Refining Gold from Gold Filled Jewelry

[Oneal58]

Thanks Butcher, believe it or not I am starting to understand some of this language you are talking now. I didn't take any Chemistry Classes in School. I am going to ask my daughter to see if she can bring me home a basic Chemistry Book from the school. I feel I need some basic knowledge of Chemistry even if Hoke feels it's not necessary. It sure can't hurt any.
I went out early this morning, still around 20 degrees F. outside. I decanted what Nitric I had off the salt crystals that formed overnight. I put a piece of copper into the cold nitric, nothing happened. I was dissapointed because just the smell of the solution told me it was somewhat concentrated. I turned the burner on and held the container with a sample of the solution and the piece of copper just above the coils without touching the coil. In just a few seconds the nitric was fumming brown gas. So, the recovery of the locked up Nitric in the salts was successful. I came back in the house, the cold was getting to me. I am on blood thinners due to my heart condition and I can't stand the cold anymore. I am going to do the same thing with the last 3 pots of salt I have. I am pretty sure this last Nitric I got is more concentrated than the first 250ml I got out of each batch. It's just so cold outside today and with me just getting over the flu I am afraid of working too much in the cold.
That's why I asked how long Nitric will stay in a solution if kept cold, in the previous post? Will any of the Nitric evaporate off slowly if solution is near or just above freezing?
I have got to try and learn how to measure density. I know that there are density meters but can't I do the same thing with my scales. I think I have read where someone has found density by weighing liquid, using the formula
Density= Mass/Volume.
But what if I still have some dissolved salts in with the Nitric. I guess the only way to be sure there is no dissolved salts in the solution is to keep decanting and then putting the solution back in the freezer untill no more salts grow? If you have any dissolved salts at all in the Nitric solution you wouldn't get a correct density reading, right?
Thanks Butcher,
Oneal

 

[butcher]

oneal.
If the acid is very concentrated, many times the reaction on metals is actually slowed down, (which if you added the recommended water it would not be).

Notice that adding water formed K2SO4, which the salts are much less soluble, and when we freeze the solution much of the salts can be removed (not all, but most of them) I would not worry about tiny amount of salt when trying to get an idea of how strong the nitric is.

With specific gravity we can use test instruments to measure (like when we check specific gravity of a battery with that little tool with the floating balls or needle), I am not sure one of these would work for nitric, but it could be used for comparison I suppose, I just never tried it.

Specific gravity we are comparing the weight of water to the weight of our acid in a 1ml sample (accuracy of sample in ml is necessary, we can weigh larger volumes to assist in accuracy), basically if milliliter water has a specific gravity of one or (1 gram per milliliter @ 20 deg centigrade), our same size one milliliter sample of acid weighs more, our one milliliter sample of 50% HNO3 would weigh 1.3 grams @ 20 degrees centigrade.
Again comparing larger samples improve accuracy of our readings of volume and weight comparisons.

Light will break down nitric acid to NOx gases, if nitric is very concentrated it fumes bad as NOx gas, more dilute the less fuming and loss as gas, temperature is also a big factor, gases do not fume as bad in cooler temperature and stay in liquids more.
I would be more concerned with light than with concentration and temperature of what nitric you’re working on now.


Getting a chemistry book and studying I highly recommend, many of the principles they use are what we are doing when we recover or refine.

 

[Oneal58]

Hi Butcher,
Ok, I have looked and there are many types of Hydrometers but I see I would need the specific gravity Hydrometer if I used one or needed one? Solid glass to measure hot liquids, acids, Etc;, with. Lets say I measure out 100ml of water and heated to 20 degree Centigrade, exactly, or heat just above 20 degree centigrade and watch Hydrometer untill liquid cools to exactly 20 degree centigrade. I then take the reading from the Hydrometer, lets say the water (weighed/specific gravity/density) of 100grams @ 20 degree centigrade. Take that reading and measure out 100ml of my Nitric and it weighed/specific gravity/density of 131grams @ 20 degree centigrade. I would then know that my Nitric was 50% Nitric in solution referring to the chart you sent me.
Butcher, Is there a mathmatical formula that you use if I ended up with my Nitric say with a specific gravity/density of 111.5 grams per 100ml @ 20 degree centigrade to come up with concentration. I can use the chart that you sent me in a previous post and know that I would have 20% Nitric Concentration. But I was just wondering if you used a formula to get that with? I can see that the same percentages does not hold true with each different concentration?
Also, could I just weigh the solutions on my scales, would this get me close enough if I use the 100ml size samples?
Thanks Butcher,
Oneal

 

[butcher]

oneal,
Normally I am really not that concerned with knowing the exact strength of my nitric, as normally I dilute it anyway, and heating the dilute nitric acid when reacting with metals will also concentrate it as it is making metal nitrates, dilution also keeps some of the NOx gases from forming as gas, mixing NOx with water to from more nitric in solution, keeping the reaction in solution to dissolve more metals, instead of just fuming off as that red brown cloud.

Most of my work in recovery where I will use homemade nitric it is not that important to me.
I buy nitric for the processes where it may a concern, and will use it on silver or where I may be concerned with purity or concentration.


Personally if I was trying to get a rough Idea of concentration, a graduated measuring cylinder, these are tall and small in diameter (not sure what they actually call these measuring vessels), so accuracy is a little better, also they are filled to read the bottom of the curve in the top of the liquid (meniscus spelling?) also accuracy of scale would play a factor, but if you measured your acid and compare its weight to the same volume of water, the acid would be heavier with both at the same temperature. (Me I would not worried about lab accuracy as long as I got a close idea of the concentration especially for poor mans nitric acid)

http://www.handymath.com/cgi-bin/nitrictble2.cgi?submit=Entry

You could also try and buy a floating glass hydrometer; it is wine country here so they may have them where supplies are sold? But I do not feel it would be worth it here, it would be nice to know exact specific gravity and concentration of the acid, and would be useful to tweak your chemistry to try and improve the batches you make, but then again to me it has not been important enough to spend the money on one.

 

[Oneal58]

Thanks Butcher,
I get it. Thank you so much for your help. As you said, it would be nice to know what concentrations I am turning out. But once familar with Nitric and it's characteristics one can probably tell what strength they have just by dropping a piece of copper in it. This will come in time for me, I feel as you do. Why waste the money just to satisfy a curiosity. I have already spent money on lab equipment that I don't think I will ever use and don't want to do that anymore.
Thanks again Butcher, I hope you have a restful night. I myself am turning in early tonight. Got to take care of some business tomorrow morning early.
Butcher, you are appreciated old Buddy. You are not taken for granted!
I just needed to say that. I feel that you could get that feeling after sooo long, I am old school Butcher, I realize the time/work involved in answering all these questions for people like me. You are made out of pretty special stuff Butcher! As all the members on this forum who helps for nothing more than a thanks. Without even knowing if the (thanks) was sincere or not? What was it that the older members called the new guys, (NOOBS)?
Just remember, when I say thanks, I really do mean it, it is not an empty thanks, it will always be a sincere one.
Oneal

 

[Oneal58]

Hi Butcher, I have got a question.
I have got down to my last batch of gold filled jewelry. I threw everything in this last batch but the kitchen sink. Usually the solution I would decant after the Nitric had stopped working would have a greenish blue color to it.
This last batch I am running has a black color to it? Very dark, I don't see any green or blue, just black. When I went to drop what silver was in solution I got no reaction, on the copper coil, none? This solution is so dark I can't even see the copper coil in the solution? Thinking that I may have depleted the Nitric completely I added some nitric back to the 1.5 gallon container full. Still no reaction. I am afraid of putting any more Nitric in solution. I thought that the solution may be too cold to get the reaction to drop the silver. I warmed the solution up to room temperature. Still I get no reaction. Now with all the gold filled jewelry I put into this lot there had to have been silver in it. I know there was silver in some of this jewelry. We are talking a hundred pieces of gold filled Jewelry?
So, I have did all I know to do to get the silver to drop and am out of options. Have you ever experienced anything similar?
If I mistakenly put some white gold or platinum Jewelry in with this batch would this have caused this? I had a large piece of platinum jewelry. I put it up but now I can't find it. My wife use to help me clean up sometimes. She says no, but that piece of platinum is gone or lost? It is possible I put some white gold in this lot. Well, not me but my wife when she was helping me. I stopped her from helping now. She has that OCD thing and everything has to be somewhere, so she drives me crazy sometimes! I incinerate everything to a red glow before desolving the jewelry. Sometimes the white will look like the yellow after you incinerate it.
But do you have any ideas on why this has happened or what is going on? Why the silver will not drop? Did I do the right thing when I added a little Nitric to solution?
Thanks Butcher,
Puzzled, Again
Oneal

 

[Oz]

Take a small sample of your solution and add a couple of drops of HCl. If no white curd forms (silver chloride) then there is no silver in your solution.

 

[Oneal58]

Thanks Oz,
I will go try that now. I remember reading about that now, but I had completely forgotten about it? I had to shut everything down and go to N.C. this afternoon. It's still pretty cold here but I will warm a little solution up and try this.
Thanks,
Oneal

 

[Oneal58]

Hi Oz, I got a 25ml sample of the solution. I then warmed to room temp. I then droped several drops of HCL into solution. No white cloud? I went ahead and dropped 3 more drops of HCL, no white cloud.
I probably done this backwards but I had some solution I knew that there was silver in. I took a 25 ml sample. I then dropped 3 drops of HCL into the beaker. I saw the white cloud in the solution you were talking about.
This tells me NO Silver is in solution, right? I also tested solution for PM's with Stannous. No precious metals. So I will just pour solution into big barrel and cover for now. Once I get a 30 gallon drum full of solution I will recover the copper that I know has got to be in it. Normally, is this what most refiners do?
Do I need to neutralize the solution with Urea before I put it up in storage?
I still can't figure out why the solution had no silver in it when all the other lots of gold filled had silver. Don't have a clue why the solution is black, any ideas?
I made some homemade Nitric, could it be that the salts left in the homemade nitric has anything to do with this?
Thanks, Oneal

 

[Oneal58]

Butcher, where did you go buddy, did you take a vacation? I have missed you.
Butcher, I have been fighting the process of making my home made nitric for about 2 weeks now. I did the process over and over and would always do good to come up with 200ml of nitric on each attempt. I tried everything imaginable to improve the amount of nitric I would end up with, nothing worked?
I weighed the nitric I was getting and it weighs 131g per 100ml. By the scale you sent me, this is about 50% Nitric.
I did this just to see what would happen, I
Instead of putting 600ml distilled water in the batch, I put 900ml of distilled water in the batch. I came up with a little less than 500ml of Nitric. I weighed the Nitric and it weighs 129g per 100ml. So, that is still almost 50% Nitric and I have 500ml of Nitric for my effort. I would much rather evaporate it down a little than to do the steps involved to only get 200ml of Nitric.
Could the problem possibly be that I am using a Potassium Nitriate Fertilizer with different concentrations than you are? I will check on the bag to see what the ratio of Potassim is to the Nitrates and let you know.
I just can't figure why sooo much salts form. I also do everything in the recipe exactly and I still end up with salts in my Nitric when using it to dissolve with. I double check my temperatures, always bringing entire mixture down to -5 degree Centigrade. Heck, I even tried bringing the solution down to -10 degree centigrade. What happened was even more salts formed and I had almost noting left in liquid in the container, just a 12 cup coffee pot full of salts? It has to be in the fertilizer, don't you think?
Thanks Butcher,
Oneal
Thanks, Oneal

 

[qst42know]

Have you tried pouring off the solution after some of the salts have formed?

You might also try keeping the salts broken up as they form and vacuum filtering the nitric from it. Your nitric is there it's just trapped as water would be in sand.

 

[butcher]

Oneal,
Potassium salts form much easier and they are more insoluble, they also hold nitric acid easily in the crystals formed potassium salts are also better for the environment, as compared to the sodium salts.

Lets look at some of these salts, which we may get from making nitric acid,

Potassium sulfate K2SO4 (potash of sulfur),
This salt is formed if you add water when making nitric acid from KNO3 potassium nitrate and (diluted) sulfuric acid.
K2SO4 solubility in water is about
8g/100ml @ 0 deg C
80g/Liter @ 0 deg C
111g/Liter @ 20 deg C
240g/Liter @ 100 deg C
Can be used as fertilizer for tobacco, fruits and vegetables, (good if your watering the garden with city water that forms chloride salts from chlorinated water).

Potassium bisulfate KHSO4,
This salt is formed if you use concentrated sulfuric acid (no water), with potassium nitrate to make nitric acid.
KHSO4 solubility in water
36g/100ml @ 0 deg C
360g/ liter @ 0 deg C
480g/ liter @ 20 deg C
1220g/ liter @ 100 deg C
can be used in reactions that normally use sulfuric acid, it acts like sulfuric acid when fusing salts with heat, can be used to make ferrous sulfate (gold precipitant), or for fusing Rhodium to dissolve it in water, or other reactions you would need sulfuric acid, note it acts like K2SO4 and H2SO4 in these reactions.

Sodium sulfate Na2SO4 (Glaubers salt),
This salt is formed when making nitric acid with sodium nitrate and Dilute (added water) sulfuric acid.
Na2SO4 solubility in water
4.9g/100ml @0 deg C
49g/ Liter @ 0 deg C
195g/ liter @ 20 deg C
425g/ liter @ 100deg C
Notice this salt is more soluble in water than compared to potassium sulfate, but also the salts will not trap as much nitric acid, when making nitric acid from sodium salts, also notice by freezing we can remove much of these salts of (sodium or potassium sulfate), at 0 degrees centigrade the solubility of these is similar

Sodium sulfate salt seems to form finer crystals than potassium salts, so it does not seem to trap nitric acid as bad.


Sodium bisulfate NaHSO4 (sodium hydrogen sulfate)
Formed when making nitric acid with concentrated sulfuric acid and sodium nitrate fertilizers

NaHSO4 solubility in water
50g /100ml @ 0 deg C
100g/100ml @ 100 deg C
NaHSO4 is easily soluble in hot water. Also NHSO4 is soluble in cold water. Soluble in 2 parts cold water or soluble in 1 part boiling water. Decomposed by
Alcohol into sodium sulfate and free H2SO4.

Oneal,
I would make the first batch more concentrated (as normal), the add water, then heat salts and re-crystallize for a second batch shooting for about 30 to 40% nitric acid, this would be strong enough to add to solution dissolving base metals with heat that also concentrates as it is reacting with metals, this more dilute nitric can also be used with aqua regia dissolving gold with heating, I would not be too concerned with just concentrating the acid by itself, but use it with heat and metals to get the best use out of it while it is concentrating and dissolving the metals in same reaction..

My byproduct metal-salts get reused (or saved), so I am not as concerned about some nitric acid trapped in potassium salts, although I use more sodium nitrate salts, and prefer them for cold reaction of making nitric acid, and if distilling stronger nitric acid I prefer the potassium nitrate salts.

 

[Oneal58]

Thanks Butcher, qst42know.
I have tried breaking the salts up while forming. The salts that form are rock hard almost. I broke 2 of my coffee pots trying to break up the salts. I finally got my drill and drilled holes all around in the salts. This did help some, I got a little more Nitric out of doing this but nothing to brag about. I haven't tried vacuuming the salts to extract the locked up Nitric. I have thought about it, but I am concerned that while working on the salts, (trying to get them broke up) to vacuum the Nitric will dissolve some of the salts back into it. I am having some trouble with salts in my solution, when dissolving base metals. One time I let the solution sit a while without stirring. I was left with a mass almost as hard as metal in the bottom of the vessel. I had to cut it up with side cutters and crush each piece with pliers to break the mass back up. Fresh Nitric would not dissolve this mass untill I broke it up? I tried all day to dissolve this mass with no success.
Butcher, I haven't tried your last suggestion. I will try that and let you know how it comes out. I have been keeping the first decant of Nitric seperated from the last decants in seperate containers.
After first decant, I would add just enough water and a little sulfuric and a touch of peroxide and heat (slowly) to get the salts to break up. Then I would go back through the process again. The last decant I would get would be about 30% Nitric after weighing it and comparing to the scale you sent me.
But I will try your last recommendation and let you know what happens.
OH, the bags of Potassium Nitrate I have are marked, (Krista-K /13.7-0-46) Soluable KN03 Is this the concentration that everyone uses with this type method?
Thanks Everyone,
Oneal

 

[qst42know]

Potassium Nitrate I have are marked, (Krista-K /13.7-0-46) Soluable KN03

This is 5.3% higher nitrogen and 4.5% higher potassium than the numbers I have seen for potassium nitrate. You could try a single batch using 5.3% less nitrate and see if this helps.

13-0-44

 

[Oneal58]

Hi qst42know, Butcher
Thank you for your post, qst42know I will try this to see if this is causing the problem? I made another batch today, got the same results as always. Poured off the concentrated first batch and followed Butcher's advice on the remaining salts. The salvage of the remaining Nitric in the salts are in the freezer now. A lot of work, Potassium Nitrate and time for 200ml of concentrated Nitric though. Butcher, I will let you know what concentration I come out with on this second run on the salts.
Qst42know, I will decrease the amount per your directions and try that to see if that's the culprit. The Farmer's Supply I bought the KN03 from asked me what type I wanted. I told him that it (KN03) had to be soluable and I wanted the cleanest, best grade that he could get me. I guess that's why I ended up with what I did. The Potassium Nitrate cost me $38.00 per bag? I thought this was kind of expensive for 60 pound bags? I have used 80% of 1 bag, so I have been at this for a while trying to get good Nitric to work with.
Question, If I take the temperature lower than -5 degree Centigrade will more salts form? Or has all the salts formed that will form at that temp? I can't tell because I used some of the lower strength Nitric that I know had salts in it on the last couple of batches of gold filled I have ran. Just to see if I would get the brown gas when I added the diluted Nitric. When I was (evaporating) driving off the Nitric I got a (whiff) smelled the salts in the solution.
Thanks, Oneal

 

[Oneal58]

Hi Everyone,
I have been refining gold filled Jewelry lots plus Sulphuric Cell lots, now for a couple of months. I have small buttons, medium size buttons, and want to make 1 large button. I went to the extra work on each lot following Butcher's and Harold's advice on Making Gold Pure.
Each button looks good but my question is,
Should I take this opportunity to re-refine all the buttons while putting them all together?
When I do the re-refine will I lose any weight (gold) during the process? I know I will lose a little weight but what can I expect to lose percentage wise just through handling losses? Even if all the gold is near .995 or better, with a re-refine are there losses due to just handling the gold again? Should I use a new melting dish for the final melt? I have a melting dish that I use to melt gold only.
How often do you need to put more Borax on the melting dish?
On each melt of values I have not used any Borax on the gold buttons. I could see no particulate on top of the buttons so I didn't use any borax.
Would you suggest using borax on the final button?
What has been your experience in this area as far as losses?
What would be your recommendation here?
Thanks, Oneal

 

[butcher]

Others may give better advice on this.

Here are my thoughts.
but I would probably, just re-refine them, (depending on percentage of gold to base metal involved in-quartering with silver, then parting, could be needed), but from your description that is probably not the case, it sounds as though they may already be of very high karat gold, if they are fairly pure already in this case they will dissolve in aqua regia or the HCl/bleach methods (without in-quartering or pretreatment of nitric), melting and pouring shot, or flattening with a clean hammer and anvil will help them to dissolve into acid faster.

You will loose some weight in acid treatments (base metals left in solutions) when re-refining your gold, but you should not loose any gold if your careful with procedures, you will bring the quality up on the gold, possibly to the point a buyer will not have to refine it and then he can give you a better price it, also a jeweler may be interested in high quality shot.

If dish is clean, gold is fairly pure, just enough borax to wet the dish is all that is needed.
Also base metal contamination in a dish melting pure gold would lower purity of your gold, the dishes do not cost much (compared to the price of gold and the chance of lowering its purity), considering all the work you put into refining just get a new dish to melt the re-refined gold in.

The color of the precipitated gold can be somewhat of an indicator of its purity, if it is black or dark brown I would refine it again before melting, did you have any dimple pipe, or crystals on the gold button.

 

[Oneal58]

Hi Butcher,
Thank you so much for your post, I really appreciate you. I have called on you so often that I feel guilty sometimes. I don't want you to ever think that what you have done for me since the beginning isn't appreciated. I keep needing to say this to you, just so you know how big of an impact you have had on me. I just don't want you to feel like (he is overstaying his welcome)? Like company that comes to see you and then will not go home, If you know what I mean? :lol:
But, I guess until you do tire of me I will just keep aggravating you. :lol:
Butcher, I have a dimple/pipe on every button. Each button is consistent in color. I haven't noticed any crystals on the buttons. I have seen 24K gold before and I declare my buttons are the same color. My brother in law has a 5 oz. bar. I compared the color of my buttons to it. Same color. I went through the extra steps (Making Gold Pure) that you guided me through to turn out high purity buttons. I did this on each and every refine. I am hoping I am in the range of .995 at least?
1- Butcher, I will refine a couple buttons at the time instead of throwing all in one pot, just to be safe. Will this be best to do?
2-I will order a few new melting dishes and use new ones.
3-I will drill one out for making shot.
4-I will try to dissolve in AR after making small shot/not using the pre-Nitric treatment. Or would you do the pre-Nitic/could it hurt?
5-I will check for Indicator colors/Black or Dk. Brown to see if a new refine is needed?
6-Borax, just enough to wet dishes.
7-Do I need to Borax the one that I use to make shot with?
8-What does the crystals on the button mean? How should they look? Would they just glisten/shine when light hits them or is there a better way of determining if crystals are there?
Thank you Butcher, if you see where I made a mistake please let me know.
Thanks Butcher,
Oneal

 

[Harold_V]

If you have a buyer that intends to use your gold when it's sold, he may prefer shot (jewelers often do, for it's much easier for them to alloy a specific amount of gold), but if you intend to sell it to an unknown buyer, you would be far better served to sell it as a button. Follow butcher's advice---use a clean dish, one that has been properly seasoned, and remove the gold the moment it freezes. That way it won't get trapped in the flux as it cools. Clean the button with heated dilute sulfuric to remove traces of flux.

When gold freezes, the surface should be shiny. If it has a complex series of tiny crystals (or a general frosty surface), that's a pretty good sign it is contaminated. A shiny surface broken up by a large crystal structure is very good, as is a deep pipe. Any discoloration, regardless of color, is not a good sign. The melting dish should have, at the worst, a hint of pink through purple after melting. If the flux is discolored (brown, green, black, blue), that's a sure sign your gold was contaminated.

Assuming you do choose to pour shot, yes, the dish should be prepared in the same way a dish is prepared to melt pure gold. It should have a 1/8" hole drilled in the center, then it should be warmed slowly to dry it fully. At that point it can be heated to redness, then sprinkled with borax. Borax glass or anhydrous borax are the best choices because they melt without issue, but any borax will serve. Coat the dish sparingly. Too much borax and it combines with the shot. Should that happen, boil the shot in dilute sulfuric until the borax has been dissolved. Rinse the gold well, otherwise traces of borax will remain, coating the shot making it white when it dries.

Harold

 

[Oneal58]

Thanks Harold for your post.
After reading your post I went out and checked my melting dish that I used to melt all the the gold buttons in. But just the buttons in. My melting dish has a blue/blackish tint to it in the bottom and pink on the higher edges. The buttons must not be as pure as I thought and I guess I do have some contamination in one, two or more of the buttons? I can't remember or could I tell if all the buttons contributed to the coIor of the melting dish or just 1 did the discoloring? Just to be sure I guess I will just take the buttons back through a new refine, just to be sure I have the gold as pure as I can possible get it. Thank you Harold for your post and your guidance.
UPDATE,
Harold, I went back out and took a picture of the melting dish I have been using. I have melted 7 buttons in this dish. You tell me what you think? Do I need to refine all the buttons again. I looked closely at the buttons again and it looks as though 1 of them has a tint of purple on it. This one could very well be the culprit of what you are seeing in the image below. But I am not sure of this? I see the pink you mentioned earlier and the purple, but how bad does it really look. The picture is true of condition of melting dish. What would you do if you were me?

Thanks,
Oneal