having trouble with ceramic chips

[golddigger2]

the other day i put some ceramic chips into a nitric solution and after 2 days everything looked fine the acid had turned that nice pale blue colour and all was on track. I then had to go away for a couple of days and when i got back the acid had turned black and everything in the bucket, pins,and cpu's had turned to copper. I quickly assertained that the copper was coating everything in the bucket. I am assuming that something forced the copper out of solution and made it plate out on any available metal. I poured off and filtered the waste acid and then tried to precipitate out the silver using sodium chloride but nothing happened. I have kept everything. Would adding some HCL cause the copper to redisolve into solution where it can be removed. I am not really sure what i did wrong.

anyone have any suggestions?

 

[Harold_V]

What you experienced is exactly why I keep harping on not using AR to process gold.

Ok, I do understand that that's not what you're talking about, but it is a great example, on a fundamental level, of exactly that.

When you left, your acid was still likely active. At some point in time, it weakened to the point where the copper you had in solution began cementing on what is likely iron (steel). Only when it was fully cemented was it happy, unless it ran out of base metal. Sounds like it didn't, otherwise there'd be nothing to be copper plated.

Black stuff? Hard to say what it is, but you can trust me on this one. If you have managed to cement copper, there's not a chance in hell that there'd be any silver remaining in solution, assuming you had any at the outset. Had there been silver present, it would have been the first thing to cement, then the copper. In effect, you just recovered any values, along with copper, just as if you had introduced your solution to a stock pot.

You may wish to investigate a different process to get rid of what is likely iron. If not, there may be considerable zinc (or aluminum) present. If that's the case, unless you can get all of it in solution, it will continue to cement other elements.

By the way, you can capitalize on that feature, assuming you have base metals that can't be sorted otherwise.

Harold

 

[geonorts]

wouldn't simply adding fresh nitric acid to the cpus solve the problem, redissolving base metals and silver as it should dissolve faster now as the copper is on the outside, ive had it happen and i just put all the pins that dropped into some new nitric acid slightly stronger concentarion

 

[Oz]

Adding more nitric would put the cemented elements back into solution but seems to be the expensive route. In most places nitric is more expensive than HCl. In this case there seems to be an abundance of base metals that would go into HCl unless there is a barrier of silver or gold.

You do not want to add HCl now as Harold explained, but in the future if you have the same material I would use HCl first.

Then after, as Harold preaches, incinerate before changing acids.

 

[butcher]

look onto the EMF series of metals, a web search will explain what Harold is talking about, this is a list of metals in a series, it will show you which dissolve easiest which will displace or precipitate others from solution and which will plate out to another (the metals must be ables to disolve or be soluble in that solution also).this is why we try eliminating the metals, that will disolve easiest and, and cause us problem's in refining, these base metals can replace our valuble metals from solutions, or can even hold our valuble metals in solution, or drag our valuble metals with them, they are just problem if we do not eliminate them.

Some time spent reading Harolds posts can help alot here, only thing is seems he keeps saying the same thing over and over (well not really because every time I read it I learn more, but when it comes to the problems, then he does seem to be preaching,eliminate base metals, incenerate yada yada.)

cementing out your values with copper, and drying then incenerating and start over.

if HCL was used, or in your case you added salt (sodium chloride) (which now if you add any acid Which will contain hydrogen, you will make HCL in solution and adding nitric to this would make an aqua regia which will still be the problem you have now). base metals pushing gold out of solution, or metals higher in series displaceing your values, thing is there may be values in both solution and pushed out of solution at the same time,

this inceneration will remove your acids from the powders,so you are not adding nitric to chloride salt's

a metal when dissolved in an acid makes a salt of that metal
Example if copper dissolved with HCl (of coarse we would need an oxidizer such as peroxide, because copper is below hydrogen in the EMF series and would not dissolve with out it to any extent), so now we make a solution of copper chloride, when powders these are copper chloride salts, notice they still have chloride, and if we add an acid ( acids contain hydrogen), the hydrogen from the acid would make HCL with any acid even nitric HNO3, the hydrogen from nitric joins with chloride salt, making HCL + HNO3 + copper (and if we had many metals (salts) in this soup we still have a soupy acidic mess)

were is your gold, here is where testing with stannous chloride will also be a key to sucsess, this all seems complicated if you are first starting but as time goes you will easily see it. My Hope is that I don't confuse you more with my inability to explain this, I have a hard time saying what I would like to.

 

[butcher]

here is a sermon for the reverant out there, pay attention here, no sleeping this is important to reaching our goals. :lol:

Do you understand the principle of values cementing on base metals?
One of the biggest mistakes newbies make is to process everything in one lot. When you do so, you can expect a few things. One of them is, assuming you achieve your goal, the gold will not be very clean. That's not a big problem because it can be refined a second time to improve quality.

The biggest problem is the cementing I mentioned. I'm going to assume that you know what you're talking about, and that you did, indeed, dissolve some, if not all of the gold. The problem comes when you allow the gold solution to remain in contact with the remaining base metals. The gold you dissolved is cemented down, and the base metals, regardless of what they may be, go into solution. That will happen until one of two things happen. One of them is that you exhaust all of the values, which are then converted to a powder, and will be found mixed with the solids that remain. The other is that the cementing process will continue until all of the base metals have been consumed, at which time there may or may not be some of the values left in solution. It can go either way.

I saw no mention of you testing your solution with stannous chloride. Did you? If not, why not? Would you drive a car without vision? This appears to escape many that attempt to refine, and it's the biggest mistake you can make. You have no clue if a solution is worth keeping for further processing, or if your gold is still in solution. Color alone isn't always a reliable indicator, which you will come to understand after you've discarded some values, thinking they were no longer in solution.

From your description, I think you're wrong. I don't think you have gold in solution, and if you do, the majority of it is not. Test your solution for a purple to black reaction. If there is no reaction, eliminate the existing solution and go after the values once again. This time, insure that you dissolve all metallic substances before you stop the process. Otherwise, you'll experience the same thing, although it may be a slightly different reaction, depending on how much gold and base metals are present.

The very best policy when you attempt refining is to eliminate base metals as much as is possible------before you attempt to dissolve gold. Otherwise, you can expect the problems outlined, above, routinely.

Read Hoke.

Harold

Edit: Upon re-reading your post, if, by chance, you have dissolved all of the base metals (no metallic substances remaining), your gold may well be in solution. That might account for the green color you mention (a combination of iron, copper, or what ever is present, along with gold). Again, without testing, you can't know that. Testing with stannous chloride is key to your next move.
_________________
Wise people talk because they have something to say. Fools talk because they have to say something.

The above is a quote from Harold,
from another post, but how many time's, we see the same problem and the same answer from such a devoted person, no wonder he looses his patients with us, we need to read more of this, and understand it, we should all be grateful for his patients, there are so many people here so dedicated to helping others, spending their time for us, we need to also spend time studing what they have written, reading through the forum can open worlds of information to us,I know when you are new your main goal is to get that yeller metal, but reading will get us that metal, keep us safe, and out of trouble, and open a fortune of knowledge in the metal refining trade, secrets kept for centuries reveald all free for the reading.

 

[golddigger2]

thanks everyone more valuable info for me to digest. After a test with stannous showed no gold in solution I disposed of the solution and put the remaining sludge aside to deal with once my knowledge has caught up to my enthusiasm.