# Stainless Steel for AgCl + NaOH + Glucose



## amesametrita (Oct 21, 2012)

Dear forum members,

Is it possible to use stainless steel reactors for silver refining process?
I mean AFTER washing AgCl may I put the salt in SS reactor, heat it, then add NaOH, then after AgO formation add Glucose.
I'm afraid that SS is weak to Cl ions.

Any advice for reactor material for 100 liters batches?

Best regards!


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## goldsilverpro (Oct 21, 2012)

amesametrita said:


> Dear forum members,
> 
> Is it possible to use stainless steel reactors for silver refining process?
> I mean AFTER washing AgCl may I put the salt in SS reactor, heat it, then add NaOH, then after AgO formation add Glucose.
> ...



Personally, I would not use stainless. You're probably considering stainless because you think heating is necessary. It isn't.

I've done this many times in about 140-150 liter, 900-1000 oz, batches, more or less (note: see *** below). I used a plastic 55 gallon drum with the top cut out close to the rim, but leaving the top reinforcement rim intact. I never found it necessary to heat the solution. Stirring is very important. The best way to stir is with a mounted, SS prop, SS shaft, electric stirrer or mixer - Lightin' is an excellent popular brand here. This provides sort of a chopping action and helps insure a complete reaction. 

If you don't have a power stirrer, you can stir manually but it's not as effective and requires a lot more labor. However, I have done it many times and have gotten 100% conversion. If the AgCl has been kept wet and has never been allowed to dry, it works quite well. For manual stirring, I cut about a 6" disc of the thick plastic from the drum top, drilled a hole in the center (to fit the pipe), and mounted it on the end of about a 4.5 foot length of 3/4" PVC pipe, using a short nipple, a coupling, and a cap. In order of assembly, that would be pipe - coupling - nipple - disc - pipe cap. The nipple should be short enough so that the disc is held snug between the coupling and cap after cementing all the PVC fittings together. To make the pipe more rigid, I put a length of 1/4" or 3/8" rebar inside it and secured it with a cemented pipe cap on the other end of the pipe. It also helps to drill a few 1/2" holes in the disc. I stirred with this, slowly, using an up-and-down, plunger motion. Much more effective than stirring in circles with a rod. Also, much less effort is needed. Go slow on the upstroke or you'll slosh it onto you. Use a full face shield.

I used water, NaOH, and Karo original light (as opposed to the dark variety) corn syrup. For 1 troy oz of silver, by a series of lab experiments I ran, I found it takes 133ml of tap water, 20g of NaOH, and 13.3ml of syrup. I always used 10% extra of the 2 chemicals. I used liquid 50% caustic soda solution (6.25 pounds/gallon - 750g/l - of NaOH) which is available in drums and is much more convenient and somewhat less dangerous than dissolving dry NaOH. If you only have solid NaOH, I would add it very carefully in increments to all of the necessary water, while continually stirring. Once dissolved, let it cool a bit and add the AgCl in increments, with continuous stirring. Then, add the syrup with stirring. Then stir it for at least 30-60 more minutes and test it (see below). With manual stirring, you can trade off with a partner. All in all, I stirred it almost continuously from start to finish. It definitely helps to have 2 people.

With the chemicals I used, the solution turned a dark reddish color. The silver settled quickly. I removed the stirrer, raised the drum up (using a forklift - the drum was originally placed on a pallet before starting the process), let it settle, siphoned, filtered, rinsed well, melted it, and ran the bars through a silver cell. If you don't have a forklift, you can first put the drum on a very heavy duty table or a stack of very heavy duty pallets. The solution might weigh 400 pounds. To siphon into another drum, I like the bottom of the upper drum to be at least level with the top of the lower drum. The upper drum could be a little lower but it won't siphon as fast near the end.

*Notes:* Once the AgCl is formed, it should never be allowed to dry out. I would have the NaOH dissolved and ready before filtering and rinsing the AgCl. If the AgCl does dry out, it crystallizes, and a 100% conversion can sometimes be difficult even with extended stirring times using a power stirrer. When you melt the silver, unconverted AgCl will show up as a separate greenish (usually) layer between the slag and the silver bar after cooling.

You can test for complete conversion by dipping out a small sample (say, 2 or 3 grams) of the silver powder, putting it in a small beaker, rinsing and decanting it VERY well, a number of times, in hot distilled water (also, rinse the entire inside of the beaker each time with distilled water from a squirt bottle), and then dissolving the silver in a small amount of 50/50, nitric/distilled water. About 2.4ml of 50/50 nitric will dissolve a gram of silver. After dissolving, any unconverted AgCl will appear as a white cloud or powder. The trick is to rinse out all of the dissolved chlorides before using the nitric (you can test for chlorides in the rinse by pouring some into another small beaker and adding a drop or two of silver nitrate solution). If the nitric test shows unconverted AgCl, keep stirring the solution in the drum. If you didn't know the total silver and, therefore, the chemicals you added was a guess, you may need to add more.

To me, it was always important to know the amount of silver I was dealing with. Therefore, I always used the quick and simple Volhard titration method to analyze the silver in the nitric solution before adding HCl to precipitate the AgCl. Otherwise, excess NaOH and Karo would be necessary. You can also get an idea of the total silver by knowing exactly how much HCl or NaCl (in solution) it took to precipitate the AgCl.

*** The numbers I gave above are somewhat optimistic. In thinking further about this, to prevent sloshing solution out during stirring, I would suggest not putting too much solution in the drum. I would leave at least 8" and, preferably, 12" of space above the solution to allow for this. A 55 gal drum is about 31" tall. Therefore, 12" of space would allow about 38 gal. of solution. Figuring about 175ml of solution per tr.oz. of silver, that would allow about 730 oz/ batch.

Note that, in my method, everything except the AgCl is in liquid form. I prefer it that way. Makes things simpler.

*EDIT:* Since first posting this, I have edited it 20 or 30 times. I'm probably finished with it but, who knows? Therefore, if you want to use this process, re-read it before you start. If you have any questions, please ask them.

Hope this helps,
Chris


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## amesametrita (Oct 21, 2012)

goldsilverpro said:


> Hope this helps,
> Chris



Clear!

Thank you very much!


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## kadriver (Oct 23, 2012)

5 gallon buckets work good also. I just did a batch of silver chloride this evening - 2.5 liters.

It took 4, one pound bottles of sodium hydroxide (lye) to turn the silver chloride completely black.

I used plain table sugar to convert the silver oxide to elemental silver.

I use a 2 foot section of 3/8 PVC with bamboo skewers inserted into holes drilled into one end, and attach the other end to an electric hand drill to power the stir rod.

I have to keep a watch on the bamboo, they deteriorate and put bits of bamboo into the silver if I am not careful. I check frequently and change when they start to fray.

I like the idea of a plastic disk instead of bamboo skewers.

When I rinse the silver, I test the rinse water with pH test strips to ensure there is no NaOH in the silver. I keep rinsing until the pH tests neutral, then I rinse one more time.

I etched the bottom of one of my corningware dishes by adding silver powder (to dry it for melting) that was not completely rinsed of all the lye solution.

Lye will etch glass. Molten NaOH will dissolve glass.

kadriver


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## goldsilverpro (Oct 23, 2012)

kadriver said:


> 5 gallon buckets work good also. I just did a batch of silver chloride this evening - 2.5 liters.
> 
> It took 4, one pound bottles of sodium hydroxide (lye) to turn the silver chloride completely black.
> 
> ...



For buckets, a cheap red rubber toilet plunger with a wooden handle works great. An all plastic one with the pinched bottom part cut off would work better. Up and down.


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## kadriver (Oct 24, 2012)

goldsilverpro said:


> The trick is to rinse out all of the dissolved chlorides before using the nitric (you can test for chlorides in the rinse by pouring some into another small beaker and adding a drop or two of silver nitrate solution).
> 
> Chris



After adding a drop or two of silver nitrate solution, what should we observe as the result to see if the chlorides are gone or not.

Thanks - Kevin


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## goldsilverpro (Oct 24, 2012)

kadriver said:


> goldsilverpro said:
> 
> 
> > The trick is to rinse out all of the dissolved chlorides before using the nitric (you can test for chlorides in the rinse by pouring some into another small beaker and adding a drop or two of silver nitrate solution).
> ...


A white cloud if chlorides are present.


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## kadriver (Oct 25, 2012)

I drew out a small sample of the silver from the batch of silver chloride that I processed with NaOH and cane sugar.

I washed it repeatedly, checking pH with test strips until neutral. I used tap water first, then switched to boiling distilled water for at least 4 final rinses.

I took about a gram of the silver from the washed silver sample, added 2ml distilled water and then nitric acid drop by drop until all the silver dissolved.

The sample was cloudy, I set it in the freezer and the silver chloride settled to the bottom of the small beaker.

Because I was getting a cloudy sample from this test, I added some more sodium hydroxide and sugar to the whole batch and stirred it for about 15 or 20 more minutes with my electric drill and stirring rod.

Then I repeated the test. This time the sample dissolved and it was clear, but I added some distilled water and it clouded up again so I repeated the test, but first I washed the sample with more boiling distilled water to ensure no chlorides from the tap water rinses remained.

Below is a photo of each of these last two tests - they each started clear after dissolving in nitric, but both clouded up after adding distilled water.

In the second photo I added about 1 or 2 ml of ammonium hydroxide to the beaker on the right and the cloudiness went away - this tells me that it is probably still some silver chloride in my silver.


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## kadriver (Oct 25, 2012)

So I added more NaOH and sugar and stirred for 15 minutes longer with the drill and stir rod.

I repeated the test, this time using boiling distilled water for all the rinses.

It dissolved crystal clear, but clouded up as soon as I added distilled water.

I concluded that there is probably enough chemicals in the mix, I just need to stir it some more.

I am going to the hobby store tomorrow and buy a model airplane propeller, trim the ends down so its only about 4 inches total length, attach it to the 3/8 PVC with a nylon bolt and stir it some more with this new stir rod setup.

kadriver


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## goldsilverpro (Oct 25, 2012)

Have you tested your distilled water for chlorides using silver nitrate? Otherwise, there would have to be some solubility of silver chloride in the nitric. I've never seen that happen but I guess it's possible. Of course, you're probably using the same distilled water when you dissolve the silver. Is there any way you're contaminating the distilled? It's a mystery.

I've had problems with distilled water before. I found the purest was Walgreen's more expensive variety - about $1.50 to $1.75 - they used to sell 2 different ones.


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## kadriver (Oct 26, 2012)

I have tested the distilled water by adding a drop of silver nitrate to a sample of the distilled water that I am using to do these tests - no cloudiness at all.

Plus I digested some silver crystals from my silver cells and added distilled water (from same container used for these tests) and the resulting dilute silver nitrate solution was crystal clear.

I think that there is small clumps of silver chloride (wth silver metal surrounding them) that is not coming in contact with the chemicals.

I did another test after more stirring and it turned cloudy - I am going to keep stirring this batch until I get a clear test.

Thanks for your help - Kevin


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## sena (Oct 26, 2012)

i used to split the agcl clumps , put in a filter bag with big pore size and allow to flow down by adding water , so the clumps break down evenly , then would start 
conversion process ,this allows to break down the clumps , i do stirring manually .

Thanks 
Sena


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## kadriver (Oct 26, 2012)

sena said:


> i used to split the agcl clumps , put in a filter bag with big pore size and allow to flow down by adding water , so the clumps break down evenly , then would start
> conversion process ,this allows to break down the clumps , i do stirring manually .
> 
> Thanks
> Sena



Did you test the resulting silver (like the testing done in this post) to determine if all the silver chloride had converted?

I have processed silver chloride in the past and one can't tell by looking if the silver chloride has completely converted.

The test (like the one done in this post) is the only accurate way to tell if all the chloride is gone.

This is the first time I have used this test. But I will never process another batch of silver chloride without doing this simple test.

kadriver


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## kadriver (Oct 26, 2012)

We keep learning as we go, this forum and those who contribute are absolutely unbeatable.

I have been converting silver chloride, but not testing to see if all the chloride had converted.

Thank you goldsilverpro for posting this simple test to see if the silver chloride has completely converted.

I wondered why I was getting a green color in my melt dish.

The silver from this melting was absolutely beautiful, even though the dish turned green.

Here is the big question; does a little silver chloride in the silver powder produced from converting silver chloride to elemental silver metal have an effect on the purity of the melted silver bar?

Does the silver chloride cause contamination of the melted silver thus reducing the purity below 3N fine?

kadriver


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## goldsilverpro (Oct 26, 2012)

The presence of silver chloride would not contaminate the silver, except maybe on the surface. If it does stick to the surface of the silver, it could be removed mechanically or, maybe, an extended soak in ammonia. I've always worked with much larger quantities in a crucible furnace and have rarely done a torch melt on silver. It's a somewhat different deal.

I'm still puzzled as to why dilution of the nitric solution produced a cloud. I've never seen that before. I know that aqua regia will dissolve some AgCl, which will mostly drop when diluted (and cooled), but haven't seen this with just nitric. It shouldn't make any difference but, what happens if you use about a 10-15% nitric solution, by volume, to dissolve the silver and then let it cool?

For 100% conversion, the most important thing is to first convert all of the AgCl to silver oxide with the NaOH. If the AgCl is clumped, the silver oxide can form on the surface of the AgCl and prevent the NaOH from penetrating to the remaining AgCl inside the clump. Therefore, a mixer with good chopping action is best. I've never used a blender but that would seem to provide a perfect chopping action, at least for smaller quantities. The only problem I could see would the blender gasket holding up to the NaOH. According to the compatibility charts, neoprene has a Good rating with 20% NaOH if it's not too hot. Also, I found that the gaskets on the Sunbeam Oster blenders are made from neoprene (at least, that's what the replacements, which supposedly fit all Oster models, are made from). If I were using solid NaOH, I would dissolve it and let it cool before putting it in the blender. When you dissolve NaOH, it gets quite hot.


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## kadriver (Oct 26, 2012)

I have experienced this before when trying to set up my silver cell.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=8589&p=80542&hilit=+Cloudy#p80542

I dissolved the silver in dilute nitric and it was crystal clear, but when I added distiller water it clouded.

If you read the post you will see I was using cement silver to set up my silver cell.

I boiled the cement silver in HCl and then washed in boiling distilled water.

When I dissolved the washed cement silver in dilute nitric it looked perfect, until I added distilled water, then it would go cloudy (just like I am experiencing now).

To solve the cloudiness problem, Harold told me to incinerate (melt) the silver before dissolving in nitric and that did the trick.



There are still small clumps in the silver from this batch. I think these are the culprits. I still have to find a hobby shop to get an model airplane propeller to attach to the end of my stir rod.

The sharp edges of the propelle should cut into these clumps releasing the silver chloride that they must contain.

More to follow - I had no clue that this was going on in my batches of silver chloride conversion.

Kadriver


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## qst42know (Oct 26, 2012)

I have one of these for mixing paint with an electric drill. It's not a blender but it has 6 blade surfaces and does a nice job on a 5 galon bucket of paint.

http://www.toolfetch.com/mud-resin-drill-mixer-15-180.shtml?gclid=CKbs46Dnn7MCFY1DMgodxQcALA


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