Recovering precious metals from polishing sweeps

[Harold_V]

Ok Harold, we havent discared any solution and all of them have been filtered.

I'm pleased to hear that. I feared you took a wrong turn and had discarded your gold, as you may have noticed.

I just re-read hoke's book and revised some of the important areas. A quick question on what she says.

Basically she mentions that you should Incinerate, sift, magnet then if there is shellac/grease etc.. to boil in caustic soda/lye (to remove it). Then she mentions to wash in nitric/water acid unlike your procedure which is HCL/water, it says in her book you can use HCL but it doesnt dissolve copper or nickel (which will be present in these sweeps), the only draw down with using nitric/water is that it will dissolve silver but you can store that and recover it at another time.

* so im interested to know why you choose HCL over the nitric?

It was my reasoning that there is far more iron in the waste (from polishing compounds) than copper or nickel, each of which will be dissolved to some degree because they are oxidized by incineration. HCl is an excellent solvent for iron, unlike nitric, although it, too, will dissolve iron. The solutions are very different, however, with the nitric solution eager to precipitate the iron as rust, which would occur when you rinsed the material. That can complicate your processing, and leaves behind unwanted iron.

My experience in running my wastes by this manner tended to support that logic in that the solution, after precipitation of gold, was relatively clean. If you test your initial wash solution for copper and nickel, I'm quite sure you'll find that a good deal of it does, indeed, get dissolved with the HCl operation. A drop of ammonium hydroxide in a drop of the solution will turn dark blue if there is copper present. Likewise, a drop of the solution, along with a drop of ammonium hydroxed and a drop of DMG (see Hoke) will disclose nickel with a pink display. It left the silver behind either as a chloride, or in the elemental state, although I imagine it was converted to chloride by the gold chloride solution if that was the case. You would be unlikely to be able to recover any silver by this process, but it is not lost, it's still in the dirt. More on this, below.

Note that I did NOT process filings by this method. Only floor sweeps and polishing wastes. Filings are processed with nitric acid, then AR.

You see considerable evidence of my claim in the color of the original HCl wash. Beyond that, what you'll come to discover is that solutions that come from dirty substances and a nitric wash tend to be difficult to filter. Without the HCl wash, your gold chloride solution has a tendency to plug filters. I've had a liter of solution take as long as three days to filter. From that, I learned to incinerate suspect materials and then do an HCl wash, even if the material had already undergone a nitric wash. In that case, the material must be incinerated a second time, to kill any nitric that is present. I found nothing to equal HCl's ability to clean material of substances that were difficult to filter. That is particularly true of refining gold filled objects in volume. There is often a little lead and tin included in gold filled objects. They respond to the treatment I mention in a very positive way.

What you have been instructed by me is a process that evolved through trial and error and was used for many years. To be quite frank, I don't recall what Hoke recommended, so it's been interesting to hear that her version varies from mine. I assure you, if you follow my instructioins, you'll achieve a level of quality and extraction that is very good, although if you have doubts, don't hesitate to follow her instructions. I've commented time and again, I learned refining from her book, and know that aside from her recommendation to use gasoline freely when incinerating, her information is trustworthy.

* And why not boil in caustic as she mentioned to remove the shellac/grease etc?

It's redundant. A boil in lye will remove a good deal of the unwanted material, but it won't eliminate everything that will be troublesome. In the end you still must incinerate, so I see no good reason to duplicate operations unless there is some gain. Incineration performs every possible useful function, and eliminates the hazard of using lye. Should you splash lye in your eye, blindness is guaranteed, yet a drop of nitric in the eye, while painful, is not serious. I've been through that and came out fine. Learned from that to wear eye protection.

And i cant see anywhere that stannous chloride is mentioned in hoke's book, is this to determine what metals are present in the solutions???

That's correct. Read the chapter that involves testing of precious metals, and follow her instructions in buying and building the necessary solutions. In her book, I recall that she refers to stannous chloride as testing solution A, but I could be wrong. I haven't looked at a copy in well over 12 years.

If you do not have stannous chloride, immediately work in the direction of obtaining it. Do a search on the board if you must, for there's a lot of information available. Many of the guys here are making it with 95/5 solder. Personally, I preferred to use pure tin and stannous chloride crystals, which was my routine. Without it's use, you run blindly, not knowing the status of any of your solutions. Also, do yourself a favor and discard solutions by proper means the moment you conclude they have no value. It takes very little time to find yourself inundated with a huge variety of unknown and unwanted solutions, so you not only trip over them, but you spend a good amount of time screwing with them unnecessarily when you finally decide on disposal.

P.S the sweeps we are using is my partners and he has plenty to spare and experiment with.

P.SS i think im getting you now Harold

I hope so. I'd like to see you succeed. This method is quite good. I have serious doubts that you could come up with one any better.

Correct me if im wrong but when you say combining the wash waters (yellow) solution is the colour yellow because its suppose to be gold?

That's correct. Gold chloride that isn't contaminated with copper or nickel is yellow, deepening to a dark red/orange, depending on concentration. The wash water is nothing more than dilute gold chloride, which is why you combine it with the darker yellow solution. If you had stannous chloride, you'd see by testing that the solution would react with a purple stain. That's what gold looks like when combined with stannous chloride. As the concentration deepens, so too does the color. Very slight presence of gold will yield a faint purple reaction.

we havent discarded this solution and if im understanding right we are suppose to evaporate that yellow solution to basically have clean gold??? Is this correct???

No----evaporation does NOTHING to improve gold quality. That's determined by the washes you do prior to dissolving the gold, by the precipitant you choose to use, and by the washing you do after the gold has been precipitated. Evaporation serves two purposes. One is to concentrate voluminous solutions so you aren't working with gallons when a liter is adequate, but most importantly, it, when carried out properly, eliminates unused nitric acid. That is a requirement to recovering your gold. If you leave it behind, it will react with not only the precipitant, slowing or stopping the operation, but assuming you are successful in precipitating your gold, when you wash it, the residual nitric will re-dissolve some of your gold, until it has been consumed. That's not desirable, as you might understand. Please read Hoke on evaporation of solutions, and learn to do so. Also, if you have a button of gold at your disposal, it really helps to add one, as I've already mentioned. Weigh it before introducing to the solution you're evaporating, and weigh it afterwards if you want to know how much of the button was dissolved in the process of eliminating any free nitric. The use of a button will avoid evaporating the gold solution down to a heavy syrup, so it saves a lot of time. If you choose to use a button, you must still add some free HCl as the solution thickens. That way it will form AR and consume the free nitric by dissolving the gold button. Very slick way to process, if I must say so myself.

If it is i will add more AR to the mud to dissolve any more undissolved gold then wash with the HCL.

I'm not convinced you understand the wash purpose in using HCl. It is NOT used to wash the material once you have introduced AR. In this case, if you subject the material to more AR, simply boil the material in the AR and water mix, then add a small amount of HCl to insure that you haven't depleted what you introduced with AR. If, when you add the HCl, you see brown fumes coming off the beaker, that's a sign that you did just that. If you see no reaction, the next thing to do is add a few drops of nitric. If there is any undissolved gold present, you should see brown fumes coming from the beaker. If you do not, you can safely assume that the dirt is now barren of undissolved gold, and needs no further processing. At this point, add a little water, stir well, and allow the solution to settle.. Decant the solution, then add a generous amount of water and stir, again allowing the contents to settle well. Your objective here is to rinse the mud clear of all dissolved gold-----which requires NO HCl. Just plain old tap water will suffice. Wash the mud until you're satisfied that you are not getting a return worth the trouble, then get the dirt in a coffee filter and extract the last of the liquid, which should be combined with the balance of the yellow solutions we've been dealing with.

The dirt, at this point, is relatively valueless, although it will contain traces of values that you haven't recovered. Included in that there can possibly be platinum, which dissolves very slowly, and silver in the way of silver chloride. I suggest you dry this material by heating, just as if you would to incinerate. You'll see nitric fumes coming off at the very end of drying. Heat until you no longer see the fumes, then cool the material and store in a covered drum. If you collect enough of the polishing waste in this fashion, it has market value, or, down the road, when you have enough, you can run it in cyanide and extract the silver, along with traces of gold, all of which are never fully recovered, try as you might.

DO NOT STORE WET WASTE MATERIALS. THEY WILL RUST EVERYTHING IN YOUR WORK AREA THAT WILL RUST.

Hope some of this helps.

Keep us all informed on your progress.

Harold

 

[Harold_V]

Just re-read hoke's washing:
Correct me if im wrong but when you say combining the wash waters (yellow) solution is the colour yellow because its suppose to be gold? we havent discarded this solution and if im understanding right we are suppose to evaporate that yellow solution to expel the excess nitric then once that is all done

When evaporation is concluded, you dilute the gold chloride solution and filter the solution until it is clear of flocculance. Do not precipitate any solution that is cloudy---all you do is recombine the gold with unwanted junk.

make a seperate iron sulfate solution with water and add some HCL to make it a clear green (as the book says) and then slowly add it to the main gold contents to precipitate the gold. Once the dark cloud fumes stop then it should be done.

Do NOT assume it's done. Check with stannous chloride. This is important for a solution that has iron dissolved within will still be yellow in color. You'd have no way of knowing if the color was gold or iron without testing. You may also detect the presence of the platinum group when gold has been precipitated. If you get a yellow to brown display, that's a sign of platinum in solution.

So i filter the gold then rinse it with water a few times and finally a few times with hcl/water mix until its the gold powder is clean. Then filter again and let it dry in the funnel. After this its ready to be melted.....

This sound about right???

That is one place where I depart from anything you may read, and I encourage you to listen to me. Do NOT filter the gold powder. There is nothing to be gained by doing so, and you lose some in the process, although you would recover it in future processing.

What I would like to see you do is, after you have precipitated your gold, and tested the solution and know that it is barren, to allow the gold to settle by gravity alone. This may take a day, but you can see the progress by the stratification that comes from the finest of particles, which are slow to settle. When the solution has settle totally, decant with a hose, then place the beaker on a burner and add some HCl and water. You will do the three wash and rinse phases without ever removing the gold from the beaker. You will also dry the gold in the same beaker. If you do your work properly, when the gold is dry, it will be a light brownish gold color, and will cling in clumps, making handling very easy. Again, I strongly encourage you to follow my advice in this regard. It is the fastest and easiest way to deal with your gold.

Harold

 

[Ageo308]

Ok so next step before i do anything is to purchase some stannous chloride crystals & pure tin and read hoke's book on testing precious metals.

Once i read the crap out of it we will continue the process

i will keep you updated

thanks for the info and i wasnt judging your experience before just clarifying the difference between hoke's methods and yours and you cleared that up for me rightly so.

cheers

 

[Ageo308]

At this point, add a little water, stir well, and allow the solution to settle.. Decant the solution, then add a generous amount of water and stir, again allowing the contents to settle well. Your objective here is to rinse the mud clear of all dissolved gold-----which requires NO HCl. Just plain old tap water will suffice. Wash the mud until you're satisfied that you are not getting a return worth the trouble, then get the dirt in a coffee filter and extract the last of the liquid, which should be combined with the balance of the yellow solutions we've been dealing with.

Quick question Harold, when you add the generous amount of tap water do you bring it to boil again? or just stir and let it settle? If you dont bring it to boil then i did this wash process successfully before as stated in my earlier posts. And will do the same next time round

 

[Harold_V]

At this point, add a little water, stir well, and allow the solution to settle.. Decant the solution, then add a generous amount of water and stir, again allowing the contents to settle well. Your objective here is to rinse the mud clear of all dissolved gold-----which requires NO HCl. Just plain old tap water will suffice. Wash the mud until you're satisfied that you are not getting a return worth the trouble, then get the dirt in a coffee filter and extract the last of the liquid, which should be combined with the balance of the yellow solutions we've been dealing with.

Quick question Harold, when you add the generous amount of tap water do you bring it to boil again? or just stir and let it settle?

While boiling would likely do no harm, I don't think it would be a necessity. At this point, anything that will dissolve has done so, so all you're doing is rinsing the values from the solution. Assuming the material isn't overly porous, I'm of the opinion that a simple stirring and settling will serve the purpose well enough. I sure as hell hope so, that's all I ever did!

If you dont bring it to boil then i did this wash process successfully before as stated in my earlier posts. And will do the same next time round

Good show! We've talked about so much in the past couple days that I'm a bit lost as to what, exactly, we have discussed. At any rate, I feel you're getting the picture.

Once you've been through a batch of this stuff, and see what happens, and why, it will start answering some of your questions. In a sense, it's all perfectly logical. You incinerate the material to eliminate oils and other contaminants, screen it to separate solids from dirt, dissolve unwanted substances with HCl and water, then dissolve the gold and recover it from the dirt. If you look at it that way, jumping through each necessary hoop, it's real easy to know what to do, and when to do it.

Be certain to keep us all advised. I'm in hopes that others have been following your experience, and learning as you go, so it would be good for all involved to know how it ends.

Harold

 

[Ageo308]

Sure Harold, i will update once we continue the process.

thanks again for everyones help

 

[Ageo308]

Harold i purchased the Iron Sulphate from a garden store and when i opened it the granules were white. They could have a green tinge to it but you would need a loupe scope to pick it up. Would this be useless? it says on the contents 20% iron sulphate (thats it). Does it have to be stronger?

Or would a few drops of HCI along with water be enough? Im going to try it and see if a green solution appears so i will update you.

 

[Harold_V]

I bought a reagent grade once, and found the crystals to be a very light green color (similar to the color of the inside of a lime), with traces of white. I'm of the opinion that what you have will work. It's real easy to make a test. Take a drop of the yellow AR solution and place it in a spot plate cavity. If you have no spot plate, use a shot glass or some such, something that will keep the drop in a small area. Place one of the crystals of ferrous sulfate on the drop and observe if you see gold forming. It will be dark, or may even form a thin sheet, much like gold leaf. If you get any kind of precipitation, it's exactly what you wanted. When you dissolve it to introduce it to your gold solution, if it's not perfectly clean, filter the solution. Be certain to add a few drops of HCl to the dissolved material. Watch it closely and you'll see it flash a slightly different color, and get clearer. You may or may not see that, depending on how clean the material is. Make sure when you introduce the solution to the gold solution that each of them have been filtered to the point of absolute clarity---meaning no flocculance. They will each have their distinctive colors, but they should be absolutely clear.

If you don't have stannous chloride yet, you can use the same test to determine if you have precipitated all the gold. When you introduce a crystal to a drop of solution, it won't show any precipitate. It's not as sensitive as stannous chloride, and it won't replace it for testing for the platinum group, but it's a reliable test for gold.

Edit for more comments:

It's possible your material has a filler, something that limits the speed of dissolution, or buffers the material so it won't burn plants as easily. If that be the case, when you filter it, it should be fine. As far as the percentage of iron goes, I don't know if what you have is typical, or not.

Typically, an ounce of ferrous sulfate will precipitate an ounce of gold, but a little excess does no harm.

Hope this helps. Let us know!

Harold

 

[Ageo308]

As always thanks Harold and i will keep you posted.

 

[Ageo308]

Hi Harold, question:

when we started our boil in AR i was wondering when do you know exactly all the gold has been dissolved?? i mean testing with stannous only tells you if there is gold present but it doesnt tell me if "all" the gold has been dissolved. Is it when i add a fresh batch of AR (when the last batch has been killed off, small amounts at a time) and the brown fumes change to clear does this mean there is no more reaction? i mean the brown fumes simply mean the reaction with the base metals from the nitric and the dissolving of gold yes?

We boiled for well over an hour (we only had 20grams of dust/mud to test) adding small amounts of AR at a time until each amount died off and each time it died off we poured the solution into a beaker (gold solution that is). I think where we went wrong is over boiling and we evaporated some gold (is that possible?) Anywayz i will post a photo of a 2 gram gold button we got (im happy we got this far) i just know along the lines we had more wastage and lost some gold. P.S As we were melting we noticed that the borax become real thick and sludgy and we couldnt retrieve all the gold, im assuming that we didnt clean the gold properly and that will need some more attention on our next test run.

Ill see if i can post the photo tomorrow sometime.

cheers

P.S the stannous does become real handy in testing solutions to see if they are worth keeping or discarding.

 

[Harold_V]

Hi Harold, question:

when we started our boil in AR i was wondering when do you know exactly all the gold has been dissolved?? i mean testing with stannous only tells you if there is gold present but it doesnt tell me if "all" the gold has been dissolved. Is it when i add a fresh batch of AR (when the last batch has been killed off, small amounts at a time) and the brown fumes change to clear does this mean there is no more reaction?

That's a good indicator, with one exception. Once action has ceased with AR, it's a good idea to introduce a little more HCl. That way, if you've depleted the original amount, but have not depleted the nitric, it will start dissolving more gold, assuming it isn't all in solution. The addition of more HCl costs very little, and does not complicate the recovery of your gold, unlike excessive nitric.

i mean the brown fumes simply mean the reaction with the base metals from the nitric and the dissolving of gold yes?

That's correct. If there is anything present that can be dissolved, fumes will be produced.

I think where we went wrong is over boiling and we evaporated some gold (is that possible?)

Yes------very possible----and you likely did unless you had a watch glass covering the beaker. If you had it covered, you'd notice that gold chloride solution forms on the inside of the watch glass and drips back in the beaker. Anything that is not condensed on the watch glass is lost. That's why I worked in a fume hood that had a condensing chamber, along with a filter. While the amount of gold lost is a small percentage, when you handle large amounts of gold, it adds up.

Regards the boil time, in the case of screened polishing wastes, the largest particle of gold will still be quite small, and will dissolve readily. The amount of time that you boil the material should be relatively short. An hour is far more than is necessary. I would suggest that a few minutes would be adequate. The moment fumes cease to evolve, you have either consumed all of the acid, or all of the material that will go into solution. Prolonged boiling won't change anything, and puts you at risk of losing values via rapid evaporation. Hoke cautions against evaporating too fast for that reason. You should keep the material covered while dissolving, for the effervescence carries minute bits of value out of the beaker. A watch glass returns to the beaker that which would be lost.

P.S As we were melting we noticed that the borax become real thick and sludgy and we couldnt retrieve all the gold, im assuming that we didnt clean the gold properly and that will need some more attention on our next test run.

Unless you heated the melting dish for a prolonged period of time, overheating the flux and dissolving some of the dish, the flux should have done nothing aside from assume a little purple cast, the result of colloidal particles of gold being picked up by the flux. If it changed color beyond the purple I mentioned, your gold is not very clean. Don't skimp on the wash process. I've noted some that have reported on its use have put time constraints on how long it is boiled in HCl and water rinses. That makes no sense. It should be boiled as long as there is a change in results. Stopping too soon leaves contaminants behind that would have been removed. If your objective is high quality gold, it should be washed until it is clean-----until the last application of HCl yields no change in color (of the solution. The gold powder will also become lighter in color as it is cleansed). The alternative is to stop after a good first wash and rinse, then to re-dissolve the gold and precipitate a second time. That is the procedure I followed, and got exceptional results. I never short changed the first wash, however, so the gold was already of decent quality.

P.S the stannous does become real handy in testing solutions to see if they are worth keeping or discarding.

I hope all readers see the wisdom in its use!

Harold

 

[Ageo308]

Hi Harold, thanks for the advice.

I was wondering thow lets say we do a 10min boil in AR and extract all the gold solution. Correct me if im wrong but when we evaporate (with the lid off, to get rid of excess nitric) would the gold evaporate aswell? since its still a chloride (liquid) and the evaporation process takes at least an hour if not more depending on quantity?

Besides the washing process (which we will improve next time) im sure we evaporated some gold (if its a liquid and its evaporating long enough surely you would lose some amount)?

We are doing the next test on Sunday so i will keep you posted.

 

[Harold_V]

Hi Harold, thanks for the advice.

I was wondering thow lets say we do a 10min boil in AR and extract all the gold solution. Correct me if im wrong but when we evaporate (with the lid off, to get rid of excess nitric) would the gold evaporate aswell?

No, not if you do it properly. (Don't hesitate to read what Hoke says about evaporating). You will have separated the solution from the mud, and will be evaporating only solution. It is done at a reduced temperature, never allowed to boil. It must remain tranquil, and have little or no effervescence. If a button of gold is introduced to consume the free nitric, it will react relatively slowly, assuming you don't have a huge amount of nitric present. I strongly advise the use of a gold button, which minimizes the amount of evaporating that must be accomplished. Frankly, I think that's one of the reasons I enjoyed considerable success, and never ever used urea.

When evaporating, you must observe the vapors that leave the dish. If you see any signs of color in them, you're going too fast (too hot), so heat must be cut back. It's not a hard thing to do, it's just a little strange at first. It becomes routine once you've done it a few times, and you know exactly what to look for, and how to react to your observations.

Besides the washing process (which we will improve next time) im sure we evaporated some gold (if its a liquid and its evaporating long enough surely you would lose some amount)?

Actually, how long you evaporate makes no difference. If you evaporate at or below the correct temperature, the solution will slowly condense, changing color as it thickens. If you continue the evaporating process, the solution will finally bake out as a dark brownish black substance, precipitating some of the gold in the process. Try to never take it that far. When it gets to the point of being a dark red color, that's a great time to introduce a little HCl. A half ounce or so. If, when you add the HCl it does not result in brown fumes coming off, that's a pretty good sign you have eliminated the nitric. You'll notice that as the solution thickens and darkens, that it takes a higher and higher temperature to make it boil. Armed with that knowledge, you should see slight boiling when you add the HCl. If the solution boils but you don't see any fumes, the job is done. Take it up with water, then it's time to filter, which will eliminate traces of silver chloride and lead. Remember, during the evaporation process, you should have introduced a few drops of sulfuric acid, which will have precipitated any traces of lead that may have been put in solution. Lead is death of gold quality, so don't skip that part.

We are doing the next test on Sunday so i will keep you posted.

Sounds like a plan! Looking forward to your next post.

Harold

 

[Ageo308]

Hi Harold, good news. We did our 2nd test batch with going through the proper washes and it come out as 24ct (not sure on the exact purity thow). This time it melted with ease and took about 2min to melt and pour (only very small amount).

Basically after we let the gold precipitate and dropped the gold completely we washed in HCI/water until the liquid discoloured then rinsed off (it became clear after 1 rinse). We were left with a fine brown powder which was then melted with ease and poured. I didnt rewash with ammonia and then again with HCI as i wanted to see the results without doing those and even thow we might not achieve the highest of purity its not a matter for us as the gold will be sold off, basic 24ct is good enough for us for now.

That stannous is excellent as we test all solutions before discarding them. The silver chloride which is caught in the filters is dried and stored in a jar for processing later down the track. Once we have mastered this a few times and get the ball rolling we will concentrate on extracting palladium and other precious metals which are also in the sweeps. A big thankyou from us over here again and anyone that 2nd guesses you will have to be crazy, your information is 2nd to none.

Thanks heaps again Harold :lol:

 

[Harold_V]

I didnt rewash with ammonia and then again with HCI as i wanted to see the results without doing those and even thow we might not achieve the highest of purity its not a matter for us as the gold will be sold off, basic 24ct is good enough for us for now.

The additional washes serve to insure quality. The one thing that may have been of service would be the ammonium hydroxide wash, which is intended to remove traces of silver (as chloride) which often hitches a ride with the gold. The theory is well documented by Rose, whereby small amounts of silver behave as gold, and will follow the solution in spite of having been introduced to chlorine.

GSP suggested that diluting the solution at least three volumes will cause the silver to precipitate, at which time it can be easily removed from the batch by proper filtration. You often see evidence that he's right in that a solution that is clear of flocculence will often cloud up when water is introduced. The ammonium hydroxide wash is intended to remove the traces that make it through filtration. No harm done even then, assuming the gold is to be used for yellow, green or rose gold. Each have silver added, anyway. Not so good for white gold, which contains no silver. No matter-----you've done a great job and are to be commended.

Once we have mastered this a few times and get the ball rolling we will concentrate on extracting palladium and other precious metals which are also in the sweeps.

Do check your solutions for values after you're precipitated the gold. If they show anything in the way of a green/brown or orange reaction, that's a sign of platinum group metals. If you prefer to not pursue them directly, pour the solution on some scrap steel that you have in a plastic bucket. Here in the states they sell ice cream in 5 quart buckets. That makes a reasonable size container for the purpose. The scrap steel will precipitate the values, which you will eventually run in a furnace with the saved silver chloride. It will be reduced to elemental silver and act as a collector for the values. It's a wonderful savings plan---one that allowed me to retire at a relatively young age.

A big thankyou from us over here again and anyone that 2nd guesses you will have to be crazy, your information is 2nd to none.

Thanks heaps again Harold :lol:

Chuckle!

Thanks for the kind words. I know you'd have done the same for me were conditions reversed. Your success is my pleasure, believe me.

Well done!

Harold

 

[Ageo308]

The additional washes serve to insure quality. The one thing that may have been of service would be the ammonium hydroxide wash, which is intended to remove traces of silver (as chloride) which often hitches a ride with the gold. The theory is well documented by Rose, whereby small amounts of silver behave as gold, and will follow the solution in spite of having been introduced to chlorine.

Ill keep that in mind, i mean an extra 20min wont hurt since its giving us more pure gold.

Do check your solutions for values after you're precipitated the gold. If they show anything in the way of a green/brown or orange reaction, that's a sign of platinum group metals. If you prefer to not pursue them directly, pour the solution on some scrap steel that you have in a plastic bucket. Here in the states they sell ice cream in 5 quart buckets. That makes a reasonable size container for the purpose. The scrap steel will precipitate the values, which you will eventually run in a furnace with the saved silver chloride. It will be reduced to elemental silver and act as a collector for the values. It's a wonderful savings plan---one that allowed me to retire at a relatively young age.

Well i did check the solution once it was precipitated and the reaction changed to a green so im assuming there could be some platinum in there. We have 4 litre ice cream containers which is very similar to your 5 quarts, so your saying have some scrap steel in there and pour the liquid in? once precipitated dry off the dirt/mud and put it in the furnace? ill have to try that with the next batch.

You see being in the jewellery industry we have some contacts and a few of those are polishers (people that polish jewellery all day long). These guys do about 10kg's a week on polishing sweeps and work with a variety of 9ct, 18ct and platinum also. With such large quantities it will be worth extracting these other precious metals. Anywayz i will take some pics this sunday and show you some of our results.

Keep you posted

P.S ill need to ask you later about how to handle large batches (stock pots, burners, evaporating dishes etc...). But we will leave that for another time

 

[Harold_V]

Well i did check the solution once it was precipitated and the reaction changed to a green so im assuming there could be some platinum in there.

A green reaction is likely palladium, although you may have both elements present. There is generally only a small amount of either of them unless you find the polishing waste to be a green color after incineration. That's a sign that the producer is polishing a great deal of platinum. Polishing compound for platinum is not typically rouge or Tripoli, each of which yield burned waste that is reddish brown in color.

We have 4 litre ice cream containers which is very similar to your 5 quarts, so your saying have some scrap steel in there and pour the liquid in? once precipitated dry off the dirt/mud and put it in the furnace? ill have to try that with the next batch.

That's correct. It think you'll find that that's the best way to recover the values. The problem is that the platinum group of metals doesn't respond to precipitation the same way gold and silver do. When you find traces of them in your solutions, you can go through the proper procedures for their recovery, yet not achieve any results. In heavily concentrated solutions that isn't true, so you can achieve reasonable results, although even then you may not get full recovery. For that reason, you should place solutions that test positive on scrap steel, and allow enough time for the values to precipitate. Test the solution and decant only after it tests barren. In the process, you'll precipitate any copper that is present, but that tends to be a good thing, for if you recover the values by furnace, anything that forms a molten metal will help by acting as a collector for the values.

You can recover these values chemically, and you can even precipitate them on copper instead of scrap steel. In that case, all you precipitate is the values, for all base metals will remain in solution. The problem with that is that you will produce very little value from most of these solutions, so the values may adhere strongly to the copper, making recovery difficult. It's the same principle as recovering silver on copper, but in that case you generally produce a lot of metal, which converts the copper to liquid in the process, shedding the silver. I highly recommend you not worry about trying to recover these values on copper, for you'll spend far more time screwing around with it than you would with steel.

Assuming you choose to go the steel route, simply decant the solution after it is barren. Discard it by your preferred method, assuming it tests barren. Simply leave the residues in the same container (plastic bucket), and reuse it constantly. When there is a generous amount of black sludge in the container, remove the steel pieces, rinsing them to remove free sludge. Don't be concerned about getting them clean, for they will go back in the stock pot for further use. Remove all the steel, then get the sludge in a filter and allow it to dry. Once dry, incinerate well, then store the material for future processing. I'll be able to give you an excellent recipe for fluxing for furnace reduction. If you choose to chemically process the stuff, that will work, too, but you should have a generous amount of it before you do so. That will insure that you have enough value present that it will precipitate.

Hope some of this helps.

You mentioned posting some pics. Looking forward to your offerings.

As you suggested, we can talk about large volumes at a later date, but in the mean time, don't discard any solutions that test positive for values. Start immediately with a stock pot, even for minute traces. You'll be pleasantly surprised at how they add up!

Harold

 

[Ageo308]

Ok Harold, sorry for no photo's but we hit something quite weird. We followed the exact same process as we did the last test batch but added the extra ammonia wash and HCI wash in the end. Thinking the more washes the better it actually showed up less karatage then the last button we refined. Im still trying to understand how this was possible as everything was followed as planned. Any suggestions on this?

 

[Harold_V]

Unless you introduced something to the yield in the wash process, there's no good explanation. Washing has no ability to contaminate the material, and in the worst case scenario, you would have achieved nothing. I would suggest to you that you may well have shorted the wash process. The last wash in HCl should come out with little or no color change. If it comes out with considerable change, it's entirely possible you stopped way too soon.

You should look to your procedures when something like this happens. How clean the material was before dissolving the values, and how clean the gold solution was when you precipitated the gold. What you used for precipitation, and if you used more than was necessary (assuming you used something like copperas), and didn't wash it until you had removed all of it. That's why you keep hearing garbage in--garbage out. The cleaner you work, the cleaner you can expect the end product to be.

I'd suggest you review your process and see if you made any minor deviations. I'd also suggest that when you do your final filtering, you do so with an appropriate filter. If your solution does not come out clear of flocculence, anything you leave behind will report in your gold. The only question is will it become an alloy with the gold, or will it be left behind in the dish, trapped by the flux.

Is there any way for you to determine what the contaminant is? Are you sure of your results? If you are not paying for an assay, can you tell me the method you used to determine the relative purity of each batch? If you are making visual observations, the type of contaminant can make a huge difference. Some are not really detectable visually.

Harold

 

[Ageo308]

Harold the only thing i can think of is the filtering, although the filters we use are so fine that they take a while before filtering right through. The last wash is clear as water can be.

The tester we use is this one http://www.mineralab.com/M24GoldTester.htm

We have tested numerous 9ct, 18ct and other karatage jewellery items and they have all come up accurate. Its not enough to tell you the purity (9999 terms) but its enough to tell us if it falls in a certain karatage (which is all we need for quick testing).

Quick question, when rinsing the washes as you let it settle then pour the liquid any dust thats flowing out should not be gold correct? as the gold is heavy and sets on the bottom? If im reading right the dust particles that flows out of the water is called flocculence.

Anywayz i will update you on the re-purification process.