Alloy Gold Down

[Anonymous]

Is anyone familiar with using copper to alloy the Gold down prior to the chemical refining process. The procedures I have come across with (haven't attempted at this writing) is to use a certain % of copper, based on karat and weight of scrap, i.e., 14k -use 30% of the item(s) weight.

 

[qst42know]

Copper can be used this way but silver is more economical. It takes less acid to dissolve the same weight of silver. Silver can be recovered and possibly reused many times if there are no PGM's present, and refined if there are. Any copper used to dilute gold is lost.

 

[Oz]

Dano,

You are referring to inquartation. Using the refining of karat gold as an example most karat gold is pure enough that using nitric to dissolve the impurities is less than effective because copper and silver can be “hidden” within the thick matrix of gold not allowing the nitric to reach it. With inquartation you are spreading the gold to a lower concentration in the matrix with the addition of another element that is susceptible to nitric. This will leave you with finely divided gold that is reasonably free of the common elements used in gold alloys. The gold being in a finely divided state also allows it to go into solution easier than if it was in massive form.

Something to consider is that it requires roughly 3 times as much nitric to dissolve copper than it does the same amount of silver. Using silver to inquart (alloy) your gold saves on nitric consumption. Although the use of silver seems more expensive than copper it is not due to the extra required nitric. The better use of your copper is to use it to recover your silver from your nitric used for digestion in inquartation by cementing the silver out of the nitric as elemental silver. You can the reuse the silver after washing for your next inquartation. In rough terms copper will also displace 3 times its own mass in silver from your nitric.

Lastly to prepare gold for inquartation you want to have an alloy that is between 25-30% gold. Experience will tell you what works for you but the lower your starting gold content the finer your gold residue will be but you will have greater dissolution of impurities. Many shoot for a compromise by targeting a range of purity that leaves them with a porous sponge of gold so they do not need to deal with the fine gold powder.

 

[Oz]

qst is correct that the silver can be re-used many times. PGM accumulation poses little problem unless you are processing white gold. Your silver will collect palladium and some of your platinum from white gold alloys. Your gold will be “contaminated” with platinum and rhodium in your white golds. If you process mainly yellow gold it will be sometime before platinum group accumulation becomes problematic.

 

[61 silverman]

Hi all ,
A Question about the nitric solution that was used to remove the silver from the inquarting process.. does there need to be a little bit of active nitric ( unused ) available in solution, for a exchange,??


As I write this I remember reading that if any NOX fumes are produced when the copper is introduced, No silver will be released until no more fumes, Hensce NO FREE NITRIC...


If I have answered my own question would somebody confirm for me ..
Thank You...
Mark

 

[Harold_V]

My experience indicates that you should have a trace of nitric, but an excess will simply result in digestion of your copper. Until equilibrium is achieved, silver cements on the copper, only to be re-dissolved by the excess acid. Finally, when the acid level is low enough, that comes to an end. When you have a respectable balance, I don't recall seeing any fumes coming off from the cementation process. If they do, you definitely have too much nitric.

Harold

 

[Oz]

The only thing I would add to Harold’s comments is that the solubility of copper and silver in nitric changes with temperature. When inquarting I keep the solution heated to speed the reaction. Sometimes after filtering or decanting hot, silver nitrate crystals will grow upon cooling. I am guessing that copper nitrate crystals would as well (after the silver nitrate crystals) if the copper concentration was high enough (but this is speculation). Dilution with water is necessary to dissolve these before cementation if you wish to avoid a mixed precipitate. If you find it happens accidentally the cemented elemental silver can be washed free of the silver nitrate with water. Save the wash obviously.

 

[Harold_V]

The only thing I would add to Harold’s comments is that the solubility of copper and silver in nitric changes with temperature. When inquarting I keep the solution heated to speed the reaction. Sometimes after filtering or decanting hot, silver nitrate crystals will grow upon cooling. I am guessing that copper nitrate crystals would as well (after the silver nitrate crystals) if the copper concentration was high enough (but this is speculation). Dilution with water is necessary to dissolve these before cementation if you wish to avoid a mixed precipitate. If you find it happens accidentally the cemented elemental silver can be washed free of the silver nitrate with water. Save the wash obviously.

The comment about silver nitrate crystals growing is fact, and happens readily. My silver cell demanded 30 troy ounces of silver in roughly 2½ gallons of solution. I dissolved my silver in a liter of nitric, along with a liter of distilled water, heated. I actually boiled the electrolyte towards the end, to eliminate all traces of nitric. Proper pH was established after building the proper volume of electrolyte in the cell, using Hydrion papers, and dribbling a few drops of nitric into the cell.

The excess silver crystal (crystal that had been harvested was used in making the next batch of electrolyte) that may remain undissolved was simply poured to the cell, to be included with the next harvest.

Note-----by using the previous harvest for making new electrolyte, you can roughly determine its purity by the presence, or absence, of color. Boiling the solution at the end eliminates any traces of NO2, which tends to shift the color of the solution.

On the rare occasion where I'd permit the solution to cool, it formed a solid mass of silver nitrate crystals. It happened so fast you could watch them grow. In order to prevent the formation, the solution required dilution, which I accomplished by adding more distilled water. That was generally after pouring the concentrated silver nitrate to the cell. I avoided making the solution prior to need to avoid the formation of the crystals. They are easily digested by heating and the addition of more water.

Harold

 

[Oz]

A more precise answer to what Harold and I have talked about in regards to silver nitrate in solution forming a silver nitrate crystal at a certain amount of grams per liter at different temperatures may be better addressed by someone with a chemistry background like Lou. I do not envy him if he takes on the task as I know by empirical evidence, but it is entirely different to try to put this to words on a page. I would be interested in his opinion of my speculation that if silver and copper are in a nitric solution at say 200 degrees F in high concentration, with copper being the higher concentration, that as the solution cooled that silver would form as a nitrate crystal before copper would be able to as the solution cooled and solubility decreased.

I have never had the occasion that I had a nitric solution higher in copper than silver other than with cementations done at room temperature.

 

[61 silverman]

Thank You Gentelmen,, That is a bit of information,, Very much appreciated , My appologies to NOXX , as I mis- spelled in my earlier post, NO OFFENCE MEANT..
Here is a picture of a silver pour , On top of the furnace is 100oz. ingots the total weight normally poured would be around 1400 oz..Troy

 

[61 silverman]

The ingots are positioned around the lids feed hole of the furnace as a pre-heat and ellimination of any possible moisture...

 

[Junkman Jim]

I need an expert,
I desolved a fairly large quantity of gold plated pins in nitric acid. Some of them had stainless steel sleeves around them, others had wires soldered on them protected by heat shrink tubing. The nitric process didn't completely disolve the solder and base metal under the heat shrink. I decided to heat the gold flakes to get rid of the heat shrink so I could better deal with the undesolved base metal and solder. I heated the mix in a pan, it appearently got too hot, the plastic went up in smoke and every thing else melted at a fairly low temperature.
So now I have this mystery alloy (about 6 Troy ounces) which is impervious to AR. I heated it to a very high temperature and drove off some of the tin and lead, still won't desolve in boiling AR. I inquarted my mystery metal with silver, still impervious to boiling AR. Should I try just nitric then desolve the sludge in AR? Does anyone need a new super metal that's very corrosive resistant?
Help would be greatly appreciated,
Thanks,
Junkman Jim

 

[lazersteve]

Jim,

An alloy of greater than 25% silver will not dissolve properly in AR, instead a purple-gray colored coating of silver chloride will form. The Silver chloride coating (if it is such) can be dealt with either by treating the alloy with hot ammonium hydroxide, or heating in a melting dish with soda ash.

If you decide to try and break through the silver chloride layer using ammonium hydroxide your alloy will still be intact, except the layer of AgCl will be removed.

If you proceed using soda ash be sure you do not breath the fumes as they are very unhealthy. The silver chloride will convert back into elemental silver and combine with the remainder of the alloy.

After one of the two above processes you should attack the alloy with dilute nitric acid. This should leave the gold behind and dissolve the silver you used in inquarting. Always remember that high silver alloys will not dissolve in AR, they will only form a coating of silver chloride.

Steve

 

[Junkman Jim]

Thank you Steve,
Junkman Jim