Precipitating gold

[Anonymous]

Hi,
I have just started with gold refining. I have dissolved my gold findings in Aqua Regia; the solution turned a deep, almost black green color. I neutralized the nitric acid with Urea and added Ferrous Sulphate but nothing happened; no gold precipitated out of the solution.

There was not much reaction when I added the Urea to the AR. Is it possible that the Urea I am using is bad?

Can you please give me advice?

Thanks in advance! :

 

[lazersteve]

Does the solution test positive for gold with stannous chloride.

What did you dissolve and how much of it?

Steve

 

[leavemealone]

Not that familiar with using Fe sulfate for dropping in AR,but should be easy enough.Just test your AR to see.Take a small sample and put some gold plated fingers in it.If the gold dissolves then you know either your urea is bad or you didnt add enough before precipitating.If your AR has been sufficiently neutralized then you may want to consider using a different precipitant.Just make sure you clean your powder extra well after dropping,you may even want to dissolve and drop it again.
Johnny

 

[Anonymous]

Hi Lazersteve/Leavemealone,
Thanks for the responses. The solution did test positive for gold with stannous chloride. I receive a 25.3g gold nugget from a friend who melted some old jewelry and ended up loosing interest. I dissolved it in 200mL of AR overnight and added Urea (1lb dissolved in 1 liter water). As I mentioned earlier there was not much of a reaction; very little fussing and then it stopped.
I could not do anything further since I had to leave on an overseas trip and will only be back next month to try out everybody’s advice.
Any ideas?
I will try the advice provided by Leavemealone when back.

 

[lazersteve]

The gold jewelry must have been Gold Filled if you have a negative stannous test and only a small amount of powder from 25.3 grams. Expect between 1% and 2.5 % yield from gold filled scrap.

Steve

 

[Gold Trail]

leavemealone: the use of plated fingers is a great idea for testing the nitric content of AR i have been pulling my hair out on a batch this weekend. i expected 15 - 20 grams and only got about 5. the AR, even diluted with water tests positive (as black as the ace of spades it self) so i put some in a beaker with some fingers and away it went.

so i put a basket full in my reaction bucket, now correct me if i'm wrong but once the fingers stop disolving, the nitric is out and the rest of my gold should drop when smb is added.

i have heard the big boys talk about putting a gold button in to eat up the nitric, but i worked too hard to loose them if somethings goes wrong.

yep its eating the gold plating away. i put urea in untill no more fizzing (this was my 1st attempt at a big batch of processors. i normally do small batches with Steve's controlled used of sodium nitrate, but all i have is a 2000 ml beaker and its just not big enough any more!)

its funny how we get so wrapped up in the complexities of this refining thing and a simple 1/2 lb of pc fingers seams to be doing the job

in future batches, could adding more gold to the ar thake the place of boiling or UREA?

AS always great forum and great info on here.

 

[Harold_V]

so i put a basket full in my reaction bucket, now correct me if i'm wrong but once the fingers stop disolving, the nitric is out and the rest of my gold should drop when smb is added.

Am I following you properly?
Are you telling us that you put base metals in what was gold chloride, albeit with an excess of nitric acid?

One of the tough lessons that most folks will learn is that processing base metals with AR isn't a good idea.

Reason?

Well, there's at least two of them.

First, when you dissolve everything in a common solution, the chance of precipitating clean gold is remote. In spite of using a selective precipitant, there is considerable drag-down of anything that is in solution, so the gold comes down quite dirty----and rarely can be washed sufficiently to remove all of the contaminants. Re-refining the material will cure the problem, assuming you have clean work habits.

The second problem, the one that can be the source of considerable trouble, is that when you have gold in solution and introduce base metals, depending on the volume of gold in solution and the amount of base metal present, you risk cementing the values from the solution. The only way you can avoid doing so is to insure that there is more acid present than is needed to dissolve not only all of the base metal, but all of the values as well.

Armed with that idea, why in hell would anyone want to dissolve base metals along with the values in order to effect a recovery? That is rarely necessary, and almost NEVER desirable. Doesn't it make more sense to strip the gold by electrolytic action (gold stripping cell), or to dissolve the base metals, leaving the gold behind for further processing?

If you added any copper based materials to your gold solution, the chance is better that you have lost some of the dissolved gold to cementing. Had you inserted an abundance, you would have all of your gold cemented to the base metal, with none remaining in solution.

i have heard the big boys talk about putting a gold button in to eat up the nitric, but i worked too hard to loose them if somethings goes wrong.

Lose it how?

As long as you don't evaporate too quickly (never boil a gold chloride solution that is being evaporated), or otherwise discard a solution, even if you mess up badly, the gold is still there-----you simply have to learn how to recover from mistakes.

Adding gold to eliminate excess nitric is a great solution to a problem, one that avoids buying unneeded and (in my case) unwanted reagents (urea). I refined for more than 20 years and never once used urea. There was no need.

Harold

 

[Gold Trail]

Harold, it was allready a "dirty" AR solution from CPU chips. you are correct, the solution clear overnight, with little precip, but still test positive for gold. I assume the black / discolored fingers now have gold cemented to them.

I assume, that even though i allready added smb prior to ridding ALL the nitric, i need to add it again, and the cemented gold on the fingers is a loss?

and yes, i ALWAYS re refine my e scrap percipitants.

Still learning

Ryan

 

[Harold_V]

Harold, it was allready a "dirty" AR solution from CPU chips. you are correct, the solution clear overnight, with little precip, but still test positive for gold. I assume the black / discolored fingers now have gold cemented to them.

That's likely the case. When gold cements down from solutions such as that, it isn't necessarily yellow in color. I would expect the black to be gold.

I assume, that even though i allready added smb prior to ridding ALL the nitric, i need to add it again, and the cemented gold on the fingers is a loss?

You may or may not enjoy success. It is worth a try, but you should remove everything solid and filter the solution before doing so. If SMB fails, you can recover the gold with copper, then re-process. You more or less forced yourself into that position by adding the fingers. It's never wise to add base metals once you have dissolved the values unless your intention is to recover them by cementation.

Gold is not lost as long as you don't discard anything. It is there waiting for you---all you have to do is apply the correct procedure and it can be recovered.

and yes, i ALWAYS re refine my e scrap percipitants.

Still learning

OK, that makes sense. Re-refining is one of the fastest and easiest ways to improve the quality of recovered gold. I routinely double refined and was more than pleased with the end results.

Do learn from this experience. Don't use any solution that has values dissolved within to process any base metals. It can work, but it is most likely to yield problems.

Only on very special occasions is it a good idea to dissolve base metals with AR, and when you do, you must be patient, allowing the base metals to cement down all of the values. Once that's done, you can discard the dissolved base metals, then re-dissolve the values. By careful manipulation you can eliminate the vast majority of the base metals without losing any of the values.

Harold

 

[goldsilverpro]

Harold,

I didn't follow this advice every time, but almost everything I've ever read in the literature about re-refining advises the following:
(1) Melt the gold before re-refining. In other words, don't just dissolve the powder. Maybe, incineration would accomplish the same thing.
(2) Use a different precipitating agent for the 2nd refining. This makes sense to me if Pt is present. In that case, I would use ferrous sulfate first and a sulfite second. The FeSO4 does a better job of eliminating Pt and the sulfite does a better job of removing everything else, including the iron from the FeSO4.

What do you think?

 

[Harold_V]

Harold,

I didn't follow this advice every time, but almost everything I've ever read in the literature about re-refining advises the following:
(1) Melt the gold before re-refining. In other words, don't just dissolve the powder. Maybe, incineration would accomplish the same thing.
(2) Use a different precipitating agent for the 2nd refining. This makes sense to me if Pt is present. In that case, I would use ferrous sulfate first and a sulfite second. The FeSO4 does a better job of eliminating Pt and the sulfite does a better job of removing everything else, including the iron from the FeSO4.

What do you think?

I agree in principal, although I didn't bother with a different precipitant. I had excellent results with the method I used, so I wasn't concerned.

The idea of melting before dissolving a second time has merit. Not being a chemist, and not being able to identify what the contaminant was, I know from repeated experiences that certain of my customers got something in their wastes that was troublesome. What ever it was was water soluble, not so much in acid, if that makes sense. When I'd wash the gold after precipitation, if the material was present it would never cease washing out. It left the solution a coffee color, and created some sparking when the gold was melted. I learned that melting it before it was processed a second time improved the quality immensely, so when ever I encountered the material I would use the resulting gold for my added gold in evaporation. That way the material got processed three times, insuring the contaminant was removed totally.

I read that using a different precipitant was a good idea, and I would have pursued that avenue had I not enjoyed the success I did, but when second refined gold will melt without forming any oxides, forms a deep pipe, and a broad, crystalline surface, free of frosting, I really couldn't see a need for making any changes. That is not to suggest that making changes such as using a different preciptant isn't a postiive step. I believe it would be, especially when a worker has less than excellent housekeeping habits and is having problems with quality.

Do understand that I was very particular about melting my gold, which I firmly believe was key to my end product quality. Before I'd melt, the hood was cleaned out, the tip of the torch was cleaned well (down to shiny copper) and I made sure I had just showered, so nothing could fall from me. Remember, I did all my melting by torch, having experienced both torch and furnace melting. There was no doubt in my mind, torch melting was faster and easier, although if I was casting large ingots (more than 25 ounces--gold), I would have preferred a furnace.

Regards traces of platinum, I didn't have any problems eliminating it in the first washing, but that isn't true of palladium. I found it far more troublesome than platinum. It often precipitates along with the gold. There appeared to be more going on than just drag-down. When it's present in an appreciable quantity, it's obvious that it has co-precipitated, and does not wash out well. A second refining appears to eliminate it, at least to a point where it is not troublesome. I expect it would show in a fine assay, although only a trace. That's one of the reasons I promote inquartation. Platinum and palladium will follow the silver nitrate, eliminating the bulk of the trouble. (As a side note, readers may understand that in the presence of silver, platinum will dissolve in nitric, which I witnessed on a regular basis).

Questions?

Harold

 

[leavemealone]

HEYYYY HAROLDDDDDDDD!!!!!!!!!!
What rock have you been hiding under?!?!?!?!? 8)
Quick question,why does the plat dissolve in the presence of silver in nitric?I just dont get the reaction there.Not that it really matters,I don't process plat.,But I could always stand to learn something,and who better than from the ninja master.....lol.
I can see Im gonna have to take a trip to see the new house huh?????? How about it? 8 days of straight driving just to see how far you've gotten? LMAO.Ok don't get scared Im not coming up there but me and mary are still keeping our eyes peeled for the new pics.Ok going to watch a movie with mary......good night guys.
Johnny

 

[Harold_V]

Sigh! Not being a chemist, I am unable to explain the reason platinum dissolves in the presence of silver, but I can assure you it does. It reports in the silver nitrate, albeit scarcely. Not all of it is inclined to dissolve, although I'm sure that given enough time it would.

If you've ever tried to digest platinum with AR, you'll understand the significance of the above statement. It takes a great deal of time to dissolve thin wire, which I used to do to make my platinum standard solution. That any platinum dissolves at all is a mystery when one uses just nitric.

By the way, I believe Hoke addresses that issue. Might not hurt to check the book. My copies are in storage, so I am unable.

House pictures?

I need to take one, Johnnie. I have the best of intentions, but each day I go out there and work on finishing the drywall, and don't remember until I come in at night, much too dark to take any pictures. I'll do my best to get one up in the next day or two. Wouldn't hurt to nag me a little! :lol:

Harold

 

[leavemealone]

Oh you know that NO ONE can nag you like I can! :mrgreen:


Thanks for the info on the plat,I'll just send it all to you when I get it lol
And if she talked about it I can't find it,but like I said,I try to stay away from it so if I run into that problem I'll let you know and you can show me where she put it.It would seem if you ran an extraction on the silver in the cell (gold anode/steel cathode)you could illiminate the silver first,to stop that,just a thought.
Johnny

 

[Harold_V]

The fact that platinum dissolve with silver is used to advantage. It concentrates what would normally be small amounts of platinum for future recovery. When silver is recovered on copper, platinum and palladium cement down as well, although they are slow in coming down. That's how I recovered most of my platinum and palladium.

Here's a current picture of the house. I got stopped on the vinyl trim last fall, and am waiting until we are assured of dry weather before I return to the outside. It is normal for us to get rain until early July, although this year has been dryer.

I've been spending my time finishing drywall, a chore I did not want to have done by others. I am not pleased in the least with the attitude most drywallers have---one of poor workmanship. Grab the money and run appears to be the attitude. I'm slow, but the results speak for themselves.

At the rate I'm going, I should get it finished sometime in the next 15 years or so! :roll:

Harold

 

[leavemealone]

YESSSSSS

That is beautiful bud.I only see one problem,I have to find something new to bug you about now.... :mrgreen:
Seriously that is just gorgeous,it looks like it is very quiet around there.I understand that would be hard to tell from a picture but that is the feeling I get when I look at it.Thanks again for FINALLY getting that picture....lol.
Talk to you later,
Johnny

 

[Harold_V]

it looks like it is very quiet around there

Indeed!

We built almost in the center of 5½ acres of wooded land. The smallest parcel of land in our area is 5 acres, with some ranging up beyond 60 acres. We have deer in our yard almost daily---with lots of other wildlife.

The nearest traffic light, which is nothing more than a 4 way stoplight----is 8 miles distant. We travel 26 miles to the 'big city".

Harold

 

[leavemealone]

Well I know where Im going on vacation?!?!?!!? lol.
That sounds awesome harold.You don't prospect do you?You never have talked about it with me so I assume that you don't.You are about a days drive from white horse and the jewelry box right?Ever been up there?That is one place I would love to go hiking with a minelab GP3000.Gotta run to the store guys,I'll be back this afternoon.
Have a good day everyone,
Johnny

 

[Harold_V]

Well I know where Im going on vacation?!?!?!!? lol.
That sounds awesome harold.You don't prospect do you?You never have talked about it with me so I assume that you don't.

No. My interest was in owning gold---and I'm very much a realist, not given to being a dreamer. Damned few people ever find enough metal to make their efforts worthwhile. I chose a path that would be successful (refining scrap instead of hoping to find values). I just didn't understand how successful it would be.

You are about a days drive from white horse and the jewelry box right?Ever been up there?

I'm not familiar with the name, Johnnie. While we've been here a while, all of our time has been spent building. We started with heavily timbered land, so we've had a ton of work to do. Once we had the interior logged and scarified, we started installing all of the underground work, plus drilled the well, which ran dry after six months. A second well was required, which is 365 feet deep. 7 gallons/minute of excellent water.

Once we got past the underground work, we built the shop (2,600 square feet), which is where we live while the house is being built. Don't feel too sorry for us----the shop has a tiled bathroom, accommodations for washer and dryer, built in vacuum cleaner system (which also extends to the house), and hydronic heating. It's very comfortable, totally finished inside with painted walls. The room that will be my investment casting room has counters and a sink, plus an exhaust fan, so Susan has a great room for use as a kitchen. Were it necessary to stay here the rest of our lives, we would be perfectly comfortable and want for nothing.

Harold

 

[leavemealone]

Well it just sounds like a wonderful place to be,and clearly well thought out(I would not expect anything less from you).

You are about a days drive from white horse and the jewelry box right?Ever been up there?

I'm not familiar with the name, Johnnie.

The jewelry box is a place just north west from you in canada near a town called white horse.It recieved that nickname from the heart shaped one pound gold nuggets that were found there in a stream.Back in the 1800's some american miners employed some chinese workers to divert a raging stream so they could have access to the river bottom,and thus the gold.I don't need to tell you what happened next......the dam broke,killing very many chinese and americans alike.There is still alot of gold to be had in that area,though extremely difficult to recover,seeing how it takes a FULL day of hiking just to get to the location.Would be a nice place to live though if you had access to a store.
Johnny