# Seeking all advice,tips and hints before I begin.



## timmadsen (Dec 7, 2011)

Hi all, My name is Tim and I have read been lurking around here and reading for the better part of a month now, I have read all the suggested material and manuals and absorbed what I feel is enough information to begin my project. I would like to explain to everyone what I am going to do and how I am going to do it and ask a few questions and maybe get some responses that could help me catch any problems I might run into before I begin. 

I have accumulated a large quantity of gold filled items, most of the stuff is 1/10 12k vintage eyeglasses, but there is also a good amount of misc jewerly,watchband tops, and other things too. I am not going to attempt to refine this stuff to pure gold. I have been buying 10~22 karat scrap for over a year now and selling it to a local refiner (who is also a friend of mine). For now my goal is to only refine this stuff to better then 45% or better and then I will send it to my refiner with my other stuff. Once I have perfeced this step to the best of my ability and I am confident I can minimize my gold loss I will move on to doing my own refining.

I have set up a work bench outside and purchased a rolling mill to maximize the surface area of all my material. I have a large electric hot plate set inside a larger metal tub, I will have a casserole dish on top of the hot plate and my coffee pot inside the casserole dish. 

I will probably start with smaller batches of gold filled material (maybe 200 grams or so) that have been flattened with the rolling mill and then twisted somewhat to prevent anything from laying flat on the bottom of the coffee pot. I will then add distilled water to the material. I will completely submerge my material in distilled water. 

I have purchased 5 gallons of Nitric acid (67%), I have not seen the container yet but hopefully I will figure out a safe and easy way to remove small amounts of the nitric from the container and into my glass beakers (any suggestions?). I will start by measuring out 1.5ml of nitric for every gram of material I have (this is only a rough guideline of how much nitric i will use). Then with a syringe I will slowing add small amounts of nitric to the material. I will start with no heat and then slowly add heat. I will not be in a hurry and will most likely keep the heat low to medium during the entire process. 

I expect to see the reaction and the resulting red/brownish fumes. And of course I will be taking all precautions to ensure i am not breathing these fumes. From what I have read I believe that when I see a significant reduction in fumes and reaction I can continue to add more nitric acid a little at a time. Hopefully I will get a good 'feel' for when i can add more. I will continue this process untill I see very little reaction and fumes when i add more nitric acid at which point I will remove the heat and allow the mixture to cool. Question : should I be adding any distilled water during this time? I have read that some people have had problems with the mixture turning into a 'goo' or 'paste' in the bottom of the pot and they suspected it was the result of not enough water ?

I then plan on pouring off a majority of the liquid into a safe container for storge. this is the part I hope to recieve some suggestions on... once i pour off a majority of the liquid I will be left with either solids in the form of a powder or in the form of small pebbles or sand along with a small amount of liquid. My goal from here is to transfer these solids into my large graphite bowl and melt into a solid block. As of now (pending comments and suggestions) I intend to pour the remaining solids and acid into my bowl together while using a spray bottle with distilled water to ensure i get all my solids out of the coffee pot and into the bowl. Then slowly heat the bowl until all the liquid evaporates and then turn up the heat and melt the solids into a block. I am using a large sized graphite bowl / mold with a lid and a torch to heat it. 

This is as far as I want to go for now, I know this is not pure gold, but I will wait untill after I have done this several times before I attempt to do a complete refining on my own.

I welcome all suggestions and or comments.


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## samuel-a (Dec 7, 2011)

Hi timmadsen 

Welcome aboard. 
Seem like a man with a plan 8) 

Your process looks fine, though, with gold filled, you should expect using more then 1.5ml nitric per gram.
But looks like you are prepared for that as well.

In my mind, there no need to roll flat GF jewellry, as the underlying is base metals / silver anyway and react very fast with nitric.

It will be wise to dilute the leach to some extant after the hot reaction is done to prevent crystallization. in any case, it could be washed later.
20-30% should do.

I'd suggest you to run the leach through some sort of filtration to catch any stray solids (gold foils or powder/rhodium foils/ss springs etc'...).
Probably want to wash the solids 2-3 times with d water.

Then, test the leach solution with HCl for silver presence (and even for palladium with SnCl/DMG) and act accordingly.

Good luck.


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## timmadsen (Dec 7, 2011)

> In my mind, there no need to roll flat GF jewellry, as the underlying is base metals / silver anyway and react very fast with nitric.



I have read that this is the case, I bought it because I thought it would be a small investment when compared to the amount of scrap i buy. and that rolling them will help me eventually minimize the amount of Nitric I use to help decrease the cost and increase profits. 




> It will be wise to dilute the leach to some extant after the hot reaction is done to prevent crystallization. in any case, it could be washed later.
> 20-30% should do.



Please forgive my ignorance, but am i correct in understanding that you are suggesting I dilute the acid in my coffee pot prior to pouring it off into another container for storage ? and that by doing so it will help make the process of extracting the precious metals (such as silver) from the stored liquid at a later date (when i am better educated on that process) by preventing crystalization of the acid/water/ dissolved metals ? or am I way off on understanding your advice ?


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## samuel-a (Dec 7, 2011)

I'll try clarify...



timmadsen said:


> I have read that this is the case, I bought it because I thought it would be a small investment when compared to the amount of scrap i buy. and that rolling them will help me eventually minimize the amount of Nitric I use to help decrease the cost and increase profits.



By increasing surfce area, you will not change the amount of reagent needed.
One gram of copper wire and one gram of copper strip are still one gram of copper metal. Just with different surface area (in favor of the strip of course).
By rolling the jewellry, you only change the reaction time.




timmadsen said:


> Please forgive my ignorance, but am i correct in understanding that you are suggesting I dilute the acid in my coffee pot prior to pouring it off into another container for storage ? and that by doing so it will help make the process of extracting the precious metals (such as silver) from the stored liquid at a later date (when i am better educated on that process) by preventing crystalization of the acid/water/ dissolved metals ? or am I way off on understanding your advice ?



A solution of 50/50 nitric acid will dissolve a certain amount of base metals /silver.
A heated solution of 50/50 nitric acid will dissolve much more metal then the unheated one.

When the heated leach is cooled back, it can become, what's known as "supersaturated" and start crystallize metals salts.
In very simple words, supersaturation in our case refers to the fact that the solution while hot, holds much more metal salts ions in their aq. phase than it could hold while cold. As it cools down, the solution start to push out metal ions in the form of a solid salt.
To compensate for that pushed out metals salts, i suggested to add some more water before the solution cools down. (or after, doesn't matter)
(i hope i had explained my self in an understandable way... please exuse me if i didn't, english is not my native language)

Doing that, will have no effect on future silver recovery, jusr create for you a little more solution to store.

The reason i suggeted doind that, is that you do not leave base metals/silver nitrates salts with your gold and melt them together.
This way, you will melt mostly gold, far from being pure, but much more then 50%, probably above the 90 percentile.

-----------------------------------------

edit: read some more on wiki - Supersaturation

Ohh... and don't forget, that while heating, water is evaporated, which also increasing concentration.


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## lazersteve (Dec 7, 2011)

Gold filled should be heated to a dull red heat before any acid treatment.

I would not melt the solids all together. Instead I would finish the job by dissolving them in HCl-Cl or AR. You can then filter and store in an open topped beaker with a loose fitting lid or filter cover.

You can process the liquid later. 

Melting directly in graphite molds is not a great idea; silica or fireclty dishes are better suited for this. 

Steve


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## timmadsen (Dec 7, 2011)

Thank you. I understand your advice .


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## butcher (Dec 7, 2011)

samuel-a, 
you explained that better than I could, and english is my language.
(well actually a hillbilly english).

when plating is thick it is sometime's helpful to cut material into pieces where acid has more exposure to base metals under gold, if gold layer is thick this will leave gold foil tubes, if gold plate is thin cutting not needed, and gold may form powders when base metals are in solution.


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## philddreamer (Dec 7, 2011)

"(well actually a hillbilly english)."

:lol: :lol: , mine is new yorican spanglish! Most of the time I think in spanish & need wiki to spell check; no wonder it takes me forever to post! :roll: :lol: 

Phil


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## butcher (Dec 7, 2011)

:lol: 
Phil maybe that is why we can understand each other.


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## Geo (Dec 9, 2011)

"heh" most of the time i think in english and speak in espanol.


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## glondor (Dec 9, 2011)

I find there is only one way to deal with a keg of nitric. I decant via siphon into 2.5 liter jugs. I use jugs that Nitric acid came in. I set the keg up on a bench near the edge. My bench is the right height to allow the following>>> Below the keg on the floor I set a 5 gallon pail with a lid. I place a 10 liter pail on top of the bucket. I put a 2.5 liter jug into the 10 liter pail. 

Then I open the keg with the bung wrench, insert the siphon and cover around the bung and siphon with a poly cloth. Proceed to fill the jug, breaking the siphon effect before the jug overflows. When the jug is full I cap it and take it to a sink full of water and place it in, grab another jug, repeat. 

The 10 liter pail catches drips. Except for the ones that drip off your jug and fall on your shins while walking to the sink.  You will realize later if some drips on you. After about the 6th jug you may need to tip the keg to keep the flow going. Decant it all,put your siphon in the drip bucket, cap your keg, wash your jugs and store, Take your bucket with the siphon to your sink and pump water thru the siphon to clean it. If you have a lot of drips in your bucket either use it right away or funnel it into one of your jugs. 

I wear safety glasses, heavy rubber gloves and a respirator. NOTE> there is no effective respirator for nitric acid. A respirator will how ever cut down on the amount of aerosol you generate any time you pour or decant a liquid. Keeps those invisible little droplets out of your mouth.(and lungs) This process is all done at the mouth of the fume hood . I found out last night I do not have acid proof pants. The whole process can be done in 15 minutes once you do it a few times. 

Modify as needed.


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## timmadsen (Dec 11, 2011)

Well I am less than satisfied with my first attempt. I started with 400 grams of 1/10 12k gold filled eyeglass frames cut into pieces about 1.5 inches long. I slowly started adding my nitric and it seems like too often that i had to add more to get red fumes again. way too much nitric later and what seems like way too many hours later (close to 6 hours) still had alot of base metals left. The gold was obviously falling off the base metals and the job was working but I finally had to go to bed so I cleaned and rinsed and picked out a few of the larger chunks of base metals that the gold had fallen off of. 

Question : with good heat, how long should it take to dissolve the base metals


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## Harold_V (Dec 11, 2011)

I can't provide a meaningful answer in the way of time, but know that if you are using nitric to process eye glass frames (that's precisely how I ran them), they are not all made alike. Some of the alloys used will dissolve quickly, leaving others well behind. I rarely processed just a few---mostly ran them by the hundreds. 

A couple observations. While there's base metals present that dissolve very easily, the process goes quite fast. 

When you have eliminated the easy to dissolve elements, the process slows to a crawl. It also becomes very temperature sensitive. Additions of nitric will appear to do little. At a particular point, assuming you are using heat, the acid suddenly reacts, and will easily overflow a beaker that is filled only to 10% capacity. The addition of water to cool the reaction helps prevent an overflow, but you must remain vigilant, as it quickly erupts again. 

I am of the opinion that you will not achieve success if you do not heat the acid. 

You should notice a visual change in the solution. Early on, the color coming off tends towards being blue. The solution from the later operation will be green. The early solution will contains silver, whereas the later solution likely will not. 

You are best served to dilute the solution prior to pouring off, and to allow any light weight particles (stripped gold, for example) to follow the solution to the settling container. In the end, you will siphon the vast majority of solution away from the solids that have accumulated, then you'll filter the solids from the entire lot to fee them of solution. 

When the solids have been collected and filtered, incinerate the lot, including the filter. This is a very important step--it will be key to the removal of unwanted substances, plus you'll have much better luck filtering the gold chloride prior to precipitation. 

When the solids have been incinerated, screen them well, removing all screws. They do not contain values, so they can be discarded. I always rubbed them well in a mortar, to extract any values that may have hitched a ride. 

Boil the screened solids in HCl. Rinse well, then dissolve the values. 

Because the volume of solution will be large compared to the small amount of silver that is contained within, this is one of the rare cases where I suggest you make the silver recovery by using salt or HCl. You likely understand that the silver will be recovered as silver chloride. 

Harold


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## timmadsen (Dec 11, 2011)

Thank you, I am using heat. and yes some of the base metals go quick and some linger forever (like the coiled ends of the earpiece that wrap around the ear), yes my solution started blue and finished green. 

My next batch will not have any pieces over 1" long, maybe that will help with the time. 

Do you ever stir the solids while in the nitric ?


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## timmadsen (Dec 11, 2011)

BTW... I want to thank everyone agian for all the comments. I have learned alot.


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## qst42know (Dec 11, 2011)

It doesn't hurt at all to stir some. The shape of some pieces allow gas bubbles to shield certain areas, turning things over once and a while speeds digestion.


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## butcher (Dec 11, 2011)

Cutting to small pieces expose the base metal to nitric and the acid does not have to go far into the tube (or through layer of gold) to get to the base metals, and as qst42know, said sometimes the bubble will keep acids from entering.

siring also helps to get fresh acids to the metals, I believe it also helps to keep gases that may just escape circulating them back down into the solution where they can get a little more work done, stirring can also help to remove an oxide coating or a layer of passivated metal that may slow or stop a reaction.

Heat can also help to increase the acids strength, but also will help to stir.
Heating can also concentrate acid (drive off water that may slow progress) so water may be needed later.

Some times I find it better to remove saturated acids and add fresh reagents.

Eye glasses can be made of many different metals and alloy’s some of these may be very resistant to acids, (chosen for use in glasses worn on the face because they are resistant to acids and sweat, and also for strength flexibility and so on).

Also consider your acid concentration; dilute acid (70% HNO3 + H2O 50:50) is usually better than using concentrated acid.


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## timmadsen (Dec 11, 2011)

I have been reading all weekend while i am doing my nitric baths.... yes once i was gone too long and had a boil over. I am learning alot. there are definately some base metals in there that dissolve quickly and some that take forever. One thing I have learned is that I am going to definately invest in a vacume filter.

Couple questions tho... is the black sand gold ? and do you lose much gold when pouring off the acid ? I am tempted to pour all the acid through a filter to eliminate the possibility of losing any gold.


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## butcher (Dec 11, 2011)

Black sands? If using nitric acid alone I cannot think why you would have black sands, unless chloride from homemade nitric acid or water were involved,

Everything should be tested for values before discarding or treating for waste.

You should loose no gold in processing. And knowing where it is at all times through testing will keep you from losing it.


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## Harold_V (Dec 12, 2011)

timmadsen said:


> Do you ever stir the solids while in the nitric ?


No need to if you heat adequately, nor is there need to cut them in pieces. 
When I processed, I busted the glass with a pair of linesman pliers, which also split the ring in which the glass was held. I next removed pieces that contained no gold. Not all pieces do, which you will come to understand. I'd just clip them quickly, near the junction, allowing a trace of the non-gold bearing portion to remain. I'd also remove any aluminum that was present. Don't allow any to follow the frames through the process--it is troublesome.

The now well cut up frames were incinerated in a small furnace, directly in the chamber. It was a small open topped furnace (natural gas fired) in which I could drop the glasses as they were hand trimmed. Once in the furnace, plastic and oils were immediately consumed. I'd continue to add until there was a concentration, which then got stirred with a steel rod. All pieces were exposed to the flame, which heated them to the point of solder melting. Now I had just components of eye glass frames, no longer assembled frames. These dissolved with no issues, and there was no oil included in the process. Everything that came from the furnace was processed, even fine "dirt", which may well contain values. 

Harold


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## Harold_V (Dec 12, 2011)

timmadsen said:


> yes once i was gone too long and had a boil over.


A tip here. Do NOT process eye glass frames by this method unless you pay 100% attention during the initial nitric digest. The boil-over happens in just seconds, even when the vessel may be filled only 10%. It happens with explosive speed and is difficult to stop once it begins. I can't tell you the number of times I had to clean up boil-overs. I'd wipe up everything (paper towels), dry, incinerate, then re-combine the resulting solids with the lot in process. No losses to speak of (thanks to my hood design), just a lot of inconvenience. 



> One thing I have learned is that I am going to definately invest in a vacume filter.


A vacuum filter (Buchner funnel and flask) can be a valuable asset, but you don't need one for this process, although it might pay dividends for the final filtration, where you gather all of the solids for incineration. Simply pour off the solution (after dilution with water) and allow it to settle. It happens quite quickly. The solids can be easily filtered if you eliminate the bulk of the solution by siphoning. No need to use a tight filter, either. I used to use Sharkskin for this filtration, which was fast and retained the values 100%. They are not finely divided, so a tight (slow) filter isn't a requirement. A coffee filter would be a decent substitute for Sharkskin. 



> Couple questions tho... is the black sand gold ?


Black sand? It's not clear to me what you're talking about. If you're making reference to junk that follows the eye glasses through the process, yes, include it, but be certain that when you incinerate that you do a proper job, so carbon and other combustible matter is eliminated. 



> and do you lose much gold when pouring off the acid ?


You certainly could if you're an idiot (I expect you are not), but if you follow my instructions, you'll see that all the solids will have settled to the bottom. Siphon such that you don't pick up any---including the pink/purple material that seems to settle out. You want that to remain with the solids. It's the color it is because it contains traces of gold. You'll recover them all if you don't discard anything. 



> I am tempted to pour all the acid through a filter to eliminate the possibility of losing any gold.


As I said, just filter the solids after you've allowed the solution(s) to settle well. You'll save a lot of time and aggravation if you don't try to filter everything. Wouldn't make much difference if you're processing a few pair, but when you process hundreds, the volume of solution becomes unreasonable. Let gravity do the bulk of the work. You have nothing to gain by filtering. 

Harold


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## timmadsen (Dec 12, 2011)

Thank you for the tips.

as for the "black sands" yes i was refering to the small amounts of junk that follow the glasses. i guess black sands was a poor choice of words but i don't know what to call them lol.

So whats the big problem with aluminum, won't nitric dissolve aluminum. What do you suppose is the composition of the base metal on some frames that takes forever to dissolve. I can see the gold has fallen off of it early on in the process and it is dull silver in color. but unless i want to pick them out by hand i had to wait a long time for them to slowly dissolve.


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## lazersteve (Dec 12, 2011)

Some stainless steel and aluminum passivate with nitric acid.

Titanium is also used in some plated frames.

Steve


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## Harold_V (Dec 13, 2011)

Yep, what Steve said. Aluminum does not dissolve in nitric, although some aluminum alloys contain copper and zinc, which do. It is a great way to clean aluminum of smut.

The metal is that is so difficult to dissolve in eyeglass frames is unknown to me. I have long wondered if it was just a nickel alloy. You can perform a simple test with some of the solution to determine if that's what it is. If I performed the test, I don't recall. It's been a long time since I last refined---I retired in '94. Want to perform a test? Do it like this. When you have eliminated all of the solution from the lot that came from the easy to digest materials, after the next application of nitric has done its work (the solution should be a dull grass green color), take a drop of solution and apply it to your spot plate. Add a drop of ammonium hydroxide to the drop. If it's nickel, it should turn a dark blue. To ascertain it's nickel, add a drop of DMG. That should yield a vivid pink color if it's nickel. (This test is outlined in Hoke's book). 

Here's a little tip that is nice, assuming you have the good fortune to find a few. The bridge on (precious few) eye glass frames is made of 14k gold. Those I encountered (just a few amongst, literally, thousands of frames) were ladies glasses, partially covered in plastic, with a fancy bridge. I can't say if they are marked, for they have been discovered after the nitric digest, but I recall with clarity from where they came because the bridge was fancy. 

Aluminum doesn't dissolve in nitric, but it does dissolve in HCl, with gusto. The problem is, if you include it in your material and it gets digested with aqua regia, the resulting solution won't filter. Aluminum tends to form a gel, much like tin does. That's one of the reasons I suggest you incinerate the recovered gold, then perform a wash with HCl before digesting the gold. Any aluminum that may have managed to follow the gold (because it didn't digest in nitric) will have been eliminated, along with other troublesome compounds. 

Harold


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