Water Cooled Sulfuric Stripping Cell

After joining this forum nine years ago, I'm finally getting around to doing some refining.

I set up a Laser Steve style cell, with a Pyrex dish, but I set the dish into a tank of water to cool it.

I did not use the drain cleaner acid, I used 98% from Duda.

http://www.dudadiesel.com/search.php?query=sulfuric+acid

The first image shows a refrigeration unit with the evaporator in the form of a spiral stainless steel tube, shown sitting on top.
If you set that coil in water it will freeze a block of ice around it

The second image shows an ice chest with the lid removed and the coil placed inside.
The spatula is to stir the water around.

The third image shows the plastic cover in place, with a hole for the Pyrex dish.

The forth image shows the cathode, which is made of 10 gauge copper wire. I glued wooden blocks on to hold the cathode in place, but they are not in this picture.

The fifth image shows the working cell, with the battery charger connected, and the wooden blocks glued in place.
The alligator clip that holds the parts is attached to a piece of 1/4 in copper wire (6mm). The wire slides up and down inside of a rubber hose

The sixth image shows the cathode, with material cemented on to it.
This material was not hard to remove, but it was hard enough that I had to brake it off with a pliers.

This only occurred when the acid was new. Later on, the material didn't cement on like this.

If you ever have this happen, I suggest you clean in off into rinse water,
not into the acid, as it tends to float in the acid and will not settle.

Early on I didn't get much bubbling from the cathode. Later on I got constant bubbling from the cathode, but the cathode did not erode much at all.

The bubbling seemed to result in the formation of some kind of metal/sulfur compound, in the form of a black mud.

I suggest you wash this mud well, then dry it and roast it. Then work it in a mortar and pedestal.
Then wash it again, maybe boil it in distilled water.
Then dry it and roast it again. Repeat the roasting/grinding/washing until you don't get any color to the water.
Get it cleaned up as best as you can before you run nitric on it.

I cleaned out the cell several times and each time the mud was some what different.
The last time it took several washes to stop getting green wash water.
When I over worked the acid at the end, it seemed to be forming a lot of the black mud,
With a lot of bubbling at the cathode. This mud was harder to clean up than first mud I got

Images 7 and 8 show the parts that I ran, about 32 pounds (14.5 kg).
The parts that I ran are described in this old thread from 9 years ago.

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=5023

This is a lot of work for a little cell like this,
and I wouldn't want to do it without some sort of cooling system.

In fact I had difficulty keeping the cell cool even when I had a block of ice in the tank.

If your going to work a little cell this hard, you might consider a stainless steel tank with a full jacket on it. With a hose going in, and a hose going out.

I was only cooling the lower part of the cell, and I measured a big difference in temperature between the top of the cell and the bottom of the cell.
The surface of the cooling water was about a half inch below the surface of the acid.

At times I would have 35 F water in the cooler and the top of the cell would be more then 100 F hotter than the cooling water.

Image 9 shows the cell when I finally quit. The acid was a total mess and the cell would no longer function properly.

It was pulling too much amperage from the battery charger and kicking out the overload breaker on the charger.
And the acid was getting too hot, too quickly.

I left about 2 pounds of the best parts unfinished, because I had no more clean acid.

If I had finished I think my total yield would have been right at three ounces troy, on 34 pounds of material.

Thanks for sharing. That's a neat cell, just enough to do the job and shows it can be done on a shoe-string budget.
I like it!

Göran