Blue sludge on bottom of beaker

[bleachsicle]

last night I boiled about 260g of gold filled scrap in nitric acid. I slowly introduced the nitric acid and in total added about 780 mL of nitric. I let the solution cool and settle over night.

I wake up and the solution is blue but there is a lot of blue sludge at the bottom of the beaker. The gold foils are still present, but there is a lot more of this sludge, which I do not see in most gold filled refining videos

Any thoughts to what this is?

 

[Martijn]

Copper salrs are blue when dilute and more green when concentrated. They can color any white precipitate blue. Like silver chloride or copper 1 chloride.

 

[Martijn]

And: Welcme to the forum.

 

[FrugalRefiner]

You didn't mention if you added any water. Since you only used nitric, it is probably mainly copper nitrate. When you boiled the solution it became saturated. When it cooled, some of the copper nitrate precipitated because cool solutions can't hold as much in solution.

Dave

 

[bleachsicle]

You didn't mention if you added any water. Since you only used nitric, it is probably mainly copper nitrate. When you boiled the solution it became saturated. When it cooled, some of the copper nitrate precipitated because cool solutions can't hold as much in solution.

Dave

Hey sorry about that!! I added about 200-300 mL of distilled water

Does this change anything? Does it mean I don’t have enough water to keep the copper in solution?

edit: what's the best way to continue? Do I pour off as much solution as I can while keeping all the solids on the bottom then do another nitric boil with more water?

 

[FrugalRefiner]

Usually we use about equal amounts of water and nitric (50/50). So, you were short on water to start. Some evaporated during your boil. It's probably still copper nitrate. Just add some distilled water and stir and it will probably dissolve.

Dave

 

[bleachsicle]

Usually we use about equal amounts of water and nitric (50/50). So, you were short on water to start. Some evaporated during your boil. It's probably still copper nitrate. Just add some distilled water and stir and it will probably dissolve.

Dave

Thank you, Dave! Have a great rest of your weekend

 

[Proffshuggarn]

Is the liquid blue as well? I should have tested it for eventually Ag 😉
/Dennis

 

[bleachsicle]

Is the liquid blue as well? I should have tested it for eventually Ag 😉
/Dennis

Yes, the liquid is blue

 

[Proffshuggarn]

Yes, the liquid is blue

So have you tested it for contents of silver? Put 3-4ml of the blue liquid in a regular test tube. Solve a gram tablesalt in hot Water and add it to the blue liquid and then tell us what did happened 😉

 

[slsmp40]

The sludge is zinc nitrate. It is kinda semi soluble and it is a gelatinous pain in the ass. Its the reason I use HCL and peroxide to slowly etch the brass out of gold filled. Separate the silver backed GF from the brass backed is probably a good idea if you have both.

 

[bleachsicle]

The sludge is zinc nitrate. It is kinda semi soluble and it is a gelatinous pain in the ass. Its the reason I use HCL and peroxide to slowly etch the brass out of gold filled. Separate the silver backed GF from the brass backed is probably a good idea if you have both.

I added water and most of it dissolved into solution. I might just need to add more water idk. Not messing with it for awhile while I fix my hood

 

[bleachsicle]

So have you tested it for contents of silver? Put 3-4ml of the blue liquid in a regular test tube. Solve a gram tablesalt in hot Water and add it to the blue liquid and then tell us what did happened 😉

I’ll let you know 😁