Silver Metal from Silver Chloride Overview- Updated

[Harold_V]

(3) parts waste material (in this case, that would be your silver chloride)
(1 ½) parts silica sand
(3 ½) parts soda ash
(1/2) part fluorspar
(2) parts borax
Tap water to make a batter much like a cake when poured in a pan.

You'll have to experiment to determine how much water is required for your particular setup.

Dry mix the material briefly then add the water. Mix fast as the material stiffens up. The mix should be wet enough to go into a slurry. If it isn’t, add a little more water. Too much doesn’t hurt, it just makes a mess. It isn’t necessary to mix very well. Once again, the mixing of the furnace will do the job nicely when the charge is molten. (That may not be true when melting in a crucible. My tilting furnace was a modified reverberatory of my own design----with the flame impinging directly on the charge.)

Pour this mix into some disposable forms, such as lids from sour cream containers, or the sour cream containers themselves. Just don't make them very thick, so they can be broken easily if necessary, and they can dry readily. They set up rapidly into a solid. Allow a day, then remove them from the forms and allow to dry completely before melting. Once set, the plastic forms release them easily. They can be melted while wet, but require a lot more time and energy. The resulting material can be heated without losing any of the constituents. Keep in mind, I introduced these to a furnace, they were not torch melted. That may or may not work well. Dunno!

The fluorspar in the flux makes it very thin, almost like water, and it's very aggressive in dissolving everything in its path. The thin flux allows prills to agglomerate easier---and makes pouring off the charge easier as well. A cone mold makes separating the flux from values no chore.

Harold

 

[goldsilverpro]

Steve, although I have great respect for you, some of the things you do worries me. It's obvious that you fear nothing but, in this field, that could sometimes get you, and others, in trouble. One reason I am probably attracted to this chemistry is the inherent dangers. I haven't done much pyrotechnics but, I'm sure it produces a similar thrill. I have played around with thermite and thermate, using magnesium fuses.

The thing that really worried me was when you were converting the silver chloride to metal with a torch. I would never use a torch for silver because it's very easy to get things too hot. Silver chloride melts at a low 850 deg F (the flow you saw) and starts evaporating at less than 1560 deg F., along with the NaCl that is produced in the conversion. This was the white smoke you saw. The silver losses you experienced probably went into the air. I hope you were wearing your SCBA gear. The extremely rough button produced, in the photo, is not only an indication of high purity but, also, of way too much heat. I had a friend that died from breathing these fumes. He always had his head over the furnace because, he liked watching the AgCl convert. Some years back, a man named Kunda came up with a much lower temp. furnace method for conversion. This method is used widely today.

 

[lazersteve]

Chris,

You've put the fear of God in me now! :shock: I wasn't wearing scba, but the 16 ft wide garage door and side door were wide open and a nice breeze was blowing thru. I guess someone upstairs likes me!

Do you recommend a furnace for this type of smelting?

Thanks for keeping an eye on me!

Steve

 

[goldsilverpro]

I would use a chemical method, such as Karo/lye or aluminum, as Harold suggested. You can also use powered zinc or mix it with slugs of iron and dilute sulfuric. Before melting, I would test for complete conversion using the simple method covered here in my post - item #5. When the conversion is complete you can melt it quickly with a cool torch or in a furnace.

http://goldrefiningforum.com/phpBB3/viewtopic.php?t=120

Silver metal will also evaporate, if you get it too hot for too long. Several times I have forgotten and left a pure silver bead in a cupel in about a 1700 deg F. furnace. When I found it, after 5 or 6 hours, it had evaporated to almost nothing.

A friend of mine blends the silver chloride with enough soda ash for conversion, puts it in a crucible and covers it with borax. He then puts it in a hot pot furnace and allows it to get up to temperature. When it's hot, he turns the furnace off allows it to cool overnight. He claims good conversion.

In the last 150 years, or so, refiners have practiced what is called "chloride aversion or avoidance". In other words, they don't produce silver chloride unless they have to. I do the same. About the only AgCl I HAVE to produce is the residues from aqua regia. I really don't have to do that but, I do. It takes less work in the long run. I could inquart and get the silver out with nitric. It's really easy and tempting to make AgCl - you just add some HCl or salt water. Getting the silver out of the chloride is another story. Even with silver nitrate solutions, I don't form AgCl. Instead, I cement out the silver on copper buss bar.

I'll check on the Kunda low temp furnace process if you want but, I don't think you need it.

 

[lazersteve]

Thanks for the tip. I think I'll go with the copper buss bars from here on out and drop the silver directly.

I'm also picking up a SCBA and full Tevek body suit to sleep in for the next few nights so I feel safe again!! :lol: Just kidding, but I am ordering the SCBA breather for future use.

Steve

 

[Harold_V]

In the last 150 years, or so, refiners have practiced what is called "chloride aversion or avoidance". In other words, they don't produce silver chloride unless they have to.

Funny you should mention that, Chris. I came to that conclusion as well, so the only time I converted to chloride was when the solution was so contaminated with other substances that the resulting silver came down way too dirty. On rare occasions, when my solution contained values in the platinum group and the silver was recovered as chloride, I'd decant the solution afterwards and place it in my stock pot, where everything that would precipitate on iron was recovered*. I guess the bottom line is once you've worked with chloride a little, you come to realize it's not the best way to go, so you learn to avoid it, even when you had no idea the "big boys" had a policy of doing so. It just made sense at the time.

*The precipitated elements were processed, along with other waste materials, in the tilting furnace. The resulting metal was then parted according to conventional acid methods. By this method, traces of the PG metals got concentrated to the point of being able to be recovered. Interestingly, by nature of the methods I employed, enough silver chloride accumulated in my wastes that the silver acted as a great collector, and was in proportions that allowed parting without inquartation.

Harold

 

[goldsilverpro]

I've been thinking of how the Karo syrup method could be used to get 100% conversion. When I did this on a large scale, in an open top 55 gallon plastic drum, I had the best luck when using a Lightnin' mixer to stir the mix. This type mixer tends to chop up the AgCl, which allows the chemicals to penetrate and completely convert it to Ag metal.

On a smaller scale, I think a dedicated blender (garage sale) would work great. It would really chop up the silver chloride. It would probably work even if the AgCl was dried out. Of course, the AgCl would have to be very well rinsed before doing this, to remove any nitric and dissolved metals. The seal in the blender might be attacked by the sodium hydroxide but, if no excess is used, this may not happen. With the blender action, the conversion wouldn't take long. After removing everything from the blender, one might rinse the blender with a little vinegar to remove any traces of sodium hydroxide. Then, rinse it well with hot water.

For 1 tr.oz. of silver metal, about 41.5 grams of silver chloride, it takes about 20 grams of sodium hydroxide, 13.3 mL of light Karo syrup, and 133 mL of water.

Just an idea. I think it would work great. The only problem might be the seal.

On a medium large scale - bucket size - one of those stainless paint mixers chucked in a drill might work well. They also have a good chopping action.

 

[lazersteve]

Chris,

Great post!

I added your figures to the Reactions List.

Steve

 

[Toobigfortx]

Im Sorry for asking a really stupid question but, Is it possible to just dry the Silver Chloride and put it in a crucible then torch it? wont the heat break the bonds between the Chlorine and silver atoms, Leaving you with Chlorine gas and Silver metal? or am I way off base?

 

[element47]

All I can say is that this is one incredibly interesting and informative thread for us silver devotees! I feel like I'm getting the benefit of about 40 years of silver refining/processing experience.

 

[goldsilverpro]

Im Sorry for asking a really stupid question but, Is it possible to just dry the Silver Chloride and put it in a crucible then torch it? wont the heat break the bonds between the Chlorine and silver atoms, Leaving you with Chlorine gas and Silver metal? or am I way off base?

I can't find any specific data to back me up, but I know from experience that that won't work and to attempt it could be dangerous. Silver chloride melts at a fairly low 850F and, when this gets a little hotter, I know you evolve white toxic AgCl fumes. I did find this reference that states that silver chloride is not decomposed by heat (#24).

http://chestofbooks.com/science/mining/Leaching-Gold-And-Silver-Ores/Roasting-Continued.html

All I can say is that this is one incredibly interesting and informative thread for us silver devotees! I feel like I'm getting the benefit of about 40 years of silver refining/processing experience.

If you're talking about just Harold and me, figure about 70-80 years total.

 

[Toobigfortx]

WOW really That toxic....Hell Im glad I didnt try it!!! thanks for the info

 

[saadat68]

I watched your AgCl to Ag conversion video, with interest, and would like to make a few comments. Please don't take offence, but I feel that your technique will not usually convert all of the chloride to metal. It might work sometimes but othertimes it won't. I think that most of the problem lies in the understanding of what is really happening. Have you tried melting any of this metal? Have you noticed a tenacious, milky, iridescent layer on top of the cooled metal. If so, this is unconverted silver chloride. Probably the best way to prove your process would be to dissolve a weighed amount of silver in nitric, salt it out, convert it, melt it, remove any coating, reweigh it, and compare the weights. You will probably lose a little silver in a torch melt but it shouldn't exceed 1 or 2%.

About 30 years ago, I spent some time in a lab determining exactly how much Karo syrup and sodium hydroxide (caustic soda, lye) it would take to convert a known quantity of silver chloride to silver. Since then, I have processed at least 10,000 ozs of silver using this method. This is what I found:

1) If you don't crush all of the dried silver chloride to a very fine powder, you won't get complete conversion. I noticed a few chunks in the video. When you try to convert these chunks, a layer of silver oxide or silver metal forms on the surface and blocks the chemicals from penetrating to the center of the chunk. I would suggest grinding in a mortar and pestle. Actually, the best way is to never dry the silver chloride. Keep it submerged in water, cover it when in storage to keep the light out, and stir it good before adding and while adding the chemicals. You're going to need water, anyway, in the process.

2) The purpose of the sodium hydroxide is to convert the silver chloride to silver oxide. The silver oxide is then converted to silver metal by the Karo syrup (corn sugar). The purpose of the Karo syrup is not to act as a flocculating agent. It is actually what produces the silver metal. Theoretically, you don't really need the syrup. You could easily flux melt the silver oxide directly to convert it to metal. However, it is a bear to filter silver oxide and it is, therefore, best to use the syrup.

3) When I did the lab experiments, I used 31.1 grams of silver chloride, which contains 23.4 grams of silver metal. This took 15 grams of sodium hydroxide, 10 mL (cc's) of light Karo syrup, and 100mL of water for complete conversion. In practice, I use about 10% extra chemicals.

4) If the process is being used to semi-purify items of known silver content, such as sterling silver, keep track of how much silver you have so you'll know the amount of needed chemicals. If the silver amount is unknown, such as in aqua regia residues, you'll have to make a guess. Just make sure you add enough. A little extra won't hurt.

5) To test for complete conversion: Put a small sample, about a half gram, of the converted solids into a beaker and cover with distilled water. Stir and then allow the solids to settle. Carefully pour out the rinse water without disturbing the solids. Repeat several times until the rinse water runs perfectly clear. Add a small amount of good nitric acid and an equal amount of distilled water. This will dissolve the silver metal. When the silver has dissolved, add distilled water to about an inch depth. If a white cloud (silver chloride) forms, the conversion is not complete and, either you need more chemicals or, the chunks weren't completely broken up.

Hi
I have some questions
1- What happen if we add 20 or 30 percent extra chemicals (NaOH or Syrup)?
2- I want to add just NaOH to convert silver chloride and then decompose it to silver metal by melting. As I can't find Karo syrup here I think it is better for me. You said it's problem is filtering. Is there another problem in don't using Karo syrup ?

Thank You

 

[goldandsilver123]

1- What happen if we add 20 or 30 percent extra chemicals (NaOH or Syrup)?
2- I want to add just NaOH to convert silver chloride and then decompose it to silver metal by melting. As I can't find Karo syrup here I think it is better for me. You said it's problem is filtering. Is there another problem in don't using Karo syrup ?

2- I use sugar instead of karo syrup, I just dissolve it first, never had any problem with it.

1- Excess sugar/syrup never made difference to me, too large excess of NaOH produces a fine powder that doesn't settle.

 

[saadat68]

1- What happen if we add 20 or 30 percent extra chemicals (NaOH or Syrup)?
2- I want to add just NaOH to convert silver chloride and then decompose it to silver metal by melting. As I can't find Karo syrup here I think it is better for me. You said it's problem is filtering. Is there another problem in don't using Karo syrup ?

2- I use sugar instead of karo syrup, I just dissolve it first, never had any problem with it.

1- Excess sugar/syrup never made difference to me, too large excess of NaOH produces a fine powder that doesn't settle.

Thanks

Can you say how much sugar I must use for 31.1 grams of silver chloride according to this post :

When I did the lab experiments, I used 31.1 grams of silver chloride, which contains 23.4 grams of silver metal. This took 15 grams of sodium hydroxide, 10 mL (cc's) of light Karo syrup, and 100mL of water for complete conversion

20% excess of NaOH is too large ? I really can not exactly estimate how much silver I have in solution

 

[goldandsilver123]

Around 300 g of refined sugar per kilo of silver, I use excess, even if you use 1kg of sugar per kilo of silver it's fine.

20% excess NaOH is OK

 

[silver1]

1 gram of sugar = 3ml of Kayro syrup
65-70 grams of sugar per lb of silver metal.
.