Washing cement silver using a centrifuge.

[Amol Gupta]

So here is a video showing the silver refining process pretty standard untill he starts washing the cement silver.

The process looks very unorthodox but seems pretty effective given the volume of he is dealing with.

From what I can understand he is squeezing the cement silver to remove the copper nitrate before he goes onto melting the silver.

I like the principle and I was wondering if the squeezing part can be done using a centrifuge...?

Washing the cement silver is a pain in the butt for everyone involved here.

I'd like the opinion of fellow refiners here, I think it's pretty do'able but id like opinions on how the improve the process or do it more efficiently.

Thanks regards.

 

[Shark]

I have allowed it to drain and used a salad spinner to finish off the drying process. I would think a centrifuge would work even better. I placed mine in a large filter and turned by hand as fast as I could. It felt completely dry in about 10 minutes.

 

[Amol Gupta]

I have allowed it to drain and used a salad spinner to finish off the drying process. I would think a centrifuge would work even better. I placed mine in a large filter and turned by hand as fast as I could. It felt completely dry in about 10 minutes.

Any idea with respect the copper nitrate content before and after the spin and XRF maybe...?

 

[Shark]

Any idea with respect the copper nitrate content before and after the spin and XRF maybe...?

No, I washed it fairly decent, no color was left in the wash. Then spun it dry and melted for use in a silver cell.

 

[4metals]

The difference in purity from needles refined in a silver cell is considerable, often going from .995 if melted after air drying to .999+ when spin dried. But those are needles or crystals from the cell. The removal of any remaining copper nitrate after rinsing is critical if you want high purity.

The down side with a centrifuge is you need to bag the basket or very fine crystals will spin out and into the centrifuge.

For silver refining the centrifuge needs to be made of stainless steel because plain steel centrifuges are destroyed in short order by the copper nitrate, testament to the fact that there is enough copper nitrate remaining on rinsed silver to. make a difference.

 

[4metals]

There are many things done in that video that were eye popping and I'm not talking about personal protective equipment as that is obvious.

Like, why make those silver "snowballs" to dry when the cement can be melted directly? Maybe that worker just likes to go through life with black stained hands!

 

[nickvc]

I think this was the guy using concentrated sulphuric and nitric to strip silver plate , absolutely horrifying to watch!

 

[Amol Gupta]

There are many things done in that video that were eye popping and I'm not talking about personal protective equipment as that is obvious.

Like, why make those silver "snowballs" to dry when the cement can be melted directly? Maybe that worker just likes to go through life with black stained hands!

He is squeezing the cement silver and creating "snowballs" to remove any aquos copper nitrate instead of washing the copper nitrate from the cement silver he is squeezing it out with his bare hands(unfortunately).

 

[Amol Gupta]

The difference in purity from needles refined in a silver cell is considerable, often going from .995 if melted after air drying to .999+ when spin dried. But those are needles or crystals from the cell. The removal of any remaining copper nitrate after rinsing is critical if you want high purity.

The down side with a centrifuge is you need to bag the basket or very fine crystals will spin out and into the centrifuge.

For silver refining the centrifuge needs to be made of stainless steel because plain steel centrifuges are destroyed in short order by the copper nitrate, testament to the fact that there is enough copper nitrate remaining on rinsed silver to. make a difference.

Alluminium should work instead of steel as well.

 

[4metals]

He is squeezing the cement silver and creating "snowballs" to remove any aquos copper nitrate instead of washing the copper nitrate from the cement silver he is squeezing it out with his bare hands(unfortunately).

Plastic buchner funnels would do the job. A vacuum would make it better.

What was throwing that hot crucible into a quench tank all about?

Alluminium should work instead of steel as well.

I don't know that I've ever seen an aluminum spin drier.

 

[Amol Gupta]

Plastic buchner funnels would do the job. A vacuum would make it better.

What was throwing that hot crucible into a quench tank all about?

I don't know that I've ever seen an aluminum spin drier.

So there are cases where the 'graphite' crucible being used for melting is substandard(not actually graphite) and the molten metal sticks to the crucible, some sort of thermal shock to remove all the metal stuck to the crucible.

 

[4metals]

So there are cases where the 'graphite' crucible being used for melting is substandard(not actually graphite) and the molten metal sticks to the crucible, some sort of thermal shock to remove all the metal stuck to the crucible.

Some would defer to a ball mill and sifter, less drama. To each his own!

 

[Amol Gupta]

The difference in purity from needles refined in a silver cell is considerable, often going from .995 if melted after air drying to .999+ when spin dried. But those are needles or crystals from the cell. The removal of any remaining copper nitrate after rinsing is critical if you want high purity.

The down side with a centrifuge is you need to bag the basket or very fine crystals will spin out and into the centrifuge.

For silver refining the centrifuge needs to be made of stainless steel because plain steel centrifuges are destroyed in short order by the copper nitrate, testament to the fact that there is enough copper nitrate remaining on rinsed silver to. make a difference.

Your thoughts on using the centrifuge to clean the cement silver instead of the silver needles coming out of the silver cell(while using a bag offcourse).

 

[Shark]

Service life would be longer using stainless steel. And less accident prone I think. For my scale the salad spinner worked pretty well. If I went any bigger, I would need better. Maybe build one from an old enameled dryer tub?

 

[4metals]

Your thoughts on using the centrifuge to clean the cement silver instead of the silver needles coming out of the silver cell(while using a bag offcourse).

Cement Silver is rarely pure enough for resale, as I doubt the Silver in the video is either. I always rinsed, dried and melted the cement Silver into anodes for a Silver cell.

I would think the nature of the cement Silver would tend to either not dry completely or to clog the bag. Because silver crystal from a cell rinses and drains quickly it dries in the spin drier quickly as the liquid is easily expelled. Something like the cement Silver may not shed it's retained copper nitrate so quickly and as a result dry with the copper mixed in. Which defeats the purpose.

 

[Amol Gupta]

Cement Silver is rarely pure enough for resale, as I doubt the Silver in the video is either. I always rinsed, dried and melted the cement Silver into anodes for a Silver cell.

I would think the nature of the cement Silver would tend to either not dry completely or to clog the bag. Because silver crystal from a cell rinses and drains quickly it dries in the spin drier quickly as the liquid is easily expelled. Something like the cement Silver may not shed it's retained copper nitrate so quickly and as a result dry with the copper mixed in. Which defeats the purpose.

Introducing water into the system is trivial, I'll give it a try sometime I guess.

 

[Amol Gupta]

While we're at at what about washing in an ulta sonic cleaner...?

 

[Amol Gupta]

Doesn't seem like a bad idea

 

[4metals]

While we're at at what about washing in an ulta sonic cleaner...?

I guess this video and you are somehow connected? And I'm guessing you are bent on cleaning up cement Silver to high purity. Yes an ultrasonic will help because it will aid in the rinse waters penetrating the particles and flushing out the copper nitrate.

 

[Amol Gupta]

I guess this video and you are somehow connected? And I'm guessing you are bent on cleaning up cement Silver to high purity. Yes an ultrasonic will help because it will aid in the rinse waters penetrating the particles and flushing out the copper nitrate.

Not necessarily connected, I'm from India and the guy in the video is from a neighbouring country Nepal(If that is some sort of relation).

I did hit him up through social media we had a brief conversation, he told me HCl is banned in his country so the best they can do to refine gold was through inquartation and acid leaching.
I was sceptical as to how do they remove lead from the gold without using aqua regia. Never got to know how that's even possible.

And yes in my part of the world if we get silver purity close to 98.5 or 99% that is good enough for most cases.