Non-Chemical How to refine kt gold ( for dummies )

[firedan525]

Hello everyone again. I have been scouring this forum to learn how to refine kt gold. I have seen some articals that really seem fuzzy to me. Could one describe this process and can I use AR in this type of refining.
Thanks again. I really do appreciate the help.

 

[goldsilverpro]

I think the reason you haven't gotten a response from your question yet, is that it's very broad. To answer you right, in every needed detail, it would literally take 2 days to write. Karat golds are probably the most difficult form of gold to process. You have to know so many different things, to do it right. I do have about 6 pages written, on the whole process, on a Word Doc. that I will eventually finish and post. I'll probably end up with 15-20 pages.

At this point, I will at least give you an outline of what to do. There are several ways to refine karat gold, but this is the way I do it. Try to search out the details on the forum. They're all here, somewhere. Actually, Harold has more experience on karat gold than I do. He'll probably add to this. If you do this, and still have specific questions, I will be happy to try and answer them.

(1) Inquartation. Calculate how much silver it will take to lower lower the gold percentage to 25%. For example, if the total gold in your whole batch runs 50%, you will need the same weight of silver as you have karat gold. Combine the silver with the gold, melt it, and pour it into water in a tall stainless steel container to form shot.

(2) Nitric Dissolving. Under a fume hood, dissolve all of the non-gold metals in 50/50 nitric acid, leaving the gold undissolved. The gold is now a brown powder. Save the solution for silver recovery, so you can use the silver to inquart more gold,

(3) Aqua Regia. Separate the nitric solution from the brown gold powder. Dissolve the powder in aqua regia.

(4) Silver and Lead Removal. Dilute the aqua regia 3 times to drop the silver. Add sulfuric acid to drop the lead.

(5) Filter. Filter the aqua regia to remove all solids.

(6) Precipitate the Gold. There are several different chemicals that will drop the gold out of the solution as a brown powder. I use sodium sulfite. Unlike the last brown powder, this time the brown powder is pure gold.

(7) Filter. Filter the brown gold powder, rinse it well, acid treat it, rinse it some more, ammonia treat it, rinse it more. Dry the powder.

( 8 ) Melt the Gold. Melt it with a torch in a melting dish or, better still, melt it in a crucible furnace. If it's not perfectly pure, treat it with fluxes.

(9) Cast the Gold. Pour the gold into a prepared ingot mold. Congratulate yourself on a job well done.

I hope I didn't leave anything out. Except for steps 4 and 9, I could write a page or two or three on each step. Please don't get discouraged. Other people have learned to do it on this forum. It's all worth it when you pour the molten gold into the mold and see the beautiful pure gold bar you've made. There's nothing else in the world that looks like it.

 

[champ110]

why do you have to inquart the gold?

 

[lazersteve]

You need to inquart so the nitric can attack the silver and base metals leaving the gold behind as a fine powder. AR won't properly dissolve gold that has only a small percentage of silver in it. Nitric won't remove the silver in gold of greater than 10kt, the optium percentage for the nitric to work properly is preferably 6K (25% gold/ 75% base metals and/or silver). These problems are both solved if you alloy the gold with enough silver so you can remove the silver with nitric prior to treating with AR. Inquarting allows the silver and other base metals to be removed before you use the AR on the gold.

Steve

 

[Harold_V]

The information provided is first class stuff, but there's one thing I'd like to mention, and it is relatively important. It often spells the difference between immediately separating the gold that was inquarted from the dissolved base metals and silver, or waiting for days on rare occasions.

What's critical here is to stay near the 25% gold figure. If you get much lower, the gold will be powder, often black if it's fine enough. You really don't want the gold to break up like that. The ideal process allows the base metals and silver (if that be your choice) to dissolve, leaving the shot in the same configuration as it was before the process got started. The gold, in this condition, is honeycombed, which allows the acid to enter and the base metals and silver to exit, without crumbling. There is nothing that settles because nothing of value gets suspended. It is not desirable for the gold to reduce to powder, but only for that reason.

Do your level best to keep tin out of the process. It complicates filtration.

The best advice I can offer is to obtain Hoke's book on refining. By the time you understand the contents of that particular book, you should be able to handle any type of gold alloy you're likely to encounter. You need not be a chemist for it to make sense. It was written expressly for people that don't have a chemical background.

Harold

 

[AgAuPtRh]

So let me ask this about the silver to be used.

I've read here in the forum and in other places about keeping recovered silver chloride moist for future melting.

Is this silver chloride what I want to use for inquartation? or do I need to have some shot on hand?? Would there be any major difference between the Two??

Steve K

 

[goldsilverpro]

Don't melt the silver chloride. You have to convert it to silver metal before you can melt it. You can either use Karo syrup or aluminum to convert it. Read this thread thoroughly.

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=120

 

[Harold_V]

So let me ask this about the silver to be used.

I've read here in the forum and in other places about keeping recovered silver chloride moist for future melting.

Is this silver chloride what I want to use for inquartation? or do I need to have some shot on hand?? Would there be any major difference between the Two??

Steve K

You do NOT use silver chloride for inquarting, nor should you entertain the idea. Converting the chloride to elemental silver would be the required step if you choose to do so.

Note, too, that you can't simply melt silver chloride and reduce it to metallic silver. It must be reduced by some means. Soda ash will do so, but it's also very hard on your melting devices, dissolving them along with reducing the chloride.

There is no advantage to drying silver chloride---but plenty of negative reasons for doing so. The fastest, easiest way to convert to metallic silver is to do it after washing the chloride well to remove copper, then convert it with a dilute HCL/water solution and scrap aluminum. Wash it well afterwards, then dry and melt. The end product is ready for the parting cell, or can be used for inquarting if needed. Truth be known, you should avoid making silver chloride----there are few good reasons to do so, for silver is easily recovered on copper.

The best source of added metal for inquartation is silver you intend to refine. In either case, it must be dissolved with the nitric process, so you get double duty from the silver.

If you aren't concerned about how often you work the silver, or you have a shortage, but prefer to use silver over copper or brass (I recommend that highly-----silver uses a lot less nitric to dissolve, and you don't risk adding lead, which can't be said for copper alloys), there's nothing wrong with endlessly recycling the silver.

The form need not be shot, but what other method would you choose to make dividing it in small quantities so it can be added in the proper proportions? Shot makes it easy. An ingot or button may be the wrong size----so pour shot. It takes little time and is very functional.

By the way, if you pour from a melting dish, freehand, you won't get shot----you get what I like to call corn flakes. Achieving shot is more involved.

Harold

 

[AgAuPtRh]

Thank you GSPRO and Harold and Lazer

You're all good professors. I'm trying to get as much in my mind as possible -- and you boys are certainly giving me plenty to go on.

Steve K

 

[goldsilverpro]

Harold,

Remember the IMPI article on silver chloride we discussed the other day? I attended the seminar and found a note that I had made on the paper, while listening to the lecture. The author said that, when silver chloride dries, it combines together to form crystals and that is why it becomes so impossible to work with. Even if ground fine, the fine particles are still crystals and the AgCl would only convert on their surface.

BTW, you were right. This Symposium was held in 1981, not 1980. I have the loose leaf version also.

 

[Harold_V]

The author said that, when silver chloride dries, it combines together to form crystals and that is why it becomes so impossible to work with. Even if ground fine, the fine particles are still crystals and the AgCl would only convert on their surface.

That's all news to me, and I thank you for bringing it to my attention. I knew that keeping the chloride wet was in everyone's best interest, but didn't have a clue why!

BTW, you were right. This Symposium was held in 1981, not 1980. I have the loose leaf version also.

I would assume that if I was to study those documents, I'd be enlightened considerably. I know they talk about a different approach to separating the PG metals----and I was always tempted to experiment with them, but never found the time. The platinum group, to me, was a bonus from refining---I dealt chiefly with gold and silver. Fact is, I sold my platinum sponge in a questionable state of purity as a result, and took a bath on the settlement. That was one of the chief reasons I no longer have respect for major refiners. When they don't come close to agreement on the content of submitted samples, you know they're fishing for a sucker.

Thanks for the information on the chloride, Chris. Sure helps me understand why I was so doggedly entrenched in how I converted it to elemental silver. It was never a problem for me, so I lucked out.

Harold

 

[goldsilverpro]

It was news to me when I read it yesterday. I had forgotten it for 26 years. It probably made an impression at the time. That's about when I started to never let it dry out.

The book is all good but I've used the silver chloride article the most, by far.. It may be the definitive work on the subject. I think the guy lists 15 - 20 ways of converting it. Also, excellent info in converting in the melt. All of the IMPI books are excellent. After all, they come from the horse's mouth.

 

[grainsofgold]

3) Aqua Regia. Separate the nitric solution from the brown gold powder. Dissolve the powder in aqua regia.

(4) Silver and Lead Removal. Dilute the aqua regia 3 times to drop the silver. Add sulfuric acid to drop the lead.


(6) Precipitate the Gold. There are several different chemicals that will drop the gold out of the solution as a brown powder. I use sodium sulfite. Unlike the last brown powder, this time the brown powder is pure gold.

I have some questions in the above process-

a. Why not go straight to AR to suspend the gold into solution and do away with inquartation?

b. In number 4 you say to dilute the AR solution 3 times- Do you mean add 3x the volume with water to dilute the solution?

c. How much Sulfuric acid do you need to add to pregant AR solution to drop the lead?

d. Do you add sodium sulfite into the pregant solution right after you add Sulfuric acid or do you boil down the pregant solution to drive off the Nitric acid or do you use urea in warm water to drive off the nitric acid before adding the sodium sulfite to drop the gold?

Thanks

Grainsofgold

 

[Noxx]

Dilute 3 times to drop the silver ?

As far as I know it, silver won't dissolve in Ar...

 

[Harold_V]

I have some questions in the above process-

a. Why not go straight to AR to suspend the gold into solution and do away with inquartation?

For all practical purposes, silver will not dissolve, but instead forms a hard crust over the gold. This crust isolates the gold from AR and prevents dissolution. Virtually all karat golds have some silver in their makeup----the sole exception being some strange colors (blue,purple), plus white gold. There is no silver in white gold, and it will readily dissolve in AR without any pretreatment. It is not the best approach if your objective is pure gold---there's too much nickel involved to expect a clean precipitation. It's best to inquart the white gold, too, so you can eliminate the nickel in the preliminary digest. It is not a necessary step.

There are exceptions to this---one of them being if the gold is small or thin enough that it is totally dissolved before the hard crust from silver forms. Filings from a jeweler's bench are an example that need not be inquarted, but the quality of gold that comes from such an operation is of very poor quality for a first refining. When processing such materials, it's always a good idea to incinerate first, to remove unwanted substances (wax from carving patterns, paper bits, fingernails, hair, oils, etc.), sift through a sieve to remove larger pieces for inquartation, and going through the sieved materials with a magnet to remove magnetic particles, which are almost always present. Once that is done, the material is best subjected to a boil in nitric acid, to remove as much of the base metals as is possible. The remaining material will easily dissolve in AR.

c. How much Sulfuric acid do you need to add to pregant AR solution to drop the lead?

Just a few drops should be adequate, depending on the source of material being refined. If you know lead was processed, you may find you need a fair amount. Keep lead out of the process as much as is possible. It destroys gold's ductility----even in trace amounts.

Considering your questions were directed to GSP, I'll leave the balance for him to make a response. I specialized in karat gold wastes, whereas he has a much broader background.

Harold

 

[grainsofgold]

Thanks Harold-

I always thought that if you melted kt gold and poured shot or rolled it and twisted it into cornets that the silver chloride would not be a problem in keeping the AR from dissoling the gold-

I am new to this forum and in looking around there is a lot of info.

I mainly recover gold but also am interested in PGMs as well- Any good topics to be found on this?


Thanks
Grainsofgold

 

[Harold_V]

Thanks Harold-

I always thought that if you melted kt gold and poured shot or rolled it and twisted it into cornets that the silver chloride would not be a problem in keeping the AR from dissoling the gold-

True enough if the alloy is thin enough, but the problems don't stop there, and that process is not free of trouble. If, by chance, you end up with bits that are too thick (from pouring shot, which is usually not very uniform in thickness and size), they won't break down completely with AR, so you end up with tiny bits that are encrusted with silver chloride and won't go into solution, even when boiled for a prolonged period of time. My personal choice was to avoid that problem.

The method I employed for filings avoided that problem as well, as I already mentioned. For all large pieces of alloy, I inquarted routinely-----and I highly recommend anyone that works with karat gold do the same. If you get involved with silver refining, which is hard to avoid if you process dental or jewelry wastes, you refine silver, or toss it. By using scrap silver for inquartation, you get double service from the metal, which has to be dissolved anyway.

Keep in mind, silver becomes a carrier of the PGM's. Even platinum will dissolve in nitric in the presence of silver, so you can't avoid cross contamination. You recover the PGM's when you part silver.

When you don't eliminate the silver with a preliminary dissolution, the silver chloride that forms when you introduce the AR tends to trap a great deal of gold chloride. If you don't care about having very dilute solutions from washing the chloride to liberate the gold, that may not be much of a problem, but if you refine in quantity, the volumes you generate can be limiting factors. I used ONLY lab ware for refining, with the largest beakers being 4,000 ml. That limits you to a concentrated solution of about 18 ounces troy of gold per beaker, so when I re-refined in volume, it was important to keep the level of concentration high so I wasn't using more than four beakers. That's the amount of room I had to work in comfort. Bottom line is if your objective is to produce high quality gold, and not be concerned about un-dissolved metals being left behind, shortcutting the processes is counter-productive.

I've mentioned on more than one occasion that the objective of some folks appears to be gold recovery, not necessarily gold purification (or refining). While the processes bear much in common, they aren't necessarily the same thing. Recovery can be nothing more than concentrating values, with little concern about the level of purity. My objective was to refine to the highest possible level of purity with what I had at my disposal. It was right for me, but may not be for the other guy.

I mainly recover gold but also am interested in PGMs as well- Any good topics to be found on this?

Hard to say. In a nut shell, it all depends on what you're looking for. I've processed platinum and palladium enough to be fairly comfortable with each of them, but there's not many that have extensive experience with the Pt group metals that posts here. Anything specific? Are you working with dental alloys?

Harold

 

[grainsofgold]

-ard to say. In a nut shell, it all depends on what you're looking for. I've processed platinum and palladium enough to be fairly comfortable with each of them, but there's not many that have extensive experience with the Pt group metals that posts here. Anything specific? Are you working with dental alloys?

The PGMS would be mostly in filings from a jewelers bench that have kt golds combined with 90-95% Plat alloy metals mixed in with it-

Solid PGMs are easy enough to separate by heating them with a torch and then metling them into buttons to send of to sell-

Thanks

Grainsodfgold

 

[Harold_V]

The PGMS would be mostly in filings from a jewelers bench that have kt golds combined with 90-95% Plat alloy metals mixed in with it-

That was one of the sources of the PGM's that I accumulated through the years. Again, it all depends on how you're processing the materials. If you get them in to solution, which I usually did, unless they were well concentrated, you can't really recover them well with chemical reagents. Platinum is recovered with ammonium chloride, and palladium is recovered with ammonium chloride and sodium chlorate.

One of the peculiarities of that group of metals is they don't precipitate from dilute solutions, and if you get precipitation from medium solutions, they don't always come down 100%. When that happened, I'd collect the traces with scrap steel and include them in my waste materials. That's the "stock pot" process discussed time and again in Hoke's book, which will tell you everything you need to know to recover metals you're inclined to encounter.

If you work with silver, which you must if you're doing bench wastes, you'll be surprised to find that the PGM's follow the silver, so you can recover them fairly well from the silver when you part it, assuming you're recovering your silver with copper. They're slow to come down, do so only after all the silver has been precipitated. You can often tell by the color of the solution when you have the PG metals present, it will usually be green in color instead of blue. Needless to say, you should always test your solutions with stannous chloride to insure that you're not discarding values. You can easily do that with the PGM's because of their propensity for following silver. The silver cement will darken as the PGM's precipitate----they come down as a black powder.

It's not a straight forward proposition----you have to use several approaches in order to recover them totally, as you can see.

How are you handling bench filings? I would expect that you'd put the majority of platinum in solution when you digested the gold. Because of the amount of insoluble materials involved with filings, I used to give them a hard boil in AR to insure that I was dissolving everything. Traces of materials that won't dissolve should always be recycled, never discarded. I ran all my waste materials in a furnace, using silver chloride residues as a collector. It was very effective.

Harold

 

[Mida]

At the step seven we can read Filter the brown gold powder, rinse it well, acid treat it, rinse it some more, ammonia treat it, rinse it more. Dry the powder.


The ammonia treat in the step is used to neutralize the renmant acid or to
get rid of the silver chloride present?

How many times we have to rinse it with water?acid and ammonia make an exotermic reaction.There is also this danger....

At step 4 the gold chloride is diluited three times and drops of sulfuric are added.But sulfuric acid get rid also of the nitric if the solution is heated?