Conversion of AgCl via NaOH and Karo Question

[nōnāgintā trēs]

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.

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

 

[jimdoc]

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.

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

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

Jim

 

[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!!

 

[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

 

[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.

 

[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

 

[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.

 

[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

 

[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

 

[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.

 

[goldsilverpro]

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

 

[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

 

[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:

 

[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.

 

[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

 

[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?

 

[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

 

[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.

 

[Garagetinkerer]

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?

 

[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