# Conversion of AgCl via NaOH and Karo Question



## publius

I tried the method for reducing silver chloride using sodium hydroxide and sugar. I really like how fast it works. I would like to understand the process more. I know that sodium exchanges the hydroxide ion for the chloride ion and the silver takes an oxygen molecule to form sodium chloride and silver oxide and heat. (Lots of heat!)

The next step of the process is the one I am not sure of. Does there need to be an excess of sodium hydroxide? Is it possible that someone could show the reaction so I could have a better understanding of what is going on? Also is there a way to calculate the required amounts of NaOH and sugar to use so the waste of these to chemicals is kept to a minimum?

I am concerned with waste disposal and purity issues. If my silver chloride is not well rinsed, will this process also take the copper back to copper oxide and then to metallic copper?

All in all, this seems to be the fastest way to extract silver from solution without introducing additional base metals. 

Thank you, lasersteve, for the outstanding video of the process.

Robert Jeffery, CWI


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## kurt

Rob - I have actually done quite a bit of the salt sugar lye method with silver (as well as cementing) they both have there pros & cons. (I have done over 400 T oz of silver in the last 16 months using both methods) I don't have time right now but will do my best to point out some of the things I have learned about going with the AgCl method tomorrow morning.

Kurt


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## publius

kurt said:


> Rob - Snip... *ut will do my best to point out some of the things I have learned about going with the AgCl method tomorrow morning.
> 
> Kurt*


*

Thank you sir. I normally use iron and dilute sulfuric acid and was looking for a different way to avoid the contamination issues.*


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## philddreamer

Hi Rob!
How pure do you need or want your silver? This will determine the best procedure to follow. If you want .999, I feel that cementing with copper is faster, with a purity of .99 or so, followed by processing thru a silver cell. My expirience with the lye & sugar is, its okay, but too much work.

Here are some ratios for the lye sugar method, that Juan Manuel shared with me some time ago for 500g of scrap silver:
600g of salt (without iodine)
1000g sodium hydroxide (Lye)
600g of sugar
200 ml. of HCl (for rinsing)
I find that, that's too much extra chemicals (& time) in order to end up with metallic silver, when just cementing with copper will do the job. Having the expirience of converting thru salt, lye & sugar prosess is great, if that's what you want.
Just my opinion...
Take care!

Phil


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## goldenchild

philddreamer said:


> Here are some ratios for the lye sugar method, that Juan Manuel shared with me some time ago for 500g of scrap silver:
> 600g of salt (without iodine)
> 1000g sodium hydroxide (Lye)
> 600g of sugar
> 200 ml. of HCl (for rinsing)
> I find that, that's too much extra chemicals (& time) in order to end up with metallic silver, when just cementing with copper will do the job.
> Phil



Interesting. I recently processed a batch of nearly 500g of sterling and some of these numbers look a little high. The salt sounds about right if you use it to bring down the chloride but the sodium hydroxide and sugar seem excessive. I used HCL to bring down the chloride. Maybe 300-400ml. Then about 300-400 grams of sodium hydroxide with a few good squirts of kyro (5-6). I know Juan knows what he's doing though. Maybe there was something different in his process? I'd be curious to know what he has to say.


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## goldsilverpro

I have done a lot of conversion using Karo/NaOH. For each troy ounce of silver (41.3g of AgCl), it took 20g of NaOH and 13.3ml of Light Karo syrup. These figures were proven in a lab. In practice, I used 10% extra of each.


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## goldenchild

goldsilverpro said:


> I have done a lot of conversion using Karo/NaOH. For each troy ounce of silver (41.3g of AgCl), it took 20g of NaOH and 13.3ml of Light Karo syrup. These figures were proven in a lab. In practice, I used 10% extra of each.



I definitely have to record these numbers for future reference and will convey them to a member that was recently asking about figures to use for AgCl. I was almost spot on just adding and eyeballing the reaction. According to GSP's figures it would take 197.8 ml of syrup and 297.4 grams of NaOH to get elemental silver from a 500g batch of sterling. Then add an extra 10% just to be certain. So the 1000g of NaOH and 600g of sugar would be about 3 times more than needed. Thanks for these numbers GSP.


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## goldsilverpro

Sounds like Manuel was using a solid form of sugar instead of Karo syrup. That would make the numbers different and they would most probably depend on the type of sugar he was using.

You can also use only the NaOH to convert the silver chloride to silver oxide and then decompose the silver oxide to silver metal with heat. According to Wiki, the decomposition temperature is about 540F. In practice, I would get it somewhat hotter than this.


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## lazersteve

I never measure when performing the sugar-lye method. I simply go by the color of the silver chloride and proceed to the next step as the color of the powder matches the correct shade and cosistency.

First I cover the wet silver chloride with a volume of water equal to twice the volume of silver chloride.

Secondly, I slowly add dry lye pellets and stir. This step produces lots of heat so proceed very slowly and stir a lot. I add the pellets until the entire mass of powder is a dark brown, almost black color.

Now I mix up a saturated solution of table sugar and warm water. I use more sugar than the water will hold and stir until the water is no longer cloudy. A small amount of solid sugar remains in the bottom of the vessel that the sugar is mixed in. I make up a volume of this solution equal to the volume of the silver chloride. The cooled clear liquid (no solids) from this solution is slowly stirred into the dark brown silver oxide until the color shifts to light gray and the beaker becomes coated with a mirror of silver. I scrape the mirror off of the beaker glass with a glass road while stirring.

Finally I allow to the solids to settle and rinse (three cycles of settling and rinsing with fresh water). The rinsed solution/sludge is then vaccum filtered and rinsed one final time with clean water. The final rinse should run clear.

The keys to sucessful conversion are making sure the silver chloride starts out wet (never allowed to dry), the color of the solids is 100% the same color throughout after each step, and good stirring.

I love this method as it is very fast and clean. 

Steve


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## philddreamer

> I never measure when performing the sugar-lye method. I simply go by the color of the silver chloride and proceed to the next step as the color of the powder matches the correct shade and cosistency.


This is how I do it too. The ratios Juan Manuel gave me, helped me see what the transition would look like, plus more information shared by other fellow members. So, I just look for the right color.
But, since trying cementing with copper, I prefer cementing method. I recover plenty of copper for my "batches", so I found a good use for it & re-cycle it. I have accumulated AgCl from batches of AR and other processes and that's where the salt, lye, sugar comes in handy. It's good to have experience with both methods.

Phil


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## goldsilverpro

I should mention that, for each tr.oz. of silver, I used 135ml of water. In most cases, I was converting large batches, usually in a 55 gal cutoff plastic drum. I used a power stirrer (usually a Lightin' mixer with a prop blade which provided a chopping action) and constantly stirred it for at least an hour after adding everything. Using the stirrer, I found it wasn't necessary to wait until the NaOH converted it to silver oxide to add the Karo. I usually added the NaOH first and then immediately added the syrup. I don't like doing things in the dark, so I always analyzed (using the Volhard titration) the silver in the nitric before precipitating the AgCl with HCl. That way, I always knew how much NaOH, Karo, and water to use when converting. Using this method, I always got 100% conversion.


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## samuel-a

2 AgCl + 2 NaOH = Ag2O + 2 NaCl + H2O

That means that every gram of expected silver would need 0.37g of dry NaOH prills to convert.
To accomodate the resoulting NaCl in the solution, you need to have 1.42 ml of water (at least) for each gram of expected silver.
(this would have been much simpler to present in moles rather then grams)

These are the masurments i'm using in the rare cases is do need to produce and process AgCl... Seems to be working just fine.
Similar to GSP, i too prefer to add masured excess of Water and Lye.


I don't take the extra step to reduce the oxide with sugar, i just make dry cakes and melt as it is going to the cell anyway.
Also, i'm not so sure about the actual redox between the sugar and the silver oxide so i can't calculate it. Sucrose baing a molecule composed of glucose and fructose make thing all that confusing to me.

It is mentioned in this report, that Sucrose (table sugar) in it self is not a good reducing agent, but rather its individual components are (i.e. glucose and fructose), they mention therw the need to acidify the Sucrose solution to promote hydrolysis into the two simple sugars that actually perform as reducing agent and in turn oxidized by the silver oxide (to... Formic acid??)

That's of course, somewhat contradicts our experience as we seen with our own eyes that plain sugar water does in fact reduce Ag2O... 
So the questions remains... does the water itself hydrolyse Sucrose ?

I'm out on a limb here, so feel free to currect me if i'm wrong.
I'm struggling barely with inorganic chemistry as it is... So it's safe to say me and organic chemistry are not such a good friends


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## goldenchild

As far as the reduction of chloride to oxide goes I never really worry about getting it 100% In fact unless you are using a blender, tumbler or stirrer of some sort I think you would be hard pressed to reach 100% reduction. I let the additions of the karo do all the work. With the heat and boiling that occurs with the karo additions, any bits of AgCl that weren't reduced will then come in contact with the NaOH and of course immediately convert to elemental Ag. As long as there is enough NaOH in solution everything should convert to elemental Ag in the end.


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## Geo

when im doing this process, i have quite a bit of fine brown powder that forms and takes some time to settle. ive been collecting it because i dont know what it is. any ideas what it might be?


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## qst42know

> It is mentioned in this report, that Sucrose (table sugar) in it self is not a good reducing agent, but rather its individual components are (i.e. glucose and fructose), they mention therw the need to acidify the Sucrose solution to promote hydrolysis into the two simple sugars that actually perform as reducing agent and in turn oxidized by the silver oxide (to... Formic acid??)
> 
> That's of course, somewhat contradicts our experience as we seen with our own eyes that plain sugar water does in fact reduce Ag2O...
> So the questions remains... does the water itself hydrolyse Sucrose ?



In the lye the sugar is simply carbon source to form CO2 from the oxide isn't it?

Unrelated but in the food industry citric acid is often used to form the sweeter tasting simple sugars from sucrose.


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## publius

I understand, now, the conversion from AgCl to AgO. Can someone show the formula for the reaction of the AgO with the sugar?
:roll:


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## samuel-a

qst42know said:


> In the lye the sugar is simply carbon source to form CO2 from the oxide isn't it?



I thought so too, but the more i go about it, it seems it is not that simple as we might think.
For me, it is just a theory, but it seems that the reaction of simple sugars to Ag2O, like Glucose for example, will not couse decomposition as you suggested, but rather an oxidation to Gluconic acid or some gluconate salt....

It will be wonderful if a chemist could chim in here and explain to us what's really happning in this reaction and and therefore we could calculate stoichiometric amounts instead of guessing...

Some more related info i think may be relevant:
Reducing sugars


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## qst42know

No carbon in that glucose model.


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## Juan Manuel Arcos Frank

Here is the trick:

Common sugar(sucrose) is a non reducing sugar,I mean,if you add common sugar to black silver oxide then the reducing reaction will not take place.When you add an excess of NaOH to the white silver chloride you will convert it to black silver oxide and a lot of NaOH remains in solution,this NaOH excess reacts with common sugar breaking it in glucose and fructuose,glucose is a reducing sugar so the reaction with silver oxide will reduce it to metallic silver.

Karo syrup is glucose but it is very expensive and not founded in some countries.The difference between Karo syrup process and sugar process is time and money,Karo syrup is faster than sugar process but more expensive,sugar process is slower than Karo syrup but it is cheaper...When you add sugar to your silver oxide/NaOH solution you have to mix the solution very hard ,the reduction reaction takes some time to start but once started it is very very exothermic and a lot of foam is released,like a volcano explotion,so be careful.

I hope it helps

Kindest regards.

Manuel


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## samuel-a

According to this paper:
http://www.jbc.org/content/264/17/9901.full.pdf
And several other resources i have found across the web, Hydrolysis actually do ouccur once sugar is dissolved in water. And might even be promoted further with lowring of pH with weak acids....

Cool, now we know why it works.

According to wiki (and if i understand correctly), both the Glucose and fructose (eventually) will have aldehyde group which are capable to reduce.
Anyone knows how to expess this redox in a balanced equation? Ag2O + Glucose + fructose = ??


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## kurt

Sorry for the delay in responding to this one but yesterday morning we had a sever storm blow though here (80 mph winds) that blew out our electric power (no computer) & today was spent cleaning up the storm damage.

Anyway – I see most of best minds in refining (those I have learned “so much” from) have already posted replies – lots of technical info to help understand what’s going on in the process.

I still consider my self a beginner at refining with so much yet to learn so I hope my post here doesn’t sound like a student trying to be smarter then my teachers & as much as the technical info is good to know for understanding the process of working with AgCL – in practice the process is simple & I have figured out a few things to even make it easy.

Whether doing AgCL or cementing end product of course depends on how clean or how dirty your starting material is (concerning base metals) if you start with a dirty source (like contact points) you are going to get drag down whether going with AgCL or cementing. What I like about AgCL is that I seem to get a cleaner end product.

Based on XRF read out I have had my cement come back as low as around 95 but my worst AgCL has been around 97 (from contact points) On the other hand the best cement I have had (from sterling) has been 98.5 with AgCL coming in at 99.95

As a “hobby” refiner doing batches of 20 oz to 40 oz – this is what I like about going with AgCL instead of cementing - I can achieve 999 in less time & with less hassle.

Once you have your Ag nitrate – if your starting material was a clean source like sterling there is no reason why you should not have 999 powders ready for drying after 4 – 6 hrs. If your starting material was dirty like contact points 3 days once you have your Ag nitrate. Day 1 – drop Ag CL wash – convert – wash – dry over night, --- Day 2 – weigh – re-dissolve to nitrate. --- Day 3 same as day 1 with 99 plus Ag in the end. --- On say a 40 oz batch with cementing & running a 1 or 2 liter cell off a computer power supply it would take 5 to 7 days with much time spent watching the cell to keep the crystals knocked down to prevent shorting the cell.

The 2 reasons most people avoid going with AgCL is first the concern of not getting complete conversion due to the cottage cheese clumping nature of AgCL & concern that the NaOH wont get to all the AgCL in the middle of the clumps to complete the conversion. And the clumping is made even worse if you use hot water wash’s to wash out water soluble CL’s like Lead CL etc.

The second is washing out the NaOH. Its nasty stuff & can take a LOT of water washing to really get it out. (I have had to do as much as 5 or 6 washing to really get it out) --- But there is a solution to both of these problems.

First “cold” water along with a kitchen egg beater “whip” will brake most of the clumps down to much finer particles & smaller clumps. – Then “before” adding your NaOH – take your corn syrup – dilute it about 50/50 with warm water (I always use D-water) so it’s still syrupy but flows nice & add it to your AgCL & whip the living day lights out of it with your kitchen whip. The vast majority of your AgCL will brake down to very fine particles with only some very small clumps. More of a milky slurry. (note - you should have your AgCL in plenty of water when you ad the corn syrup)

Now you can ad your NaOH while stirring vigorously (I use 98.5% NaOH dry form & I ad it dry) & your end result should be a nice gray fine divided silver cement.

Now to get the NaOH out --- ad small amounts of HCL stirring it till you get a ph of 7 or 6.5 (keep it just slightly alkaline) & you should now only have to wash it 2 or 3 times before its ready to go to drying. 

There is no reason to not get 995 to 999 silver in short order with the AgCL method – the only delay being maybe to give it a couple days to settle if you need to re-dissolve & run a second time. 

Trace amounts of Pd = DMG --- if there are more then trace amounts of PGMs – then its cement & silver cell.

Kurt


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## sena

Hi 
Tried to convert agcl using Naoh process today.i never tried karo earlier its not available where iam , so i tried sugar , the output was fast and easy to filter 
no karo syrup just concentrated sugar solution , thats like magic, followed the steps of the laser Steve above , used concentrated sugar water solution, here is the picture.Thanks Lazer steve 
Regards
Sena


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## duncan

I am doing a similar process. I got to the silver point then dried it.

Tricky part has been melting the powder and getting ingots. 

I'll try and post some photos of my failures.


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## sena

duncan said:


> I am doing a similar process. I got to the silver point then dried it.
> 
> Tricky part has been melting the powder and getting ingots.
> 
> I'll try and post some photos of my failures.




Incernation the sludge would help the "trickyness" surpass it .please do incernating the resulting sludge for easier melting .

Regards
Sena


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## kurt

duncan said:


> I am doing a similar process. I got to the silver point then dried it.
> 
> Tricky part has been melting the powder and getting ingots.
> 
> I'll try and post some photos of my failures.



duncan - I am not sure what you mean by the melting being "tricky"?

sena - you mention incinerating the sludge before melting - i have never needed to do this - what is the reason for doing so?

I can see a problem with the melt &/or a need to incinerate if you are not getting all the NaOH & sugar washed out before drying & going to melt.

washing the NaOH out can be a real pain - its nasty stuff & can take multiple washings to get it out (it tends to cling or hang in the sludge) Its one of the reason this method is avoided as a silver refining method.

However - if you use some HCL to neutralize the NaOH before washing - it will cut the amount of water & time for washing by half or more.

After you have done your sugar/lye convertion - adjust the ph from being a strong alkaline to being just slightly alkaline on a litmus test. Then after you decant the solution - it should only take a couple water washings & much less water.

In fact - if you use HCL - instead of salt for your AgCL convertion - you can use that to make your ph adjustment - it just takes more volume of the old HCL convertion solution because it is diluted (as opposed to using straight HCL to adjust the ph)

Just don't let it go to the acidic side when making this adjustment as that will result in "some" of your Ag sludge converting back to AgCL - so ad your HCL a little at a time testing with litmus paper till you achieve just a slight alkaline test.

Kurt


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## Marcel

I have followed the threads about the conversion of AgCl, but I am uncertain how to proceeed:
I have dissolved the plastic foils of silverplated CD-Rs using Chlorox. The silver plating went off and small black particles were created.
I then filtered the slug of plastic and liquid with a quite large screen and received the dark-purple colored wet substance, which I suppose is AgCl.
I know that it usually is white if sealed under HCl and turn very dark when exposed to light and air.
My question now is ( I still have the wet slug). How do I proceed from here?
1.) Cement with copper - What should I use to fill up the beaker: HCl or water or else?
2.) Lye and sugar method: Is this appropriate in this case, since you always talk about the white AgCl, that will need to be turned into a black sludge by adding NaOH. Now my sludge is already black (but not AgO I suppose).

Dissolving the silver using chlorox:



1. Filtering:



Filtered Liquid:



2.Filtering



Now how to go on from here? I have collected the sludge, rinsed with water. It is still wet but very compact.
I tried melting some of the material as a test right away, it did melt and form some tiny silver balls, but as I can tell from the scope, there are still 50% impurities in the button that look like salts (green) also the silver does not melt together as one nicely.


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## lazersteve

Marcel,

I have never recovered silver from cd-roms, but I can help you with testing the unknown purple precipitate.

1) Collect a small sample of the precipitate in a test tube.
2) Add four times the volume of the unknown material of 10% ammonium hydroxide and stir vigourously.
3) Filter off the liquid.
4) Add 30%+concentration muriatic acid until the solution tests acid to pH paper (<pH7) and stir vigourously.
5) A white curd like precipitate should form that settles fast and changes purple when exposed to sunlight if silver is present. This is silver chloride.
6) Convert the silver chloride with any one of the methods outline here and on my website videos.

Note: Always add HCl to left over base solutions to make them acidic before storing. Basic solutions (specifically ammonical) can form explosive compounds when shelved for long peroids of time. 

Steve


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## Marcel

lazersteve said:


> Note: Always add HCl to left over base solutions to make them acidic before storing. Basic solutions (specifically ammonical) can form explosive compounds when shelved for long peroids of time.
> 
> Steve



Thanks for that hint!


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## RESET

Are you dissolving the silver with straight Clorox or HCl and Clorox? Also, I thought CD-roms were plastic coated in aluminum.

Can you provide source material, where you learned this process?


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## glondor

Just to throw this hat into the ring..... I use Harold's method of HCL and aluminum. Just add some HCL to your clean chloride and add a clean aluminum billet heat sink and stir it around with an aluminum paddle cut from an aluminum computer panel. Vigorous reaction. Fun to do and if you are doing computer recycling you already have every thing you need in your shop. HCL and aluminum. 

Stir and agitate until your silver is a uniform grey colour with no white specks. 

Caution.....Do not do this near an open flame as the offgas is Hydrogen.


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## nōnāgintā trēs

I've done the silver and karo syrup a few times. I don't like the sticky mes I have to purify at the end. If it's AgCl I have I'd rather just put a piece of zinc in there. I usually cement my Ag with copper wire or pennies from a mix of 50ml silver nitrate to 3 liters of water.


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## g_axelsson

Do not use zinc to cement silver, you would get copper and other metals mixed into your silver.
Copper is the correct metal to use to cement silver to get it as pure as possible with this method.

/Göran

Edit : This was obviously wrong for silver chloride and only applies to silver nitrate solutions. Read more below.

/Göran


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## nōnāgintā trēs

g_axelsson said:


> Do not use zinc to cement silver, you would get copper and other metals mixed into your silver.
> Copper is the correct metal to use to cement silver to get it as pure as possible with this method.
> 
> /Göran



I said I use zinc to cement silver from silver chloride. I use copper for silver nitrate. Try adding copper to silver chloride and tell me what happens. And no you wont contaminate your silver chloride with zinc so long as you wash with HCL after. I do it all the time.


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## butcher

I think the confusion here comes from the misuse use of the word cement,.

You do not, or cannot cement silver chloride with zinc.

Silver chloride is already insoluble and does not need cementing from solution.

But we can convert silver chloride to metallic silver metal powders, using zinc in an acidic solution like dilute HCl.

Iron metal and dilute sulfuric acid will also convert silver chloride to silver metal.

Using copper metal is the better metal to cement silver from solution to form insoluble silver metal powders called silver cement.


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## nōnāgintā trēs

I wanted to let you all know that I've tried this method with gold. When I had a solution of gold chloride I added NaOH, droped the gold as gold hydroxide, then syphoned off the ammonia smelling liquid, and added karo syrup. It seemed to precipitate but I wasn't 100% sure. All I can say is it changed colors same as with silver. The problem came when I tried to melt it. Unlike silver which is heavy and thick, the gold was a fine powder now surrounded by syrup. I had Hell trying to melt the crap and gave up!!


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## butcher

nōnāgintā trēs,

I really do not understand why you would try something like that; the gold can be cemented or chemically precipitated from the acidic solution as a fairly pure gold metal leaving most all of the other metals in solution.

When you removed the acid from the gold using NaOH where then the gold was no longer soluble in the salt water that formed, it would also precipitate hydroxides of the other base metals from solution, I do not think the gold would have formed a gold hydroxide, or even a gold oxide because gold is so un-reactive (caustic I do not believe would be strong enough at this stage), and since gold would most likely still be a chloride or elemental gold, I do not think the Karo syrup would have any action on the gold, as the way it does on silver oxides (silver forms oxides with NaOH), when using Karo syrup on silver oxide the sugars in Karo syrup assist in converting the silver to metal by removing the oxygen atoms, converting the oxide from the silver to water with the added hydrogen from the sugar in the syrup.

I would expect a mess in the melt, but as long as you kept this mess you should be able to get your gold back.


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## g_axelsson

nōnāgintā trēs said:


> g_axelsson said:
> 
> 
> 
> Do not use zinc to cement silver, you would get copper and other metals mixed into your silver.
> Copper is the correct metal to use to cement silver to get it as pure as possible with this method.
> 
> /Göran
> 
> 
> 
> I said I use zinc to cement silver from silver chloride. I use copper for silver nitrate. Try adding copper to silver chloride and tell me what happens. And no you wont contaminate your silver chloride with zinc so long as you wash with HCL after. I do it all the time.
Click to expand...

My bad, I didn't read enough. But on the other hand you didn't describe the complete reaction, leaving out the diluted HCl. If I just put a piece of copper or zinc in a silver chloride solution without additions I wouldn't get any noticeable reaction.

To all the readers, for the exact way to convert AgCl into pure silver via zinc or iron in a weak acid solution, search the forum. I haven't tried it myself and I'm not going to describe a method I'm not familiar with.

/Göran


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## goldenchild

butcher said:


> nōnāgintā trēs,
> 
> I really do not understand why you would try something like that; the gold can be cemented or chemically precipitated from the acidic solution as a fairly pure gold metal leaving most all of the other metals in solution.
> 
> When you removed the acid from the gold using NaOH where then the gold was no longer soluble in the salt water that formed, it would also precipitate hydroxides of the other base metals from solution, I do not think the gold would have formed a gold hydroxide, or even a gold oxide because gold is so un-reactive (caustic I do not believe would be strong enough at this stage), and since gold would most likely still be a chloride or elemental gold, I do not think the Karo syrup would have any action on the gold, as the way it does on silver oxides (silver forms oxides with NaOH), when using Karo syrup on silver oxide the sugars in Karo syrup assist in converting the silver to metal by removing the oxygen atoms, converting the oxide from the silver to water with the added hydrogen from the sugar in the syrup.
> 
> I would expect a mess in the melt, but as long as you kept this mess you should be able to get your gold back.



I believe nōnāgintā trēs is silentiumestaureum93 on youtube. The reason he is set on using NaOH to precipitate gold is because he seems to not be able to get SMB to work. I have given him the typical advice about excess nitric and testing with stannous but he claims he still can't make it work. So I referred him to the forum. Hopefully he finds his answers here.


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## butcher

goldenchild said:
“I believe nōnāgintā trēs is silentiumestaureum93 on youtube. The reason he is set on using NaOH to precipitate gold is because he seems to not be able to get SMB to work. I have given him the typical advice about excess nitric and testing with stannous but he claims he still can't make it work. So I referred him to the forum. Hopefully he finds his answers here.”

There is no reason he cannot find the answer here on the forum, but it does take work in studying, all of the answers are here, there is a lot to recovery and refining, it takes some time to really understand it, and how it works, or the principles involved.

The first step in understanding is to study Hokes book, learn from reading forum, learning the tricks of the trade and how to do things properly from beginning to ending, understand why problems occur and how not to cause them in the first place, or how to correct them during the processes.

Some of the things needed to be able to precipitate gold, is having a clean gold in solution (proper pretreatments to remove base metals and tin), limiting the amount of nitric or other oxidizer, and removing these before attempting to precipitate the gold, testing of solutions can let you know if you have eliminated these oxidizers, know if you have gold in solution or, know when you have precipitated all of the gold out of solution.

To get the gold to precipitate without problems, begins in the first steps of recovery of your gold, and in each step you take in that process, and all of the steps in the refining stages, these steps throughout the process will determine what you will have up to the point of recovering the gold from solution when precipitating the gold, things done wrong early in these processes can affect the ending part of your process, when things are done right in your processes they work better and the outcome is better, things done wrong in a process can give problems latter on in the process, or cause the process to not work at all.


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## nōnāgintā trēs

To answer everyones questions of why I would try such a thing, I had only pyrosulfite to work with and for whatever reason I could'nt get it to work. At the time real SMB or "stump out" was not available to me. I tried oxalic, I tried ferris, ect,. ect,. ect,. I was new at the time and determined. I had more knowlege of chemistry than refining! So rather than waste the gold I dropped it with NaOH! I had a MASS of this orange brown insoluable powder that doesn't melt easily!!! So I tried different ways to turning AuOH3 (or what I thought was) into Au. 1 year later I turned it back using HCL to AuCl3 and now have access to SMB from sigma Al. Now all is well and I have experience of working with NaOH.

93


----------



## nōnāgintā trēs

goldenchild said:


> butcher said:
> 
> 
> 
> nōnāgintā trēs,
> 
> I really do not understand why you would try something like that; the gold can be cemented or chemically precipitated from the acidic solution as a fairly pure gold metal leaving most all of the other metals in solution.
> 
> When you removed the acid from the gold using NaOH where then the gold was no longer soluble in the salt water that formed, it would also precipitate hydroxides of the other base metals from solution, I do not think the gold would have formed a gold hydroxide, or even a gold oxide because gold is so un-reactive (caustic I do not believe would be strong enough at this stage), and since gold would most likely still be a chloride or elemental gold, I do not think the Karo syrup would have any action on the gold, as the way it does on silver oxides (silver forms oxides with NaOH), when using Karo syrup on silver oxide the sugars in Karo syrup assist in converting the silver to metal by removing the oxygen atoms, converting the oxide from the silver to water with the added hydrogen from the sugar in the syrup.
> 
> I would expect a mess in the melt, but as long as you kept this mess you should be able to get your gold back.
> 
> 
> 
> 
> I believe nōnāgintā trēs is silentiumestaureum93 on youtube. The reason he is set on using NaOH to precipitate gold is because he seems to not be able to get SMB to work. I have given him the typical advice about excess nitric and testing with stannous but he claims he still can't make it work. So I referred him to the forum. Hopefully he finds his answers here.
Click to expand...


Thank you kind Sir! I believe you could well be "Indeeditdoes" on youtube!


----------



## jimdoc

nōnāgintā trēs said:


> goldenchild said:
> 
> 
> 
> 
> 
> butcher said:
> 
> 
> 
> nōnāgintā trēs,
> 
> I really do not understand why you would try something like that; the gold can be cemented or chemically precipitated from the acidic solution as a fairly pure gold metal leaving most all of the other metals in solution.
> 
> When you removed the acid from the gold using NaOH where then the gold was no longer soluble in the salt water that formed, it would also precipitate hydroxides of the other base metals from solution, I do not think the gold would have formed a gold hydroxide, or even a gold oxide because gold is so un-reactive (caustic I do not believe would be strong enough at this stage), and since gold would most likely still be a chloride or elemental gold, I do not think the Karo syrup would have any action on the gold, as the way it does on silver oxides (silver forms oxides with NaOH), when using Karo syrup on silver oxide the sugars in Karo syrup assist in converting the silver to metal by removing the oxygen atoms, converting the oxide from the silver to water with the added hydrogen from the sugar in the syrup.
> 
> I would expect a mess in the melt, but as long as you kept this mess you should be able to get your gold back.
> 
> 
> 
> 
> I believe nōnāgintā trēs is silentiumestaureum93 on youtube. The reason he is set on using NaOH to precipitate gold is because he seems to not be able to get SMB to work. I have given him the typical advice about excess nitric and testing with stannous but he claims he still can't make it work. So I referred him to the forum. Hopefully he finds his answers here.
> 
> Click to expand...
> 
> 
> Thank you kind Sir! I believe you could well be "Indeeditdoes" on youtube!
Click to expand...


Nope, that would be Samuel-a. Goldenchild is metalicmario on Youtube.

Jim


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## nōnāgintā trēs

I owe Metal Mario an appology. I once commented that I didn't believe the silver powder in his video was from the same batch of silver scrap. I thought it was from numerious piles he'd been saving. Then I recently scraped 36 knives, forks, and spoons, and got a huge amount. I do it differently to him but still, MM if your reading this I do owe you an appology!!


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## staurum

I've got a problem with this method. Before applying this method, I used to recover silver by way of iron & sulfuric acid method. It worked but the problem was a lot of iron residues remained when silver is melting. Therefore I migrated to NaOH/sugar method.

I tried this method to recover my 40KG silver batch (after refining 15KG of gold dore). It worked fine initially until I discover that during melting the silver, there is a lot of NaOH remaining in the silver, wearing out my silica crucible after being used only 3 times. I tried to remove the NaOH by adding vinegar or HCl when rinsing the silver cement solution. Another problem occurred: the salt remains in the silver when melting, thus creating a lot of white fumes (I assume this is the lost AgCl in the air, and also my gold has gone completely out of calculation, i.e. loss of gold in form of AuCl).

I am wondering where I went wrong in the process.

Attempt 1. Silver Chloride in the water, Add NAOH, stir vigorously until all silver chloride looks jet black, add Dextrose sugar powder mixed in a bit of water, mix until all silver turns grey-ish. Then wash 6 times. 
Problem 1: a lot of suspended silver in the final rinse, thus I have to store lots of suspended silver water in plastic gallon buckets.
Problem 2: silver melts very quickly but lots NaOH fume is released, then breaks my silica crucible very quickly.

Which lead me to think: How do I get rid of the NaOH from the silver --- attempt 2

Attempt 2. Silver Chloride in the water, add NaOH, stir vigorously until all silver chloride looks jet black, then Wash 2-times to reduce the NaOH concentrate in the solution. Then I only add a little bit of Dextrose sugar powder. BOOM! the silver turns grey-ish right away. Wash again for the 3-rd time. After wards, I pour vinegar water or HCl until I see no suspension. Works WONDERFUL because I can see that all the silver settles very quickly. Only takes 3 rinses until the solution looks clear.
Problem 1: It dries slower, and when it melts, WHITE FUMES all over the place. Loss of SILVER (which is worse than the problems in attempt no.1 - above).


Somebody help me please


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## butcher

Silver chloride builds a type of crystals when it forms and precipitates, if in acid solution the crystals remain white even in the sunlight, but if the acid is rinsed from these crystals and left in water in the sun the sunlight can change the outer surface of the crystal from white to a violet or black looking color, the sunlight reducing the outer layer of silver chloride to silver metal.

It is my belief these crystals are hard to penetrate the tight bond of the silver chloride bond of the crystal, it seems bound up tight, hard to break up to a point where we can actually reduce all of the the silver on the inside of these crystals, to be able to reduce the silver back to metal, something else like your reducing agent (sunlight, iron/H2SO4, aluminum/HCl ,NaOH/Karo, or other) would have to give the silver an electron, the reducing agent basically break the bond of silver Cation and chloride Anion bond, normally with the reducing agent becoming the chloride freeing the silver metal, so if we do not get a good conversion we will still have silver chloride inside the crystals with only the outside of the silver being reduced to metal, I have found using an old household blender to do the very vigorous stirring need and to break up clumps of AgCl helps in the conversion to get a much better conversion not leaving some silver still bonded as a chloride.

You never want to let the silver chloride dry out as when dried the crystals lock up even harder making conversion even much more difficult than it is, keep the AgCl covered with water.

If you do not get a good conversion with the NaOH method you can be left with some silver chlorides, silver oxides, and some sodium and chlorides trying to make salt, along with your silver powders, A good conversion and good washings are needed.

Rinsing of the converted silver is also important, if you did a good job of silver conversion, NaCl is water soluble but it can still be hard to get it all out of the silver powders, and with the syrup it can be a little more of a challenge, Here again stirring and breaking up the silver powders well is important, heating the rinses helps to remove the sugar residues, it will help some removing the salt NaCl, but the trouble with salt is its solubility does not really change that much with temperature.

If you leave silver chloride unconverted, you will loose silver in the white smoke when melted, if you leave NaCl, the salt will convert silver back to a silver chloride in the melt, and again you loose silver in the white smoke of the melt.

One more point how much of the NaOH and Karo syrup are you using per ounce of silver? Too much or too little? GSP (Gold Silver Pro), gives us the amounts of these in a recipe or formula, to use for a good conversion.

Try finding a used kitchen blender to do the conversion and help with rinsing, or a drill and a good paint stirrer something to bust it up and mix it well...

I do not like dealing with silver chloride, when I have a choice I will not make silver chloride, silver nitrate is a breeze to cement the silver wash and melt with out having to convert it, it is always less trouble than the silver chloride which I believe is so much harder in several ways to convert or get back all of your silver.


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## staurum

Conversion of silver chloride to silver oxide - I am sure that I have it has all been converted because I did the vigorous stirring and I always checked that there is no more white colours on my silver oxide. Besides when you are processing a 10 KG batch in a plastic gallon bucket, Kitchen blender wont help much.

Proportion of NaOH and Kyro Syrup - I havenot really counted how much I used as I just went by colours and reaction. When it stopped reacting, I stopped adding more.

The reason I am using chloride method is its speed and efficiency. Copper here is very expensive. I wonder how much copper would I have used in every 40KG silver recovery


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## goldsilverpro

It takes a minimum of, theoretically, 20 g of NaOH and 13.3 ml of Light Karo syrup to convert 41.3g of AgCl to 31.1g of Ag (1 tr.oz.). To make sure it works, I add 10% extra (total of 22g NaOH + 14.6ml Karo syrup per troy oz of silver). This requires a lot of stirring to convert it. For the amount you are talking about, I would use a Lightin' type mixer in a topless plastic drum, with a prop that creates a chopping action, to break up the crystals, for at least 30 minutes.

You can't go by color. If the AgCl has crystallized, the Ag2O will coat the crystals and produce the proper color on the surface, but there will still be unconverted AgCl on the inside. Since you first posted this, I have thought the white fumes came from unconverted AgCl.

To do this properly, you need to know how much silver you are dealing with. The best way is to analyze the silver in the nitric solution before precipitating the AgCl. The simplest way to do this is with the Volhard titration.

You have a lot of silver. You can afford to spend some money to do it right.


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## staurum

Thank you for your tips. Really appreciate it. In the mean time I am very much forced to melt the silver cement first before inquarting my next-10 kg gold batch. The fumes are just unbelievable. No wonder I never got the silver back like I have calculated - it went up in white smokes. The next silver recovery would be lots of stirs! Will give you guys some update later. Thank you


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## lazersteve

If you melt a test sample and see smoke, simply repeat the sugar and lye application, rinse/wash cycle, and test another sample. No need in melting a full batch contaminated with silver chloride.

I use test melts all the time when working with silver conversion. Not only will test melts give you insight to silver chloride problems, but also melting a test sample can let you know if you have other metal contaminates present.

A small test melt is a good way to 'look before you leap' when working with silver.

Steve


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## staurum

I did repeat the sugar and lye mix, and rinse/wash cycle and re-melt it. The white fume still flies up. It's too troublesome to repeat the process again. I gave up and melt it down as I need to go on with the next gold refining order. 

I will try the POWER MIXER.


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## goldsilverpro

I forgot to mention that I use 100ml of water per troy oz of silver when converting.


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## lazersteve

I mix with a large plastic spoon and have no conversion problems at all. I *never* let my silver chloride dry out as it always stays wet under a layer of clean water in a large bucket until it is converted. Reaction is fast and complete most of the time with one pass. I scoop out a spoon of the converted silver and clean it up with hot water rinses, then melt the sample if everything is in order I precess the rest of the batch the same. If I get silver chloride I add a little more sugar and lye. I never measure, everything is by eye and the color of the liquid/powder. When the silver is done it tends to settle very fast and turns very light gray.

Steve


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## staurum

It does settle very fast and looks light grey, but after 2-3 rinses, the solution turns cloudy and lots of suspended silver occurred, thus very annoying to rinse. Do you reckon that I always have to use hot water to rinse? What is the best way to get rid of the NaOH and sugar from the silver sludge? Remember I am dealing with 10kg of silver batch times 4. I am tempted to use all the water in the world :lol:


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## butcher

staurum,
I would use small batches to experiment with. This way you can try several different things to see what works best. Knowing that what may work on a small batch may need more for a larger batch, like amount of acid rinse, best water temperature for acid rinse (how hot the water), like amount of time for the reaction, amount of stirring and what type of stirring is needed during the reaction, amount of reagents needed for complete conversion, what type of conversion may work better, or if you may make more money and save more time by not making silver chloride but using copper to cement silver wash and melt, small experiments with amount of rinsing needed and how to get the best results, what type of stirring works best, and time, amounts of reactants needed or temperatures needed...

I still do not understand Why you want to make silver chloride, especially in large batches that would be harder to deal with, 1 gram of copper will cement 3.4 grams of silver from AgNO3 solution, so if my math is right one pound of copper (453.5 g) will cement approximately 1,542 grams of silver (3.4g x 453.5g = 1,542g), or 1,542 / 31.103g = 49.57 ounces of silver per pound of copper, the copper cost I am guessing 2 to 3 dollars a pound, at 27 dollar silver spot ($27 x 49.57oz = $1,338.39 of silver for using 3 dollars of copper), copper price compare to the price of silver that is cheap, and you could just be losing more silver than that in your smoke right now, try a few experiments on a few small batch's, the copper could be recovered and reused after washing from the copper nitrate solution, to help save some on the copper you would need to purchase, you may also try and find a cheaper source for your copper. 

If your rinses look milky it can be silver chloride (possibly from a still acidic solution using up the NaOH before all of the silver chloride has reacted completely), if you did not rinse the acid out of the silver chloride well, you will have more acid for the sodium hydroxide to convert to salt, this could use up a good portion of your NaOH even before the NaOH has a chance to react with the silver chloride, the silver chloride can also trap acid especially in larger batches that are not stirred well or chopped up well during the rinsing of your acid hot water here can help also, giving enough time for the reaction to occur and a good stirring to break up and mix the solution well so that all of the silver gets converted, each silver atom needs to be freed from the chloride, and each chloride must be freed from the silver to join the sodium to make salt NaCl, if the silver chloride is in lumps or crystals, and not stirred very well for good exposure the reaction may not occur if the reagents and the reactant do not get good contact and stay in contact long enough to react, then the electron will not be able to move to every tiny atom in this large volume of heavy powders that need to give or take those tiny electrons, crystal can be like huge clumps of atoms to a small electron, and the this big clump of silver chloride may need broken up to expose the inside silver chloride atoms to the caustic solution to the tiny electron wanting to free the silver atom from its chloride bond.

Most things are more soluble in hot water than cold water, and hot water will normally do a better job, here the hot water will help with the syrup, and help to free the salt from the powders but NaCl itself is not that much more soluble in hot water compared to cooler water as many of the other salts are.


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## bee

hi i am new here but have a small refining setup i love to process the agcl the hoke gives very good accurate process i think i didnot lose the Ag yet as i always calculate the amount of ag and get accurate results .usually i recycle jewelers waist. some time the bulk solution force me to use the nacl then according to hoke,s take equal volume of borax and sodium carbonate mix them and take equal volume of this mixture and mix with dry agcl every thing should be mix and looks like sand then heat slowly for ten minutes then increase slowly donot let it boil when every thing melt wait for 5 to ten minutes .
how to check if all agcl converted to ag or not?.
pour a pinch of above mixture to crucible gently if you found its immediately boil over then the reaction is complete 
if nothing happen then let it stay on strong heat for a while. again check it with a pinch of mixture and you found immediately the melt is try to bubble up and try to boil over, the reaction is complete.
thanks
Big bee


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## staurum

Thank Butcher, GSP, and Lazersteve for the tips. I bought a drill and put a wood stick with mixer-shape at its end, and used it to chop up the silver chloride. It did store some clumps and the elemental silver I got is now very pure. I will post some pictures later.

Now the only problem I have is trying to minimise the lye in my silver sludge cement solution. I am affraid to use vinegar or HCl due to previous experiment failures.I tried hot water rinse whilst filtering but the lye didnot seem to come off so easily. Any opinions?


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## butcher

Sodium hydroxide should is very water soluble, but I believe unless you overused the amount of NaOH you should not be left with much to wash out after the reaction.

sodium hydroxide reacts with hydrochloric acid to form sodium chloride (common salt and water):
NaOH + HCl --> NaCl + H2O

With silver chloride, sodium hydroxide and Karo syrup,the salt will also form.

2AgCl +3NaOH + C6H12O6 --> 2Ag + 2NaCl + C6H11O7 . Na

Sodium hydroxide solubility in water:
109g/100ml @20 deg C
174g/100ml @60 deg C

Sodium chloride solubility in H2O:
35g/100ml @ 0 deg C
38.9g/100ml @ 100 deg C

mixing well is also important in rinsing the silver.

For 5 gallon buckets a paint stirrer works great on a drill (the bottom of the bucket should be scrapped with a flat wooden stick to remove solids which seem to stick to the bottom of the bucket), The paint stirrer rotates material from the bottom and circulates the material through the blades of the mixer chopping up and stirring solution very well.


http://en.wikipedia.org/wiki/Solubility_table


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## staurum

Yes butcher, I found that the stirrer is the solution. but the other one is rinsing the silver sludge with the water waste which you get when you rinse your AgCl. The suspended silver settles very quickly. and now I am able to recover at least 97% of my silver. leaving 2.xx% in the stored waste.


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## Garagetinkerer

publius said:


> I am concerned with waste disposal and purity issues.



Hi there. New to the forum. I have been experimenting with conversion of AgCl using the karo/NaOH method. However, I am concerned with the disposal of the "waste" products post reaction. Once I have converted the AgCl to elemental silver, I am left with a dark greenish/brownish liquid that I am not sure what to do with. I've read that the constituents are Ag, NaCl and sodium gluconate. Is that correct? And can this waste be disposed of or converted into something useful? Any hints?


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## butcher

Silver Chloride and sodium hydroxide with Karo light corn syrup (glucose) gives us elemental silver metal, sodium chloride (salt) and gluconic acid (gluconate neutral pH).
2AgCl (s) + 3NaOH (aq) + C6H11O6 --> 2Ag(s) + 2NaCl (aq)+ C6H11O7 Na (aq)

The salt and reduced sugar are not a problem to dispose of, these both have uses, but I do not see where we would gain anything by trying.
This being an organic I do not mix it with my regular waste stream, it can keep magnesium or calcium from precipitating easily, at least from what I understand, and many times I use forms of these to treat my waste.

http://en.wikipedia.org/wiki/Gluconic_acid 
http://www.google.com/#hl=en&sclient=psy-ab&q=uses+of+gluconate+&oq=uses+of+gluconate+&gs_l=serp.12..0i22i30l10.6579.14009.1.23461.9.9.0.0.0.0.283.1502.0j8j1.9.0...0.0...1c.1.11.serp.r4i3ApAABUw&psj=1&bav=on.2,or.r_qf.&fp=a1053594b2a81dec&biw=939&bih=563


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## Yves_Michel

Butcher's equation is: "2AgCl (s) + 3NaOH (aq) + C6H11O6 --> 2Ag(s) + 2NaCl (aq)+ C6H11O7 Na (aq)" 
My question is how many electrons the C6H11O6 (glucose or fructose) the aldehyde group gives? Correct me if I am wrong but is not suppose to be only one. Therefore we have 2 Ag+ that need one electron each the equation should be written "2AgCl (s) + 3NaOH (aq) + 2C6H11O6 --> 2Ag(s) + 2NaCl (aq)+ 2C6H11O7 Na (aq)" ? That is doubling the amount of the glucose. 

Yves


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## butcher

2AgCl (s) + 3NaOH (aq) + C6H11O6 --> 2Ag(s) + 2NaCl (aq)+ C6H11O7 Na (aq)

Those are moles of units of silver and moles of glucose...
one mole of silver is 107.8 grams of silver, so in the equation we are talking about converting two moles of silver or 215.6 grams of silver metal from the silver chloride, using one mole of C6H11O6 karo syrup.

so we need more than one electron to react with the silver chloride to convert almost 7 troy ounces of silver metal, and one mole of glucose should contain enough electrons to handle the job.

the molecular weight of one mole of C6H11O6
C =12g/mol 
H = 1g/mol
O = 16g/mol
we have 
C6 (6x12g/mol = 72g for 6mol carbon)
H11 (11x1g/mol = 11g for 11mol hydrogen)
O6 (6x16g/mol = 96g for 5mol oxygen)
or
72+11+96=179 grams 

NaOH
Na = 22.9g/mol
O = 16g/mol
H = 1g/mol
NaOH =40g/mol
3NaOH = 120grams

so 179 grams of glucose needed to react with 2moles of silver in the silver chloride.

silver chloride 
AgCl
Ag = 107.86g/mol
Cl = 35.4g/mol
AgCl =143.3g/mol
We have two moles of silver chloride so 2 x 143.3g =286 grams of silver chloride in the formula.

So from the equation we see that two moles of silver chloride 286 grams, and 179 grams of glucose and 120 grams of sodium hydroxide will give us about 7 troy ounces of silver metal (with billions of atoms in their shell all with a full shells of electrons.


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## g_axelsson

Butcher, that was a really detailed and exhaustive answer... sadly it's wrong and not what was asked. The question was in other words "To convert 2Ag+ to 2Ag you need two electrons. One comes from C6H11O6 that turns into C6H11O7-+Na+, where does the second electron come from?"

Well, maybe your answer wasn't totally wrong, but at least it contains an error.



butcher said:


> 2AgCl (s) + 3NaOH (aq) + C6H11O6 --> 2Ag(s) + 2NaCl (aq)+ C6H11O7 Na (aq)


Both sides contains only neutral compounds so obviously the electrons should balance out, but does the elements balance?

2AgCl + 3NaOH + C6H11O6 --> 2Ag + 2NaCl + C6H11O7Na

2 Ag on both sides, 2 Cl on both sides, 3 Na on both sides, 9 O on left but 7 on right, 14 H on left but 11 H on right, 6 C on both sides.
You have forgotten 3 H and 2 O on the right hand side, sounds like an H2O and OH (Without charge! :shock: ).

I suspect that the equation is more like (Where the aldehyde group -H-(C=O) > turns into a carboxylic acid (-COOH)) and the Na is actually Na+ associated with OH-
2AgCl + 3NaOH + C6H11O6 --> 2Ag + 2NaCl + C6H11O7 + H2O + NaOH

A second step could turn the carboxylic acid group (-COOH ) and the NaOH into (-COONa) and H2O so the total equation is (changes in red)

2AgCl + 3NaOH + C6H11O6 --> 2Ag + 2NaCl + C6H10O7Na + 2H2O

The answer to the question is : The change in oxidation state of the 2Ag+ reduced into 2Ag is powered by the aldehyde group is oxidized into carboxylic acid by an oxygen atom.



butcher said:


> Those are moles of units of silver and moles of glucose...


It doesn't matter if we are talking about electrons and atoms or moles of electrons and atoms. The equations must balance in the end.

Disclaimer : I'm a mathematician and physicist so my chemical knowledge is nothing but a couple of google searches and wikipedia, but I can count and spot an error. So I'm standing by my statement that there is an error but my solution could be just as wrong or even worse. Time to let the chemists check my reasoning.

Göran


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## butcher

g_axelsson,
Thanks, I was only trying to show there were a lot of atoms and electrons in the equation, and it was a formula of moles, so there are definitely more than one electron.

I believe this is more of a chemical reaction,used to reduce silver back to metal not just an electron exchange.


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## butcher

Actually I am still unsure how these long carbon chains would react, and what the actual byproduct from the reaction would be.
http://en.wikipedia.org/wiki/Glucuronic_acid
http://en.wikipedia.org/wiki/Category:Sugar_acids
http://en.wikipedia.org/wiki/C6H12O6
http://www.chemspider.com/Chemical-Structure.23253896.html
https://www.google.com/#q=C6H11O7


----------



## g_axelsson

butcher said:


> g_axelsson,
> Thanks, I was only trying to show there were a lot of atoms and electrons in the equation, and it was a formula of moles, so there are definitely more than one electron.
> 
> I believe this is more of a chemical reaction,used to reduce silver back to metal not just an electron exchange.


We never use formulas of moles, it is just chemical formulas. If we are using single atoms, single moles or thousands of atoms as an unit is of no consequence, it's just a scale factor.

If we create water from oxygen and hydrogen we use the formula 2H2 + O2 -> 2 H2O. This is the most basic formula of this equation, but nothing says anything about the scale of the reaction, if it involves atoms or moles. A mole is just a large number, 6.02214129×1023, but instead of mole you can use any number you like... or if you really insist on counting with moles...

1.204428258x1024 H2 + 6.02214129×1023O2 -> 1.204428258x1024 H2O

If you are missing an electron in the simple formula, then you are missing a mole of electrons if you scale it up to moles. Just because there are a lot of electrons doesn't mean it is enough of electrons.

By the way, 99% of chemistry *is* electron transfers, the rest is folding and chirality.

Göran


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## moose7802

I need to start understanding how these equations work. Could someone point me in the direction of a basic chemistry book that I could start learning this from? Sorry for the outside post! 

Tyler


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## butcher

I often use formulas of moles all the time, the formulas and equations of moles, so that I have an idea of how much of one chemical I need to react with another chemical to get the reaction I am trying to achieve. 

I tried to find the formula for glucose sugar conversion of silver chloride in a caustic solution, from this paper the byproduct is thought to be, or presumed to be Gluconic acid (C6H11O7), but they did not really know for sure either.
I do not know but the gluconic acid may also be converted to sodium gluconate (NaC6H11O7). 

2AgCl + 3NaOH + C6H12O6 --> 2Ag + C6H11O7.Na +2NaCl + 2H2O

http://library.deerfield.edu/pdfs/ChemAgAckerman.pdf

http://en.wikipedia.org/wiki/Glucose

http://en.wikipedia.org/wiki/Gluconic_acid

http://en.wikipedia.org/wiki/Sodium_gluconate


Basically to me, just by looking at this the sodium is taking the chlorides from the silver, this may be where most of the electron transfer occurs although the glucose carbon compound is reduced also in the reaction,this looks like somewhat of a replacement reaction assisted by the reduction of the sugar, I cannot explain what is actually happening here, I have enough trouble trying to learn and understand just a little bit of the inorganic chemistry, and have not studied the organic chemistry, of these long chain carbon compounds like sugar, I will leave that to the biochemist,or chemist who learn it in school, I have enough trouble just trying to get the silver back from the silver chloride.

edit word from inorganic to organic


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## samuel-a

I think the equations above are over simplified, thus making it hrad for us to wrap our mind around the reaction dynamics.

I believe there are several reactions taking place, some in sequential order and some simultaneously:
- Silver Chloride is converted to Silver Oxide by adding Lye.
- Glucose react: 1. with lye solution to form Sodium Gluconate 2. with Silver oxide to produce Gluconic acid and Silver metal 
- Sodium Gluconate reacts with Silver Oxide to form Silver metal and H2/CO2

The process seems to produce vast amounts of H2 and/or CO2 gases, and i see no mentioning of that in Ackerman's report... Though there's might be other side reactions i can't think of.

To be honest, i couldn't find any reliable source who can give us a direct answer as to what exactly going on in this reaction.


----------



## butcher

I think this mystery will probably continue at least unless we learn more about the complicated organic chemistry.

I believe samuel-a is correct on the reaction of silver chloride forming an silver oxide in solution as an intermediate reaction, and here in our formula with karo syrup we see we also have excess sodium hydroxide (1 mole excess) (after Ag2O forms) for the sugar to react with the excess sodium hydroxide in solution to react with the silver I oxide that was formed.

2AgCl + 2NaOH --> Ag2O + 2NaCl +H2O


In our formula for silver chloride reduction using sodium hydroxide and glucose (karo syrup):
2AgCl +3NaOH + C6H12O6 --> 2Ag + NaC6H11O7 +2NaCl + H2O

In looking at the glucose reduction we see the glucose gives up an H in its chain and gains an O in its place.
I assume with the reaction of that extra mole of NaOH and the Ag2O.

I could not draw the chain here, but if you look at the pictures here (wiki link below),for glucose, then for sodium gluconate we see this. 
We Know the silver gives up it chloride, and sodium ends up with it as salt water, we also assume the glucose sugar forms sodium gluconate in solution. 

http://en.wikipedia.org/wiki/Glucose
http://en.wikipedia.org/wiki/Sodium_gluconate


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## butcher

Again with no knowledge of organic chemistry, some of these things have me wondering and wanting to learn more. While confusing me more, the more I try to figure it out.

Apparently glucose (sugars) contains an aldehyde group.

I wonder if this does not play a major part in converting silver chloride to metal when using glucose (Karo syrup and NaOH method of reduction of silver chloride to silver) similar?
Similar to the formaldehyde reduction methods?
Or 
Something similar to oxidation of formyl oxxidation in making mirrors with formaldehydes? 

The formyl group readily oxidized in an oxidation reaction is the basis of the silver mirror test. In this test, an aldehyde is treated with Tollens reagent, which is prepared by adding a drop of sodium hydroxidesolution into silver nitrate solution to give a precipitate of silver(I) oxide, and then adding just enough dilute ammonia solution to redissolve the precipitate in aqueous ammonia to produce [Ag(NH3)2]+ complex. This reagent will convert aldehydes to carboxylic acids without attacking carbon-carbon double-bonds. The name silver mirror test arises because this reaction will produce a precipitate of silver whose presence can be used to test for the presence of an aldehyde.

A further oxidation reaction involves Fehlings reagentas a test. The Cu2+ complex ions are reduced to a red brick coloured Cu2O precipitate.
https://www.google.com/#q=aldehyde+group+reduction+silver+salts
Aldehydes are strong reducing agents and reduce the metal ion and are oxidised in the process
i.e. RCHO + [O] ==> RCOOH
Reduction of silver(I) ion to silver metal
RCHO + 2Ag+ + H2O ==> RCOOH + 2Ag + 2H+
Or
Reduction of copper(II) to copper(I) i.e. the blue solution of the Cu2+ complex changes to the brown/brick red color of insoluble copper(I) oxide Cu2O.
RCHO + 2Cu2+ + 2H2O ==> RCOOH + Cu2O + 4H+
Oxidation sugars:
http://butane.chem.uiuc.edu/pshapley/GenChem2/B7/book.pdf
http://en.wikipedia.org/wiki/Reducing_sugar


I am sure there is a simple explanation as to what happens in our reaction of reducing silver chloride to metal with glucose (karo syrup) and sodium hydroxide.
But I do not see it yet.
This mystery still alludes me.


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## Lou

Butcher,

To answer your question:

What does the reduction is the aldehyde (http://en.wikipedia.org/wiki/Aldehyde) functionality on a sugar. Simple sugars with an aldehyde group are called aldoses ( http://en.wikipedia.org/wiki/Aldose ). More complex sugars that have an aldehyde or can form one via hydrolysis (basically OH- from caustic attacking the glycoside bond at the anomeric carbon, breaking the hemiacetal by ring opening) are called _reducing sugars_ ( http://en.wikipedia.org/wiki/Reducing_sugar ).

This is the chemical basis for the Tollens' test, where Ag2O oxidizes that aldehyde into a carboxylic acid.

This means that the better sugars to use for this process are simple, small sugars that are easily oxidized and do not have to undergo hydrolysis to make the reducing part of it accessible. 

Generally, it is preferred to use simple sugars rather than plain aldehydes like formaldehyde because of the ease in handling, and their inherent low toxicity.

A simple effective sugar for silver reduction is:
glucose/dextrose

These sugars polymerize as well to yield active reducing sugars.


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## samuel-a

Lou,

Can you breake it down into simple redox equations?
Considering side reactions (if there are any), what would the stoichiometric ratio be?
What would be the optimal water volume per mole AgCl to accommodate the reaction?


On a side note, what is your take on reducing Agcl with Sodium borohydride (other than the fact it is expensive)?


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## butcher

Lou, thank you very much for taking the time out of your busy day to add helpful information to this topic.


The organic chemistry is a real mystery to me, I begin to get real confused with so many H’s and O’s tied up in those long chains attaching themselves to those carbons, and the funny drawings of those complicated circles, and all of those big long funny names, and trying to follow what those scientist who write about them are trying to say.

I see where glucose C6H12O6 can be expressed as C6 (H2O)6, showing the hydrolyzed carbon.

I was just wondering if sodium gluconate NaC6H11O7could not be expressed something like this?
My presumption NaC6(H2O)5 (HOO)
(If some knows the correct way to express sodium gluconate showing it’s hydrolyzed carbon formula (something like this) I would like to know how it is written properly).

If so this kind of shows where in reduction, one of the (H2O) in glucose carbon chain, becomes HOO replacing a hydrogen in its chain with an oxygen in the glucose reduction to gluconate, I also understand the (H2O) is not water, and is just used expressed in this manner to show hydrolyzed carbon (sugar).

Another assumption on my part would be writing the formula something like this:

AgCl + 3NaOH + [C6(H2O)6] --> 2Ag + [Na C6(H2O)5 HOO] + 2NaCl +2H2O

I wonder if this would be correct to express the formula for reduction of silver using karo syrup (glucose) and sodium hydroxide this way.


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## g_axelsson

I wouldn't write a formula with (H2O) as a grouping, that implies that water is an integral part of the molecule. By writing H2O it implies that the hydrogen atoms is connected to the oxygen atom. In the case of glucose it is apparent that no H2O molecules are involved in the molecule, any oxygen is either part of an OH group or double bounded to a carbon atom.






Disclaimer: I'm writing this under the influence of C2H5OH

Göran


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## butcher

hydrolysis of carbon does implies that water is an integral part of the molecule.
hydrolysis the breaking of water H+and OH- bonds.
Although the bonds with carbon are no longer water, when bonded to the carbon chain.
Cn(H2O)n is just another way to show the hydrolysis of carbon in a formula.

Glucose can be written as C6H12O6 or as C6(H2O)6 either is correct, neither of these show how the water is broken or how the H or OH are in bond with the carbons in the chain.


I was just unsure of the proper way to express sodium gluconate as NaCn(H2O)n in the formula.

I thought also by expressing the equation in this fashion: 
AgCl + 3NaOH + [C6(H2O)6] --> 2Ag + [Na C6(H2O)5 HOO] + 2NaCl +2H2O
We may be able to see easier where the H in the chain is replace by an O, as written in a chemical formula expressing the reaction.


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## Lou

Butcher:

The stoichiometry of the reaction is dependent on if one is using a sugar that doesn't have a free aldehyde; if it's a disaccharide, you will need an equivalent of base to open it up, above and beyond what is needed for the conversion of AgCl--> Ag2O.* Based off of Butcher's mechanism he kindly provided, you'll need just two equivalents of base alone for the aldehyde.

For the reduction, it's one electron (Ag+ --> Ag(0)) so it will take one equivalent of silver for every equivalent of sugar. It will take 1 equivalent of caustic soda for every two equivalents of silver. Then one should add an excess of caustic to help bring the Ag2O into solution more as its soluble hydroxide complex, which helps shuttle silver into the aqueous phase where it is reduced.

@Samuel_a:

Borohydride is a great, nonselective reducing agent. It's what I call a kitchen sink reductant, because it goes after pretty much every metal above -700 mV. Issue with it is, it's transient and hydrolyses quite rapidly in acidic milieu. Basic solutions like Dow's Venmet, are 12% solutions in 50% v/v NaOH, and store for years. Unlike N2H4 which only works well on PGMs (with perhaps the exception of the easy to reduce Pd) when there is plenty of base in solution, borohydride works best from pH 1-4, optimally at 2-2.5. The reduction is instant, and quantitative when excess is used. 

As it is capable of a 4 electron reduction and has a low molecular weight, it's very efficient on a gram for gram basis. Nickel and copper (which are reduced by borohydride, to their respective borides, which then hydrolyze and reduce further to the metal). I don't know how expensive the powdered material is, but 5 gallons of 12% material is about $300 and will reduce hundreds of thousands of dollars in PGMs. I think it would be a waste to do with silver.

I don't even know why people are so caught up on the sugar reduction. Makes much more waste. I think it's preferable to just make the silver oxide (which won't quantitatively give you your silver, it is slightly soluble, particularly in excess base) and filter that, then melt with borax/carbonate.


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## samuel-a

Thanks Lou,

I too share your thought about the actual need to use the sugar reduction. But i do use it in cases when time doesn't permit the long long evaporation -> drying -> decomp. of Ag2O. This is just my point of view according to my specific setup capabilities. 
I really like how the silver powder comes down heavy and chunky after dextrose reduction and is quick to dry too. I usually never even wait for it to dry completly and put it damp in a hot crucible and let it steam out (important to say, i never add damp powder to an already molen metal).


As to the NaBH4, i can get dry powder (reagent grade) for 35$/Kg.
I'm not quite sure what the reaction is exactly,b but i deduct it will cost me appx. 14$ per Kg (assuming an 15% excess) of silver reduced. 
Unless i did the calculation wrong I agree it's quite borderline for Silver refining usage.


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## butcher

Although from a different reaction (Tollens reagent) reduction of a silver complex, this shows the aldehyde group of glucose (portion of the carbon chain)being converted to gluconic acid as silver is reduced from the complex.
http://www.walkingitaly.com/tuserg/tuserg_metallo/D-Tollens-e.htm


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## Lou

You're getting borohydride for that cheap? I'll be glad to buy some of it--Dow has been ripping me off!


I don't think it'll cost that much.


37.83 g/mol gives four electron-mol reducing power.

So 0.03783 kg will (theoretically: there are side reactions) reduce about 0.431 kg of Ag.

More like $5/kg Ag at the top end.

Like I said, we don't use for silver (between pyro and cell, no need to use any hydrometallurgy).


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## samuel-a

Thanks Lou, seems like i had to factor in the H2 generation as well.
If that's the case, this might work for me.



Lou said:


> You're getting borohydride for that cheap? I'll be glad to buy some of it--Dow has been ripping me off!
> 
> 
> I don't think it'll cost that much.



Yes, that is the price i can get it for. But there is a catch, as it means i need to join in a "pool purchase" (if you will), where the material is imported in bulk by several entities and the minimum buy-in is for 100Kg.
Don't know what in the world i'll do with so much material...


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## Lou

If it's lab grade, probably about $200/kg.


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## samuel-a

Lou said:


> If it's lab grade, probably about $200/kg.



I suppose it might.
Though i was referring to reagent grade material.


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## au-artifax

butcher said:


> I think this mystery will probably continue at least unless we learn more about the complicated organic chemistry.
> 
> I believe samuel-a is correct on the reaction of silver chloride forming an silver oxide in solution as an intermediate reaction, and here in our formula with karo syrup we see we also have excess sodium hydroxide (1 mole excess) (after Ag2O forms) for the sugar to react with the excess sodium hydroxide in solution to react with the silver I oxide that was formed.
> 
> 2AgCl + 2NaOH --> Ag2O + 2NaCl +H2O
> 
> 
> In our formula for silver chloride reduction using sodium hydroxide and glucose (karo syrup):
> 2AgCl +3NaOH + C6H12O6 --> 2Ag + NaC6H11O7 +2NaCl + H2O
> 
> In looking at the glucose reduction we see the glucose gives up an H in its chain and gains an O in its place.
> I assume with the reaction of that extra mole of NaOH and the Ag2O.
> 
> I could not draw the chain here, but if you look at the pictures here (wiki link below),for glucose, then for sodium gluconate we see this.
> We Know the silver gives up it chloride, and sodium ends up with it as salt water, we also assume the glucose sugar forms sodium gluconate in solution.
> 
> http://en.wikipedia.org/wiki/Glucose
> http://en.wikipedia.org/wiki/Sodium_gluconate


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## ashapura refinery

Hello Everybody

I have gone through the posts on this topic and I tried the procedures mentioned here. 

The steps I did for the silver refining:

1. Mixed Salt (With Iodine), sugar and caustic soda together
2. added the above mentioned mixture to the Silver Nitrate Solution - the metal started settling down
3. filtered the solution 
4. washed the solution with HCL

The outcome looks something like this -


Does this look correct or is there something wrong in this? And since I have used salt with iodine - will it create problems?


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## 4metals

You seem to have combined all of the steps into one. It doesn't work like that.

First add salt or hydrochloric acid to your silver nitrate, non iodide salt will prevent the formation of silver iodide. 

Filter the silver chloride from the solution and rinse it well.

Now slurry the silver chloride to make it a thin paste and add the sodium hydroxide to the slurry. You will see the solution turn dark. Mix it well to eliminate any small white specs which are unreacted silver chloride. You now have silver oxide.

Then you add your corn syrup to reduce the silver oxide to metallic silver.

The down side to this method is it takes a lot of rinse water to get the purity high.


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## ashapura refinery

4metals said:


> You seem to have combined all of the steps into one. It doesn't work like that.
> 
> First add salt or hydrochloric acid to your silver nitrate, non iodide salt will prevent the formation of silver iodide.
> 
> Filter the silver chloride from the solution and rinse it well.
> 
> Now slurry the silver chloride to make it a thin paste and add the sodium hydroxide to the slurry. You will see the solution turn dark. Mix it well to eliminate any small white specs which are unreacted silver chloride. You now have silver oxide.
> 
> Then you add your corn syrup to reduce the silver oxide to metallic silver.
> 
> The down side to this method is it takes a lot of rinse water to get the purity high.



Thank you for the reply. I will re-try the method as per the instructions. 
Can you explain further what is the difference between corn syrup and sugar syrup? And sugar syrup is made by mixing sugar in water - right? 
And right now I am not able to get corn syrup so can I go ahead with Sugar?


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## Palladium

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=14618#p147119


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## ashapura refinery

Palladium said:


> http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=14618#p147119



Thank you for the reference.


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