Time to swallow my pride & what is this?

[drgoodbar]

Hi everyone. Well I joined this forum quite a while ago and have been reading posts regularly trying to decide if this was something I wanted to get into. I have access to a lot of e-scrap and get thermocouple scrap on nearly a weekly basis. Well I decided I would give this a shot and started with the recommended step one: Hokes book. I found it to be an easy read and nothing in it seems to technical so I took the next step and started to collect equipment. About three weeks ago I set up out in the yard and started with some nice pins (2 pounds) and using the method that came on the link from the person I bought my chemical kit from on eBay. I dissolved the gold from the pins using Nitric and Hydrochloric. This went well. I tested the solution with Stan-nous chloride and it was positive. Well this is when I should have come for help but my foolish pride got in the way. I was supposed to mix the Urea with one quart of water but I mixed it with one gallon, oops. I did not catch this blunder until I had already mixed it into my solution.
Back to the forum for some reading. I found that most of the experienced people here shy away from Urea electing to use the evaporation method so I set up a fan, got out the hotplate and spent the next Saturday babysitting my evaporating blunder. I retested, (still positive) and tried to drop again with no success. I retested, (still positive) so I started my stock pot.
Second attempt:
I had about three pounds of really high grade blank boards that were about 1 1/2" X 2 1/4" with gold tracing on one side and completely plated on the reverse. I stripped them the same way and the gold was completely off in a couple of hours. It looked good. There was gold floating all around in the solution and I was excited. I opted to not use Urea for the evaporation method. I evaporated down to a syrup, added some hydro and water then repeated two more times. By this point I had consumed all of the SMB that came with my kit on my earlier blunder so I went to Home Depot and bought some Sump Out. I came home and tried to drop my gold and I am getting a white powder and not the brown ugly gold I am expecting. We were expecting rain the next day here in the Silicon Valley so I put the solution in a small pale and locked everything in the shed so it would be safe.
Yesterday I removed it from the shed and poured the solution into a beaker to re-evaporate and this was in the bottom of the bucket:

 

[rich_2137]

flubber! :lol:

 

[eeTHr]

Dr---

What you need, to initially separate the gold from the base metals, is a recovery process.

Aqua Regia is a refining process.


Also, with dropping gold from A/R, using SMB (especially after evaporation), you need to dilute the solution with some water. You should also add a little HCl, after the last evaporation, so there is some free HCl in there. The HCl (Muriatic) is already about 1/3 acid and 2/3 water. You should add at least 2x water to the solution, so if you start with 1 quart, add water to make it total 3 quarts.

But what you currently have is a "dirty" solution. That is, it's got a lot of contamination (the base metals you dissolved along with your gold). Contaminated solutions don't drop gold as nicely as clean solutions do.

You might be better off, at this point, to use another recovery step, which is to suspend a piece of solid copper in the solution. This will drop the gold, along with any other precious metals in your solution. There should be some free HCl in there, too. Most gold should precipitate by the next day. Decant the solution to another container, and put the copper in the new container for a week. Rinse the powders which are still in the original container, and refine them using proceedures recommended on this forum (with proper rinses and so forth). A week later, do the same with the solution in the second container (if there were any PGMs in the solution, they will probably be included this second batch).

I don't know what the green balls are, but they will probably dissolve with dilution, using some water and a little HCl. They might be physically or chemically holding some gold, so they should be dissolved.

The copper method is referred to as "cemeting," because it has the appearance of cement, especially when using it to drop silver from a nitric solution. You can use this on the solution you just started your stock pot with, too.

 

[drgoodbar]

eeTHr,

Thank you for thorough reply. I did actually add some Hci and water but not nearly enough water. Hoke says to keep the Hci low so I did. I have a nice thick copper bar at home and when i get there I will dissolve everything together and put the bar in the bucket. Do I need to add anything or just start the cementing?

Thanks Again,

Bill

 

[eeTHr]

Just start cementing.

All the water in the highly diluted urea is probably enough, and there is probably some free HCl in that solution, too.

 

[eeTHr]

Also, most people on here prefer to avoid using urea. For one thing, it's just more stuff in your solution, and you don't really need to use it.

For the refining procedure, to avoid urea, put HCl in a container with your gold, heat it (not to boiling), and add the nitric in small increments. You can see how long it takes to dissolve some of the gold, so you can see how much nitric to add at a time. Leave a little bit of gold undissolved (that means all the nitric is used up), and decant the solution into another container. Then add the water, then filter the solution into the container you want to precipitate it in. Precipitate with your SMB.

Recover the undissolved gold which remained in the first container, and save for your next refining.

An alternate method to achieve the same thing is to put a small button of gold into the A/R after your last increment of nitric has dissolved all the original gold. The small increments will prevent too much nitric being added, and the gold button will use up what little extra nitric remains. Just weigh the button before and after, to be able to keep track of your actual batch yields.

 

[drgoodbar]

eeTHr,

Thanks for your help! Here it is: 8) 8) 8)

 

[eeTHr]

DR.---

Nice recovery. Do you intend to refine it?

 

[NobleMetalWorks]

The way you described it sounds to me like you evaporated some of the solution that was holding onto copper, so when it evaporated off, and you diluted with water in the pale, the copper had no where to go. Evidently conditions were right to facilitate a precipitation of some of the metals that were suspended in solution, it looks like to me, just off the top of my head, to be made up of a lot of copper. But it's such a bright green that there must be other metals in it as well.

Did you test for gold in the solution that was left over? I believe gold is the last to go into solution, so that could very well mean it's the last to precipitate out of solution. You may have fold that precipitated and still in solution. If that is the case, you might want to finish each separately instead of running it all through the start again. You could combine them once they were of like qualities and then continue with the rest of your process, using less chemicals to re-process the green mass.

Or you can put the green mass that looks like copper crystals, on eBay as a work of art and probably make a lot more money than you could if you sold all the metals. Just an idea, it kind of looks interesting!

 

[butcher]

Study Hokes, and get that pride back. We all have to start learning somewhere.
You did get back metal, now you need to learn to make it more pure.
Practice makes perfect, along with more homework.