What does cemented gold look like?

[cejohnsonsr]

Hi butcher. Thanks again for a lot of good info. I couldn't believe what I had written when I read it again as quoted in your reply. I don't know what I was thinking, but I'm pretty sure I got my thoughts & writing mixed with 2 subjects. The good news is I didn't add HCl to the solution. I did settle & decant the blue solution & "scum" from the Nitric bath. I replaced it with a fresh 50/50 Nitric/water solution. Haven't had a chance to apply heat yet. We had a snow storm & I have to be able to move outside for positive ventilation. There was no reaction to the fresh solution & after more than a day there has been no color change. The solution is still perfectly clear. I can see the sediment more clearly now. There is fine powder & some clumps. It's still quite a bit darker than I've seen from other examples, but whereas it was black, it is now definitely brown. Just very dark brown. As soon as the weather permits I intend to heat the solution to see if any more base metals will dissolve. I guess after that, provided no more reaction occurs, I can rinse & move on to AR.

If I have my head on straight this time, the hot Nitric bath & subsequent water rinses, will finish removing anything that's NOT gold. Then I'll cover the remaining sediment with HCl, heat gently & add Nitric a few drops at a time to dissolve the gold. I should be able to watch the gold dissolve & see when the reaction stops. If I do this right this time, the Nitric acid should be completely consumed in the process of dissolving the gold. I don't know precisely how much gold I have here. Maybe 1 gr. I think it should take 1 ml of Nitric (max) to dissolve 1 gr of gold (Hoke, lazersteve). So if the reaction stops & I still have undissolved sediment, I should probably add HCl to see if that finishes it up before I add another drop of Nitric.

All the solutions & filters from this have been segregated so I can treat them separately later. In fact I've kept everything so far. I have AP still working, spent HCl/Cl that was dropped with SMB, the solutions & rinse from this attempt & some rinse water. All segregated by process used. The one exception is the solution this gold was cemented from. After I cemented with copper I then cemented with steel & neutralized with baking soda until the PH was about 8 or 8.5. No problem with disposal. The local recycling/disposal center would have taken it even if I hadn't neutralized it as long as it was labeled to their specs. Everything I'm doing so far is more for learning than for actual production so I'm working with very small amounts of everything.

Wish me luck.

Ed

 

[butcher]

Ed, from reading your last post it sounds like your education will be better than luck, but I wish you luck anyway

One point, when you dissolve the gold, after about half of the calculated nitric acid reacts, and the initial reaction slows, I would add heat heat this will help the acids involved become more reactive, slowly concentrating these acids more metal will dissolve, add the nitric in small increments, as the solution concentrates, by the time your gold is almost all dissolved, you will have used most of the nitric acid you calculated and the solution will almost be concentrated, just a little more and it will be concentrated (for the first evaporation), at this point add a few drops of sulfuric acid, (you could add a little sulfamic acid solution, instead of sulfuric acid if you have it, it can help De-nox and will make some sulfuric in solution from the reaction), finish concentration, then you should have an orange gold chloride concentrate, at this point a little HCl to wet, heat until the water you had in this added HCl evaporates (HCl is 32% acid, 68% H2O), this will also help to remove any free HNO3 (you may see some red NO2 fumes if any),the added HCl also insures plenty of chloride for the gold, this second concentration will not take long, do this HCl and evaporation one more time, after this you should have pretty well used up all of the nitric in solution, or vaporized of any excess, now you can lower heat and dilute, and let it sit overnight, for any silver chloride or lead to settle out, before decanting and filtering solution into a clean vessel for precipitation of your gold...

 

[cejohnsonsr]

Thanks, butcher. I don't trust to luck very much either, but I'll take what I can get!

I printed out your last reply so I can have it on hand as I'm working. I do have some sulfuric on hand. Rooto. Now I have one more question.

after about half of the calculated nitric acid reacts, and the initial reaction slows, I would add heat

When you say, "add heat", do you mean, "increase heat"? When I get to this point, it had been my intention to heat the HCl until I get a little steam & some condensation on the watch glass. Only then was I going to add any Nitric Acid & only a few drops so I could watch it react. And just to be very complete, I intend to do this for approximately 1 gr of gold in a 1000 ml beaker using 100 ml HCl & Nitric Acid added 3 or 4 drops at a time up to a maximum of 1 ml. No water. I don't think I need to dilute the HCl for this reaction.

Looks like the weather might be clear enough for me to do the Nitric bath today. No hurry for the rest.

Ed

 

[butcher]

Ed,
when I begin heating will usually depend on the materials I am working with, at first the reaction can create a lot of gas and NOx fumes having water in solution and not a strong heat can help to keep these fumes in solution doing more work (NO2 dissolving in the water to re-form more HNO3 in solution), also powders if treated with acids can be quite reactive, solid metal pieces will be less reactive, and you also generate some heat by the chemical reaction alone, basically you can use your own judgement when to begin adding heat, but starting without heating the beginning, can make the acid go a little further, and can help to keep fumes down somewhat, and depending on material can be less reactive, and it does not hurt to raise the heat as needed after you see how the initial reaction reacts, also consider sometimes when acids are added there may be a delayed reaction, taking a few minutes for the acids to get busy as the begin building their own heat in the reaction, and act on the metals.

 

[cejohnsonsr]

Surprising/disappointing update:

Heating the Nitric/water solution caused most of the sediment to be consumed quickly. The solution turned a very light, clear blue/green. What is left floats & is being very slowly consumed. I know there's gold in here, but it can't be very much. No where near the 1 gr I had predicted. The remaining material looks almost organic. Like fine grass clippings. I don't know how that could be. Is it possible that the copper split bolt I used to cement with could have contained tin? If so, will it be consumed by the Nitric? The reaction is in progress now & I need to return to monitor it. I'll post more later when I have a chance.

Update:

I wrote the previous update at 2:03 PM. It's now 4:20 PM. About 5% of the original material remains. The reaction continues. Digestion seems to be continuing slowly. I'll let it go as long as I can. I'm curious to see what will be left & if there will be any gold at all. If it's not gold, what was cemented? I admit to being a bit befuddled here.

Ed

 

[cejohnsonsr]

Well I let this run as long as I could. After a couple more hours nothing more had been digested. I let it sit to cool over night & took these pics. One shows the color of the solution (pale blu/green) & the other shows what was left of the cemented metal. I'm guessing it must be tin. Apparently my copper split bolt was alloyed. I decanted the solution through a charmin plug & saved both the liquid & the filter in case I might want or need to try anything else or find some way to get any more use out of it. I may not have any gold from this exercise, but I did learn. One thing I learned for certain is to make sure I have pure, clean copper.

Thanks to all who helped. (butcher) Now on to my next project.

Ed