Hello From California

[modern49er]

New to the fascinating world of precious metals recovery. I came across this science when I did a search for a process for extracting gold from old heavy gold-filled watch cases. I have been repairing old mechanical watches for 20 years as a hobby. During this time, I have collected maybe 30 to 40 pounds of rolled-gold and heavy gold-filled watch cases from retired watchmaker's estates and non-salvageable repairs. Most of these rolled-gold watch cases are guaranteed not to wear for 20 years. I imagine that there must be enough gold to be extracted from these watch cases to make it worth my time and money. My approach thus far is;

1. Expose surface area by grinding the cases down to smaller pieces. The finer, the better.
2. Treat metal with nitric to dissolve base metals.
3. Dry the remaining gold and weigh.
4. Inquart the gold with 75% 999.9 silver.
5. Use the AR method to recover fine gold.

If I'm on the right track please let me know. If there is a more economical way to achieve the same results, also let me know

Looking forward to learning more about my newly acquired hobby. And thanks in advanced to all the members who have made contributions and made this forum possible.

Once again,thanks!!!

 

[martyn111]

There is another thread running on this subject, take a look at the link below
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=48&t=11945
Welcome to the forum

 

[Harold_V]

1. Expose surface area by grinding the cases down to smaller pieces. The finer, the better.

Lose that idea immediately. There is NO need to do anything aside from incinerate, to eliminate oils. Heat them to a dull red, by torch. That's it. (Although you should remove any ferrous materials)

2. Treat metal with nitric to dissolve base metals.

Correct, but make it dilute nitric. 50/50 will serve you well. Don't be afraid to heat the vessel, and to use a watch glass to return vapors to the solution. Be mindful that this process is going to yield silver nitrate, too, although not a lot. Likely to have some tin and lead present, too. They're a PITA if you don't know how to handle them.

3. Dry the remaining gold and weigh.
4. Inquart the gold with 75% 999.9 silver.

Blink! Blink!
Any particular reason you'd want to do that?
The purpose in processing with nitric is to eliminate base metals. When you do the initial digest, you'll be left with very thin wafers of gold, along with considerable junk that may not even look like gold. It requires NO melting. If you're wise, you'll gather it all in a filter, then incinerate, filter and all. You would then do a wash with HCl (heated) and then rinse well.

5. Use the AR method to recover fine gold.

Correct, but before you do any of these things, read Hoke. Don't jump in with both eyes closed thinking you have it down---you'll save yourself a lot of grief by following my advice. Also, if you don't understand the use of stannous chloride, you're nowhere near ready to attempt refining.

Read Hoke. Read Hoke again.

If you still don't understand what you read, read it again. Read it until you do.

Harold

 

[modern49er]

Harold,

Thank you so much for your advise. I went back and read Hoke's, chapters SOME SPECIAL CASES and REFINING PRECIOUS METAL WASTE. Specially the sections regrading tin, lead and gold filled, and using sulfuric acid to deal with them. Although I have read Hoke's 3 times, it only shows that much knowledge retention is needed, and the endless possibilities where mistakes can be made. I have never been an abstract learner, I learn by the actual hands-on process. I will take your advise and process a small practice batch of items. I will also document the entire process with starting weight and final product weight along with photos and all.

Any information on a retail store or distributor where I may be able to obtain the necessary chemicals for this job in Los Angeles or San Bernardino Counties California?

Thanks.

 

[Harold_V]

You can, for the most part, eliminate tin and lead when you do the initial nitric digest. The worst case scenario would be that you had some silver in solution, which may be difficult to separate. The nitric solution may be difficult to filter (I expect it would be), but you may be able to separate it when the nitric is exhausted, take up the solution with a little water, then allow it to settle. Siphon off the solution and repeat the nitric digest until all of the solids that can dissolve have done so. When you have the base metals dissolved, with all of the solution separated from the remaining solids, you can recover the traces of silver with either copper, as cemented silver, or with salt or HCl, as silver chloride. Main focus, though, would be the remaining solids. They'd get incinerated, then given the boil and rinse I spoke of. That will limit the amount of both lead and tin that follow the gold when it's dissolved, so it won't be troublesome. You can dissolve the gold by other means than AR if that becomes necessary. You can use Clorox and HCl, as an example.

In regards to where to buy the needed chemicals, you'll come to understand that nitric acid is a huge stumbling block. You may have to make your own, or you may be able to buy the required amount to handle your project. Not being in or from California, I'm not able to make any suggestions, but there's no shortage of guys on the forum that both live there and know where to make purchases. With a little luck, one of them will step forward with some advice. In regards to almost all of the other chemicals you'll need, they are, for the most part, available at many of the stores you may already frequent. Keep reading the posts on the forum, where these guys discuss this on an ongoing basis. I'm not much help in that regard because I used only commercially prepared acids and compounds when I refined. These guys are masters at working without them.

Harold