Non-Chemical Melting gold filled that has enamel paint,

[CR2008]

How much smoke etc would be given off if I melted down some gold filled items with enamel paint on the surface? I wish to run the pellets/flakes through nitric to remove base metals. Thanks.

 

[Harold_V]

Why would you want to melt the material? That makes no sense, and contributes greatly to problems that are best avoided.

Heat the object(s) in question until they have been freed of any carbonaceous material, then process them directly in dilute nitric. There is no reason to melt them unless you intend to use them for inquartation. You didn't allude to that, so I will assume that's not your goal.

If I've missed something, clue me in. I may have a different response.

Harold

 

[Brandt]

Sounds like your working with gilding gold some of that is is as low as 3K also has a lot of copper in. Brandt

 

[CR2008]

They are stamped 1/10th 10k GF on the back, and have enamel painted on the front... I did some reading from Hoke's book and someone elses material and it was suggested to melt it down, where I would thing the enamel and other such material would be vaporized.... Hoke also suggested using HF acid but I don't want to go that root.

I also have some solid karat gold jewelry, but would not want to add to this gold filled material bec I want to find out the yield in each batch of different gold containing material.

 

[Harold_V]

As I suggested, there is no need to melt. If you do, the gold ends up in tiny particles, even colloidal, which give problems in retrieval. Incinerate the items, then dissolve in dilute nitric. That will eliminate the base metals and return the gold alloy in a form that is much easier to handle. You gain nothing by melting, and a great deal by following my recommendation.

Melt only if you would use the material for inquartation, where the gold percentage is elevated and becomes a collector of the small amount of gold present in gold filled objects.

Trust me on this one.

Harold

 

[qst42know]

Paint is destroyed well below melt temp however many enamels are powdered colored glass fluxed to fuse into the recesses in the metal. As such they won't smoke when incinerated nor will they be removed by melting.

They won't do any harm, sometimes remain whole among the gold foils when the base metals are gone. And remain as a solid when you dissolve your gold, then end up in the filter before you precipitate.

Hydrofluoric acid is an unnecessary hazard and expense you can do without.

Trust Harold, he wouldn't steer you wrong.

 

[CR2008]

Thanks guys, I never knew the gold would be hard to recover if in such low % if I melted these gold filled items.

 

[Harold_V]

Thanks guys, I never knew the gold would be hard to recover if in such low % if I melted these gold filled items.

Once melted, it is so finely divided that you end up with miniscule particles, often, as I've already mentioned, colloidal. They take for ever to settle, and are easily lost with the solution. You're so much better off just processing directly that it's not a contest.

The nice thing about this is the gold surface is relatively thin, and usually not high karat stuff, so it gets well leached in the process. The end product, if you do your work properly, can be excellent quality. Be sure to use a trace of sulfuric after you've dissolved the recovered gold. It's not uncommon for gold filled material to have lead used in the assembly process. It's death on gold quality. Sulfuric will insure it's removal through filtration.

Harold

 

[CR2008]

Thanks guys, I never knew the gold would be hard to recover if in such low % if I melted these gold filled items.

Once melted, it is so finely divided that you end up with miniscule particles, often, as I've already mentioned, colloidal. They take for ever to settle, and are easily lost with the solution. You're so much better off just processing directly that it's not a contest.

The nice thing about this is the gold surface is relatively thin, and usually not high karat stuff, so it gets well leached in the process. The end product, if you do your work properly, can be excellent quality. Be sure to use a trace of sulfuric after you've dissolved the recovered gold. It's not uncommon for gold filled material to have lead used in the assembly process. It's death on gold quality. Sulfuric will insure it's removal through filtration.

Harold

Thanks, Hoke had a chapter on dealing with lead and tin, and I am trying to read as much as possible from that book as well as some patents. I just got my 22L reaction flask (lady sent me a BIGGER flask for CHEAP, it was a surplus lab item from ebay), looks like straight up over kill but it gives me options in the future to do larger batches in the future when I get acquainted with the process. Trying to get things together to have something set up like the Afftech gold refiner, exept it will be manually controlled. Doing research on gas scrubbers now.

 

[Palladium]

Trying to get things together to have something set up like the Afftech gold refiner, exept it will be manually controlled. Doing research on gas scrubbers now.

:mrgreen:

This is a single-pass six stage absorption system that operates entirely under a vacuum (negative pressure), through the contact of chlorinated air and a neutralization solution, the concentration of exhausted air can be reduced to 1ppm. Two moles of sodium hydroxide (80 pounds) is required to neutralize each mole of chlorine (70.9 pounds). The amount required to neutralize the 1 pound of Cl2 is obtained by the below formula;

NaOH = 80.0 / 70.9 = 1.13 times to Cl2

The 20% by weight of sodium hydroxide is usually used to neutralize the chlorine gas. Each gallon of 20% solution contains 2.04 lbs of NaOH.

Neutralization of chlorine with sodium hydroxide is an exothermic reaction. The heat of reaction is 44,600 Btu/mole of chlorine. Reaction is in liquid phase. If there is no heat loss to the air and other components of neutralization system, the temperature rise of sodium hydroxide solution can be calculated from the following equation:

H = mCpDT

Where,
H = total heat released by reaction, BTU
m = total weight of caustic solution, lb
Cp =heat capacity of causitic solution, BTU/lb
DT = temperature rise, oF
Heat capacity for 20% by weight caustic solution is 0.9 Btu/lb. One (1) gallon of 20% NaOH is equal to 10.21 lbs.