I dissolved to gold and now have a dark brown liquid. tryed to adjust the ph but no fizzling. so I added the precipiate. the precipitate fizzed up in a brown foam then disappear after a few seconds. Now I have what appears to be brown powder on the bottom. I filter the powder into another jar. then dipped a paper towel into the solution and with a drop of the precious metal detection liquid i got a green color. even if i drop a drop of the detection liquid onto the powder i get a green color. is this normal? is the powder actually gold? I wieghted it while still wet and i got about half a ounce from half a pound of processors. Is this normal?
getting green color with detection liquid
- Thread starter Axlrod2
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Indications are you have gold. I'm assuming you tested your solution before adding the precipitant you used and it tested positive (purple to black display).Axlrod2 said:
If the solution now tests only green, that's an indication that you made a full recovery. Testing the resulting material with stannous chloride won't indicate anything unless there is gold in solution remaining. Stannous chloride does not work on metals, just salts of metals. Keep the testing solution (stannous chloride) away from precipitated material---it's a contaminant. Test by withdrawing a drop of fluid, using a spot plate or other methods (paper, cotton swab).
I don't endorse your method of handling the resulting gold. All that is necessary is for you to test the solution, to ensure that you have made a full recovery, then allow the solids to settle. At that time, carefully pour off (or siphon) the barren solution, then begin the washing process. Leave the gold in the container (which must be heat resistant and non-metallic) until is has been fully washed and dried. Only then should you even consider weighing the material. To weigh wet material makes no sense, considering it will hold a serious amount of water. Precipitated gold should be weighed ONLY after being properly washed and force dried (heated well beyond 200°F). Otherwise you will be weighing substances that are not gold, and you'll wonder where you lost values.
Harold
rewalston
Well-known member
Harold_V said:
Harold when force drying gold, I'm assuming that you heat it while it is in the beaker that it was precipitated in? Also is there a clear indicator as to when the gold powder has been dried sufficiently?
Rusty
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That's correct. Washing and drying take place without removing the gold, reducing the chance of loss or contamination.rewalston said:
As for drying, it will be perfectly obvious to you when the gold is dry, and even more obvious why you are admonished to incinerate substances when switching between acids, and you don't wish to dissolve values.
As the water evaporates, the color of the precipitated gold changes, getting lighter. Before that happens, you should be swirling the gold regularly, to prevent sticking to the beaker. This will make sense once you've been there, done that.
Once dry, continue to heat the gold. You're not finished, yet. As the temperature rises, you'll notice vapors, or light smoke, comes from the gold. There are substances that stick with the gold doggedly. What they are I have no idea, but it will be quite obvious that there is a presence of acid, assuming you (lightly) sniff the fumes. Heat until you no longer see the vapors, then allow the beaker to cool. Do not remove and place on a cold surface, for that will cause thermal fracturing of the beaker.
I heated my beakers on a gas hotplate. I had a pad of asbestos between the beaker(s) and the flame, to limit uneven heating. The pads of which I speak used to be readily available from chemical supply houses. That is no longer the case, due to asbestos no longer being available. They likely have a replacement material now that performs the same function.
Harold
rewalston
Well-known member
Thank you Harold. I'm not there yet, but everything I read is being stored for later use. As long as I don't loose my head I'll remember it. I remember about swirling the beaker. All I need is a hot plate now. Once I get enough material I'll probably use an old crockpot for everything as a heat source...possibly put some sand in the bottom of it as a heat buffer and even distribution. I have gobs of heat sources here but if I used any of them I might be killed by inlaws 
Rusty
Rusty
qst42know
Well-known member
If nothing else go to a second hand or dollar store and get an electric skillet or griddle. Drying first on the warm setting will prevent steam explosions that can launch gobs of powder out of your vessel. They lack the high heat to destroy salts but can be useful for warming solutions as well.
freechemist
In Remembrance
Hi rewalston,
A simple criterion to judge, if a precipitate (not only gold!), after thourough washing, has been completely dried, is it's weight. In practice, the dried sample is weighed, and the drying-procedure repeated. Again, the now doubly (or even more) dried material is weighed. If this second weighing delivers the same result, as the first one, the sample is definitely dry. If a further loss in weight is detected, the drying-procedure has to be repeated again, and so on..... In quantitative analytical chemistry (gravimetry) this general procedure is often referred to as "drying to a constant weight".
freechemist
A simple criterion to judge, if a precipitate (not only gold!), after thourough washing, has been completely dried, is it's weight. In practice, the dried sample is weighed, and the drying-procedure repeated. Again, the now doubly (or even more) dried material is weighed. If this second weighing delivers the same result, as the first one, the sample is definitely dry. If a further loss in weight is detected, the drying-procedure has to be repeated again, and so on..... In quantitative analytical chemistry (gravimetry) this general procedure is often referred to as "drying to a constant weight".
freechemist
