# Help with silver chloride melting w/ sodium hydroxide/syrup



## adoreman (Nov 8, 2012)

Good morning fellow refiners,

I used the sodium hydroxide and syrup process to be able to melt my silver chloride.
i done a couple of tests to be able to determine the best way to recover the silver from the silver chloride.
in some instances i lose about 2-10% of my pure silver in the process.

i found out that during the melting process, (if the silver chloride has not been fully converted)
the silver cement will emit a white smoke which i conclude is the silver going into the air and being a loss. 
i checked my melting crucible and the missing silver is not there; the missing silver is also not in the liquid sodium hydroxide solution i used because i had it assayed with negative result of silver content.

is there a way to be able to recover this silver going into the air? for instance, can i put some kind of scrubber/air collector when melting in which
i will be able to recover this silver. thanks for the help.


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## publius (Nov 8, 2012)

Typically, the white "smoke" you see may be chlorine, sodium chloride, sodium Hydroxide, sugar or any combination of the a fore mentioned substances. Most likely the losses you are seeing is due to poor or incomplete washing.


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## adoreman (Nov 8, 2012)

publius said:


> Typically, the white "smoke" you see may be chlorine, sodium chloride, sodium Hydroxide, sugar or any combination of the a fore mentioned substances. Most likely the losses you are seeing is due to poor or incomplete washing.



thank you sir publius. what do you mean by incomplete washing? 

i am not sure about the smoke because when i am melting, i use like an open cover over my melting crucible; and after the melting process, there are very small silver particles on my cover. this cover does not touch the main silver during the melting process and i suspect the build up of these particles is from the white smoke. [aslo the white smoke usually only occur nearing the end of each melting process / and there is a green flame which is emitted when the white smoke appears; (similar green flame to those green torch lighters) ] ... thanks


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## butcher (Nov 9, 2012)

If the gases of your melt were sodium chloride (would not happen as salt would burn to chlorine gas, or form silver chloride with the silver oxides in melt), chlorine gas would convert silver in your melt to volatile silver chloride fumes and your silver is going up in white smoke. You should not have salt in your melt or any chlorides that would form chlorine gas in the melt with silver. The silver chloride should be converted to silver metal and oxides and washed well of chloride salts.

Silver chloride is volatile and will burn off in white fumes, silver chloride should not be melted, sodium carbonate in the melt my help to convert the silver chloride to metal but even this does not seem to work that well in my opinion, as silver losses are still high in the melt, especially if you use a torch melt.

The best way is not to try and melt silver chloride, but convert it to silver metal or silver oxides rinsed well of any chlorides, or even better do not make silver chloride in the first place.

It sounds like you were trying to convert your silver chloride with the sodium hydroxide and karo syrup method, complete conversion is sometimes difficult as crystals if not stirred well and broken up to fine powder silver chloride can be trapped in the crystals, all of the silver chloride can be hard to get converted, there are other methods to convert silver chloride to silver metal before melting your silver, dilute HCl and aluminum method, or dilute sulfuric and iron metal method, if you can avoid making silver chloride it is best, as silver chloride can be a pain to convert to silver, and melt without losses, cementing silver from silver nitrate using copper should be used any time you can, much easier and your silver yields will be much better.


I find a kitchen blender is useful for stirring the silver chloride conversion well, when using NaOH, Karo syrup, and stirring water washes.

(Melting salt sodium chloride with your gold (or any other chloride metal salt) can also burn your gold off in the yellow volatile gold chloride fumes, as chlorine gas formed dissolve's the gold and these volatile gold chloride fumes leave the melt as a yellow gas that condense on cold surfaces around the melt).


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## adoreman (Nov 11, 2012)

butcher said:


> If the gases of your melt were sodium chloride (would not happen as salt would burn to chlorine gas, or form silver chloride with the silver oxides in melt), chlorine gas would convert silver in your melt to volatile silver chloride fumes and your silver is going up in white smoke. You should not have salt in your melt or any chlorides that would form chlorine gas in the melt with silver. The silver chloride should be converted to silver metal and oxides and washed well of chloride salts.
> 
> Silver chloride is volatile and will burn off in white fumes, silver chloride should not be melted, sodium carbonate in the melt my help to convert the silver chloride to metal but even this does not seem to work that well in my opinion, as silver losses are still high in the melt, especially if you use a torch melt.
> 
> ...



Thank you butcher for the useful information. yes i am using a torch to melt my silver. yes, i done a couple of experiments an was able to get at least 97-98% weight recovery an 99.99% of my silver, this was done only in small batches of 200g silver. however, when i do my large batches and use the syrup/ sodium hydroxide method; i am not sure if i am able to recover the silver fully because i am recovering from scrap silver and from recycled soils in which i have no basis the exact amount which i will be able to recover from that. i am wondering if there is a way to collect this siver chloride fumes?

yes, i previously used the copper method to recover from my silver nitrate but sometimes i am not able to recover in 99.99% purity because some of the copper may chip off and mix into the cemented silver. may i ask you how the process of aluminum method and dilute sulfuric and iron metal method works? do you have like a link somewhere where i can find this? thanks you very much for your time.


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## goldsilverpro (Nov 11, 2012)

adoreman said:


> yes, i previously used the copper method to recover from my silver nitrate but sometimes i am not able to recover in 99.99% purity because some of the copper may chip off and mix into the cemented silver.



You will NEVER be able to get 99.99% purity from cementation. If you do things perfectly, you might just get 99.00%. If you then run the cemented silver in a silver cell, you might get 99.99%, if you know what you're doing.


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## butcher (Nov 11, 2012)

If you end up with pieces of copper in your cemented silver the copper metal you are using is either too thin or small, try a thick piece of copper like a buss bar from electrical panels, this way the copper only leaves the bar as copper ion into solution, and will not fall apart as pieces of copper coated in silver like copper wire will.

I cannot understand making large batch’s of silver chloride, if the silver is dissolved as silver nitrate use copper to cement the silver, save yourself the headache.

As far as capturing fumes from a melt I suppose it could be done, but I think it would be better not to burn off silver chloride in the first place, I suppose a furnace flue could be fitted with some type of scrubber and bag filters.

Adding soda ash, washing soda to your melt may help; they use about 3 parts sodium carbonate Na2CO3 to silver chloride in the melt to help convert silver chloride in the melt.

Larger batch's of silver chloride are harder to convert, stirring and mixing it, getting the bottom of the barrel to mix well, the clumps need broken up well.

I have also converted silver chloride with NaOH and hydrogen peroxide.

I have not used the aluminum and HCl method, so no comment there.

The dilute sulfuric acid and iron method to convert silver chloride I like I use the iron bar to stir with, this is a contact replacement reaction, so you have to have the silver chloride particles in contact with the iron bar, so the iron will give an electron to the silver, here again stirring is important, as the iron reacts the iron dissolves into solution as ferrous sulfate, and ferrous chloride, silver chloride converts back to silver metal.

As far as more information on where you can read about these processes of silver chloride conversion using iron and sulfuric, or aluminum and HCl, and the metal replacement reactions in chemistry, try Hoke's book or a search of this on the forum, and reading about chemistry metal replacement reactions, I cannot think of a particular place to study this.

GSP's (Gold Silver Pro's) posts and book is always a go to place when trying to learn about silver.

I believe Harold spoke of his use of the aluminum and HCl acid method to convert silver chloride.


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## adoreman (Nov 15, 2012)

Thank you mr GSP. yes that is my reason that's why i stopped using the normal copper cementation method, because i am not able to get the 99.99 even if i am using larger pieces of copper bars. 

@butcher : the reason i am doing large batches of silver chloride is because i used to do the copper process first to cement my silver from the silver nitrate; then jus use salt for the remains. however i changed my method to mixing salt into my silver nitrate straight away without doing the copper process. i done the salt process then the caustic soda/ sodium hydroxide and syrup- this gave me better percentage in the purity; however there are some losses. ]

QUOTE BUTCHER: As far as capturing fumes from a melt I suppose it could be done, but I think it would be better not to burn off silver chloride in the first place, I suppose a furnace flue could be fitted with some type of scrubber and bag filters. 

i will try to place a furnace flue or some sort of air filter/scrubber which will collect the smoke in my melting area. this scrubber will have caustic soda in the solution to neutralize and collect the smoke. i am now testing to put ""sodium sulfate"" into my caustic soda solution to precipitate the silver/ metal contents : however im not that sure if this method will work yet because it is my first time. has anyone tried using this sodium sulfate method before?? thankss

( i tested the sodium sulfate on my sodium hydroxide waste from the previous process' waste in a small beaker and the metal pieces seemed to precipitate) any ideas on this method?

i will try out this soda ash and sodium carbonate method or hydrogen peroxide to convert my silver chloride. do u have details or a link on this process? thank you very much=)


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## kadriver (Nov 15, 2012)

Hello

I have this problem also.

I believed (incorrectly) that the silver chloride conversion was a short cut to getting 3 nines fine silver.

One time I lost about 100 grams of silver due to incomplete conversion of the chloride to oxide with NaOH.

Another time I ruined a big corningware dish while drying the silver due to incomplete removal of the NaOH.

The blender idea is good because it will completely grind all the chloride ensuring complete contact with the NaOH.

The silver chloride tens to clump and the NaOH can't get to the chloride inside the clumps.

I recently surrendered and restarted my electrolytic silver cells. It is the best way to get you fine silver with fewer losses.

Plus the silver crystal from the silver cells make better looking bars.

Kadriver


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## MysticColby (Nov 15, 2012)

I heard going the silver chloride route is easy to have lead contamination (if lead is present) if you don't rinse enough with hot water


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## butcher (Nov 15, 2012)

Silver chloride is a fluffy powder that normally does not settle well (easy to collect impurity, then it can clump to crystals and be hard to wash impurity, or to get a good conversion.
The only way I see to clean up the impurity in silver chloride is after washing to dissolve in ammonia and re precipitate the silver as a chloride, but it still will not be pure, but better, then converting it to metal before melting. (all of this work and you’re not much better off in purity than if you used the cemented silver using copper buss bars, , and washed the silver well before melting, you could always refine it again and re-crystallize the silver for a little higher purity, but why, it too would need run through the cell anyway.
Besides silver chloride is just a pain to deal with.

I would rather deal with silver metal cemented from solution with copper any day. 
That is Just my choice.


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## nickvc (Nov 16, 2012)

butcher said:


> Silver chloride is a fluffy powder that normally does not settle well (easy to collect impurity, then it can clump to crystals and be hard to wash impurity, or to get a good conversion.
> The only way I see to clean up the impurity in silver chloride is after washing to dissolve in ammonia and re precipitate the silver as a chloride, but it still will not be pure, but better, then converting it to metal before melting. (all of this work and you’re not much better off in purity than if you used the cemented silver using copper buss bars, , and washed the silver well before melting, you could always refine it again and re-crystallize the silver for a little higher purity, but why, it too would need run through the cell anyway.
> Besides silver chloride is just a pain to deal with.
> 
> ...




I'll second that very loudly, I used the silver chloride method for years knowing no better but I always cement now as silver chloride is a royal pain in volume :evil:


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## goldsilverpro (Nov 16, 2012)

You should have both methods in your arsenal. If you have a lot of free nitric, and/or a lot of solution with low silver concentration, it is usually more economical to go the silver chloride route. 

In some cases, you are forced to do silver chloride. I learned the silver chloride system over the years mainly by running 100s of 1000s of pounds of silver brazed stainless jet engine parts, heat exchangers, etc. On this stuff, the silver only runs about 1-2%. It was run on a multi-tank hoist line in large rectangular stainless baskets. There were usually from 1 to 3, 100 gallon, 50/50 nitric tanks and several rinse tanks on the line. When it started to slow down, the solution was pumped into a large plastic vessel. The solution was then analyzed (Volhard titration) for total silver and the correct amount of HCl was added to precipitate only 90% of the silver. The H+ from the HCl combined with the NO3- that was freed from precipitating the silver and this, in essence, built up the nitric concentration somewhat. The silver chloride was separated and the solution was returned to the stainless tanks on the line. The reason I only precipitated 90% of the silver was to prevent the existence of any chlorides in the stainless tanks, which would have been attacked by them. After doing this 5-10 times, or so, the dissolved copper from the braze slowed the action to a crawl. At that point, 100% of the silver was dropped and the solution was scrapped. I used Karo syrup and NaOH to convert the AgCl and a silver cell to purify it. In one case I remember, one worker ran 50,000# of this material in about 30 days, or less, without changing the nitric solutions or adding more nitric to them. At 1.4%, which was about the average, that's 10,000 oz of silver.

In that case, copper cementation would have been stupid. Lots of expensive copper, lots of fumes, more waste, and much more nitric. I also remember 4metals recently mentioning a case where AgCl was the most economical way to go. Each situation must be evaluated separately. The more knowledge and experience you have, the better your decisions will be.

A neat thing about silver is that most every reaction is stoichiometric. It's all math. If you know the factors, you can (and should) easily calculate, usually within a couple of percent, how much nitric it takes to dissolve it, how much HCl or salt to drop it, and how much NaOH and syrup to convert it.


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## NobleMetalWorks (Nov 16, 2012)

If you allow your silver chloride to dry and cake, at all, it will be more difficult to mix the sodium hydroxide with it, and make contact with all your silver chloride. You have to keep it hydrated.

Scott


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## goldsilverpro (Nov 16, 2012)

SBrown said:


> If you allow your silver chloride to dry and cake, at all, it will be more difficult to mix the sodium hydroxide with it, and make contact with all your silver chloride. You have to keep it hydrated.
> 
> Scott


Of course. That is always a must.


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## adoreman (Nov 30, 2012)

hi everyone. thanks for the time and replies. sorry i have been busy working on my stuff so havent really posted up here yet. 
yes keeping it hydrated is important. ive tried it before on one of my first attempts on the caustic soda/syrup method and mixed it with a dired up silver chloride and it was a fail. thanks for all the advice everyone. yes gsp i will try doing the copper method again. i have heard of a process of cementing the silver using copper bars, and putting like an aerator into the solution to produce air and bubbles white it is cementing the silver. the person told me that this will make for better recovery percentage/ purity and time wise. anyone here tried this method before?


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## adoreman (Nov 30, 2012)

the aerator he told me to use is like the ones you use in the aquarium for fishes


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## NobleMetalWorks (Nov 30, 2012)

adoreman said:


> the aerator he told me to use is like the ones you use in the aquarium for fishes



You can use aquarium stones but it's a toss up if they will hold up or not. I have tried several, even when you purchase two that are exactly the same, same company, same composition, identical, one might stand up to chemical attack and the other will crumble.

I found the best type of air stones to use are very tightly compact ceramic stones.

Scott


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## nickvc (Nov 30, 2012)

I would suggest just sealing the end of the pipe and piercing with a hot pin or needle along the tube and weighting it down with something non reactive or placed behind the copper bar and fed to the bottom.


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## goldenchild (Nov 30, 2012)

Here are two keys that I've found to making the AgCl method successful. The first is using a vessel that is very large opposed to the amount of AgCl you have. By this I mean a vessel where the AgCl can lay flat and very thin on the bottom. This is for the rinsing stages. I keep a dedicated, very clean 5 gallon bucket for rinsing the AgCl right after it has been created. In the 5 gallon bucket the AgCl will move around freely making contact with the rinse water easily. I can also use a garden hose to spray the AgCl with force breaking up any of those troublesome clumps that retain unwanted contaminants.

When the AgCl yields crystal clear water after a rinse, it’s ready to be put into a reaction vessel (I use glass). Here the size of the vessel need not be excessive. When I start reducing the AgCl to silver oxide I actually expect it not to fully convert but that’s ok. As the oxide forms its gets much easier to stir as oxide is less dense than chloride. The reduction is completed as thoroughly as possible. At the end I can still see a small amount of unreduced AgCl but again this is ok. Now here is the magic. The way to get 100% conversion to elemental silver is to add your sucrose source while the solution is still very hot from the NaOH additions. While adding the sucrose the solution will get extremely hot, sometimes causing boiling. This boiling along with the heat causes enough agitation and penetration to allow any unreduced AgCL make contact with the NaOH.

The elemental silver is now rinsed. The only pain I have in this process is rinsing the sugar solution from the final product. There always seems to be some sugar left when melting. It doesn’t contaminate your silver but can make you question the purity of your silver when you see what's left in the melting dish/crucible. I'm currently working on an AgCl method involving HCl and zinc which should make for a cleaner final rinse product. 

Here are two shameless plug videos although I really don't care as I'm not making money from them. Some of you may have seen them but, it’s me using the techniques I just described(rinses not on film). The second is melting some silver. The second video is relevant because some of the silver (the shotted silver) was from the first video. The final bar was .9999 purity and I have the XRF to prove it if anyone is interested.


[youtube]http://www.youtube.com/watch?v=xM-YsiFnJ1I&list=UUulJxV7L-c3hiBhghfk1MYA&index=2&feature=plcp[/youtube]


[youtube]http://www.youtube.com/watch?v=kdYbBu5MAeU&list=UUulJxV7L-c3hiBhghfk1MYA&index=1&feature=plcp[/youtube]


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