with diluted nitric acid. The results are as you saw in my previous post.
Steve
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Steve,
We'll get this figured out now!
How I wish I'd have had a chance to talk to you about the material from the cell before you inquarted.
One of the purposes of inquartation is to expose gold so it can be dissolved. In your particular case, the gold was already very finely divided------which explains its color (colloidal), as you know. In this instance, there is nothing to gain from inquartation, although I figure you probably did so for a tutorial.
This material would have been a perfect candidate for a direct AR process, no inquartation required, simply because you already had it finely divided. You can even reduce unwanted elements when in this state. The nice thing is, with proper pre-treatment, you very well could come up with 9995 (or better) gold without a second refining. The finely divided state of the material is ideal!
One of the great ways to eliminate an unwanted acid, so it won't affect the next operation, is to incinerate. That also oxidizes elements, so they might go into solution when they, otherwise may not have. Copper oxide, for example, is soluble in sulfuric, but clean copper is not. I've mentioned this because there are times when you must go from a nitric dissolve to an HCl wash before extracting gold. Jewelers floor sweeps are a good example. Incineration eliminates the nitric, so the HCl doesn't touch the gold, but cleans up the material so you don't have problems with filtering your gold chloride solution.
Anyway, I'd have incinerated what you had, then boiled it in HCl, which would have removed substances that make filtration of gold chloride difficult. That's a critically important step if the source of your gold is related to tin, which, in electronic scrap, is very likely.
After the HCl wash, I'd rinse the material with water, allowing everything to settle well before decanting. Hot water accelerates the settling time. If the solution was quite dirty, I might give it more than one rinse. Once I was satisfied, I'd go directly to AR.
Now that I understand the source of your material, can you tell me how much silver you used as compared to the weight of the gold? In this instance, you'd have to use roughly three times the weight of the gold, which you would assume to be pure for the sake of the calculation.
If you used less, and you didn't stir, you have probably landed on the source of your problem. The un-dissolved bits are likely high karat alloy---better than 10K. They won't break down in nitric once you've dissolved the surface away. The gold, which normally honeycombs, is too dense to permit penetration of the nitric. That condition is to be expected if you didn't use enough silver, or some of your gold didn't get well mixed with the silver you added. I still have no explanation for the growth you've experienced.
Harold
We'll get this figured out now!
How I wish I'd have had a chance to talk to you about the material from the cell before you inquarted.
One of the purposes of inquartation is to expose gold so it can be dissolved. In your particular case, the gold was already very finely divided------which explains its color (colloidal), as you know. In this instance, there is nothing to gain from inquartation, although I figure you probably did so for a tutorial.
This material would have been a perfect candidate for a direct AR process, no inquartation required, simply because you already had it finely divided. You can even reduce unwanted elements when in this state. The nice thing is, with proper pre-treatment, you very well could come up with 9995 (or better) gold without a second refining. The finely divided state of the material is ideal!
One of the great ways to eliminate an unwanted acid, so it won't affect the next operation, is to incinerate. That also oxidizes elements, so they might go into solution when they, otherwise may not have. Copper oxide, for example, is soluble in sulfuric, but clean copper is not. I've mentioned this because there are times when you must go from a nitric dissolve to an HCl wash before extracting gold. Jewelers floor sweeps are a good example. Incineration eliminates the nitric, so the HCl doesn't touch the gold, but cleans up the material so you don't have problems with filtering your gold chloride solution.
Anyway, I'd have incinerated what you had, then boiled it in HCl, which would have removed substances that make filtration of gold chloride difficult. That's a critically important step if the source of your gold is related to tin, which, in electronic scrap, is very likely.
After the HCl wash, I'd rinse the material with water, allowing everything to settle well before decanting. Hot water accelerates the settling time. If the solution was quite dirty, I might give it more than one rinse. Once I was satisfied, I'd go directly to AR.
Now that I understand the source of your material, can you tell me how much silver you used as compared to the weight of the gold? In this instance, you'd have to use roughly three times the weight of the gold, which you would assume to be pure for the sake of the calculation.
If you used less, and you didn't stir, you have probably landed on the source of your problem. The un-dissolved bits are likely high karat alloy---better than 10K. They won't break down in nitric once you've dissolved the surface away. The gold, which normally honeycombs, is too dense to permit penetration of the nitric. That condition is to be expected if you didn't use enough silver, or some of your gold didn't get well mixed with the silver you added. I still have no explanation for the growth you've experienced.
Harold
Harold the ratio of silver to gold was just shy of 3 parts sliver to 1 part gold. Lack of proper stirring must have been the problem.
Trying to understand all that's going on in this topic is a little above myself. Although I did learn a lot. Just trying to figure out what evaporate means.
Anyhow, I took Harold's advice on washing the gold & got a lot of garbage out. On 2nd refinement I tried to control the nitric as best I could, but it still needed a little urea.
Before I precipitated, I diluted 3x water then added a good slug of sulfhuric acid like GSP says, and filtered it. I warmed the solution on a coffee plate and precipitated with sodium met. I boiled a little water and mixed the sodium met then dumped it in. It kinda boiled in a flash when I added it. The plastic spoon I used to stir it with came out coated with yellow shiny gold.
The gold that dropped was also a shiny gold color. As if it was gold dust. Not all of it dropped, so I added a little more sodium met. and the rest dropped a light brown like it normally does.
Anyone know what happened that it dropped all shiny? It's a real light tan / gold color and acts slippery like silica sand. Or is it really that clean and supposed to be that way?
In the pictures, the little white dots are reflections of light on the shiny gold mud.
Anyhow, I took Harold's advice on washing the gold & got a lot of garbage out. On 2nd refinement I tried to control the nitric as best I could, but it still needed a little urea.
Before I precipitated, I diluted 3x water then added a good slug of sulfhuric acid like GSP says, and filtered it. I warmed the solution on a coffee plate and precipitated with sodium met. I boiled a little water and mixed the sodium met then dumped it in. It kinda boiled in a flash when I added it. The plastic spoon I used to stir it with came out coated with yellow shiny gold.
The gold that dropped was also a shiny gold color. As if it was gold dust. Not all of it dropped, so I added a little more sodium met. and the rest dropped a light brown like it normally does.
Anyone know what happened that it dropped all shiny? It's a real light tan / gold color and acts slippery like silica sand. Or is it really that clean and supposed to be that way?
In the pictures, the little white dots are reflections of light on the shiny gold mud.
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Congratulations, Phillip!
That light color you referenced is exactly what the pure stuff looks like. When I used to discuss the second refining, I'd often comment on how
"blonde" the gold came down.
I'm not sure I know what I'm going to say is true, but my thoughts are that when there is little in the way of contamination present, the crystals of gold will grow larger, thus they begin to develop faces that reflect light directionally. Very finely divided gold doesn't do that, and eventually diffuses light in all directions, so you see it as black, or dark purple. In addition, because the gold has little in the way of contamination, it's far more eager to agglomerate. You'll notice that when you abrade the stuff, it will shine as if it's been melted. Dirty gold powder won't do that, or, if it does, it takes a lot more energy to make it do so.
There is no doubt in my mind, the color of the gold, as it precipitates, is a good indicator of the purity, but in no way should be construed as an assay.
I'm pleased to hear you found evidence of contamination upon washing---it's an important step that can't be stressed too much. Relying on flux to purify gold is a serious mistake. Sort of like wearing perfume instead of taking a shower!
I'd like to comment on the use of plastic when precipitating gold. I've already stated that I don't recommend it. It has a strong affinity for precipitated gold, so unless you recycle the containers after use, you'll lose values. Your gold plated spoon is exactly what I'd have expected.
If you use a glass vessel that isn't scratched, you can use a plastic policeman to rid the glass of clinging gold. Scratched vessels become a real problem. Gold will firmly attach to the scratches, making removal almost impossible. My work habits revolved around using specific beakers for precipitation. As old beakers were retired, I'd promote the beakers, and start using the new ones strictly for precipitation. If you're using other vessels, the same concept would apply------so keep that in mind when you select your labware.
Evaporate can be taken literally. When you use too much nitric, one of the options to rid the solution is to evaporate it until it's expelled. You heat the solution (best done in an evaporating dish, which presents a very large surface for evaporation, but it can be carried out adequately in a beaker) at a low heat, allowing the contents to go into the atmosphere. If you do it at the proper speed, it happens with no losses of values. If you go too fast (too hot), you can often see a slight yellow tint to the gasses------a sure sign you're losing gold.
As you evaporate, your solution changes color. It borders on the impossible to tell you from what to what, because the color is heavily influenced by the metals contained within. Assuming you have only gold, it starts life somewhat honey colored, and darkens to a deep red as the solution evaporates. If you add HCl (which actually helps expel the nitric, but you have to carry the evaporation to the red stage before it does), the solution reverses color and gets lighter, and you can often see a brown cloud coming off (that's the nitric being expelled).
Hope the explanation helps. The best advice I can offer you is to get a copy of Hoke's book------it's totally outlined. Get the book, even if you can successfully process gold. There's one hell of a lot of useful information in it for the novice. I can't over state the value of that book.
Harold
That light color you referenced is exactly what the pure stuff looks like. When I used to discuss the second refining, I'd often comment on how
"blonde" the gold came down.
I'm not sure I know what I'm going to say is true, but my thoughts are that when there is little in the way of contamination present, the crystals of gold will grow larger, thus they begin to develop faces that reflect light directionally. Very finely divided gold doesn't do that, and eventually diffuses light in all directions, so you see it as black, or dark purple. In addition, because the gold has little in the way of contamination, it's far more eager to agglomerate. You'll notice that when you abrade the stuff, it will shine as if it's been melted. Dirty gold powder won't do that, or, if it does, it takes a lot more energy to make it do so.
There is no doubt in my mind, the color of the gold, as it precipitates, is a good indicator of the purity, but in no way should be construed as an assay.
I'm pleased to hear you found evidence of contamination upon washing---it's an important step that can't be stressed too much. Relying on flux to purify gold is a serious mistake. Sort of like wearing perfume instead of taking a shower!
I'd like to comment on the use of plastic when precipitating gold. I've already stated that I don't recommend it. It has a strong affinity for precipitated gold, so unless you recycle the containers after use, you'll lose values. Your gold plated spoon is exactly what I'd have expected.
If you use a glass vessel that isn't scratched, you can use a plastic policeman to rid the glass of clinging gold. Scratched vessels become a real problem. Gold will firmly attach to the scratches, making removal almost impossible. My work habits revolved around using specific beakers for precipitation. As old beakers were retired, I'd promote the beakers, and start using the new ones strictly for precipitation. If you're using other vessels, the same concept would apply------so keep that in mind when you select your labware.
Evaporate can be taken literally. When you use too much nitric, one of the options to rid the solution is to evaporate it until it's expelled. You heat the solution (best done in an evaporating dish, which presents a very large surface for evaporation, but it can be carried out adequately in a beaker) at a low heat, allowing the contents to go into the atmosphere. If you do it at the proper speed, it happens with no losses of values. If you go too fast (too hot), you can often see a slight yellow tint to the gasses------a sure sign you're losing gold.
As you evaporate, your solution changes color. It borders on the impossible to tell you from what to what, because the color is heavily influenced by the metals contained within. Assuming you have only gold, it starts life somewhat honey colored, and darkens to a deep red as the solution evaporates. If you add HCl (which actually helps expel the nitric, but you have to carry the evaporation to the red stage before it does), the solution reverses color and gets lighter, and you can often see a brown cloud coming off (that's the nitric being expelled).
Hope the explanation helps. The best advice I can offer you is to get a copy of Hoke's book------it's totally outlined. Get the book, even if you can successfully process gold. There's one hell of a lot of useful information in it for the novice. I can't over state the value of that book.
Harold
PhillipJ,
Great looking gold. You've really come along fast. If you rinse and melt it well, you're going to have a very high purity ingot.
Harold,
I agree with you in most every aspect. You know my feelings in the plastic vs glass controversy, so I won't get into that. I would like to discuss the subject of cleaning up impure gold in the melt.
It's much more difficult to clean off purity gold in a melting dish than in a crucible furnace. However, it can be done in both. I'm talking about gold that still has base metals in it. I'm not talking about gold contaminated with Pt group metals. With Pt group contamination, you have to start over and redissolve it in aqua regia.
I try, as you do, to do everything possible to get the gold very pure before melting it. Sometimes, though, it is slightly off purity and needs a little flux work. At this point, I will play with it until it is pure. It takes, at the most, 10 extra minutes. Probably, 98% of the time, I am successful. If I understand your past posts, you see the need for fluxing as a bad thing and will put it right back through aqua regia. I don't understand your reasoning and maybe I have misunderstood you. I look at flux cleaning as only another gun in my arsenal. The end product is all that counts. It doesn't matter how I get there.
The blond gold is great when you get it, but it's not necessary for pure gold. At least, not that I've ever noticed. Most times, the darker gold is just as pure. The darker gold is more finely divided and, therefore, is harder to rinse. I never really paid much attention to color, since I had developed good rinsing techniques and I knew I could clean most anything off purity in the melt. We both knew what high purity gold looked like. The gold we both produced met these stringent visual requirements. You ran your gold through twice. I ran mine once and cleaned up problems in the melt. Both ways worked. Same end product. Same deep pipe, gorgeous color, and super well-defined crystal.
I worked for a guy that was the best refiner I've ever known. Along with silver cells, his main expertise was karat golds and he could do them faster than either of us could imagine. He didn't inquart but he cast a bar and ran it through a huge set of power rolls. He rolled it paper thin, then coiled it up and put it into aqua regia. If it was brittle, the rolls crumbled it into a jillion pieces. In both cases, it had much more surface area than any shot you've ever seen*. After aqua regia, he melted in a dedicated pure gold furnace and was a master at flux cleaning. I would guess that he could clean gold as low as 99.5%, or less. For gold he couldn't clean - a rarity - or gold with Pt group, he ran it back through aqua regia and used a different precipitating agent.
* I noticed that, in the link for the Italian refining machine that aflac gave, they use a metal atomizing gun to shot the gold. This would be the absolute best way to optimize the dissolving speed of the aqua regia.
Great looking gold. You've really come along fast. If you rinse and melt it well, you're going to have a very high purity ingot.
Harold,
I agree with you in most every aspect. You know my feelings in the plastic vs glass controversy, so I won't get into that. I would like to discuss the subject of cleaning up impure gold in the melt.
It's much more difficult to clean off purity gold in a melting dish than in a crucible furnace. However, it can be done in both. I'm talking about gold that still has base metals in it. I'm not talking about gold contaminated with Pt group metals. With Pt group contamination, you have to start over and redissolve it in aqua regia.
I try, as you do, to do everything possible to get the gold very pure before melting it. Sometimes, though, it is slightly off purity and needs a little flux work. At this point, I will play with it until it is pure. It takes, at the most, 10 extra minutes. Probably, 98% of the time, I am successful. If I understand your past posts, you see the need for fluxing as a bad thing and will put it right back through aqua regia. I don't understand your reasoning and maybe I have misunderstood you. I look at flux cleaning as only another gun in my arsenal. The end product is all that counts. It doesn't matter how I get there.
The blond gold is great when you get it, but it's not necessary for pure gold. At least, not that I've ever noticed. Most times, the darker gold is just as pure. The darker gold is more finely divided and, therefore, is harder to rinse. I never really paid much attention to color, since I had developed good rinsing techniques and I knew I could clean most anything off purity in the melt. We both knew what high purity gold looked like. The gold we both produced met these stringent visual requirements. You ran your gold through twice. I ran mine once and cleaned up problems in the melt. Both ways worked. Same end product. Same deep pipe, gorgeous color, and super well-defined crystal.
I worked for a guy that was the best refiner I've ever known. Along with silver cells, his main expertise was karat golds and he could do them faster than either of us could imagine. He didn't inquart but he cast a bar and ran it through a huge set of power rolls. He rolled it paper thin, then coiled it up and put it into aqua regia. If it was brittle, the rolls crumbled it into a jillion pieces. In both cases, it had much more surface area than any shot you've ever seen*. After aqua regia, he melted in a dedicated pure gold furnace and was a master at flux cleaning. I would guess that he could clean gold as low as 99.5%, or less. For gold he couldn't clean - a rarity - or gold with Pt group, he ran it back through aqua regia and used a different precipitating agent.
* I noticed that, in the link for the Italian refining machine that aflac gave, they use a metal atomizing gun to shot the gold. This would be the absolute best way to optimize the dissolving speed of the aqua regia.
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goldsilverpro said:
The thinking is flawed where fluxing to purify is involved. Fluxes do not remove clean metals, only the oxides. Unless you introduce something to fully oxidize the metals, they won't be removed, regardless of the system. The only improvement you can expect is the removal of already oxidized metals, and then only if the entire mass is exposed to the flux. To further complicate the matter, If you get stupid and add reducing agents (soda ash, for example), you not only don't remove the oxides, you reduce them and add them back to the gold as clean metals. The gold will come out shiny if kept under a flux cover, but it is not pure.
Clearly, melting under a flux cover has a limited effect on the fineness of gold, Were that not the case, all a refiner would have to do is melt his gold with flux and have it come pure. Both of us know that doesn't happen. Fact is, that's the reason I started double refining. Fluxing alone would not improve the quality to my level of satisfaction. I can't speak for others.
That may have happened to you, but it didn't happen to me. Now you understand why I asked you about your reports of consistent 9999 gold. As I've already stated, I double refined my gold for years to avoid the problem----secure in the knowledge that it rarely comes down in good quality the first precipitation----. Further, the quality suffers far more with gold from dirty solutions. Directly dissolving karat gold with AR by thinning it is a great example of asking for problems. The base metals, along with silver, are included in the solution. Why would you expect to precipitate 9999 quality, when drag-down alone would be significant. Remember, I never said it wouldn't work----fact is, I refined bench filings that way, and got terrible quality gold as a result. It was that gold that became my added metal for evaporating solutions. By melting it, the quality was slightly improved, but the second dissolution proved the key to success. Buttons that came from that gold were always off color (oxides).
It's been well documented that it's not easy to exceed 9995 with the AR process, although not impossible. As a result, I double refined my gold-----if for no other reason, I am an honest person and don't enjoy lying to myself, let alone a customer. I made no guarantee that my gold exceeded industry standard of 9995, although it surely did----but I did guarantee it met the standard. It was a safe way to conduct business-------no one calls you a liar when they get more than they bargained for, but you'll never be forgiven if you advertise 9999 and deliver 9997.
Notice that my ingots were marked simply "Fine Gold"? It was.
My method of melting was very telling of impurities. For one, the gold had every opportunity to get fully oxidized, not being melted under a flux covering, and an oxidizing flame used, not a reducing flame. That was on purpose. Should there be any base metals, the gold not only would come out discolored, but the melting dish would show signs of oxides. I'm very proud to announce that my melting dish was used until it was too thin to be of service, and was colored light purple-----time and again. So, my friend, while my first run gold may have been questionable, my second run gold was not-----ever. The only purpose flux served in my case was to "grease' the melting dish. There was NEVER a flux cover, just enough flux to keep the dish wet. There is no oxide to absorb when there are no base metals present. My second run gold never required a pickle.
On the subject of the color of gold when it precipitates, I made observations, and not once, but over years. I was always more concerned with quality than I was profit------so, to me, this was an important issue. The things I mention, below, are absolutes as far as I'm concerned, and were well supported by the end results I achieved. Please bear in mind that I used sulfur dioxide to precipitate, so nothing was added to my solutions to influence colors.
1- Gold that precipitates from dirty solutions will come down dark. It's a function of the contamination level. It is NEVER pure. It isn't just a matter of being finely divided, although being finely divided is symptom of being dirty.
2- Gold that precipitates from clean solutions will come down blonde---without fail. The sole exception is if the solution is quite dilute, at which time the gold forms smaller crystals, but they never lean towards black, they are slightly darker golden colored, and not as bright as larger crystals. The color, when washed, does not change, for they are dark because they are finely divided, and not reflecting light directionally.
3- Gold that precipitates dark, from dirty solutions, will always lighten in color with a good and proper washing. That involves more than a rinse---it requires boiling with HCl, rinsing well, and the use of ammonium hydroxide. There is no question, the quality of the gold is improved by this process.
4- Gold that precipitates light in color (blonde) generally changes little, if any, when washed. The color is light, and it stays that way. A sure sign the gold is pure. The wash solution does not change color, for it is absorbing nothing.
To me, the observations I've made indicate that the color of gold as it precipitates is a very good indicator of the quality. It would take a lot of evidence to sway my opinion, and I've not seen enough thus far to have that happen.
Harold
Harold,
We could argue about these things till the cows come home. I just hope our bantering is instructive to the readers. I think we both have to search our memories to come up with this stuff. I know I do. No matter how we did it, we both came out with very similar final products. I admire you for perfecting a system to put out pure gold. You should realize, however, that probably no one else in the world uses your exact system yet, there are many other aqua regia refiners that put out gold as pure as yours, with one drop, myself included. From day one and many 10's of thousands of ounces later, besides the economic aspects, super pure gold has always been a pride thing with me. You're the only person I've ever met that routinely uses double aqua regia. I see your logic behind this. I just took a different approach.
About half of the gold I sold went into the manufacture of gold plating salts. Since I started out in the gold plating salts industry, this is where my contacts were. This industry has some of the most stringent gold purity requirements of any other industry. These salts were mainly sold to electronics mfgrs. and were all made with 9999 gold. Anything less would show up in faulty plating and the salts mfgr. would be out of business. My gold was suitable to enter this system.
Since pure gold ingots have a specific visual appearance, I chose to do nothing that would eliminate these visual effects. I wanted any educated buyer to have no doubts that my gold was pure. I didn't fire polish or buff the surface, for example. I didn't stamp my bars. I NEVER tried to sell gold that had oxide discoloration and never used acid to remove it. In my system, this discoloration was rare. When it happened, I remelted and cleaned it up. When I couldn't clean it up, I put it back into aqua regia, the last resort, as far as I was concerned.
In your post, you used words like, "the thinking is flawed" and "stupid", when referring to my methods. Although these words get my blood pressure up a bit, I try to calm down and look at this thing logically. I think that sometimes you feel that anyone with different experiences than you is flat out wrong. When we were refining, we operated in different worlds of industry. Your business was mainly with jewelers. Mine was in the more broad high tech world in L.A., mainly in the electronics manufacturing sector. We both satisfied our customers with pure gold. Most likely, your gold would be satisfactory in my sector and mine in yours. As Steve's signature says, "The proof is in the pudding."
I don't know where you got the idea that I cover the gold with flux. I never allowed that to happen. That would have really been stupid. I only used very small pinches of flux, mainly alternating between borax and niter. I usually used one pinch of soda ash, at the start, to adjust the flow of the flux. If it did reduce oxides, it made no difference, since all were eventually removed with niter. The molten gold forms a convex meniscus and the flux slides to the edge of the button. When I had too much flux, I usually let the gold barely solidify and then poured off the still molten flux. I'm talking about when using a melting dish. When using a crucible, its diameter was much larger than a melting dish and the buildup of flux around the edge of the meniscus isn't as much of a problem. When you add niter, you can see the oxides rise to the top from the interior. The melt is always kept moving with the torch. When base metals are still present, there is a whitish film on the surface. This is a surface effect caused by the oxidizing flame and/or the oxygen in the air. When the base metals are gone, the gold has a brilliant metallic mirror surface with no evidence of white. Further additions of niter don't affect this surface. All of this is much easier to perform in a crucible furnace.
In order of decreasing particle size, gold goes - shiny metallic - blond - tan - light brown - medium brown - dark brown - almost black - black - black slime - purple, all with intermediate shades in between. With all of these, on a microscopic level, the individual particles are bright and shiny and probably crystalline. Only the eye sees them in bulk, in these colors. I would wager that I could, with some experimentation, start with 9999 gold and produce each of these colors, by varying the parameters. When refining, I have seen every one of these. In my experience, the finer gold is, the more difficult it is to filter, leach, and rinse out the contaminates. When really fine, these things become impossible. Therefore, the finer the gold, the more likely the gold will be impure. I always shot for lumpy, fluffy, light or medium brown gold. More like a sponge than a powder. This stuff rinses and leaches beautifully, maybe even easier than the heavier blond powder. Sometimes, the last, maybe 1%, of the gold dropped darker than the rest. I don't know why this happened, but it seemed to cause no problems, since the bulk was of good color..
When filtering, our leaching/rinsing system was a bit different. I went hot water rinses - approx. 50% nitric leach - hot water rinses - ammonia leach - hot distilled water rinses. We both used ammonia. I used it for silver chloride and, I think, you used it to detect any blue solution of nickel or copper. Only traces of these metals produce a strong blue color in the ammoniacal solution. I rarely got any blue because of the large amount of rinsing done, on my spongy gold, before the ammonia. You used HCl and I used nitric. I feel that nitric will remove everything that HCl removes, plus more. I never did understand why you used HCl.
By "dirty solutions", do you mean those that have base metals in them or those that have been improperly filtered?
We could argue about these things till the cows come home. I just hope our bantering is instructive to the readers. I think we both have to search our memories to come up with this stuff. I know I do. No matter how we did it, we both came out with very similar final products. I admire you for perfecting a system to put out pure gold. You should realize, however, that probably no one else in the world uses your exact system yet, there are many other aqua regia refiners that put out gold as pure as yours, with one drop, myself included. From day one and many 10's of thousands of ounces later, besides the economic aspects, super pure gold has always been a pride thing with me. You're the only person I've ever met that routinely uses double aqua regia. I see your logic behind this. I just took a different approach.
About half of the gold I sold went into the manufacture of gold plating salts. Since I started out in the gold plating salts industry, this is where my contacts were. This industry has some of the most stringent gold purity requirements of any other industry. These salts were mainly sold to electronics mfgrs. and were all made with 9999 gold. Anything less would show up in faulty plating and the salts mfgr. would be out of business. My gold was suitable to enter this system.
Since pure gold ingots have a specific visual appearance, I chose to do nothing that would eliminate these visual effects. I wanted any educated buyer to have no doubts that my gold was pure. I didn't fire polish or buff the surface, for example. I didn't stamp my bars. I NEVER tried to sell gold that had oxide discoloration and never used acid to remove it. In my system, this discoloration was rare. When it happened, I remelted and cleaned it up. When I couldn't clean it up, I put it back into aqua regia, the last resort, as far as I was concerned.
In your post, you used words like, "the thinking is flawed" and "stupid", when referring to my methods. Although these words get my blood pressure up a bit, I try to calm down and look at this thing logically. I think that sometimes you feel that anyone with different experiences than you is flat out wrong. When we were refining, we operated in different worlds of industry. Your business was mainly with jewelers. Mine was in the more broad high tech world in L.A., mainly in the electronics manufacturing sector. We both satisfied our customers with pure gold. Most likely, your gold would be satisfactory in my sector and mine in yours. As Steve's signature says, "The proof is in the pudding."
I don't know where you got the idea that I cover the gold with flux. I never allowed that to happen. That would have really been stupid. I only used very small pinches of flux, mainly alternating between borax and niter. I usually used one pinch of soda ash, at the start, to adjust the flow of the flux. If it did reduce oxides, it made no difference, since all were eventually removed with niter. The molten gold forms a convex meniscus and the flux slides to the edge of the button. When I had too much flux, I usually let the gold barely solidify and then poured off the still molten flux. I'm talking about when using a melting dish. When using a crucible, its diameter was much larger than a melting dish and the buildup of flux around the edge of the meniscus isn't as much of a problem. When you add niter, you can see the oxides rise to the top from the interior. The melt is always kept moving with the torch. When base metals are still present, there is a whitish film on the surface. This is a surface effect caused by the oxidizing flame and/or the oxygen in the air. When the base metals are gone, the gold has a brilliant metallic mirror surface with no evidence of white. Further additions of niter don't affect this surface. All of this is much easier to perform in a crucible furnace.
In order of decreasing particle size, gold goes - shiny metallic - blond - tan - light brown - medium brown - dark brown - almost black - black - black slime - purple, all with intermediate shades in between. With all of these, on a microscopic level, the individual particles are bright and shiny and probably crystalline. Only the eye sees them in bulk, in these colors. I would wager that I could, with some experimentation, start with 9999 gold and produce each of these colors, by varying the parameters. When refining, I have seen every one of these. In my experience, the finer gold is, the more difficult it is to filter, leach, and rinse out the contaminates. When really fine, these things become impossible. Therefore, the finer the gold, the more likely the gold will be impure. I always shot for lumpy, fluffy, light or medium brown gold. More like a sponge than a powder. This stuff rinses and leaches beautifully, maybe even easier than the heavier blond powder. Sometimes, the last, maybe 1%, of the gold dropped darker than the rest. I don't know why this happened, but it seemed to cause no problems, since the bulk was of good color..
When filtering, our leaching/rinsing system was a bit different. I went hot water rinses - approx. 50% nitric leach - hot water rinses - ammonia leach - hot distilled water rinses. We both used ammonia. I used it for silver chloride and, I think, you used it to detect any blue solution of nickel or copper. Only traces of these metals produce a strong blue color in the ammoniacal solution. I rarely got any blue because of the large amount of rinsing done, on my spongy gold, before the ammonia. You used HCl and I used nitric. I feel that nitric will remove everything that HCl removes, plus more. I never did understand why you used HCl.
By "dirty solutions", do you mean those that have base metals in them or those that have been improperly filtered?
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goldsilverpro said:
Why do you think I challenge you on subjects with which I don't agree? It is my objective to not only expose things that I feel are wrong, but to describe, to the best of my ability, what's wrong with them, as I see them. I'm not sue, who tossed a wet blanket on subjects but refused to say why. Readers should have every opportunity to not pick up bad habits, which both of us have, no doubt. Our discussions serve a good purpose, even if they annoy you.
If that was the case, why would any of them run parting cells, or for that matter, use the Miller process?
Sorry, I don't agree. Everything I've read indicates that even 9995 on a consistent basis isn't a reasonable expectation for a first refining, and my experiences back that notion perfectly well. That isn't to say that you can't achieve it, but to expect it routinely borders on the unreasonable. I'd be particularly hard pressed to believe you can do so with karat gold that has been directly dissolved with AR by dividing it finely in lieu of inquartation, where base metal and silver content are reduced. The direct AR process isn't a great deal different from how I processed filings from a jeweler's bench, which consistently yielded poor quality gold, and that's after a prolonged boil in nitric until there was no further action. This was after incineration and before AR. Why would you, or anyone, expect gold that comes from a dirty solution (dissolved base metals of all kinds) to be as clean as gold that comes from a clean solution? You don't feel there's more dragdown?
Sorry, you're wrong. I did not make reference to them because they are "your methods". I made my comments because they're true. Note that I did NOT tell you you were stupid, nor that your thinking was flawed. I have no clue where you were taught to use those processes, which could have very well been passed to you by someone that was well meaning, but poorly informed.
If you use those procedures, that's your choice, but I outlined exactly what's wrong with them. Remember, doing something for an eternity that is not in your best interest will not turn it to something that is in your best interest. Hundreds of people doing something stupid doesn't make it smart. You get my drift.
You may have learned to live with the consequences of these things, but I don't think I can stand by in clear conscience while you endorse methods that have a potential to create more problems than they solve. Both of them do exactly that.
Wrong again. I've clearly stated that there are many ways to achieve the end result, but I've also stated in clear English that if readers follow the advice stated in Hoke's book, one thing is assured. They will achieve success. Not sometime, but every time. Fact is, even Hoke presented options. I chose to exercise those that appealed to me, or were most convenient. I do not think my way is the best, but it was the best for me-----having tried various means for many operations, in keeping with Hoke's recommendations. If they worked for me, they can work for others as well, saving them the task of reinventing the wheel.
This sort of lead me that direction:
http://goldrefiningforum.com/phpBB3/viewtopic.php?t=337&highlight=needle+scaling
In the link you said:
I poured gold without any flux on my ingots. How did it, otherwise, get there on yours?
Yet you clearly stated "Needle guns are quite powerful. I used to use them to remove slag from ingots."
Not only does slag leave tell-tale signs where it was on the ingot, but the removal by mechanical means, particularly by a scaler, defaces the ingot surface beyond recognition. You can't have it both ways.
That reminds me of the guy that gets pulled over for running a stop sign. He insists to the cop that he slowed down---which is the same as stopping. Cops say to him------"Tell you what we'll do. I'll start thumping the hell out of you with my night stick. When you think you've had enough, you tell me if you want me to slow down, or stop".
Tell me, which would you prefer? You have a container of hot water and some salt. You don't want the salt in the water. Is it easier to keep it out, or to get it out once it's dissolved? That's the type of reasoning you're presenting to the readers. I don't agree, and I'm not going to agree in a week or a year. What a prudent individual does is keep it out, not toss it in and pretend it's not a problem. You, my friend, are passing a perfect opportunity to learn that soda ash is a reducer, and should not be included in flux for fine gold. You want to thin your flux? Use fluorspar. It does a better job, anyway.
I don't recall EVER needing to thin my borax when melting pure gold. The only time it got thickened was when there was an abundance of base metals. I trust you read my comments about melting my second refining. Melting dishes had only one color beyond clear-----a purple tinge----from colloidal gold. Borax, when clean, is not particularly viscous at the melting point of gold, but quickly sets as the gold freezes. Pouring any off when the gold has set is a tall order. You might be successful in scraping it out.
Hoke discusses raising the quality of questionable gold by the addition of niter (potassium nitrate). I tried it several times----never with success that was in keeping with my goal. Maybe you settled for less than I wanted. Dunno. I wasn't content to have gold that had oxides----and I never was successful in eliminating them by that means, not even after a quarter hour of heating with an oxidizing flame (a Hoke torch, fired by natural gas and oxygen). There was clear evidence they were lowered (dirty flux), I'll grant you that-------but-----again------if achieving high quality gold was as easy as melting with a proper flux, that's what we'd all be doing. It doesn't work---although it does remove some oxides. Maybe if I'd have spent a couple hours!
Been there, done that, got the T shirt, learned it didn't work. You don't think I tried every dodge in the book, too? I ended up double refining because it DID work, the other dodges didn't. My original method (first year or two of refining) of returning gold was to melt in a dish, with enough flux to reach the edge of the button, but not to cover it. The moment it froze, but was still red, I'd sprinkle a light covering of borax on the surface, then extract the button from the flux with tweezers. It was then pickled in sulfuric acid. The button was delivered to the owner, not shot. The flux, by now, was very sticky, and would not pour.
This is a cause and effect situation. My observations were that gold precipitated from dirty solutions came down very fine---and dirty. I never did get gold to precipitate fine from clean solutions. It was so eager to agglomerate that the particles came down large, often very large. The contamination in dirty solutions prevents that from happening, at least from my observations. You're certainly entitled to see it the way you do------but I'm every bit as convinced that I am correct as you are.
I'm pretty sure I can address the different colors. I've already stated that color is a function of concentration. Here's one for you to consider.
On rare occasion, when I'd re-refine, I'd have a touch of nitric still left in solution. The gold came down fine, but when it came time to wash the gold (with HCl), I'd get the slightest of dissolution. Stop washing after allowing it to boil for a brief period (to consume the nitric with the precipitated gold) and then ice the solution. The precipitation from the now very dilute solution produced gold that was slightly darker than the balance of the precipitated gold. There was so little present that it did not agglomerate as well as the heavily concentrated solution on the original precipitation.
No, I had no need to detect copper. It did expose it if it was present, however, for, as you allude, the slightest trace of copper displays a bold blue color. I'd find hints of blue, but not routinely. I used ammonium hydroxide for one reason. When you change pH, elements that are in solution are prone to precipitate, so by going from acid to basic and back to acid, I had the opportunity to convert any sort of contaminant the could prove troublesome. Washing well with ammonium hydroxide is just one more step you can take to improve the quality of gold without adding anything to it that can prove harmful.
By now you should understand that I am a student of Hoke. I used HCl because it is the recommended wash. You do recall that we're talking about a chloride solution, yes? Unless you take steps to eliminate all traces of chlorides, you risk dissolving your precipitated gold when you wash with nitric. I think so, and Hoke thinks so. I wouldn't dream of using nitric for the final wash, and I'm not concerned that it worked for you, or not. Assuming you do the nitric wash, and have a negative reaction, you'd be walking a very dangerous line when you started introducing ammonia to a gold chloride solution, a risk I'd rather not take. One thing sure, you wash with HNO3 long enough and that's going to happen, just like the occasional batch that contained a trace when I washed. I don't want to be held responsible for providing even a hint of something that can jeopardize a reader unnecessarily. If you can present cites that prove my position to be in error, I'd welcome the input. You likely understand that I'm not all that keen on opinion. I already have some that we don't agree on.
I'm not concerned if readers follow my recommendations, or not. What I am concerned with is that they use practices that don't create problems, and don't harm themselves or their loved ones. Follow the advice in Hoke's book-------the pitfalls have all been addressed. It will tell you how to wash your gold-------although I'm pretty sure it doesn't address the use of ammonium hydroxide. I had to learn that from a novice refiner. Wish I had my book at hand.
Here's the deal. You bring an ounce of pure gold to my shop, and I'll provide one. We'll make a setup to refine the two ounces. I have enough nitric and HCl and sulfuric to do the processing. Together, we'll alloy it to 14 K yellow, then we'll process it by your means. If you can produce gold with a single precipitation that melts without oxides, the gold is yours. If it has oxides, any oxides, the gold is mine. I'm willing to put my money where my mouth is. I trust you have enough faith in your grandiose claims to do the same.
Harold
I'm going to bow out of this, Harold, with a few closing statements. These long argumentative posts are wearing me out and we both are saying the same things over and over. It's a fact that we both produced excellent gold using different methods. This doesn't surprise me as much as it does you. I've probably known 50 professional refiners in my life and, with few exceptions, they all had similar goals and developed their own ways of producing good gold. I once worked for a guy who could care less about making pure gold. He shipped 99% and took a beating. This philosophy drove me nuts and I quit after a month.
Maybe, your dropping gold from concentrated solutions caused the first drop to be crappy. I seem to remember having trouble along those lines, At an early point in life, I started diluting the aqua regia 3 times before filtering and that seemed to take care of a lot of former problems.
I will concede that doing double aqua regia is a more guaranteed method of getting pure gold, especially for the novice. Maybe you're right in wanting these guys to do it. For me and every other professional refiner I've ever known, however, it's a big waste of time, energy, and money. Also, few or none of these guys inquarted.
The Hoke book is the best book for the beginner that I know of. However, it was written 67 years ago and, since then, there have been a lot of innovations in aqua regia refining.
Although an old method, the Miller chlorine/Wohlwill cell method is still the state of the art for refining gold. Once the initial outlay is covered, it's the cheapest, most reliable way of refining large quantities of gold. It's not used because the refiner can't get 9999 with aqua regia, no matter what you've read. It's like a refining machine, with set parameters and few variables. It avoids the very subjective method of using aqua regia. It avoids the workers screwing up the more sensitive aqua regia process. But, since it's very expensive to set up, only the big boys can afford it.
The definition of an ingot is metal in a bar form. The standard method for processing circuit boards is to burn - grind - screen - melt the metallics - ship the dust (pulps) and ingots to a copper smelter. The ingots produced run about 65% copper and, along with the pulps, they contain all of the other 20, or so, odd metals and PM's on the boards. These big 50# ingots have slag all over them, which must be removed. The needle gun worked the best for this purpose. These are the only ingots I have ever used the needle gun on.
I haven't read Ms.Hoke for awhile but, if I remember right, she used HCl to get rid of the iron from the ferrous sulfate she used to drop the gold. You and I don't normally use ferrous sulfate so, why use HCl? I can't think of anything else that would be present for it to dissolve. I haven't done aqua regia for awhile and I told you I have to search my memory to recall how I did certain things. I'm 67 and the CRS, Can't Remember S_ _t, gets a little worse each year. Of course, I thought of the presence of chlorides in tap water and from the aqua regia. My mamma didn't raise no stooped kids. Since you reminded me, I remember rinsing with distilled water in between the tap water rinses and the nitric acid. I also remember testing the last rinse before nitric for chlorides, with silver nitrate.
On to different things. Refining isn't a one trick pony. Enough has been written on aqua regia refining for the novice to do it. The info is scattered but, it's just about all there. In 1989, I made a list of 250 refining topics to write articles on. Refining karat gold was only one item on that list. I still have that list. I was going to do a refining newsletter. I could probably double the list today. Only about 10-20 of these have been covered on this forum. On to bigger and better things!
Maybe, your dropping gold from concentrated solutions caused the first drop to be crappy. I seem to remember having trouble along those lines, At an early point in life, I started diluting the aqua regia 3 times before filtering and that seemed to take care of a lot of former problems.
I will concede that doing double aqua regia is a more guaranteed method of getting pure gold, especially for the novice. Maybe you're right in wanting these guys to do it. For me and every other professional refiner I've ever known, however, it's a big waste of time, energy, and money. Also, few or none of these guys inquarted.
The Hoke book is the best book for the beginner that I know of. However, it was written 67 years ago and, since then, there have been a lot of innovations in aqua regia refining.
Although an old method, the Miller chlorine/Wohlwill cell method is still the state of the art for refining gold. Once the initial outlay is covered, it's the cheapest, most reliable way of refining large quantities of gold. It's not used because the refiner can't get 9999 with aqua regia, no matter what you've read. It's like a refining machine, with set parameters and few variables. It avoids the very subjective method of using aqua regia. It avoids the workers screwing up the more sensitive aqua regia process. But, since it's very expensive to set up, only the big boys can afford it.
The definition of an ingot is metal in a bar form. The standard method for processing circuit boards is to burn - grind - screen - melt the metallics - ship the dust (pulps) and ingots to a copper smelter. The ingots produced run about 65% copper and, along with the pulps, they contain all of the other 20, or so, odd metals and PM's on the boards. These big 50# ingots have slag all over them, which must be removed. The needle gun worked the best for this purpose. These are the only ingots I have ever used the needle gun on.
I haven't read Ms.Hoke for awhile but, if I remember right, she used HCl to get rid of the iron from the ferrous sulfate she used to drop the gold. You and I don't normally use ferrous sulfate so, why use HCl? I can't think of anything else that would be present for it to dissolve. I haven't done aqua regia for awhile and I told you I have to search my memory to recall how I did certain things. I'm 67 and the CRS, Can't Remember S_ _t, gets a little worse each year. Of course, I thought of the presence of chlorides in tap water and from the aqua regia. My mamma didn't raise no stooped kids. Since you reminded me, I remember rinsing with distilled water in between the tap water rinses and the nitric acid. I also remember testing the last rinse before nitric for chlorides, with silver nitrate.
On to different things. Refining isn't a one trick pony. Enough has been written on aqua regia refining for the novice to do it. The info is scattered but, it's just about all there. In 1989, I made a list of 250 refining topics to write articles on. Refining karat gold was only one item on that list. I still have that list. I was going to do a refining newsletter. I could probably double the list today. Only about 10-20 of these have been covered on this forum. On to bigger and better things!
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goldsilverpro said:
This entire thread has lost its perspective. Bowing out "with closing statements" that challenge published and well accepted practice is hardly "bowing out".. (washing with HCl, for example)
The question as asked was:
Your insistence that it's easy to precipitate 9999 gold doesn't address the issue, so unless you're prepared to disclose your method, so all of us can achieve your level of excellence, I, too, see no good coming from this as it stands. Turning it into a pissing contest about how well you can precipitate gold doesn't help the guy that wants to know how to improve his quality by the AR method. That was, after all, the point. I've done my level best to address that issue-----and have Hoke waiting in the wings as my reasons. You did read my comments about being a student of Hoke, I presume? :wink:
Harold
I had this happen to me, on my 2nd refinement, 1st rinse, with HCl and water. The solution turned a little yellow. I precipitated it in the normal fashion and did not put it on ice, because I didn't know.
Is there any reason that the 1st rinse couldn't be done in plain water to avoid this?
Also. Does it really matter if the rinse is with HCl or nitric. As long as the end result is clean.
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PhillipJ said:
The ice addition may not be needed in your case. I precipitated with SO2, and know from doing so that the precipitation process is exothermic in nature. It wasn't uncommon for my solution to get hot enough to slow down, or even stop the precipitation because the heat wasn't being dissipated. By cooling the solution, that didn't happen. Often times I'd add ice to a solution that had quit precipitating, and would achieve an almost instant reaction, which I attributed to the cooling. If you add your precipitant to your solution by mixing it with water, could be you provided enough of a heat sink to do the same thing. Hard to say. I've been away from refining for a long time now, and I used the same system for years, so the other methods are sort of a stranger to me now.
My initial reaction is to say that it might be a waste of time, but maybe I'm wrong. The purpose of washing in acids is to remove undesired substances, which we both understand. Water in and of itself would be rather poor at doing that, but the fact that there's a trace of nitric remaining may be enough of an offset. I really don't know-------but my personal choice would be to stay the course and wash with HCl. I did that in practice, although I'm not saying it's the best way to go. It worked for me, so that was reason enough to do it.
That's a reasonable question------one that will answer itself if you give it a go.
Talking about eliminating the chlorides is a lot easier than doing it. The slightest trace of HCl in your solution when you introduce nitric will be no different than a trace of nitric when you wash your precipitated gold with HCl. In either case, you'll dissolve some of your gold.
Assuming you can fully eliminate the chlorides, from my vantage point it may be every bit as good as HCl-----until the drying process. If you don't force dry the gold, it will retain enough nitric to burn your skin. It's a lot less forgiving of being handled than is HCl.
The point I've tried to stress right along is that unless your thing is experimenting, there are tried and proven methods to achieve the desired end. As long as you have the necessary chemicals at your disposal, there's no good reason to deviate from accepted practice. If you're a curious type by nature, and like to experiment, one of the things that you should do before getting too creative is to read a Merck Index and understand the compounds of gold and silver. Getting creative with either of them can lead to an early death.
In Utah, where I lived, a person with a chemical degree managed to blow a wall out of a lab by experimenting with a gold solution. I don't recall the details now, for it was about 30 years ago, but that was reason enough for me to stick to the book. Not being educated, I simply don't think I'm smarter than those that went before me.
I've posted this picture before. It is a portion of the last lot of gold I re-refined just prior to selling my refining business. Note the color. Also note that it required no pickle, and was not melted under a flux covering. I know, beyond a shadow of a doubt, that my method worked----and worked very well.
No------I make no guarantee that it is 9999. That number is difficult to achieve----which is the point I've tried to make right along.
Harold
Edit: added words for clarity
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