Mini-Retort

[Bonaro]

There is mercury on every speck of gold where I usually dredge. I usually burn it off with acid then precipitate the Hg back out for safe keeping. However, this process discolors the gold and using acid is always risky.
I have a full size retort but it's bulky so I decided to build something smaller that would process up to about 1 oz of amalgam.

 

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[KevinInColorado]

Cool! Did you have to drill a hole in that brass 90? Where does the cooling water exit? What fittings did you find worked best for the amalgam chamber? What will you use for a wet cloth exit tube on the downstream end to drop into the water? Given that the interior will retain some merc after use, will you store it in a container of water or something?

 

[Capt Nemo]

How bad does the mercury stick to the copper and brass?

 

[Laz7777]

How bad does the mercury stick to the copper and brass?

it will. Hg amalgamates with copper, silver and gold. not sure, but it will with other metals as well.
never used a retort, but learned about copper on goldrefiningforum dot com.
some guy there was wondering why he wasn't recovering his merc with the copper tubing he was using.

and what I've learned further down the line: copper plates were used as an amalgam plate in the old days.
the answer is galvanized steel tubing.

 

[bill-costa rica]

black iron pipe would be better, zinc smoke is very bad for ya. ask any welder. galvanized is not the answer

 

[winners58]

from what I've read, stainless steel tubing is best, galvanized gives off zinc oxide when heated
copper forms an oxide layer it may get contaminated but for the most part the mercury
shouldn't stick to it, an amalgam plate has to be cleaned with acid and "charged" mercury immediately applied.
he'll probably have it for a long long time, maybe keep it in a box with disposal instructions after he's gone.
I'd still use it outside in an area away from pets or kids, a small piece of cold wet rag around the end to catch any fumes.
keep us updated on how well it works, I have one claim that I get mercury stain on some of the gold, something small like that is all I would need.

*just as an afterthought what if you heat it all up with some borax to glaze the copper like when they prep a porcelain crucible?

 

[russau]

Bill and winnwers58 are spot on about welding on ANYTHING galvanized ! believe me I know for fact ! If you do weld galvanized metal soon it will feel like theres a BIG FAT elephant standing on your chest and it HURTS to breath!

 

[Laz7777]

I've never retorted the merc I get, just roasted in a small stainless dipping sauce cup.
but my thoughts on it are; why not a triangular pyrex beaker, ceramic stopper and galvanized for the tubing.
no welding required there.

 

[Bonaro]

Sorry for taking so long to get back to my post :-/

I drilled the hole in the 90 with my drill press and just eyeballed the center line. I dont have a outlet for the cooling water. I just fill it with cold water and run it. The batch is so small that you are finished before the cooling water gets too hot to condense the Hg.

Mercury will amalgamate to copper but not actively like it will with gold. You usually have to scrub it onto the copper in the presence of a weak acid and any residue on the Cu will interfere. I coat the insides with candle soot and it seems to work pretty well. I dont really care if some Hg lingers, the bowl seals off one end and a plastic stopper plugs the other when not in use. In reality, elemental (liquid) Hg is not that fearsome, it's toxicity is comparable to lead. A couple taps will knock out any loose droplets and not enough remains to cause much of a problem.

I used a propane connection tube for the condenser and added a 3/8" NPT to Flare fitting with a 3/8" Flare cap for the amalgam bowl. I have a small lathe so I cut down some of the parts to reduce mass and allow it to heat up faster with less fuel.
I can cook off 1/2 oz of amalgam in camp with a citronella candle in about 6-8 minutes.

Here are some pics of the kinds of parts I used, just random stuff I had laying around.

 

[Bonaro]

I've never retorted the merc I get, just roasted in a small stainless dipping sauce cup.
but my thoughts on it are; why not a triangular pyrex beaker, ceramic stopper and galvanized for the tubing.
no welding required there.

uh...Open air roasting is probably the most dangerous way to liberate the gold from the hg. You will contaminate everything downwind. Second most dangerous would be to use glassware as it will likely shatter due to the high heat involved. I would use a potato before either of these.

Your other comment about using all galvanized is also off. Aside from the toxic zinc fumes as others have mentioned, There is another problem. If you put gold in a zinc plated container and over heat it to the point of melting the gold, the zinc will act as the perfect flux and you will end up with a gold plated container with no practical way to unscrew what you just did.

 

[KevinInColorado]

Bonaro this is awesome, thanks!!