Risks involved with inquarting with impure silver.

[Amol Gupta]

My reading and knowledge suggest people use fairly pure(925 sterling) or fine silver(999 fine) to inquart the karat scrap.
Where I belong we get close to 60% fine silver as scrap from melted silver jwellery the rest 40% mainly being copper, I have used the silver scrap for inquarting the gold and have been able to achieve gold purity greater than 99.5% after the leaching process(skipping dissolving in aqua regia) which is good enough in our use case.

The silver jewellery that is melted will surely contained cadmium and some times lead(which I suspect is the main reason people use high purity silver for inquarting).

Where I live refiners use pure silver for inquarting instead of scrap silver and I never understood why, if more experienced refiners could suggest the risks involved with inquarting with impure silver it would be of great help.

Thanks regards.

 

[Yggdrasil]

My reading and knowledge suggest people use fairly pure(925 sterling) or fine silver(999 fine) to inquart the karat scrap.
Where I belong we get close to 60% fine silver as scrap from melted silver jwellery the rest 40% mainly being copper, I have used the silver scrap for inquarting the gold and have been able to achieve gold purity greater than 99.5% after the leaching process(skipping dissolving in aqua regia) which is good enough in our use case.

The silver jewellery that is melted will surely contained cadmium and some times lead(which I suspect is the main reason people use high purity silver for inquarting).

Where I live refiners use pure silver for inquarting instead of scrap silver and I never understood why, if more experienced refiners could suggest the risks involved with inquarting with impure silver it would be of great help.

Thanks regards.

Well you have listed two very good reasons, Cadmium and Lead.
Besides that, using Sterling where the only other is Copper only leads to slightly higher Nitric consumption.
It will as such serve two purposes you will get pure(ish) Gold and Pure Silver.

Do you have any means of testing for Lead and Cadmium?

Tin would also create a mess, if it is there.

 

[Amol Gupta]

Well you have listed two very good reasons, Cadmium and Lead.
Besides that, using Sterling where the only other is Copper only leads to slightly higher Nitric consumption.
It will as such serve two purposes you will get pure(ish) Gold and Pure Silver.

Do you have any means of testing for Lead and Cadmium?

Tin would also create a mess, if it is there.

I'm pretty sure lead and cadmium are soluble in nitric acid and will be leached away, tin is something we have never encountered and is not likely to be present in the scrap metal.

 

[Amol Gupta]

Well you have listed two very good reasons, Cadmium and Lead.
Besides that, using Sterling where the only other is Copper only leads to slightly higher Nitric consumption.
It will as such serve two purposes you will get pure(ish) Gold and Pure Silver.

Do you have any means of testing for Lead and Cadmium?

Tin would also create a mess, if it is there.

I do have an xrf and can test for that, I'm pretty sure cadmium is used extensively, but cadmium has a fairly low boiling point(close to 750°C) which would boil of during the inquarting process.

 

[Amol Gupta]

Another observation with respect to lead, is'nt majority of lead removed as slag(mainly due to cupellation) during the melting of silver.

 

[Yggdrasil]

I do have an xrf and can test for that, I'm pretty sure cadmium is used extensively, but cadmium has a fairly low boiling point(close to 750°C) which would boil of during the inquarting process.

That is true but that commands that you have proper capture and waste systems to ensure it do not get out in the "wild"

 

[Yggdrasil]

Another observation with respect to lead, is'nt majority of lead removed as slag(mainly due to cupellation) during the melting of silver.

Are you cupelling it before inquarting?

 

[Amol Gupta]

Are you cupelling it before inquarting?

No we are not cupelling.
I'm talking here of the time we melt silver jwellery into a silver ingot(before using it for inquartation).
At the time we are melting the silver jwellery we have quite some slag at the top(which I guess has lead in the form of litharge) which is removed before pouring the ingot. I guess quite a lot of lead if any is removed, moreso I feel lead does dissolve in nitric acid which should be removed during the dilute nitric acid boils.

 

[goldshark]

I do have an xrf and can test for that, I'm pretty sure cadmium is used extensively, but cadmium has a fairly low boiling point(close to 750°C) which would boil of during the inquarting proce

I do have an xrf and can test for that, I'm pretty sure cadmium is used extensively, but cadmium has a fairly low boiling point(close to 750°C) which would boil of during the inquarting process.

Boiling and evaporation temperature can be 1000s of degrees apart, requiring a longer time at high temps to rid the Cadmium my evaporation.

 

[Amol Gupta]

Ok I guess I'll try and dissolve some cadmium using nitric acid and see if that helps my case.

 

[grainsofgold]

why not run your silver in nitric and distilled h2o then cement out the Ag with copper wash the AG well and you’ll have higher purity silver. 90 percent or better if done right.

use this to inquartate your gold.

this is what i would do.

the old saying goes , garbage in garbage out.

 

[didit]

why not run your silver in nitric and distilled h2o then cement out the Ag with copper wash the AG well and you’ll have higher purity silver. 90 percent or better if done right.

use this to inquartate your gold.

this is what i would do.

the old saying goes , garbage in garbage out.

Just curious if you are weighing out and adding the silver in cement form to the melted gold for inquartation?

Or...

Are you melting your silver in shot first, and then weighing and adding it in metal form for inquartation?

I have some cement silver I dropped from copper and I haven't melted yet so I was thinking there should be no reason why I can't inquart it straight into the gold melt but of course I could be wrong.

 

[Yggdrasil]

Just curious if you are weighing out and adding the silver in cement form to the melted gold for inquartation?

Or...

Are you melting your silver in shot first, and then weighing and adding it in metal form for inquartation?

I have some cement silver I dropped from copper and I haven't melted yet so I was thinking there should be no reason why I can't inquart it straight into the gold melt but of course I could be wrong.

That should be ok.
As long as it is dry and acid free.

 

[4metals]

The only thing I can for see as a problem would be if the cement silver was well rinsed it must be absolutely dry. If it is damp you will not get the weights for the ratio's correct.

 

[Amol Gupta]

Just curious if you are weighing out and adding the silver in cement form to the melted gold for inquartation?

Or...

Are you melting your silver in shot first, and then weighing and adding it in metal form for inquartation?

I have some cement silver I dropped from copper and I haven't melted yet so I was thinking there should be no reason why I can't inquart it straight into the gold melt but of course I could be wrong.

Sure enough anything that drops from the nitric solution can always go back into the solution the only issue as 4metal mentioned is to make sure it is dry so as to keep the weight ratio intact.

I prefer solid pieces for my melt to ensure all the metal is melted, improper melting which may result in high karat gold will not be leached by the nitric acid.

Always strive for homogeneous melts.

 

[Martijn]

From wiki:
'Like other cadmium compounds, cadmium nitrate is known to be carcinogenic. '
https://en.wikipedia.org/wiki/Cadmium_nitrate
Now all metal salts should be treated with respect, but some need extra caution.
Be carefull, please.
I have not seen an answer to Yggdrasil's waste treatment question.
How will you deal with the cadmium nitrate?

 

[4metals]

Big refiners charge a premium for cadmium in alloy they receive. They melt it with good exhaust, often point exhaust to pick up the cadmium fume right at the furnace, and pass it through a bag house. There are HEPA filters that will pick up 99.97% of all particles down to a fraction of a micron. This effectively will catch the cadmium fume as well as lead and zinc fume. The metal fumes also drop out of the air path as the airflow cools and often are lining the ductwork before it gets to a bag house.