silver sugar-lye method where is my mistake?

[kfadrat]

Hi guys,
i am brand new to the refining "stuff" so I thought I will try to refine silver with the sugar lye method. However after 3 tries, the best efficiency was 85% and the lowest was about 10%. This is what i do, maybe somebody will find the mistake and correct me on it, so this is what i did last time, when the efficiency was about 10%:

1. Two coins that are 0,625 Ag and 0,375 Cn (total weight 29 grams) added to a beaker with 200ml of destilled water and 50ml of nitric acid (65%). After some time i added 10ml of nitric more to dissolve everything. Kept on stove with max heat.

2. After the coins are dissolved I let the solution cool down a bit (to about 60-70 c), then added 38grams of HCl dissolved in about 180ml of destilled water. After the solver chloride stopped precipitating i added additional 5 grams of HCl just to be 100% sure that all of the cloride precipitated from the solution.

3. I rinced the chloride with desitlled water 8 times untill there was no blue/green colour in the solution. All the waste i pured to a bucket and added a handfull of HCl just to be 100% sure that i precipitated all of the cloride, nothing new formed.

4. To a beaker with silver cloride i started adding NaOH untill there was no white chloride present, total was 180grams (in 8 batches). I was stirring vigorously during the adding, mixing with a glass rod, total time of mixing about 15 minutes. No more white prcipitate was present after that.

5. I added total of 100grams of sugar(sacharose) in 2 batches. During this step a mirror started forming on the beaker. Img: https://imgur.com/mPHZBMT
Total time of mixing with a stainless steel blender was about 5-7 minutes.

6. After that i started rinsing with water to remove the sugar untill i had only metallic silver left. Total amount of silver was MAYBE 3 grams, I didn't even bother to melt it as it was waaaaaaaay off the theoretical 18grams.





So, where is the problem here? I can't put my finger on the step that makes the problem here

 

[Lino1406]

No white presence - does not insure all chloride was converted

 

[kfadrat]

the amout of chloride looks decent enough i think the problem is somewhere further, maybe in conerting silver oxide to metallic silver but i am not sure to be honest

 

[au-artifax]

Hi guys,
i am brand new to the refining "stuff" so I thought I will try to refine silver with the sugar lye method. However after 3 tries, the best efficiency was 85% and the lowest was about 10%. This is what i do, maybe somebody will find the mistake and correct me on it, so this is what i did last time, when the efficiency was about 10%:

1. Two coins that are 0,625 Ag and 0,375 Cn (total weight 29 grams) added to a beaker with 200ml of destilled water and 50ml of nitric acid (65%). After some time i added 10ml of nitric more to dissolve everything. Kept on stove with max heat.

2. After the coins are dissolved I let the solution cool down a bit (to about 60-70 c), then added 38grams of HCl dissolved in about 180ml of destilled water. After the solver chloride stopped precipitating i added additional 5 grams of HCl just to be 100% sure that all of the cloride precipitated from the solution.

3. I rinced the chloride with desitlled water 8 times untill there was no blue/green colour in the solution. All the waste i pured to a bucket and added a handfull of HCl just to be 100% sure that i precipitated all of the cloride, nothing new formed.

4. To a beaker with silver cloride i started adding NaOH untill there was no white chloride present, total was 180grams (in 8 batches). I was stirring vigorously during the adding, mixing with a glass rod, total time of mixing about 15 minutes. No more white prcipitate was present after that.

5. I added total of 100grams of sugar(sacharose) in 2 batches. During this step a mirror started forming on the beaker. Img:
Total time of mixing with a stainless steel blender was about 5-7 minutes.

6. After that i started rinsing with water to remove the sugar untill i had only metallic silver left. Total amount of silver was MAYBE 3 grams, I didn't even bother to melt it as it was waaaaaaaay off the theoretical 18grams.





So, where is the problem here? I can't put my finger on the step that makes the problem here

First, you have to get your chemicals figured out. HCl is not a solid, so how did "grams" enter the picture and why would you be dissolving a liquid in a liquid? Perhaps you meant NaCl (sodium chloride)? In either case, you have to remove the excess liquids left over after adding the sodium hydroxide. Otherwise you are creating a big batch of caramel soup, which has to be rinsed as well. Once you drain off the liquids on top of the Ag2O, you can start with the sugar.

 

[Gwar]

Great topic, for future reference in case the hosting site / original poster goes south..

 

[rickbb]

2 year old post, OP has not been back after these 2 posts.

 

[Geo]

I have tried the lye and sugar conversion many times and could never get a full conversion. There seems to be some unconverted silver every time. I always end up with black syrupy slag during melting. I saved all the slag and milled it fine. I leached it in nitric acid and recovered a fair amount of silver that I cemented on copper. I would never recommend making silver chloride unless there was no other way. Because electrical contacts used both silver and palladium, the need to separate the two metals from the same solution, forming silver chloride to separate the two is pretty much a must considering silver chloride is a solid and Pd remains a liquid. It is the fastest and easiest way to separate the two. In this way, I do accumulate enough silver chloride that converting ever so often is just something that must be done.

Melting the silver chloride directly under a layer of soda ash is one way. It does spit and sputter quite a bit though.
I bought a cast iron Dutch oven just for silver chloride conversion. I add the silver chloride and (if it's close to full) 100ml's of sulfuric acid and put the pot on heat. The silver chloride slowly starts to darken. Stir frequently as the silver chloride must come into contact with the cast iron. When the mass is as black as it can get, leave it for another fifteen minutes and remove from heat. Remove the material from the cast iron pot as soon as you determine all of the silver has been converted to save the cast iron. I've used the same pot for over a year now and it barely shows signs of deterioration.

I have heard that HCL and aluminum works as well but am reluctant to try it. I'm not doubting but when I find something that I'm comfortable with and it works, I tend to stick with it.

 

[Swissgoldrefiner]

There seems to be some unconverted silver every time.

How many % do you think still unconverted?

 

[Geo]

How many % do you think still unconverted?

Low percentage. I didn't collect numbers but if I had to guess, and I do, I would say less than 5%.

 

[PeterM]

I used Sodium Hydroxide and Dextrose... It worked fine for finely divided Silver Metal (Ag). I added the Caustic first.

 

[Gwar]

I have been contemplating performing a test run tomorrow when I start a new batch of dimes, I will start with a small amount and see if it's worth considering for future refinements, I will probably use pure sugar instead of syrup.

 

[PeterM]

Look guy, add caustic, then stir in dextrose. Filter rinse done. Don't complicate it....

 

[orvi]

I have tried the lye and sugar conversion many times and could never get a full conversion. There seems to be some unconverted silver every time. I always end up with black syrupy slag during melting. I saved all the slag and milled it fine. I leached it in nitric acid and recovered a fair amount of silver that I cemented on copper. I would never recommend making silver chloride unless there was no other way. Because electrical contacts used both silver and palladium, the need to separate the two metals from the same solution, forming silver chloride to separate the two is pretty much a must considering silver chloride is a solid and Pd remains a liquid. It is the fastest and easiest way to separate the two. In this way, I do accumulate enough silver chloride that converting ever so often is just something that must be done.

Melting the silver chloride directly under a layer of soda ash is one way. It does spit and sputter quite a bit though.
I bought a cast iron Dutch oven just for silver chloride conversion. I add the silver chloride and (if it's close to full) 100ml's of sulfuric acid and put the pot on heat. The silver chloride slowly starts to darken. Stir frequently as the silver chloride must come into contact with the cast iron. When the mass is as black as it can get, leave it for another fifteen minutes and remove from heat. Remove the material from the cast iron pot as soon as you determine all of the silver has been converted to save the cast iron. I've used the same pot for over a year now and it barely shows signs of deterioration.

I have heard that HCL and aluminum works as well but am reluctant to try it. I'm not doubting but when I find something that I'm comfortable with and it works, I tend to stick with it.

There could be a lot of difficulties with lye/sugar method. Very obviously arising from fact, that you are going two solid-solid conversions in row. Solid-solid conversion is the least efficient transformation in chemistry, because of inability to mix thoroughly.

I use this method quite a lot, and never have a real issue with it. Very convenient way how to roughly estimate the yield from certain item - in few grams experiment. Crucial step is to properly convert AgCl to Ag2O. It all come down to that solid-solid conversion. If precipitated AgCl is in bigger lumps, it takes more time and vigorous stirring to break the lumps and free the locked up AgCl.
Usually I do it in a beaker with large magnetic stirbar. For higher efficiency in terms of lye, I also heat the solution for some time to boiling, until I get uniform colour and negative "smear test" with no white spots present.

Then to still hot suspension, stirred vigorously on magnetic stirrer, sugar is added slowly and temperature is monitored with thermometer. For small batches under 10g, I do not use it, just dump one teaspoon in, followed by second after some minute of stirring.

Outcome is probably not completely converted, certainly there is some AgCl or Ag2O in measure of few %, but when you thoroughly wash and dry the powder, you get very good estimate of the silver contained.
When melting this down, I never experienced white smoke or black slag. I use Na2CO3 flux for this.

 

[Gwar]

orvi, after consideration and some thread reads, I believe you are spot on, I will refrain from such a test until I have the proper apparatus.

 

[orvi]

orvi, after consideration and some thread reads, I believe you are spot on, I will refrain from such a test until I have the proper apparatus.

Magnetic stirrer is not a necessity, but it´s a very handy thing to have in the fumehood dissolving solids to form solutions, stirring reactions which should be stirred, controlled drying of metal pastes without spattering etc.. For lye/sugar method it is espetially usable, as stirbar not only stir the mixture, but also crush the AgCl slowly into smaller pieces. But it is necessary to stay rational about stirring power - for thick pastes of large volume, stirbar just stay stuck in the "mud" Max. for a mid-grade lab stirplate is like 200g of AgCl.
This stuff is quite expensive, if purchased new. You can try your luck with second-hand stuff, but test if heating element works - most common malfunction. As I work with stirring plates for more than 10 years, I can tell you that if you decide to buy one, buy one with heating element. It does not need to have probe for measuring and regulating exact temperature (for refining purposes), but some potentiometer for regulating the heating power is a good thing.
Also look for rated heating power, do not go for less than 300W. Water has very high heat capacity, and with 200W heating element, 2 liters of liquid takes forever to heat even to luke-warm.

To the thermometer, similar one as on the photo is a good start. On Aliexpress, they go under 5 USD. Just be careful and bear in mind that stainless steel (304 or worse, unknown Chinese composition) cannot withstand AR and many times also dilute nitric acid. Hydroxides are OK with it. You can craft some DIY "sleeve" from PE or PTFE tubing of course. Heat shrinking tube for electrical installation also kinda work, but acid will slowly degrade it and possibly leach some stuff to the juice. Long glass tubing is also an option, but it is hard to get for an amateur.
If it wasn´t such pain to ship fragile mercury-containing things overseas, I would send you some old mercury lab thermometer

 

[Gwar]

Many thanks orvi !

 

[orvi]

You are welcome

 

[PeterM]

After reading all these posts with confusion some people are having, I am convinced you guys do not know how to read and comprehend English. Before you hurt yourself or someone read these books. This work is not complicated. Pre-requisite: 1. Read the HOKE book Refining Precious Metal Wastes, 2. read Recovery and Refining of Precious Metals: Recovery_and_Refining_of_Precious Metals by C.W. Ammen.pdf - Shared with pCloud

 

[123cp456]

Hi all, looking for some advice, I am doing a chloride conversion all working out great. after conversion i rinse and rinse then boil in hcl BUT i seem to be getting a sweet smell and a horrible slag, the silver under is perfect. YOUR NOT RINSING THE SUGAR AND LYE OFF ENOUGH....but im on 10 rinses with boiling water then the hcl...what am i missing? is there a better way to remove the sugar? or is that not the issue?

 

[orvi]

Hi all, looking for some advice, I am doing a chloride conversion all working out great. after conversion i rinse and rinse then boil in hcl BUT i seem to be getting a sweet smell and a horrible slag, the silver under is perfect. YOUR NOT RINSING THE SUGAR AND LYE OFF ENOUGH....but im on 10 rinses with boiling water then the hcl...what am i missing? is there a better way to remove the sugar? or is that not the issue?

How you "rinse" ? Describe precisely what you are doing. Because as simple word "rinse" is, I guarantee you there are dozens of people who think that what the water touch is suddently clean
Ag from lye-sugar can be painful to rinse, as there is always some floaty micro silver particles which refuse to settle. But you can just pour this floaty stuff with the liquid to some bigger barrel and let it settle and then decant. You need to mix everything from the top of the layer to very bottom and then let it settle and decant. Best is to use mixing extension for drill (for mixing cement/anything in bucket) - easy, convenient, cheap, thorough. Remember - it is about draining as much of the liquid as you can from the solids. Because of this, filtration is better than decant session, as filtering remove much much more juice.

That is why I love "sucking pad" for removing barren juices from precipitates. You can also easily use bigger fritted glass filter if you have one - connect the hose with vacuum and filtering flask/drum to the stem of the frit and just throw it in You do not need to pour and transfer the sludge, just stick the pad in, let it suck out the barren liquid, refill with water, mix with cement mixer blade on the drill, repeat the sucking and basically 2-3 consecutive washes like this will give you clean product.

If you are doing it in bucket/beaker, rinsing start to be somewhat effective if you remove over 70% of the liquid for one go. This means the layer of Ag is less than 1/3 of the volume, and less is obviously better. Actually, 90% drained, and it speeds up insanely if you do the math.
For the first rinse of 70% drained, you eliminate 70% of sugar and lye dissolved. Second exactly same rinse remove 70% from remaining 30% => that is 21%. So after second rinse you eliminated 91% of junk. Then third rinse take 70% from 9 (that is ca 6), so after third rinse you have 97% rinsed out. Note how slowly it start to wash away when you pass 90% efficiency. And just a miniscule ammount of sugar/NaOH/junk left will create PITA very quickly Try the maths on 50/50 solid/solution ratio and you will clearly see how slow it can get.

As the solution is strongly basic, best indicator for completeness of rinsing stage is neutral pH test with pH strip
I never used HCL for washing, I have somewhat mixed experience with acid washing silver powder... Just to say it is completely unnecessary to wash with acid. It could even be worse than little bit of basic residue - as NaOH with HCl will be converted to NaCl - which will smoke out, falsely "indicating" incomplete conversion of AgCl to Ag.