# Playing with sugar, lye and AgCl



## samuel-a (Mar 4, 2011)

For a while now I'm converting AgCl to elemental using the acid way (10% H2SO4 + Al) and found that with large quantities the process is long and tedious.
I'm producing AgCl from nitric leach of inquarted karat jewelry, the reason i produce AgCl in the first place is because it keeps test slight positive for PGM's that i cement out with Cu slab once the silver had gone out of solution.

So I've been experimenting today with the lye/sugar method with an AgCl sample.
I've pulled the sample while wet so i couldn't weight it but estimate about 10 g of the salt and placed in 250ml Erlenmeyer beaker.
Washed it well with water before, added 200 ml of tap water and placed on magnetic stirrer (set on low), i know i been using way to much water for that sample but otherwise the stir bar will splatter everything all over the beaker. 

Start adding 5g of NaOH and after 10 min of stirring noticed only a slight change of color on the powder, i reckon that the desired PH is at about 10-12 to get the the AgCl to oxide completely. I ended up adding increments that totals for about 25g of NaOH to get the oxides and left to stirr for about one hour.
To test the conversion i simply pulled a small sample after each lye addition from the main bulk, washed it with water and added nitric acid to see how much of it dissolve and how much remains as AgCl.
I didn't got a complete conversion before moving on to the sugar step and figure it will eventually will transform to oxide.

Note: The volume of the powder decreased slightly upon the addition of lye and conversion to oxide, i would say about 20-30% of the original salt volume.

Sugar was added to the mix (stirred at all times with magnetic stirrer), one gram per each estimated gram of starting AgCl, total of 10g was added.
Upon addition of the sugar the solution turned darker and into a very thick suspension with nothing settling anymore to the bottom and after 10 minutes or so of stirring, a mirror started forming on the in side walls of the beaker.




This result lead me to understand that i did convert oxide to elemental silver, but not in the known way of gray powder that have been described here on the forum before. the solution left to settle for the night.

Few things to consider:
- The whole process was done at room temp'
- PbCl may very well be present along side the AgCl at small quantities, since it haven't been boiled with water before beginning the process.
- End product purity is not a concern since it will loop back to inquarting new scrap jewelry.

Next time i will defiantly try this process with dextrose and a more control over the PH levels.
Tomorrow i will decant the solution, wash and dry the resulting powder, weight it and dissolve once again with nitric to see how much (if any) AgCl salt is left.

I would like to have your input about this process since i believe it is more suitable for few ounces batches then the acid way.
Any comments and suggestions are welcomed.

Thanks Sam


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## samuel-a (Mar 4, 2011)

And one more question while at it, is there any risk of creating any kind of explosive Silver compound using this process ?


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## Lou (Mar 5, 2011)

No, those dangerous compounds really only form a high pH with ammonia present and not instantly.

Bear in mind that adding NaOH to AgCl is not an oxidation. You're merely making silver oxide. This silver oxide is what is doing the oxidation on the sugar.

The mirror is a very common effect. Look up the Tollen's reaction. It can be done with Pt, Pd, Rh, even gold if the conditions and substrate are just right.

Lou


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## samuel-a (Mar 5, 2011)

Hi Lou



Lou said:


> No, those dangerous compounds really only form a high pH with ammonia present and not instantly.



I had a hunch that this is the case, but wasn't sure of it.



Lou said:


> Bear in mind that adding NaOH to AgCl is not an oxidation. You're merely making silver oxide. This silver oxide is what is doing the oxidation on the sugar.
> 
> The mirror is a very common effect. Look up the Tollen's reaction. It can be done with Pt, Pd, Rh, even gold if the conditions and substrate are just right.



Thank you for that explanation, there's some really interesting chemistry in this process.

According to your experience, What would be optimal conditions for getting full conversion of AgCl to silver oxide? 
pH? Temperature? Time of stirring? 

And same question for the conversion of oxide to elemental (glucose oxidation)

Many thanks again.
Sam


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## Juan Manuel Arcos Frank (Mar 6, 2011)

Sam:

Adding lye to silver chloride is the best process I have ever used....when AgCl is pure... because if it is not then the process becomes a nightmare...impurites stops reaction between AgCl and NaOH.

My advice to you is:

The black mud you have obtained is a mixure of AgCl,Ag2O,Ag and probably PbCl,add some tap water,boil for a half an hour and let settle down,pour off the liquid,filter the mud,let it dry,add its own weight of sodium carbonate,mix well and melt it.

Try to get silver chloride pure...always add some hot water to you AgCl to disssolve PbCl.If you see any other colour than white then do not use lye/sugar method...let dry your silver chloride,add the same weight of sodium carbonate,mix well and melt it.

Have a nice day.

Manuel


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## samuel-a (Mar 6, 2011)

Thank you Juan.

I will add to the nitric leach a little H2SO4 to drop lead sulfate next time before i precipitate AgCl.

I still need to re-dissolve my sample with nitric to see how much of it actually converted to Ag/Ag2O.


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## qst42know (Mar 6, 2011)

Silver will also drop as a sulfate from a nitric solution.

Lead chloride will wash out with hot water.


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## samuel-a (Mar 6, 2011)

qst42know said:


> Silver will also drop as a sulfate from a nitric solution.
> 
> Lead chloride will wash out with hot water.



Correct !

Wasn't thinking straight when i wrote this...


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## samuel-a (Mar 7, 2011)

conclusion of the process.

I finally got the converted ag dry, a tad over 2gram.
Split it to two, one to be melted and one to re-dissolve in nitric.

The melting was with no dfficulty and gave nice silvery bottun, the button weight is same as the powder that was melted, so no losses here.

The re dissolving really blow my mind! After dissolutin, a black powder remained. This powder was washed with water and dissolved easly with aqua regia and tested positive for gold.


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## mlgdave (Mar 10, 2011)

i have 10 oz of Ag powder and am going to run some of the same tests you did. I also have some AgCl that I have from a small run of placer gold that I didnt inquart, would my best bet be to either
1) covert to elemental, and digest in nitric to see what gold was locked up, or 
2) put back into AR, heat and just keep crushing/stirring to remove the AgCl and expose any Au to Ar.

I only have about 10 grams of this

mlgdave


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## samuel-a (Mar 17, 2011)

The bulk of my AgCl turned out OK using lye+sugar but i find it as hassling and time consuming as using sulfuric acid + Al/Fe.

So... seems like working with large amounts will require cementing after all.
The last time i melted cemented silver, i didn't eliminated PGM's first and that had considerable effect on melting and final silver look.

I've already experimented with 3 cementations steps.

When leach of inquarted gold is done:
(1) pure silver (>99.5%) used to cement PGM's as black sponge. Filter, PGM's Are collected for further refining.
(2) copper bar/pipe used to cement silver. Filter, Silver is melted back to 'shots' and bars and back to circulation.
(3) scrap steel used to cement copper. Copper is washed and either remelted to pour bars or used as powder to cement more silver.

Good luck


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