Bad crucible and magnetic contaminant

[madderoftime]

Posted to the welcome page and now I think I need to just ask for some help here.
Starting material:
1. All metals from many connectors and PCBs cast into 31 lb. anode 1400 deg c pour temp with all steel pulled in slag. Ran though a copper sulfate plating bath. Anode slime was pulled, washed, dried and roasted to remove sulfates. 3 lbs.
2. Plated jewelry and 2 rings. 1 ring was thought to be white gold. about 200 grams
All was combined and leeched with hot nitric and agitated until reaction was complete. Removed liquid to process for silver.
Washed until liquid was clear. Removed liquid to process for silver. Then leeched solids with AR until reaction was complete. Removed solids washed and saved. Liquid was lightly boiled until free nitric was no longer present. Then Sodium bisulfate was added until stannic test for gold was negitive. Solids were removed, washed and dried.
Had a quart jar of brown powder that I was sure was gold.
With such and amount I figured it best to us a #10 crucible to melt it all down.
Put all the powder in and brought the furnace up to 1200 deg c. The inside of the crucible was flaking a bit and the powder was still working down so I let it ride.
At 1500 deg I checked it and the inside of the crucible was failing and the powder was completely melted. But not fluid per say - more like thick syrup. In an attempt to salvage something gone astray I pulled the crucible and scraped everything out. It cooled to a solid very hard black matte finish glob with small gold flecks in it.
I took a large chunk of it and heat it with a ox-act tourch on borox and what I ended up with was 2 distinct substances.
1. Lower melting temp matches gold
2. Higher melting temp and thick even melted like borox only thicker They did not alloy together even when both melted

I took all the pieces and melted them down and started to break all the black up to get the gold dots out. While doing this I noticed the black chips stuck to a magnet. And so did my gold dots! I got the idea to wash it in hot nitric again to digest what I was figuring to be Fe3O4. Did that. For days and still if I take a magnet to the stirred bottle I get a black moss on the glass that falls away when the magnet is removed. Also I have what looks like flecks from the crucible which I don't know what to do there.

The nitric wasn't working so I filtered and washed.

Now I'm trying hot Sulfuric as I read that is one process that could be used to remove Fe.

That is the whole process followed. Any help?

 

[butcher]

not sure this would help, but I think if I had that mess I would smelt with lead, then cupel lead buttons. using a good flux to get base metals and junk into slag.

 

[madderoftime]

I can understand why the nitric didn't do much but I am not seeing how the reaction works for the sulfuric.
6H2SO4 + 2Fe3O4 + = 6FeO4S + H2O + O2 ??
FeO4S is a heptahydrate so to make it go to solution it would need 7 H2O so 41 water molacules per reaction?

 

[butcher]

those chemical formulas dont make sense to me, if you are trying to leach a half cooked slag acids may have a hard time with it.

 

[madderoftime]

with Fe3O4 having a melting temperature of 1500+ C I'm not sure it would work. Are you suggesting to alloy the gold with lead just to isolate it? The poblem is there is some iron I would suspect in the gold as well hence making it magnetic.

 

[butcher]

magnetite, hemitite, can be broken down with heat, that is why they roast black sands, they grind fine then roast in air to oxidize, time of heat is important, a flux and smelting will seperate valuble metals from other base metals and lead can act as a collector of valuble metals, a bone ash cupel is used to seperate the valuble metals from the lead.

mining techniques have used smelting to get the gold.even when magnetite has been involved in ore.

also used for assaying.

the other alternative is to finely grind your slag, roast greater than 700 degrees for an hour stirring to expose it to air, then leach with acids.
maybe starting with acids only to attack the base metals then when they are eliminated, then go for the gold.

 

[butcher]

carbon can also help to break the bonds, when burning carbon take's oxygen with it as carbon dioxide gas, or the oxide of the metal convert back to elemental metal. I Ain't that good at explaining this stuff.
hemitite Fe2O3
2Fe2O3 (s) + 3C (s) ---> 4 Fe (s) + 3CO2 (g)

magnetite Fe3O4

these are components found in the bottom of the pan, black sand.

 

[madderoftime]

Looks like the idea is first to wash, dry and roast. This is going to take a while since everything seems to want to stay in suspention. It's been two days and it hasn't settled a bit. Still a brown to mauve color with a layer of iron and the same color solid on the bottom.