Recovering precious metals from polishing sweeps

[Harold_V]

My approach was very simple.

1} Incinerate in a shallow pan, heating from below. Ignite the material to eliminate the majority of smoke and stink. It will readily burn once hot enough. Incinerate until all carbonaceous material has been eliminated. There should be no glowing embers. Allow them to burn completely. Insure the pan is hot enough by heating with a torch from the bottom. Don't burn through the pan. An old stainless fry pan works very well for this operation. Find them at Goodwill or other second hand stores. DO NOT USE ALUMINUM.

2} Screen after cooling, to remove any sizeable pieces that would be difficult to dissolve without inquartation.

3} Run a magnet through the material to remove free iron particles. They should be placed in the stock pot, not discarded. They generally will transfer miniscule traces of values.

4} Place screened wastes in a beaker, or a container that will tolerate being heated.

5} With an approximate mixture of 50/50 tap water and HCl, cover the contents with solution, then place on hot plate. Heat slowly until contents are brought to a boil. Stir regularly to prevent the container from overheating and breaking from thermal shock.

6} After a reasonable boil period, (contents will change color), remove from heat and fill container with tap water. Stir well.

7} After solids have settled well, decant solution. Test for values, then discard if barren. It is rare to find values in the solution unless you have allowed nitrates to be included.

8} Repeat the above operation until the rinse water is clear, or nearly so.

9} Apply AR @ 5 ounces per troy ounce of values expected to be recovered. Use only what is necessary, to minimize the amount of nitric that must be evaporated later. Heat to boiling, and stir regularly. Do not allow the material to dry on the bottom of your container, which will lead to thermal shock and cracking, as above. Make your AR @ 4 HCl/1 nitric, not less. If in doubt, move up to 5 HCl/1 nitric. Too much HCl does no harm, unlike too much nitric.

10} When values are in solution (note color change of solids, and the yellow color of the solution), and you see no fumes coming from the container, remove from heat and add a few ounces of water. Stir, then allow contents to settle.

11} Decant, then add more water to solids and stir well. Repeat this operation until you have removed the bulk of values. Note the color of the solution, which will slowly shift towards clear as it is washed.

After the final decantation, place the solids in a filter (Sharkskin works very well for this operation) and extract all solution possible.

Combine all solutions from the AR process and evaporate to eliminate water and nitric. Add a few drops of sulfuric to the evaporation process early on, which will precipitate any traces of lead that may be included in the process. Be very careful about adding sulfuric to hot solutions. It is best added while they are cold. Stir as it is added to prevent local generation of steam.

After evaporation, take up with water, filter, precipitate, and wash appropriately.

I suggest you do none of the extraction processes until you've read Hoke's book---so you have a general understanding of what you're doing, and why. None of this is difficult----it becomes routine after you've done it a few times. Do not allow the outline to discourage you.

Dry the waste solids by heating, then save them. Do not store them wet----they will give off fumes endlessly and destroy anything of value in the immediate vicinity by corrosion. Please take my word on this part (the solid waste material, after acid processing) ---it is a wonderful savings plan. The values remaining are not substantial, but they add up. Remember------you will have left silver behind in this operation, not just traces of gold.

Note that this process will not be suited to processing wastes high in silver. It will remain in the solids. If you process waste from the silver bench, it becomes somewhat more complicated. I can talk about that if and when it is an issue. It is a waste of time to pursue traces of silver with each batch.

Harold

 

[Ageo308]

Harold i appreciate all the advice so far, i will now wait for hoke's book (read it a few times) then get stuck into this process.

I will update you (with pics hopefully) to let you know how we went.

thanks again

 

[Harold_V]

Welcome!

Harold

 

[Ageo308]

My approach was very simple.

1} Incinerate in a shallow pan, heating from below. Ignite the material to eliminate the majority of smoke and stink. It will readily burn once hot enough. Incinerate until all carbonaceous material has been eliminated. There should be no glowing embers. Allow them to burn completely. Insure the pan is hot enough by heating with a torch from the bottom. Don't burn through the pan. An old stainless fry pan works very well for this operation. Find them at Goodwill or other second hand stores. DO NOT USE ALUMINUM.

2} Screen after cooling, to remove any sizeable pieces that would be difficult to dissolve without inquartation.

3} Run a magnet through the material to remove free iron particles. They should be placed in the stock pot, not discarded. They generally will transfer miniscule traces of values.

4} Place screened wastes in a beaker, or a container that will tolerate being heated.

5} With an approximate mixture of 50/50 tap water and HCl, cover the contents with solution, then place on hot plate. Heat slowly until contents are brought to a boil. Stir regularly to prevent the container from overheating and breaking from thermal shock.

6} After a reasonable boil period, (contents will change color), remove from heat and fill container with tap water. Stir well.

7} After solids have settled well, decant solution. Test for values, then discard if barren. It is rare to find values in the solution unless you have allowed nitrates to be included.

8} Repeat the above operation until the rinse water is clear, or nearly so.

Hi Harold, last night we started your technique and got till the end of the rinsing process and ready for the AR process. Everything is looking good so far. My partner and I read Hoke's book a few times to understand the evaporation process especially as you mentioned but 1 thing we cant find is when making AR, does it matter if you mix HCI to Nitric or Nitric to HCI? Tomorrow night will be the final stage and i will update you on the progress.

thanks again

 

[Harold_V]

when making AR, does it matter if you mix HCI to Nitric or Nitric to HCI? Tomorrow night will be the final stage and i will update you on the progress.

thanks again

I don't recall ever having any problems with mixing those two acids, regardless of the sequence of combining them. If any heat is generated, it is miniscule, so it's not a problem.

I did my mixing in a graduate, pouring from stoppered bottles, in random sequence. I usually poured my nitric first, then the HCl. It was then poured into the container where it was to be used. The only caution, aside from common ones, is to not mix any that you don't intend to use immediately. It tends to gas a little, so it's not a combination that you should make and store.

I suggest you use an excess of HCl. It does no harm, and guarantees you use all of the nitric. I favored a 4:1 ratio, and often went as high as 5:1.

Harold

 

[Ageo308]

Harold we are basically using a large syringe to transport the acid from the container to the beaker. It has the exact measurements so we can do it nice and slow (for the experimenting stages).

Its much more cleaner and we didnt spill any.

Basically we are going for the 4:1 in the AR mix but if in doubt for whatever reason as you mentioned will move up to 5:1.

Fingers crossed everything will go as planned.

 

[Ageo308]

Ok Harold we did the final process, as we are letting it dry and before we melt which flux will suffice? we tried melting whilst still wet using borax and it seemed like it did the job fine. I think we didnt do the last bit correctly thow as it still has a brown mud on the bottom along with the gold and other metals.

If you dont mind could you go into abit more detail from the AR process onwards? we are going to try some more tomorrow night.

Also for the filter we used the coffee filters which seemed like it did a very good job (have you ever used that before)??

anywayz i look forward to your valuable input.

thanks

 

[Harold_V]

Ok Harold we did the final process, as we are letting it dry and before we melt which flux will suffice?

I trust you went through the proper wash procedure? While gold that comes from this process tends to be of quite high quality, I don't recommend you melt any gold that has been precipitated without first washing properly. I've discussed the washing process at length in previous posts. Be certain you follow that, or a comparable, procedure. The wash should include at least one application of ammonium hydroxide, even if you don't feel it is necessary. It performs a valuable operation in dissolving substances that may not, otherwise, get washed from the precipitated gold.

Regards the flux you use. Use nothing but borax for melting pure gold. The use of other chemicals has the potential to reduce oxides, recombining them with the pure gold, defeating your purpose in processing the gold. If your gold is clean, you need only a film of borax covering the dish, which will serve to "lubricate" the molten gold and allow it to flow well. If your flux discolors when you melt your gold, the gold is not clean. The flux should remain clear of color, shifting towards purple. If any other color develops, the gold is contaminated. Once melted, the surface of your gold should remain shiny, with on oxide skin forming, and will cool with a large crystalline pattern. It should also pull a very deep hole in the center, as it solidifies. If it frosts up and refuses to form the hole (pipe), the gold is not pure.

we tried melting whilst still wet using borax and it seemed like it did the job fine. I think we didnt do the last bit correctly thow as it still has a brown mud on the bottom along with the gold and other metals.

This is a little confusing. For starters, while melting the mud while it's wet will work, you risk breaking your melting dish, depending on how long the wet material is in intimate contact with the melting dish, and how well it is coated with flux.

There should be noting on the bottom of your container aside from gold. If other metals have precipitated with the gold, something has gone woefully wrong. Can you tell me what you think is there with the gold?

If you've read my washing procedure, you know that the gold that is ready for melting has been well washed and dried. It never leaves the beaker in which you precipitate the gold------not until it has been through all of the process. By following this procedure, the gold gets washed and dried, and acts as its own collector for the very fine particles of gold that can be troublesome. The only time it doesn't collect all the dusty particles is when the gold is very dirty, from dirty solutions. In that case, it is usually accompanied by a dark color, but not always.

If you dont mind could you go into abit more detail from the AR process onwards? we are going to try some more tomorrow night.

I'm going to assume you have done a good hot wash with HCl and water, and have rinsed the mud enough times (tap water) that the rinse water is coming off the mud in an almost clear color. The mud at this point should be a maroon to purple color, depending on the volume of gold it contains, and what medium was used for polishing. If the benchman did a lot of platinum work, it's possible the mud could even be green in color. I've seen them vary widely, so color alone is not a good indicator of contents.

It's hard to guess the amount of value in the mud, for various reasons. The entire objective is to dissolve all the values, which can then be rinsed from the mud via a few tap water washes. Start with AR (mixed @ 4 parts minimum HCl and 1 part nitric). If you have a hunch on content, assume that amount to dissolve 1 troy ounce. Do not use too much AR----if you add unneeded nitric to the mix, it must be eliminated before recovering the gold. The negative side is that if you don't use enough, you won't get total extraction. The best policy is to estimate your recovery and use slightly less acid than is required. Let it work, heated, until it has done all the work it can, then add a little HCl to insure that you did not run out of it in the process, leaving some nitric unconsumed. If you get no further reaction (fumes) by adding the HCl, add a small amount (half ounce or so) of nitric and observe fuming, if any. Repeat this process until further additions of acid yield no reaction. At this point you're wise to allow the mud to stew for a while, to insure that you have dissolved larger bits of gold. Polishing waste usually contains bits of gold from the use of abrasives at the wheel, and they take a little longer to dissolve. The mud should have changed color completely, and reflect a cream color. Solution, if you've done your washing properly before dissolving the gold, will now be a nice deep yellow orange color, a sign of dissolved values and few, if any, base metals. If the solution is green, or darker, the preliminary wash was not carried out well, and an abundance of base metal was left in the mud.

I never used urea, so I can't discuss it's proper application. My method was to evaporate the solution, which eliminates unused nitric acid, plus was an indicator that I had used enough AR to dissolve all of the contents of the mud. Had I not, there would be no unused nitric present. I proved the unused nitric by adding a weighed button of gold to the solution, which gradually dissolved as the solution was evaporated. By weighing before and after, you can determine how much gold you added to the process, which should be subtracted from the gross yield to determine the net yield. By using the button, evaporation need not be carried to a totally thick solution, so it saves time in evaporation. Note that a few drops of sulfuric acid should be included in the evaporation process, which will serve to precipitate any traces of lead as lead sulfate. this is an important part of the process. Do not leave it out. Lead is death on gold's ductility. When the solution has been evaporated until it is well concentrated, and has shifted color towards a dark red, some HCl is added. If there is no reaction at the gold button (considerable bubbling and some brown fumes), you can consider that there is no more nitric present, and the solution can be diluted with tap water and filtered. Once filtered, it can be precipitated with the precipitate of your choosing. I favored SO2 from a bottle, but you can use any of a wide variety of precipitants. One that is easy to use and is readily available at a garden shop is ferrous sulfate. Hoke's book discusses the application in fine detail. The ferrous sulfate, if that be your choice, should be a nice green color. If the color has shifted to brown (exposure to excessive moisture), it will not precipitate gold.

Also for the filter we used the coffee filters which seemed like it did a very good job (have you ever used that before)??

No, I did not use coffee filters, although I did use something that is very similar (Shark Skin, made by S&S) for filtering the solution from the mud. Once my solutions were evaporated, I preferred a Whatman #2 paper, which I purchased in the 32 cm size if memory serves correctly. They fit, when properly folded, the filter funnels that are readily available from chemical supply houses. I found it to be the best filter on the market for filtering solutions prior to precipitation.

The exception to this is that when I filtered gold that was re-refined, I then switched to a Whatman #5, same size. That is a very tight and slow filter paper, and will remove the smallest of contaminants. Unless you're working with very clean solutions at the outset, they perform very poorly. They're quick to stop flowing, but very good at removing miniscule particles from otherwise clean solutions. That describes the gold that I re-refined perfectly, so it was a perfect match for the process.

There's nothing wrong with using coffee filters aside from the fact that they tend to allow very fine particles to pass. As long as your solution is crystal clear (of flocculence, not color), it doesn't matter if you use a coffee filter or don't filter at all, for that matter. The important thing is to separate all the particulate matter from the solution before gold is precipitated, otherwise you recombine unwanted materials with your processed gold. Gravity alone can be used to separate solutions from insoluble materials, it just takes more time, and it makes retrieving the last little bit more difficult. I was way too busy to take the time, so fast and good filtration was important to my operation. I learned to turn out solutions that would filter readily. How well a solution filters revolves around doing the proper washes before you ever dissolve the gold. By doing so, compounds that are formed by acids and difficult to filter are eliminated in the preliminary washes and rinses. These are things you'll learn as you progress.

Harold

 

[Ageo308]

Aha i feel like an ***** but we did miss a couple of things.

1: the ammonium hydroxide which we didnt add but will do next time.

2: the precipitation process, i feel like a dummy as i skipped this bit (i will go and buy some ferrous sulfate.

If you dont mind could you go into some detail with both these things, i.e how much ammonium needs to be used and do i just add it to the rinse? (with tap water)?

Also with the precipitation you mention take up water, filter, precipitate, and wash appropriately so once i filter it and have the brown mud sitting on the bottom is that when i add the sulfate? and if so how much? these 2 are the only areas i havent done and will do tonight.

Thanks again


P.S as for the wash procedure, we basically filled the beaker with tap water, stirred it then let it settle, decanted it and made sure no value were in the liquid then emptied it and repeated the process until the rinse water was clear. Sound right? We did the same rinse process with the HCI/water and the AR mix.

 

[aflacglobal]

Wash :arrow: http://tinyurl.com/yswbbw

 

[Ageo308]

Thanks af ill go through that to get a better understanding. Also Harold you said any garden center has ferrous sulfate but i couldnt find any, the closest i came to is sulfate of iron (which im assuming is the same stuff) or a sulfate ammonia both are which a lawn fertilizer, so let me know which 1 will suffice.

As for the ammonium hydroxide im assuming the chemical factory that i picked up the nitric and hcl should have some so i will contact them.

Ill await for your reply's before proceeding.

cheers

Edit: I found this product http://www.yates.com.au/Products/Fertilising/Specialised/SulphateofIron.asp

Iron Sulphate (Australian) so ill be getting some of that.

 

[Harold_V]

Aha i feel like an ***** but we did miss a couple of things.

1: the ammonium hydroxide which we didnt add but will do next time.

2: the precipitation process, i feel like a dummy as i skipped this bit (i will go and buy some ferrous sulfate.

If you dont mind could you go into some detail with both these things, i.e how much ammonium needs to be used and do i just add it to the rinse? (with tap water)?

Regards the ammonium hydroxide, be certain you understand when this process is used. It should NEVER be combined with gold chloride solution. The ammonium hydroxide operation, for me, came after the first HCl wash and rinse of the precipitated gold powder. Cover the gold powder with ammonium hydroxide and then some tap water, and heat it. You'll see a change in the color of the solution, indicating it is dissolving unwanted compounds. Usually a light blue color. If you get no color change, great! That's a pretty good indicator that the gold is quite clean. Boil for a few minutes, then decant and rinse with more tap water, bringing it to a boil once again. Decant, and add enough HCl to cover the gold. Add a little water and boil for a while. If the color of the solution doesn't change, the gold is as clean as you're going to get it by washing. That isn't necessarily an indicator that the gold is pure; it may not be. Only a second processing will put more of the contaminants in solution, where they can be left behind by a second precipitation and wash cycle. That improves gold tremendously and is worth the effort if you're striving for 4 9's quality. You should get close, if not there, by this method.

Also with the precipitation you mention take up water, filter, precipitate, and wash appropriately so once i filter it and have the brown mud sitting on the bottom is that when i add the sulfate? and if so how much? these 2 are the only areas i havent done and will do tonight.

I mentioned ferrous sulfate only as an example. As I may have mentioned, there are many things that will act as a precipitant. If you are precipitating by any other means, that's fine, so if you have brown mud sitting on the bottom of your beaker, you've already accomplished that operation.

as for the wash procedure, we basically filled the beaker with tap water, stirred it then let it settle, decanted it and made sure no value were in the liquid then emptied it and repeated the process until the rinse water was clear. Sound right? We did the same rinse process with the HCI/water and the AR mix.

I maybe should have been more specific. I have posted on this procedure and covered anything of importance in fine detail. Aflac has provided a link in the post, above. Please follow that link and read the various posts. There is a lot of information there that will benefit you far beyond the time it takes to read the comments.

Regards what you did with your wash operation, if leaves a great deal to be desired. It doesn't come close to washing the gold in the way it needs to be washed. You may not understand that until you've actually seen what comes from the gold, and how it is changed by the procedure I've mentioned. There's no doubt in my mind, you'll rarely, if ever, produce gold that rivals gold that is washed properly after precipitation. Only when it comes from a very clean solution do you have a remote chance, for drag-down (of contaminants) is the enemy. Prolonged boiling in acid and ammonium hydroxide insure that traces are removed as much as is possible. I advise that you do not short cut the process by avoiding the wash cycle.

Please read the provided link, and tell me what you feel you've learned. It might help in fine tuning what you're trying to learn.

For the record-----gold that comes from this process (polishing wastes that are well washed before the gold is dissolved) tends to be of very high quality because you start with material that lends itself to easy dissolution of the metals. Your quality may be quite good now----but washing is good insurance. You'll see that when you process dirty material, such as filings.

Harold

 

[Ageo308]

thanks Harold, ill go through that post.

cheers guys

 

[Harold_V]

Thanks af ill go through that to get a better understanding. Also Harold you said any garden center has ferrous sulfate but i couldnt find any, the closest i came to is sulfate of iron (which im assuming is the same stuff) or a sulfate ammonia both are which a lawn fertilizer, so let me know which 1 will suffice.

Sulfate of iron appears to be the one you'd buy. If you have the opportunity, look at the contents. They should be a very nice light green color. If you find brown, it's not good for use. I have used some that is mixed, brown and green, by adding a few drops of HCl to the solution after dissolving and filtering. The brown material, as I understand it, has already lost the needed electron that precipitates gold---so it stands to reason that if you use some that is mixed, it will do less work. No matter---you simply use a little more. Again, you may not need this material if you have chosen a different method to precipitate your gold. Don't duplicate processes----that makes no sense. Buy this material only if you are not happy with what you used already.

As for the ammonium hydroxide im assuming the chemical factory that i picked up the nitric and hcl should have some so i will contact them.

I used to buy it from a chemical supply house in a box of six (1) gallon plastic containers. If, by chance, you have difficulty buying-----use any unscented (and uncolored) ammonia from the grocery store.

Ill await for your reply's before proceeding.

Also, please read Hoke on processing polishing wastes----and see if I've left out anything important. It's been years since I last ran a batch. I'm quite rusty! :wink:

Harold

 

[Ageo308]

wow i have a sore head Harold is this something your referring to for a clean wash

First wash should be in boiling HCL and tap water. Boil for a prolonged period of time. Take up the solution with tap water, decant after the gold has settled, then rinse with tap water, which should again be brought to a boil. After it has boiled for a period of time, add more tap water to cool the lot, then decant as before. Rinse again, and do it until the wash water comes off clear. :arrow: Next, wash the gold with ammonium hydroxide and tap water. Heat it until it boils. You'll notice that the solution gets discolored. How much is determined by how dirty your gold was when you started. The ammonia evaporates fairly quickly, so you can't boil very long. Add tap water to cool, decant, and follow up with a tap water rinse, again, boiling the water. Add tap water to cool, then decant. You now repeat the HCL and tap water wash. You'll be amazed that suddenly more contaminants will come off. Boil well, add water to cool, decant, repeat the water rinse, decant, then, and this is important-------start the refining process all over again by dissolving the well washed gold powder in aqua regia. I'll talk about that in a minute, but these are indicators you should have observed along the way, aside from the fact that you could see contaminants being washed from your gold powder.

If thats exactly how i should do it then i have 2 more questions,
1: since i have boiled in AR already and the gold has somewhat dissolved will it be dangerous to repeat the above wash since ammonium and gold chloride dont mix well?

2: Believe it or not but i didnt use anythiing to precipitate, i simple boiled the AR then added water and rinsed but the way i stated before (without re-boiling). So do you recommend me adding some sulfate to the AR mix whilst i rinse it a few times?

Tonight im going to get stuck into hokes book again to refresh my memory.

cheers :wink:

 

[aflacglobal]

Harold is this something your referring to for a clean wash :arrow: Yes

1: since i have boiled in AR already and the gold has somewhat dissolved will it be dangerous to repeat the above wash since ammonium and gold chloride dont mix well?

:arrow: The ammonium hydroxide operation, for me, came after the first HCl wash and rinse of the precipitated gold powder.

 

[Harold_V]

wow i have a sore head Harold is this something your referring to for a clean wash

First wash should be in boiling HCL and tap water. Boil for a prolonged period of time. Take up the solution with tap water, decant after the gold has settled, then rinse with tap water, which should again be brought to a boil. After it has boiled for a period of time, add more tap water to cool the lot, then decant as before. Rinse again, and do it until the wash water comes off clear. Next, wash the gold with ammonium hydroxide and tap water. Heat it until it boils. You'll notice that the solution gets discolored. How much is determined by how dirty your gold was when you started. The ammonia evaporates fairly quickly, so you can't boil very long. Add tap water to cool, decant, and follow up with a tap water rinse, again, boiling the water. Add tap water to cool, then decant. You now repeat the HCL and tap water wash. You'll be amazed that suddenly more contaminants will come off. Boil well, add water to cool, decant, repeat the water rinse, decant, then, and this is important-------start the refining process all over again by dissolving the well washed gold powder in aqua regia. I'll talk about that in a minute, but these are indicators you should have observed along the way, aside from the fact that you could see contaminants being washed from your gold powder.

If thats exactly how i should do it then i have 2 more questions,
1: since i have boiled in AR already and the gold has somewhat dissolved will it be dangerous to repeat the above wash since ammonium and gold chloride dont mix well?

That is the washing procedure for precipitated gold---the familiar brown powder that comes from precipitation. Sounds involved, but it isn't, and it improves the quality of gold tremendously. Understand that you can stop the process after using ammonia, followed by the last wash with HCl, and a water rinse once again. If the gold came from a very clean solution and you do not intend to re-refine it, it would then be dried and melted. If the final wash with HCl comes off clean, that would certainly be the case. I always refined a second time, but you may or may not wish to do so.

As far as your concern about ammonia-----If you have washed gold powder with ammonium hydroxide, then rinsed with water, followed with another wash with HCl, there is no ammonium hydroxide present. It will have been completely replaced with the HCl wash and rinse. You have nothing to fear. Fact is, when you force dry the gold, even after a good rinse in water, you'll notice a distinct smell of HCl coming off the gold as it dries. Dry it until the smell is gone. Follow the instructions for drying the gold in a beaker. Use low heat until loose water is gone, otherwise you experience steam bumps that can throw gold out of the beaker, and usually does. I've had beakers bump so hard they came off the hot plate and broke. Be careful when drying your gold.

2: Believe it or not but i didnt use anythiing to precipitate, i simple boiled the AR then added water and rinsed but the way i stated before (without re-boiling). So do you recommend me adding some sulfate to the AR mix whilst i rinse it a few times?

If you didn't precipitate, how did you recover the gold? How did you eliminate all the garbage that typically accompanies gold in process? None of this makes any sense.

Tonight im going to get stuck into hokes book again to refresh my memory.

cheers :wink:

Right now you have me in a complete state of confusion. I have serious doubts that you have followed the instructions as they have been presented. Please------do not try processing material until you understand the process. You stand to lose a great deal of value if you do, or you can create problems that can be difficult to undo.

There are two distinct HCl washes that accompany the processing of polishing waste. One of them is to dissolve unwanted crud in the dirt you have incinerated. Only after you have processed the dirt and washed (with HCl) and rinsed it until the rinse water comes off clean do you dissolve the gold. When the gold has been dissolved, it (the gold solution) should have been separated from the dirt, with the dirt rinsed with tap water until the rinse shows little or no values. At that time the solution would be evaporated as I've instructed, filtered after it has been well evaporated, and then the gold precipitated as the familiar brown mud. The last washes with HCl occur only on the precipitated gold, and that is the ONLY time your gold should see any ammonia. If you've done anything different from the above, please detail it EXACTLY as you've done it. Include all details, even if you think they don't matter.

Harold

 

[Ageo308]

Ok let me explain what we have done so far, We incinerated the sweeps, then sifted it (removed the larger pieces and stored them), then ran a magnet through it to remove an iron particles.

* Once that was done we boiled it in 50/50 HCL/water until it changed colour (cream brown then green), basically from there we added some water to cool then decanted the solution, then added some more water but didnt bring it to boil (wasnt sure) after a quick stir and let it settle we rinsed it again (5 times roughly).

* From there we put the mud into AR and did the same process as the HCL which is wrong i know but im just explaining what we did. Tonight we basically put the dried dirt into a 50/50 HCL/water mix and boiled for about 20min then added water, decanted (the solution was yellow), and rinsed again with new tap water and again brought to boil. This time we repeated that process about 8 times and had to stop but the rinse water is becoming much clearer and the mud is now becoming a nice smooth fine dust (lightly brown) with no sludgyness. I can see gold particles in there so im guessing thats a good thing.

* Tomorrow night we are going to finish off the rinsing process then start with the ammonia rinse and do that until its clear and then finally back to HCL/water with a final rinse to make sure there is nothing left to clean.


So tell me where i went wrong and if we are going in completley the wrong direction. From what i can see thow the powder is looking much nice then it did before.

 

[Harold_V]

Ok let me explain what we have done so far, We incinerated the sweeps, then sifted it (removed the larger pieces and stored them), then ran a magnet through it to remove an iron particles.

* Once that was done we boiled it in 50/50 HCL/water until it changed colour (cream brown then green), basically from there we added some water to cool then decanted the solution, then added some more water but didnt bring it to boil (wasnt sure) after a quick stir and let it settle we rinsed it again (5 times roughly).

At this point you've done quite well. The whole idea is to dissolve anything that will dissolve, but not the precious metals. If your solution tested barren, it can be discarded. The five rinses would indicate that you had removed the vast majority of unwanted materials, so when you dissolved the gold and other values, the solution would then be quite clean. Well done to this point.

* From there we put the mud into AR and did the same process as the HCL which is wrong i know but im just explaining what we did.

No, it's not wrong--it's exactly what you were supposed to do. What you did with the solution is what I think you did wrong. If you discarded it, you tossed your gold. AR dissolves gold, which is EXACTLY why you introduced it to the mud. It is intended to dissolve the gold and other values, so they can be separated from the dirt, which has no value. You get a much better extraction by dissolving than you do by melting, unless you use litharge in melting, but that involves cupellation, which is beyond the average guy's ability, and is also very hazardous because you're burning lead and producing large volumes of lead fumes.

Tonight we basically put the dried dirt into a 50/50 HCL/water mix and boiled for about 20min then added water, decanted (the solution was yellow), and rinsed again with new tap water and again brought to boil. This time we repeated that process about 8 times and had to stop but the rinse water is becoming much clearer and the mud is now becoming a nice smooth fine dust (lightly brown) with no sludgyness. I can see gold particles in there so im guessing thats a good thing.

If you combined all these wash waters with the first (yellow) solution and have started evaporating them, you're on the right track. If you discarded the wash water, as I said before, you tossed the values. If you can still see gold in the mud, it's because you didn't use enough acid to dissolve all of it. Fact is, the mud is what you should have been trying to eliminate, not keep. By washing it until you had rinsed out all of the yellow color, you would have removed all of the gold, assuming you had dissolved all of it in the first place. For some reason you seem to think that the dirt is the target-----it is not.

* Tomorrow night we are going to finish off the rinsing process then start with the ammonia rinse and do that until its clear and then finally back to HCL/water with a final rinse to make sure there is nothing left to clean.

Don't do that. You should have evaporated the golden solution to expel the unused nitric, diluted the evaporated solution with water, filtered, then precipitated the gold FROM the solution. You're spinning your wheels working on worthless dirt, assuming you dissolved all of the gold in the first place. Your only hope is if you had enough sense to keep all of those solutions aside from the very first one, where you used HCl and water the first time, plus the rinses. If you did not, you have lost your gold.

So tell me where i went wrong and if we are going in completley the wrong direction. From what i can see thow the powder is looking much nice then it did before.

It may look "nicer", but what does that mean? You've possibly tossed the baby with the bath water. I hope you haven't.

Can you see why I suggested you not do anything until you understand the process? Do you see why I suggested you hold off until you had Hoke's book?

Had you kept the instructions near you while you were working, and checked each step to verify what you were doing, you wouldn't be where you are right now.

Let me know if you saved your gold colored solutions. If so, you must turn your attention to them.

If you think you're seeing gold in the mud, you may not have dissolved all of the values. Heating with a little more AR will disclose if you did, or did not. If there's values remaining, you'll see the solution turn yellow to orange, depending on the degree of concentration.

I haven't heard you mention stannous chloride much in your report. Did you ever bother to check solutions?

NEVER DISCARD A SOLUTION WITHOUT TESTING WITH STANNOUS CHLORIDE THAT IS KNOWN TO BE ACTIVE. That means you should have on hand a standard gold solution, which is used to test the stannous chloride. It's all in Hoke.

Harold

 

[Ageo308]

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

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?

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


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???

cheers

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

If you combined all these wash waters with the first (yellow) solution and have started evaporating them, you're on the right track. If you discarded the wash water, as I said before, you tossed the values. If you can still see gold in the mud, it's because you didn't use enough acid to dissolve all of it. Fact is, the mud is what you should have been trying to eliminate, not keep. By washing it until you had rinsed out all of the yellow color, you would have removed all of the gold, assuming you had dissolved all of it in the first place. For some reason you seem to think that the dirt is the target-----it is not.

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 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. 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???

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

Im looking forward to your reply