nitric solution too thick for filtration....

[hfywc]

hi again.

quick question.

i dissolved 1 pound of pins in a concentrated nitric acid...almost all of the base metal are completely dissolved. i would like to start the filtration process but afraid that the solution is too thick to pass through the filter...is it okay if i add water to the solution to make it thinner? would i still be able to recover the silver after adding if there are any?

thanks,
alan

 

[Oz]

You would have to describe “too thick” better, but it sounds like you have tin in your nitric.

 

[hfywc]

i didn't measure nor put some water in the nitric acid i used to dissolved the pins...what i am saying is that i probably didn't use enough nitric acid. now the solution is saturated with the base metal more than it could contain -- this is what i meant with "thick".

also, any problem with tin being present in the solution?

 

[Oz]

By concentrated nitric acid do you mean 70%? If so it should have been diluted by half before adding pins, but it will still help some now due to the solubility of the base metals.

It does not take much tin in nitric before it becomes a non-filterable gelatinous mess.

Did you use heat when digesting your pins?

 

[Higashi]

i didn't measure nor put some water in the nitric acid i used to dissolved the pins...what i am saying is that i probably didn't use enough nitric acid. now the solution is saturated with the base metal more than it could contain -- this is what i meant with "thick".

also, any problem with tin being present in the solution?

maybe there's not enough HNO3, maybe there's not enough H20.

the problem that i see is that you might not have enough water to dissolve the nitrates that formed from the reaction between nitric acid and the base metals.

a concentrated nitric acid is about 70% nitric acid and 30% water.

ie., each Kg of 70% nitric acid contain only 300ml of water.

based on that you can calculate the maximum each base metal nitrates maximum that could be contained in your solution. make some probability chart.

1 kg of HNO3 70% has enough NO3- ions to react with certain amount of copper to form copper nitrates, but not enough H20 to dissolve all of them. Do some calculations and see for your self.

My datas in my spreadsheet but this comp dont have Excell, I'm too lazy/sleepy to check and calculate the specific figures again (it's 5AM here now)...




now if you have tin in it, that's another extra problem.




adding more water doesn't make it "more acid nitric", it's just more water and more dillute solution of nitric acid.


my 2 cents.

 

[hfywc]

hi.

most of the base metals are already dissolved, if it's safe to still add water then i will go ahead and do so. however would i still be able to recover the dissolved silver after adding water?

thanks.

alan

 

[goldsilverpro]

Just add an equal amount of water as you have acid. Hot water would be best. The water won't affect the silver recovery.

 

[hfywc]

great, just the answer i am looking for..thanks gsp. alan

 

[fyatim]

I m trying to recover some gold field pieces. I use diluted nitric acid 68% to dissolve the base materials.
Here is the picture of what I end with: a red/brown thick mud hard to filter.
Can you help me identified this material?

 

[fyatim]

 

[nickvc]

Can you describe better or post a picture of what exactly you dissolved as until then we can only guess.

 

[Palladium]

If i had to guess iron! The green of the nitric tell me and the rust to go along with it!
Add more nitric and heat until completion. I think what you will find out is the items are plated and not filled and they are on a cheap iron magnetic base. Yield will be low!

 

[Palladium]

Don't dilute it or the worse it will get! Let everything settle and siphon the clear liquid off the top. Once it's concentrated again add nitric and proceed.

 

[modtheworld44]

Follow Palladium"s instructions,Iron falls out of nitric when it is diluted.



modtheworld44

 

[Justincase]

I always use hydrochloric acid with iron and iron oxide.
Fe2O3 + 6HCL -> 2FeCl3 + 3H2O
as you say settle and take off the liquor,but then may be wash and settle again.
Then try a hydrochloric leach?
Try a sample each way before you make a decision.

 

[fyatim]

Here is a picture of what has been treated as Goold field.

 

[fyatim]

For the rest, I will follow Palladium"s instructions and will let you know what happens.

 

[Topher_osAUrus]

I always use hydrochloric acid with iron and iron oxide.
Fe2O3 + 6HCL -> 2FeCl3 + 3H2O
as you say settle and take off the liquor,but then may be wash and settle again.
Then try a hydrochloric leach?
Try a sample each way before you make a decision.

That could end up dissolving the gold, unless he incinerates between the nitric leach/rinse and the hcl leach. If there is enough iron (or very little hcl) it would precipitate the gold back out via cementation, but since he is already doing a nitric leach, continuing it would be the quickest.

Though, I have had pretty good luck with using a dilute sulfuric leach after the initial nitric run. After the iron is gone, assuming more base metal exists, I do another nitric bath before going to ar, just to be certain all the base metal junk is eliminated.

 

[Palladium]

The chain marked 24k was probably the culprit and iron.

 

[Justincase]

I always use hydrochloric acid with iron and iron oxide.
Fe2O3 + 6HCL -> 2FeCl3 + 3H2O
as you say settle and take off the liquor,but then may be wash and settle again.
Then try a hydrochloric leach?
Try a sample each way before you make a decision.

That could end up dissolving the gold, unless he incinerates between the nitric leach/rinse and the hcl leach. If there is enough iron (or very little hcl) it would precipitate the gold back out via cementation, but since he is already doing a nitric leach, continuing it would be the quickest.

Though, I have had pretty good luck with using a dilute sulfuric leach after the initial nitric run. After the iron is gone, assuming more base metal exists, I do another nitric bath before going to ar, just to be certain all the base metal junk is eliminated.

I do not think there is much chance of getting any gold into solution while there is so much base metals present. Though you may put it into solution and instantly cement it as fine deposition.
As you will have to rely on settling instead of filtering that should not be too much of an issue.
You can see the remains of a ring poking out.
The sediment should wash off the remaining metal so you can see what is left.
Fine particle should be settled out.
if the nitric leach has produced such an adverse reaction ,stop and test all alternatives before you try and make a decision.
He has the gunk so only he can test which rout is best.