Advise on how to process old gold filled watch scrap

[Husker]

I have acquired about 10 pounds of old watch scrap. The first lot (about 5 lb), appears to be very clean, solid links (mostly solid links), and some clasps (and a couple of watch cases). Most of the links were new (probably 2/3's new and 1/3 used). The clasps were about 80% 1/20 12k (also many listed as ".025 gold content"), and about 10% listed as 1/40 RPG and about 10% unmarked. This lot has been incinerated. I have about 20g which I am pretty sure are karat gold, and not filled (12k, 14k and 18k). There is about another 20g that I am not sure (they might be karat, but I am not sure.) I will process this 2nd 20g in with the other known GF scrap.

The other lot was old bands, mostly mens. About 1/10 of these were listed as 1/20 GF caps. The others I could not find any GF markings, but my electronic tested about 40% of those as having both the upper and lower caps as gold (some was HIGH, like 14 or 18k). About 40% had only the top caps as gold, and the other 20% tested as not gold, but looking under a 10x loop, they looked like they were plated, Most of these watch bands were of a type that is like a scissor jack, where the ends were "riveted" together with a rivet link hinge, and a coiled spring in the middle of the scissor.

I have some questionable parts of many of these watches. There were under bands (the upper part), and some of the full scissor parts, which seemed to test as gold. Many of them tested in the 10k range, and some tested MUCH higher, like 18K or even better. These "appear" to be stainless, and even spring grade stainless, but are testing as gold, and some even as higher karat gold. I have separated out these parts, and there are about 200g of this items.


I have a couple questions about processing this scrap. I do have Steve's GF scrap DVD, but would rather use HCL to process, instead of nitric (huge cost difference).

1. Does anyone know of any reason to not try to use HCL in a covered Erlenmeyer flask, packed in sand in an old crock pot, to provide heat?

2. If there is steel (stainless probably), will the HCL deal with this? I know there will be carbon left over from disolving steel, but I think another incineration will deal with that. Is there other problems in trying to remove steel using HCL? I think have pulled much of the steel out, but am sure there still is some in there. I am pretty sure there is some (most), in those scissor bands, and some of the other under bands.

3. What might some of those scissor bands and under bands be (especially the higher testing items)? Could they be platinum? Platinum on my tester, shows up as higher than 18k. Some of these were testing like that. I do not know the age, or origin of these watch bands, but I seem to remember reading, that platinum (80-90%) is very sturdy, and until recently (due to cat converter usage), was cheaper than gold.

4. Could, instead of platinum, this material be some form of Platinum, Rhodium plated material? NOTE, I have not tested any of this, other than quickly testing with my electronic, as I ripped them apart. I have just now finished ripping the bands apart (took about 12 hours, over the weekend).

5. If this material does contain PGM's, then what changes if any, would be needed in the processing, specifically in the base metal removal stages? I am pretty sure I can separate once I get out the base metals, to where I can dissolve the valuables using HCL-CL and separate from there.

Thanks, Jim.

 

[limestonecowboy]

Husker,

I too recently processed a job lot of old watches and bands, many of which were unmarked, rolled gold, filled and plated, some were Karat gold cases.

I seperated what I thought were plated, mostly by snipping off a convenient corner with a pair of tin snips and viewing under a glass but I could identify nearly all the plated stuff just by the crunshing and creaking sound made by the plating whilst distorting the metal using pliers. These were then stripped in the sulphur cell with excellent results but many took some time (as much as 25mins) owing to some very heavy plating.

After careful consideration the rolled, filled and unknowns were eventually done in Nitric, which left only the gold, stainless bits and things like the pins and the tiny springs from the scissor bands.

The remains were seperated and the gold was then dissolved in Hcl-bleach and processed in the usual manner.

The karat gold parts became apparent and remained after the nitric. These were then processed in AR.

It may not be the method you are looking for but I just coudnt think of a better way of doing it. The extra cost of using nitric far outweighed the time and trouble of the alternatives.

Sorry I coudnt be of further help, but I though I would post my method as it was quick and effective.

Goodl luck, Best wishes, Rich.

 

[butcher]

husker I see no problem using heat Hcl and crock pot, (sand bath ok) but I just use crock directly( also I use 32% H2O2 lil @ time-care in foaming).

the heat concentrates acid, and H2O2 will dilute just little oxidizing metals eventually turning to water, but this doesnt dilute enough to keep the HCl in solution( if Hcl lower in concentration mostly water vapor escape till solution concentrated then the acid will fume out, I usually dilute it down a little when i see these acid vapors.

as far as stainless these base metals are lil hard to disolve in there combination but will, My only concern is the chromium poision gas that may form in acid vapors.

I havent processed higher grade scrap this way but if I did(me being unconventional would probably use HCL/NaOCl/32% H2O2) useing the bleach additons to attack gold layers,.

and what I do alot is get a hot concentrated solution of metals removeing a large portion of it to another vesel to cool and drop some of its metal salts then return decanted acid with less metals back to crock pot(or coffee pot on hot plate) to get loaded again repeating this till i have a jar of metal salts and then reprocess these much easier as there in powder form now .

i hope this helps, others probably have better advice.

 

[Husker]

Harold has mentioned in another thread (about processing dental scrap) that using too little AR to completely disolve the lot, will end up cementing out the precious, while converting base metals
http://goldrefiningforum.com/phpBB3/viewtopic.php?p=30234&highlight=#30234


I was wondering if:

Would using too little AR to process gold filled scrap also work to concentrate (not to refine), similar to what you list for this dental Pt,Pd,Other mix of metals?

I would think 75% enough AR to disolve the metals. Let it work until the AR fully done, filter well, test the liquid for precious, and then add a little more AR to the filtered material (smaller amount of base metals, and all precious) to get the next percentage of base metals, filter when consumed, and possibly run again, to reduce even more.

I know this would not fully refine, but it should concentrate the gold into a much smaller amount, which one should be able to easily get to 8k or 10k or 12k.

If this sounds like something that is a workable approach, then a simply poor mans AR would probably suffice. Since HCL is cheap (about $3 a gallon), and sodium nitrate is also relatively cheap, this would make for a pretty inexpensive way to process (or concentrate), pounds of gold filled, down into ounces of much higher grade, which can then be fully refined.

What are your thoughts on this Harold (or others)? This might be a way to reduce the base metals much more quickly than HCL by itself, without too much more cost.

Jim

 

[Harold_V]

What are your thoughts on this Harold (or others)? This might be a way to reduce the base metals much more quickly than HCL by itself, without too much more cost.

While I never tried the idea with gold filled materials (I stripped watch bands with cyanide), I can't see any reason for it to not work. The presence of silver may complicate things a bit----but gold filled is generally thin enough to permit total dissolution before there's a covering of inert silver chloride present. The silver would simply slough off in the solution, having been converted to silver chloride.

Properly pursued to fruition, the final solution would contain traces of base metals only, and, as in the example I cited for white dental appliances, you'd have to discard base metals that have been dissolved with each iteration of the process, save for the final one.

I would not try to characterize the remains as karat gold. What will have happened in the process is the values will have been dissolved and cemented a time or two, thus they won't be alloyed--but they would be contaminated with silver chloride and traces of dissolved base metals. Filtration prior to precipitation would remove the silver chloride, with precipitation yielding a reasonably clean product.

If you pursue this avenue, when you are in the final dissolving stages, it would pay to introduce a small amount of sulfuric acid. Gold filled is often contaminated with lead. By introducing the sulfuric, it would be precipitated as lead sulfate and removed in filtration.

Not a bid idea, really, although I'd pursue the process only if stripping was not an option.

Harold

 

[Husker]

Most of what I am working with will have little silver. Not saying there will not be some, but most of the GF over 925 or GF over 800 I have has been in the form of filled jewelry, and not in the current set of things I am working with. I do know there is some lead, especially in some of the specs that have been 'repaired'. I have tried to remove most of it, but I am sure there will be some carried along for the ride.

I currently have about 10 lbs of semi-clean (i.e. most stainless removed) watch scrap, and about 5 lb of 1/10 12k old specs to do. But if I could reduce this to a half pound of relatively pure gold mud (or corn flake it, for later processing), I would be happy(er). At least then, I would have a more clear idea on the actual value I have in this scrap.

I have already dissolved my first lb of filled scrap, which was a mix of jewelry and some watch band scrap, using hot HCL only. Took a long time. However, I think I will do the next pound using a poor mans AR, and see if I can get that process working well, or at least well enough to be called a process. The nice thing about some of the next batches, is once I get a feel for how much to use, I will have several pounds of similar material to work with.

Jim.

 

[Harold_V]

Most of what I am working with will have little silver. Not saying there will not be some, but most of the GF over 925 or GF over 800 I have has been in the form of filled jewelry, and not in the current set of things I am working with.

The silver in question is what is alloyed with the gold. That will still be present, and is the reason alloyed gold is best processed by the inquartation process. The point of my comment is that because the layer of gold is so thin, it will have been totally perforated and digested by AR before an impervious layer of silver chloride can form. You will achieve good success with very thin karat gold materials, very unlike thicker cross sections.

I do know there is some lead, especially in some of the specs that have been 'repaired'. I have tried to remove most of it, but I am sure there will be some carried along for the ride.

In my opinion, it is a mistake to process old specs by any process except direct digestion with nitric. Our lazersteve recently posted that he had processed them with success with HCl, as I recall. I can't address that issue because I never tried the process. I did, however, run literally thousands of specs in my years of refining. I had no issues with processing with nitric, although the solution tends to boil over badly towards the end of the process. A 4,000 ml beaker that contains as little as 500 liters can easily boil over, and by a large margin.

I currently have about 10 lbs of semi-clean (i.e. most stainless removed) watch scrap, and about 5 lb of 1/10 12k old specs to do. But if I could reduce this to a half pound of relatively pure gold mud (or corn flake it, for later processing)

Melting would likely be a mistake. When you melt gold filled objects, unless you use them for inquartation (not recommended with the material you have), the gold is finely divided, then when you process for recovery, you end up with minute particles, often colloidal, that are difficult to separate from the solution. There is nothing gained by melting,

I have already dissolved my first lb of filled scrap, which was a mix of jewelry and some watch band scrap, using hot HCL only. Took a long time.

As I expect it would. Remember, yellow, rose, and green gold contain silver. The silver chloride you develop presents a problem. Nitric, by contrast, dissolves the silver, eliminating the problem. Better you use AR than HCl alone, from your description. The AR will dissolve not only the base metals, but the gold, leaving far less material in native form, around which silver chloride could form. Instead, it will slough off as fluffy material.

Harold