Impossible. Never happened, look at this result.

[zzz]

After processing gold finger, with classic method, look what happened to the gold powder after final wash with nitric acid:
before

after

now is floating in beaker (from white is becoming grey), and i'm trying to redissolve in aqua regia, but is very hard to dissolve.
White cementified metal is not dissolved in hcl, nitric, ammonia and organic solvent.

Is possible that gold can become like this sometimes?

 

[glondor]

Cant access pictures....

 

[zzz]

Updated, can you see now?

 

[jimdoc]

What do you call "classic method"?

Jim

 

[NobleMetalWorks]

More information would be useful.

What method did you use to recover the Au from the finger boards.

What kind of fingerboards were you running

What did you precipitate with, or did you precipitate at all?

Any other information on what you have done up to this point would also be helpful.

Scott

 

[zzz]

Ram fingers:
-nitric for remove copper
-aqua regia for dissolve gold
-urea to denox
-potassium metabisulfite for precipitation
-2/3 water wash
-nitric wash
-result in image

As you can see in the first image the gold powder was perfect...later i don't know what is happened, what metal is cementified on the gold.
He did not dissolve in any kind of solution...i add to the list: conc sulfuric and acid peroxide >30%

 

[NobleMetalWorks]

I would test a small amount of the resulting precipitated material.

Decant until you remove most of the solution, retain the solution just in case you may have values in it. Have you tested your solution with Stannous Chloride to make sure there were no other values?

Next, make a small batch of AR, just enough to dissolve your small sample, you can easily do this in a test tube.

If everything dissolves, then you obviously do not have anything insoluble, if anything is left behind, then you may have an insoluble oxide or something else. But this is good for you because you can just simply take your precipitated material, dissolve in in AR, filter off the oxide then drop your Au again.

If everything does dissolve, then you can precipitate again, using as little SMB as possible. Some of the material you are seeing may be excess precipitant.

Scott

 

[zzz]

I would test a small amount of the resulting precipitated material.

Decant until you remove most of the solution, retain the solution just in case you may have values in it. Have you tested your solution with Stannous Chloride to make sure there were no other values?

Next, make a small batch of AR, just enough to dissolve your small sample, you can easily do this in a test tube.

If everything dissolves, then you obviously do not have anything insoluble, if anything is left behind, then you may have an insoluble oxide or something else. But this is good for you because you can just simply take your precipitated material, dissolve in in AR, filter off the oxide then drop your Au again.

If everything does dissolve, then you can precipitate again, using as little SMB as possible. Some of the material you are seeing may be excess precipitant.

Scott

100% sure that is all gold
i tryied this test today...placed a little of this stuff apart in AR...classic yellow gold solution is formed, but very little goes in solution, than i stopped for the day
because it was a very frustrating day for this event (lose a lot of time to test all possible solution), tomorrow i'll precipitate that.
I know that the gold oxide is red, but i think this is another kind of oxide or compound...there are not other explanations...in fact he was formed in nitric acid..
i checked again and now the surface is grey/little green...

 

[zzz]

Good morning guys, i have an update...the first thing I did this morning, is to try a solution that I had not tried yesterday...I transfered the grey powder in a hot solution of NaOH and boiled for 6/7 minutes and the result is this:

the white cementified metal is gone giving me an orange solution, and now black powder is settling on the bottom:

another one:

I'll keep the orange solution for analisys...

 

[zzz]

Ok, another update...as I suspected the orange solution was given by the presence of dissolved gold, due to the tons and tons of solutions that i tryied yesterday,
so i precipitated that until negative test with stannous, and now the solution is light green...i will show you later, now is settling...

The white unknow metal, is precipitated in a little piece in the test beker (AR) of yesterday, and now is floating on the solution.

 

[butcher]

I must be missing something here as I read the previous post, If the orange solution came from a caustic solution why would you think it was from dissolved gold, colors can be clues of what may be in solution, but colors without proper tests the color is worthless for deciding what is in a solution.

Never judge a book by its color or is it (cover).

 

[zzz]

I must be missing something here as I read the previous post, If the orange solution came from a caustic solution why would you think it was from dissolved gold, colors can be clues of what may be in solution, but colors without proper tests the color is worthless for deciding what is in a solution.

Never judge a book by its color or is it (cover).

Because i did not wash very well the powder when transfered to naoh, so she has some aqua regia around, so when leaved the cementified material some gold is dissolved.

I think I know the unknow material what was...maybe the compund of solder mask...this explain why it is dissolved in naoh.