After nitric acid wash. (Gold, Aqua Regia, Gold filled)

I'm wondering what is the best process after a 50/50 nitric acid soak.

I have Gold Filled jewelry that I am refining. I put about 5 ounces in my beaker. After about 3 days and 800 ml of 50/50 nitric acid(pouring off after each 200 ml) I am wondering how to proceed without impeding my future process. I normally let each 200 ml HNO3 sit on a hot plate for 4-8 hours. I will eventually put my GF lot into aqua regia.

I'm not trying to sound stupid, just looking for advice. I have already washed twice with hot water. Should I proceed to wash with ammonia? I am looking for an efficient way to get to the point where I can put my lot into aqua regia. After I washed with hot water, how long should I let it set before I pour it off? I have been waiting about 4 hours. Is this too long or too short? Hoke doesn't really say much about time frames, so I'm wondering if you have any advice.

After the 3 days of HNO3 soak, I pulled a watch case out and tested it, came up at 10K, so should I soak the lot in more HNO3? Or go right to AR?

Thanks for any advice and time you can give me!

JordanReas said:

I'm wondering what is the best process after a 50/50 nitric acid soak.

I have Gold Filled jewelry that I am refining. I put about 5 ounces in my beaker. After about 3 days and 800 ml of 50/50 nitric acid(pouring off after each 200 ml) I am wondering how to proceed without impeding my future process. I normally let each 200 ml HNO3 sit on a hot plate for 4-8 hours. I will eventually put my GF lot into aqua regia.

I'm not trying to sound stupid, just looking for advice. I have already washed twice with hot water. Should I proceed to wash with ammonia? I am looking for an efficient way to get to the point where I can put my lot into aqua regia. After I washed with hot water, how long should I let it set before I pour it off? I have been waiting about 4 hours. Is this too long or too short? Hoke doesn't really say much about time frames, so I'm wondering if you have any advice.

After the 3 days of HNO3 soak, I pulled a watch case out and tested it, came up at 10K, so should I soak the lot in more HNO3? Or go right to AR?

Thanks for any advice and time you can give me!

Click to expand...

To dissolve 5 oz (about 155g) of copper or copper alloy, it will take about 1286ml of 50/50 nitric - 8.3ml/g. This assumes an open top beaker and that, by 5 oz, you meant 5 troy oz. With only 800ml of 50/50 nitric, you most likely didn't dissolve all the copper. You could use AR now, but the AR solution would be heavily contaminated with copper. It would be best to dissolve all the copper first.

Is the watch case gold filled or solid karat gold? Was it marked? Did you just test the surface or, did you file into it and test the filed notch with nitric? Was the watch case attacked at all by the nitric?

goldsilverpro said:

To dissolve 5 oz (about 155g) of copper or copper alloy will take about 1286ml of 50/50 nitric - 8.3ml/g. This assumes an open top beaker and that, by 5 oz, you mean 5 troy oz.

Click to expand...

Thank you for that helpful tip! Any indication on time frames to let the solution settle? After HNO3, after H2O rinse? Also Is there an ideal temperature to set the HNO3 soak on?

When I rinse in water, I pour off a brown mud, is this advised to do? or may there be gold in that mud? I am saving the filter papers as Hoke advises also. Or is it more efficient to pour it off and continue with the nitric bath with what is left?

Thanks again. I am a newcomer to gold refining and am striving to be as efficient as I can. Especially because the majority of what I am refining is gold filled and there is a considerable expense for this process and a small margin of profit.


To your last post, the watch case was very thin, and ready to crumble. I just tested the edge which i realize has a more concentrated "plate" of gold. but it is very thin. The test was done after a double water rinse. It was marked 14K GF.

Is it okay to rinse with ammonia after the water rinse?

Pouring off the brown mud is likely pouring off values. think about what you are trying to do, dissolve everything in the nitric that is soluble. Gold is not soluble in nitric. Therefore, the unsettled brown mud will likely contain some gold.

When you have digested all of the base metals the gold will settle to the bottom, it may take some hours but it will settle. Then the solution can be filtered.

I like to warm the nitric / DI water mix to get the reaction going and then, once the reaction is going, the heat can be shut off as the reaction will generate its own heat.

Rinsing with ammonia will only help you if you have some silver chloride gumming things up. If you used DI Water in the mix and for rinsing that should not be necessary, just rinse well with DI Water and proceed to the aqua regia process.

JordanReas said:

To dissolve 5 oz (about 155g) of copper or copper alloy will take about 1286ml of 50/50 nitric - 8.3ml/g. This assumes an open top beaker and that, by 5 oz, you mean 5 troy oz.

Click to expand...

Thank you for that helpful tip! Any indication on time frames to let the solution settle? After HNO3, after H2O rinse? Also Is there an ideal temperature to set the HNO3 soak on?

When I rinse in water, I pour off a brown mud, is this advised to do? or may there be gold in that mud? I am saving the filter papers as Hoke advises also. Or is it more efficient to pour it off and continue with the nitric bath with what is left?

Thanks again. I am a newcomer to gold refining and am striving to be as efficient as I can. Especially because the majority of what I am refining is gold filled and there is a considerable expense for this process and a small margin of profit.

Click to expand...

When everything has settled, it is settled. When it's rinsed, it's rinsed. There are no time frames. You must learn to use visual clues. The brown mud you're pouring off most likely contains at least some of the gold. I would filter any solution or rinse that contains any solids (not crystal clear). If some of the brown powder goes through the filter paper, it will eventually start clogging and this will stop the fines from coming through. When you see the liquid coming through the funnel clear, re-filter what you've already filtered though the same filter paper. Sometimes, this will be slow.

I would suggest you first read Harold-V's posts and adhere to what he says. Most all of us that have been doing this for awhile have successfully processed a lot of gold-filled. However, all of our methods will vary somewhat. To prevent confusion, I would first read Harold and then branch out to see what other people have said. One thing about Harold's processes is that they always work if you follow them to a tee. The attached file, starting on page 29, gives Harold's process for processing gold-filled eyeglass frames. The acid work in this process and what follows would be the same for what you're doing.

I would also suggest you read the posts Harold has made on gold-filled. Here are a few to start with.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=19672&p=199963&hilit=gold+filled#p199963
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=14811&p=149251&hilit=gold+filled#p149251
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=13509&p=135942&hilit=gold+filled#p135942

Here are threads with the term "gold filled" in the thread title.
http://goldrefiningforum.com/phpBB3/search.php?keywords=gold+filled&terms=all&author=&sv=0&sc=1&sf=titleonly&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search

Thank you very much GSP, the 4 links you included are extremely helpful. I will proceed as described by Harold.

In the attachment, Harold talks about boil overs. I have had my share of boil overs and beakers breaking, believe me. This stopped being a problem when I got into using a heated catch vessel that I placed the beaker into. It must be made of a material that will take direct heat without breaking and won't be affected by the particular solution you are using. When using only nitric and water, thick non-magnetic stainless steel can be used. For AR, stainless cannot be used. For AR, the only vessel(s) I know of that won't break over direct heat (electric hot plate, e.g.) is a Corning Ware white pyroceram StoveTop dish or a Corning Ware Visions dish. These have been discussed many times on the forum. I prefer the larger, white, square, 5 liter (or, 5 quart) size for both nitric and AR. New, they are about $50-$70 but I see them all the time in flea markets. If you buy a used one, make sure the inside is very smooth (not etched), not stained, and no cracks or breaks. In other words, flawless, which most of the used ones are. The white CW pyroceram was originally developed for use as rocket nose cones.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=20640&p=211732&hilit=Corning+Ware+dish#p211732

Quick update:

I proceeded with harolds advice;
nitric bath
DI water rinse
incineration
HCl rinse
Di water rinse
AR process

And everything went very smoothly. I am looking forward to doing a couple more small batches and then moving on to double my batches! Thanks for all of your help!

Just a word of caution. Though we talk about scaling processes up the truth of the matter is the difference can be like night and day on gold filled. Take you time and learn to trust your eyes more than anything.

I proceeded with Harold's advice;
nitric bath
DI water rinse
incineration
HCl rinse
Di water rinse
AR process

Click to expand...

Well not quite all of Harold's advice.

Starting with an incineration will burn off oils, waxes, and plastic which can inhibit the contact between the metal and the acid. This results in a more complete digestion of the metals soluble in the nitric acid.

The combination of Hydrochloric and heat is much different than a simple Hydrochloric rinse. If you come across a lot which has a substantial amount of tin, a simple rinse won't cut it. Once you experience a slow dripping filter due to excessive tin clogging the pores of the filter medium you will realize the value of the time spent on heating and soaking in HCl vs. a simple rinse.

You can skip a few of these steps and you may get away with it. Then you may come across a lot which is either dirty, greasy, or all of the above and your yields will suffer, or you may get a lot with excess tin and you will lose values because the values in the solution trapped in the solution you cannot filter.

The beauty of Harold's method is it is bullet proof, the procedure will work on all of the gold filled you process regardless of how dirty the goods are to start, how much tin is in them, and the quantity of insolubles in the mix. But bullet proof only if you follow every step.

I learned the hard way that not all gold filled can be treated equally.

I have learned to test each piece with a magnet and to separate the magnetic gold filled from the non-magnetic gold filled material.

Non-magnet gold filled material usually has copper brass or zinc as the base metal and can be treated with 50/50 dilute nitric acid to recover the gold for refining. But I have also seen lead as base metal. You can catch these and get them out before using acid. When you incinerate the lead melts quickly and stays liquid just from the heat of the melt dish. Very easy to spot and weed out if you incinerate before going to acid.

If there is iron (magnetic) items in your gold filled scrap it is best (in my experience) to treat it separately from the non-magnetic material.

I start with incineration then let it cool to almost room temp and then cover with straight HCL and add low heat.

I just did a batch of MAGNETIC GF jewelry just the other day - only 122 grams.

I used a two liter beaker with a glass saucer for a cover and added about 300 ml of straight HCL (31.45% from the hardware store). There was some slight bubbling that increased as I added heat.

After adding low heat for a few few minutes I then added about 20 or 30 ml of concentrated nitric acid.

At first there was some slight increase in bubbling and a slight tint of brown fumes in the beaker - this lasted for a few minutes.

Then out of nowhere there was a VIGOROUS reaction and the foam reached half way up the beaker! If I had not been standing there watching I would have missed it because it started and was over very quickly. I thought it was going over the top but it did not. I alway use a Corning ware casserole dish under the beaker to catch any boil overs.

After a few minutes the reaction calmed and I tested with stannous - no reaction, no gold in solution. I let it simmer for an hour or so until the brown fumes were very light indicating that most of the acid reaction was over.

I then filtered the entire solution, leaving the solids in the beaker and testing with stannous chloride again to verify no gold in solution and there was none. I had to use two filter papers (Whatman #1) because the solution caused a single filter paper to fail during filtration.

Some of the base metal was still there, but much had been dissolved away with the AR treatment described above.

I added the material (filter paper and all) back to the beaker with the golf filled material and did another treatment as described above then tested again with stannous chloride. Again, no gold in solution but this time there was very little if any base metals left only hollow shells and some gold powder.

I added the filter paper back to the beaker as before and did another treatment and this time I got a positive test with stannous chloride - there was gold going into solution AFTER THE THIRD AQUA REGIA TREATMENT.

I kept adding small amounts of nitric until all the foils and powder dissolved completely.

There was a lot of junk and some grey colored powdered material left in the bottom of the beaker and the solution was green.

I filtered out all the junk and dropped the gold with sodium metabisulfite. Ended up with 2.4 grams of pure gold.

I learned about this a while back when I did a 500 gram batch of gold filled scrap that was mixed magnetic and nonmagnetic together and only got about 6.5 grams of gold. I did not know to separate the two (magnetic from nonmagnetic) back then.

Today I always separate the gold filled scrap into two piles - magnetic and nonmagnetic because they both require separate processes to recover the gold for refining.

Hope this helps.

kadriver