Murua said:
Hi everybody, I received a carpet from a jewelry shop, how, can I recover the gold?
That it came from a jewelry shop may not matter. Where it was in the shop and how it related to the bench does. If the carpet was in the fabrication area, that's a positive sign. If it was in the retail end of the store, with the benchman rarely, if ever, walking on the carpet--that's not so good.
Before you get too deeply involved in trying to recover values that may not be there, I strongly recommend that you cut a sample piece, or more than one, taken from various portions of the entire carpet. It need not be a large sample--- a few square inches from each area you choose to sample.
Place the pieces in a pan, in a fume hood, one that can withstand heating. Heat the pan from below, with the objective of burning the carpet completely. That's critical to achieving the desired results. The carpet will most likely turn to oil, then burn rapidly. if it's wool, it won't burn worth a damn, however, but wool carpet isn't exactly common today.
When the carpet has burned to ash, it must be roasted, to eliminate traces of carbon. The resulting ash, when it is ready for processing, will be anywhere from a pale gray to a pale purple color. If it shows purple, that's a positive sign there is gold present. If it does not, good chance there is little gold, but don't jump to conclusions. The pale purple color is an indicator that there is a lot of polishing dust included---the gray color could still contain filings, and not much in the way of very fine particles.
Screen the resulting ash, removing any large pieces of gold or junk. The screened ash should then be subjected to a magnet, to remove metal filings. Send them to your stock pot, where any traces of values will be recovered, and the scrap steel (iron) will serve to cement values sent to the stock pot.
After screening, place the ash in a large beaker---the larger, the better. Pay strict attention to what I'm going to say next.
The ash will not respond to most acids, but it readily is dissolved by HCl. In the process, it will liberate a considerable amount of heat. For that reason, it was my policy to use about equal parts HCl and water (tap water is acceptable). Add the acid and water in small amounts and allow the material time to work. When it slows down, add more, but small amounts, always. At first, the reaction is fast and foams very little. However, as you continue adding acid, the dissolution process takes more and more time, and the slurry foams a lot more. Keep some cold water near, so if it attempts to foam over, you can cool and dilute the solution, preventing an overflow. At this point, you should consider that the solution should be removed, so after it subsides, and the acid has done its work, add water, stir well, and allow to settle. When it has, siphon off the solution, sending it to another vessel where it can settle yet again. There may be fine particles of gold that may be discarded otherwise.
Return to the slurry, which is now well dissolved, and start with the HCl and water treatment again. When the addition of more acid does nothing, you can safely assume that you have eliminated the vast majority of the ash. Upon careful rinsing, you'll find that all you have left is sand, and, with luck, fine gold particles mixed within. You can now dissolve the values, using your preferred solvent. I used AR--but the choice is yours. If this test yields no visible signs of gold, and your test proves to be negative, don't waste your time on the carpet. You have no idea of the amount of work involved in processing a typical room size piece--it will take days.
Remember to evaporate your solution before testing with stannous chloride. If you have too much acid present, it may not respond to the test, so you'd conclude there is no value present.
A room full of carpet will incinerate and roast down to about five gallons of ash. After dissolution with HCl, you might expect to have a quart of sand, maybe even less.
Do not attempt to process this carpet until you have a firm understanding of what you've been told. To do so will most likely result in your losing the values.
Harold
