Silver Chloride Conversion With Lye and Sugar - VIDEO

Here's a video showing how I convert silver chloride with lye and sugar to pure silver metal

https://youtu.be/mqYVOT-WybE

Thanks!
kadriver

Here is another method I find gives 99.9% Ag without the cell.

Take freshly precipitated silver chloride known to be free of lead (sulfuric acid addition to generating liquor) that has been leached with dilute aqua regia to remove base metals and filtered. In the same filtering funnel, wash it with a 10% solution of sodium hydroxide sufficient to make it into Ag2O and then a saturated solution of sodium (and potassium carbonate, 1:1 if possible) carbonate in the funnel. Put that into a large stainless pan and hold at 400 C for 2 hours. Now leach this solution in water and filter the silver powder until its filtrate's TDS is 300 ppm or less or it is pH neutral. Most of these solutions can be reused for various purposes, over and over again.

The silver may be then be used for powdered metal clay, or else melted easily to pure metal. For extra cleanliness of the melted silver, you may rinse the silver powder with a 5 g/L solution of sodium nitrate and borax each.

Now this, Lou, is something i could use at school! What exactly is the purpose of K2CO3 and Na2CO3?

The last step with NaNO3 and borax sounds quite ingenious, how much impact might it have on the purity in your opinion - would it add an extra 9?

Lou,

How will you know when the total dissolved solids in the rinse water are 300 ppm or less? For the alternative, what pH range do you consider neutral?

We use cheap TDS meters we buy on eBay a couple at a time. They seem to work well enough--our tap water is 650 ppm TDS, our RO is 30-40 ppm, and our DI water is flatline at 0 on 4 meters. They're about $10 / ea and I like using them to tell when electrolytes are rinsed out of a filter cake.

Regarding the rinsing of the silver powder, I use fresh hot (near boiling DI water). I consider it done when the pH is 6.5-7.5 on the Colorfast strip. I don't like pH meters much unless they're dedicated to one task. I often find that slurrying the silver powder with water is the thing to do after a first decant of the brine, then finish it off on the funnel. It settles quite rapidly.

The objective is to get the NaCl out before melting, as NaCl makes quite a bit of fume and possible silver chloride if left in the silver powder.

kadriver,

Did you ever take a sample of the powder after rinsing and just melt it as is for testing? I get 4 9's from the chloride method alone. You may find that the cell is just an extra step.

goldenchild said:

kadriver,

Did you ever take a sample of the powder after rinsing and just melt it as is for testing? I get 4 9's from the chloride method alone. You may find that the cell is just an extra step.

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I'm still rinsing the NaOH out of that silver two days later. I rinse with about a gallon of hot tap water and let it settle. Then I siphon off to another 5 gal bucket and rinse the silver powder again. I repeat until I get between 6 and 7 pH. My tap water is slightly acidic. But I learned early on to get all the NaOH out before I go any further.

I once rushed the process and did not rinse all the lye out. When I put it in a Corning ware dish to dry the lye etched the bottom of the dish. Plus it was a nightmare to melt the powdered silver. Like Lou said, it looked like it had some powdered silver chloride in the melt dish.

Multiple rinses to pH 6-7 of the rinese water completely eliminates all these problems. The silver is a dream to melt after it is properly rinsed.

Mario, I'll still run it through the cell just to get the crystal. I have some folks who pay 140% of spot for the crystal so it is worth the extra step to convert the powder to shot and then to pure silver crystal in the silver cell.

Lou, thanks for the instruction sheet on getting the silver powder to three nines. How in the world does sodium nitrate and borax clean the silver powder?

kadriver

Lou said:

Here is another method I find gives 99.9% Ag without the cell.

Take freshly precipitated silver chloride known to be free of lead (sulfuric acid addition to generating liquor)

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Lou, I've never seen this before. To remove lead from my freshly digested 925/sterling silver all I have to do is add some sulfuric acid to the blue silver nitrate solution to precipitate any lead as lead sulfate. Then it can be filtered out as I filter the solids out of my silver nitrate BEFORE I convert to silver chloride with HCl.

Nice to know!

kadriver

Yes. You can use any soluble sulfate to remove lead. You need not add much or you'll end up with mostly silver sulfate contaminated with lead sulfate. Done right, just cupel it for silver trace. That silver chloride should be digested with dilute Aqua regia before or after the sulfate treatment. The acidic dilute HCl was of the chloride helps keep it from peptizing. After that it can be made into silver powder via the Kundu carbonate method. In no instance should it be directly melted with excess NaCl. Using K carbonate helps make a low melting eutectic for better performance.

The nitre/borax rinse homogeneously coats the silver metal and as it melts the nitre oxidizes and base metals (and Pd) get dissolved in the borax. The end product of nitre is NOx and sodium oxide (doesn't hurt the silver).

This rinse solution can be used over and over til it's gone.

Lou said:

Yes. You can use any soluble sulfate to remove lead. You need not add much or you'll end up with mostly silver sulfate contaminated with lead sulfate. Done right, just cupel it for silver trace. That silver chloride should be digested with dilute Aqua regia before or after the sulfate treatment. The acidic dilute HCl was of the chloride helps keep it from peptizing. After that it can be made into silver powder via the Kundu carbonate method. In no instance should it be directly melted with excess NaCl. Using K carbonate helps make a low melting eutectic for better performance.

The nitre/borax rinse homogeneously coats the silver metal and as it melts the nitre oxidizes and base metals (and Pd) get dissolved in the borax. The end product of nitre is NOx and sodium oxide (doesn't hurt the silver).

This rinse solution can be used over and over til it's gone.

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Man, this is great to know, thanks Lou.

kadriver

Great video Kadriver-

You've explained a process perfectly that I could never quite get my head around before. My thanks.

Jon

Lou:

The nitre/borax rinse homogeneously coats the silver metal and as it melts the nitre oxidizes and base metals (and Pd) get dissolved in the borax.

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Ingenious! Same dirty powder from H2O cell. On the right melted with borax. On the left powders soaked with nitre/borax and washed 2 times with each 1:1 of tap water.

So only this step alone has a high impact.

btw...learned something new: first time sputtering silver when I poured into a cold and maybe wet graphite mold - not lost much and learned a lot

Yep. That was a pro trick. Glad to see it work for you
So far as I know, I never saw anyone else doing the flux rinse procedure. I doubt it novel but it definitely makes an improvement.


I tried to do everything I could do get the Cu/Sn/Pb out of the stuff before going to the cells. At one time I had 6 X 40 gallon Thums and 2 X 85 gallon Moebius cells. At that level (~30-40K oz/week), keeping a mass balance and preventing impurity is done with spreadsheet, auto titrator, and flame AA.

Lou said:

Yep. That was a pro trick. Glad to see it work for you

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Lou, I think I can speak for everyone in thanking you for every one of those pro tricks you've shared with us! I know you have to walk a line between sharing with us, and giving away too much proprietary information. 8)

Dave

Right said! Thank you so much, Lou!

Only to share one of many things, you and the other pro's made possible for me, the ring I worked today (Ag999, worked out of a button without drilling, 39g - it is not finished, I think I will etch some celtic symbols into it (like a triskele - which ist the sign of my village and my school) and fill up with finegold).

Nice!

Hmmmm - somehow I missed this one till just now

Lou - "awesome" info - thanks for posting :!:

Bjorn - I really like your rings 8) 8)

kadriver - you posted

I'm still rinsing the NaOH out of that silver two days later. I rinse with about a gallon of hot tap water and let it settle. Then I siphon off to another 5 gal bucket and rinse the silver powder again. I repeat until I get between 6 and 7 pH. My tap water is slightly acidic. But I learned early on to get all the NaOH out before I go any further.

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Two days washing NaOH (& sugar) out :shock:

From what I can see part of the problem is that you are siphoning off your solution - but - you are also leaving a "fair" amount of solution behind - so although with each wash you are diluting the chem - each wash is also starting with a fair amount of chem left in the remaining solution that was not siphoned off

The more chem/solution you can remove between washes - the fewer washes you will have to do - & as well the less wash waste you will create --- the more chem you get rid of with each decant - the more dilute your next wash will be - the less washes you need to do

Here is a simple trick I use & it should reduce your wash time down to a few hours (instead of a couple days) & as well reduce the amount of wash waste you create

For smaller jobs I use a 2 gallon Kmart cookie jar - & for larger jobs I use a 5 gallon bucket --- part of the trick is the lip on the cookie jar - which needs to be re-created on the bucket --- the lip allows you to do your decant with a pour instead of by siphoning as the lip helps hold back the silver when making the pour --- you may have "some" silver go over the edge but it should be "insignificant" & will be recovered from you decant waste bucket after settling

The other part of the trick is to tilt your jar or bucket & get all you silver settled over to one side in the bottom as seen in the pic of the cookie jar (not currently working on any silver so I used some small pieces of SS I had for demonstration) then make your pour - most of the silver will stay in the bottom corner but some will wash/slide forward but be held back by the lip - make your pour to decant as much solution as possible with out washing silver (or at least very little) over the edge of the lip

then tilt your jar/bucket back & smack the bottom edge/corner under the side the silver is on three or four time - this well cause the silver to settle &/or compact in that corner & thereby bring more of the solution up out of the silver to the surface - which can then be poured off again --- do this 2 or 3 times (until your not getting enough solution to come to the surface to make the pour worth the effort)

Then add your next round of wash water & repeat the above decant process

I use this same technique as a pre-washing method to reduce the ash from incinerated IC chips before I run the ash over my concentrator table - I am able the reduce my ash (in short order) that needs to go over the concentrator table by about 2/3 by using the bucket "with the lip" washing technique --- you should be able to wash the amount of silver I see in your bucket in the video in about 3 - 4 hours

What ever "little" bit of silver makes it over the lip during your decanting (& settles in the bottom of your decant waste bucket) can then be washed into your Buchner funnel vacuum filter set up & filter/washed there

Make our pour slow (especially on the first one) so your silver doesn't "flop" forward out the bottom & out the bucket/jar

Edit to add; - now you can do another video on "Washing Technique" :mrgreen:

Kurt

For me to see two phenomenons are of great importance:

If the silver chloride is precipitated by pouring the AgNO3 into NaCl solution (probably the same with HCl), the AgCl is coagulating much better, it fact without producing clouds, but making a thick heavy white mass instead (thanks Lou, I learned this from your post and tried it today at school). Well coagulated AgCl settles fastly, even after beeing stirred.

To remove NaOH or any other soluble component just look at it's math: if you start with 1L NaOH solution, letting settle, removing only 9/10 of the clear liquid and filling up with boiling water to 1L, then stirring - and if you do this 10 times, then only 0,0001ml is left from the 1L in the beginning. If you started with 10% NaOH, you are left with 0,00001g NaOH or 0,01mg, probably less then in any tap water over pH7. My conclusion is, many washes with a little water are more effective, than few washes with much water. Also it is not necessary to get the last drops out of the powders and is only a waste of time.