First gold bar!

[Acidrain]

I tried hard to get a good clip of the gold dropping but this is best I could do. Very visual, I just love watching this part! Copper plate goes in the beaker and I slowly add sulfamic acid until red fumes turn clear/white. I keep stirring the solution which now turns deep bright green and I keep stirring and adding small additions of sulfamic acid until suddenly, the solution turns muddy brown. Immediately at that point, you see gold start falling out and the solution changes to deep brown. At this point the stannous test comes back negative. YOU MUST LEAVE HEAD ROOM IN YOUR BEAKER OR YOU WILL ERUPT OUT THE TOP! Sometimes it gets quite rowdy while doing this. This process is definitely not for someone without experience. It's fast efficient recovery but you really have to be safely minded.

 

[Acidrain]

Here's the recovered gold from that batch of 320g deutsch connectors

 

[Alondro]

THIS is peak forum keep up the good work. Notes taken.

I have some similarly sized pile of total random mix of pins that sat there for a long time... I will probably give it a shot with nitrate rather than nitric As now I am not that confined by profit margins and PM price fluctuations vs. processing time, I enjoy occasional refining much much more than before

I'll probably use poor man's nitric for gold purification at the 2nd pass. I used to use that long ago for tiny batches of karat gold purification and it worked very well. My first round of purifications will use HCl-bleach for foils, because it's so cheap and easy to degas the chlorine, and smelting for chips to recover ALL the PMs in them

Chemical methods tend to lose a large portion of the silver in the ash goo, unless you use nitric first... and nitric is too costly for such a process that wastes a lot of it dissolving base metals as well as the metastannic acid production from all those tin solder dots and tin-plated brass leg bits.

Getting my furnace ready for my first test smelts next week. Going to be smelting some impure copper and yellow brass pieces first, to make sure I can hit and sustain the desired temps, and practice pouring.

 

[Martijn]

Going to be smelting some impure copper and yellow brass pieces first, to make sure I can hit and sustain the desired temps, and practice pouring.

Beware zinc boils and evaporates above 907 C so keeping brass in longer has a good chance of zinc fumes being created.

 

[orvi]

I'll probably use poor man's nitric for gold purification at the 2nd pass. I used to use that long ago for tiny batches of karat gold purification and it worked very well. My first round of purifications will use HCl-bleach for foils, because it's so cheap and easy to degas the chlorine, and smelting for chips to recover ALL the PMs in them

Chemical methods tend to lose a large portion of the silver in the ash goo, unless you use nitric first... and nitric is too costly for such a process that wastes a lot of it dissolving base metals as well as the metastannic acid production from all those tin solder dots and tin-plated brass leg bits.

Getting my furnace ready for my first test smelts next week. Going to be smelting some impure copper and yellow brass pieces first, to make sure I can hit and sustain the desired temps, and practice pouring

There is little to no difference in the outcome if you use nitrate (Na, K) or straight nitric. Obviously, you will be working in more diluted solution since the extra HCl, which only come 30-37% (in comparison to nitric, which is 50-70%). Overall, the result of generally used refining methods (dissolve-denox-drop) will be the same.
More salts in the waste tho. Depend on how you process waste, but your waste disposal bill can hugely increase if you just pass the evaporated "slush" to the waste collector. If not, nothing major changes.

Brass isn´t the best metal for practice, and also it will burn in normal furnance, emitting zinc oxide fumes. Be prepared for that. I would rather practice with just pure copper or better - silver. Lower mp, not oxidizing upon melting...

 

[orvi]

Beware zinc boils and evaporates above 907 C so keeping brass in longer has a good chance of zinc fumes being created.

Boiling is one thing, having appreciable vapor pressure is the other
If there is moving gas/air around sufficiently hot molten zinc alloy, fumes will be generated since moving gas drag the evaporated-equilibrated mixture of vaporized oxide and that gas. Molten zinc fume even from 500 °C for example.

I just wanted to clarify that. If you are aware, just ignore it

 

[Alondro]

Beware zinc boils and evaporates above 907 C so keeping brass in longer has a good chance of zinc fumes being created.

This will mostly be aluminum brass since it's from electronics. Zinc content should be very low in this material. It'll end up making a dirty brass bar. Basically it's to reduce the volume of all the thousands of little pieces of mixed brass-copper e-scrap that are too hard to classify for scrap selling. I might try to refine the bar later with electrolysis if I can pick up a cheap adjustable power supply suitable for the purpose.

 

[Crudmudgeon]

https://www.amazon.com/（Precision-0...cphy=9005199&hvtargid=pla-2281435179578&psc=1

I've refined over 200oz of silver with one of these and plan to use another for a copper cell this summer.
Seems to do the job pretty well for $40.

 

[Alondro]

https://www.amazon.com/（Precision-00-01V，00-01A）4-Digital-Precision-Adjustable-Regulated/dp/B07M9N73YQ/ref=asc_df_B07M9N73YQ?mcid=453183856a0a3643b648328ff630ead7&hvocijid=17724564415030105945-B07M9N73YQ-&hvexpln=73&tag=hyprod-20&linkCode=df0&hvadid=730432682330&hvpos=&hvnetw=g&hvrand=17724564415030105945&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9005199&hvtargid=pla-2281435179578&psc=1

I've refined over 200oz of silver with one of these and plan to use another for a copper cell this summer.
Seems to do the job pretty well for $40.

Neat, that looks like it should do the job. I just need to work out voltages and current settings required for electrolysis of copper in a modestly acidic sulfate cell, say pH between 2 and 3. It'll be copper sulfate solution, likely around a gallon in volume, with just a few mls of sulfuric to acidify it. I'll probably use a long thick copper wire or flat strip as a cathode.

 

[Crudmudgeon]

Neat, that looks like it should do the job. I just need to work out voltages and current settings required for electrolysis of copper in a modestly acidic sulfate cell, say pH between 2 and 3. It'll be copper sulfate solution, likely around a gallon in volume, with just a few mls of sulfuric to acidify it. I'll probably use a long thick copper wire or flat strip as a cathode.

Jason at MLBB set one up in a cut off 5gal pail. He put copper mesh around the inside as cathode material and hung copper with PMs in the center. It works same as the stainless bowl silver nitrate cells (mine works awesome). I can't wait to have a bag full of PM mud... not sure why cupellation doesn't work in my furnace with the lid open, but it doesn't. Probably doesn't maintain quite enough heat.

 

[Alondro]

Jason at MLBB set one up in a cut off 5gal pail. He put copper mesh around the inside as cathode material and hung copper with PMs in the center. It works same as the stainless bowl silver nitrate cells (mine works awesome). I can't wait to have a bag full of PM mud... not sure why cupellation doesn't work in my furnace with the lid open, but it doesn't. Probably doesn't maintain quite enough heat.

Cupellation needs 2 things to work: consistent temps AND a steady supply of oxygen. If you have combustion-based furnace, getting enough air to the molten dore is not easy. I'm planning to have a ceramic tube extending to the cupel and blowing a thin stream of air directly onto the molten surface. I got the tubes out of an old hot plate where the heating coil passed through them. They appear to be able to withstand at least 1200C. I'll see how that works for a test batch of a small amount of silver-plated e-scrap in the spring.

And if you have large volumes of material or LARGE dores, cupellation simply isn't efficient or practical. It's good for testing to see what you have in your material, or if you only have a small lead or bismuth dore (cupels can only absorb so much) but for big batches, electrolysis of a copper-based dore is by far the easiest method for extracting the PMs.

You can use a method of cupellation using Portland cement and another additive (I think bone meal ground to a fine powder and mixed in, but I don't know the proportion), to make a pile with a pit pressed into the center, but that can be very tricky to get right and I don't know if it would work well in the typical furnaces hobbyists use. Might need to research the historical methods of cupelling to see how it was done long ago, since they got it to work very well with simple equipment.