My second batch, the move to nitric

Hi guys, after some help from the kind members of this form, my first batch of gold refining went well using AP and the clorox method.
I have now managed to find a source of nitric and began using this for my second batch.
I placed 15 smashed processors in an equal mix of water and 70% nitric. I did this outside and then left the scene until the brown gas was gone.
I got a dark green solution, poured this off through a filter into another bottle and placed a copper pipe in the filtered solution to recover the silver. I also put some of the same dark green filtered solution in another bottle with no copper pipe. The processors were releasing their gold flakes, and I put a small amount more nitric + water on the processors & gold flakes to make sure all base metals get dissolved and left the three containers overnight.
The next day the liquid that the processors & gold flakes were in was only a light green so I assumed all base metals had been dissolved. I filtered off the light green liquid and kept it for silver recovery again.
I was surprised to find that the two bottles with the filtered dark green liquid from the previous day had now turned a light blue. The one with the copper pipe in had some silver powder at the bottom so I filtered this off and kept it to dry out. Any ideas why the solution turned from green to blue?

I then did a few water washes on the processors + gold flakes and covered them with HCL. I added a few drops of nitric until the gold flakes started to dissapear. I then left this overnight.
The next day the solution was dark green. So it seems there were more base metals that hadn't dissolved and I needed to do more acid washes or longer acid washes before using AR. I will remember that for next time. The gold flakes have dissapeared so I have those in solution too.
I was just wondering what the best method would be from here. It seems I have two options:
Place a copper pipe in this solution which will cement out the gold and silver. I can then decant and filter out the silver & gold powder, dissolve the silver with some nitric, and then filter and refine the gold powder with AR. I can also cement the silver back out of the filtered solution using copper pipe again.
The second option would be to drop the gold using SMB, filter it out and then go after the silver with copper pipe.
Or if there is another method that you guys can think of I am happy to hear.
Thanks

Wouldn't SMB drop the gold and leave most of the impurities in solution? Waiting for a veteran to answer that one...

You can get any silver out of your nitric solutions with copper but on your AR, add a few drops of sulphuric to eliminate any lead, dilute with water to form silver chloride, if there is any, filter it for lead and silver chloride, and then drop your gold with SMB. Follow Harold's washing regimen of the powders and then re-refine for purer gold.
That would be my humble suggestion.
Also, you will have to make sure that your AR is free of any excess nitric before doing your gold drop!

Copper nitrate is blue.

Silver is very insoluble in a chloride solution as silver chloride AgCl, so you will not have much silver in the chloride solution, a very small amount of silver can be oxidized to a higher oxidized state as AgCl2 in strong chloride solutions like aqua regia, this tiny bit of silver will precipitate as AgCl with dilution of water (as mentioned above by maynman1751).

Silver chloride is insoluble in water, but dissolves to a small extent in highly concentrated chloride-solutions, forming a complex anion, [AgCl₂]^-.

AgCl + Cl^- <=> [AgCl₂]^-

The oxidation-state of silver thereby does not change. It remains (+I).

Thanks freechemist, for clarifying that.

So there is no exchange of electrons.

My question now is, does this same principle apply to many of the other salts that form "complexes" in chemical reactions.

I thought it was an interesting question and looked it up in my Holleman/Wiberg:

copper in
dilluted CuCl₂ forms blue [Cu(H₂O)₆)]²⁺
semi-concentrated CuCl₂ forms green [CuCl₂[H₂O)₄]
concentrated CuCl₂ forms green-brown [CuCl₄]^2-

in every case Cu exists on oxidation stage +II,- which is very nice of the copper, otherwise we could not think simplified to have just CuCl2 i solution.

(page 1260 in the english version, this page is not part of the google books version)

You talk about silver chloride solution. I have silver dissolved in aqua regia, would that count as silver chloride?

maynman: you talk about adding a few drops of sulphuric to the AR to elminate any lead, would this cause it to drop out of solution?

I added some SMB to my filtered solution yesterday. The first few millilitres made it fizz a bit but further additions didn't make it fizz. I'm guessing I only used a small amount of excess nitric. The next day there was a good amount of brown powder at the bottom so I decanted off, did a few water washes and then left this powder to dry.

I then put a copper pipe in the left over solution to cement out silver. I now have a silvery powder on the bottom which I have decanted off of. I have slightly more silver powder than gold powder.
I didn't read your comment maynman and also I don't have any sulphuric acid. Since I didn't eliminate lead will this mean that my silver powder could be contaminated with lead? Won't the lead stay in solution since it is more reactive than copper?

Hello KarlB...
As the great Harold would politely state...
You have just joined and are trying to do way to much before learning how it is done the right and safe way.

All of your questions so far are here in the forum and if you would stop doing things and begin learning by ready and searching, you would have no questions and there would be less posts of what to do next.
All you are doing is adding more posts to this forum and making it alot harder to find anything.

Please stop and read and learn the right way.

B.S.

Lead is also an insoluble chloride, but some lead will stay in solution with your gold solution, and if not dealt with (like using the little bit of sulfuric acid to precipitate the lead as a sulfate), the lead will follow your gold into precipitation with the gold powders.
Washing the gold powder, (see getting your gold pure and shining found in the help needed section, for Harold's gold washing method), in these washes washing your gold powder, it will help remove lead chloride which is insoluble in cold water but becomes much more soluble in the boiling hot water washes, also second refining of the gold is normally necessary especially when the gold is precipitated from a dirty solution.

Adding a little sulfuric acid precipitates the lead from the aqua regia solution as lead sulfate, with this and re-refining the gold when needed, and the proper washing of the gold, you can remove the lead contaminate that follow the gold through your process, each step to remove base metals through the processes, can be important to get that gold pure and shinning.

Even a little lead in gold makes it brittle and hard to work, pure gold is very soft and malleable being easily hammered into shape.


Lead chloride like silver chloride is a white metal salt.

http://wserver.scc.losrios.edu/~nussl/chem401/handouts/week09/SOLUBILITY%20RULES.pdf

KarlB said:

I then put a copper pipe in the left over solution to cement out silver. I now have a silvery powder on the bottom which I have decanted off of. I have slightly more silver powder than gold powder.

Click to expand...

In aqua regia ?