Silver Metal from Silver Chloride Overview- Updated

[lazersteve]

I've decided to post a new tutorial on recovering silver metal from silver chloride. I posted the segment on how to separate silver from gold with dilute nitric acid which yielded silver chloride. You can view that post here:

http://goldrefiningforum.com/phpBB3/viewtopic.php?p=887&highlight=#887

I'll be posting two parts to this topic one for the electolytic method and the other for the purely chemical method.

The quick overview is as folows:

1. Electrolytic Precipitation of Silver from Silver Chloride

Cathode: Graphite
Anode: Platinum Wire
Electrolyte: Ammonium Hydroxide and Silver Chloride
Product Retrival: Vaccuum Filtration of Powder Residue
Clean Up: Distilled water wash.
Smelting: Use borax flux
Product Purity: 99%+

2. Hydroxide Precipitation of Silver from Silver Chloride

UPDATE This tutorial is now available at :


http://goldrefiningforum.com/phpBB3/viewtopic.php?p=1208#1208

Chemicals: Dry Sodium Hydroxide
Corn Syrup
Distilled Water
Silver Chloride
Product Retrival: Filtration of Powder Residue
Clean Up: Distilled water wash.
Smelting: Use borax flux
Product Purity: 98%+

I'll begin these videos when I finish up with the last filtering video.

Please post your suggestions and comments.


Steve

 

[PRECIOUS METALS]

hey steve can you help here i just finished doing p-1 cpus mmx

now im ready to participate i tested for gold and it terned blue

any ideas what blu is

 

[lazersteve]

Are you sure it's not just a light purple? If so it means you have some gold. Remember the darker the color the more gold. The lighter (light purple) the color the less gold there is.

 

[ThePierCer]

Steve, I'm really looking forward to this one, keep up the great work!

 

[PRECIOUS METALS]

hey steve what can you do if the gold wont participate
using aqua regia tested for gold and lots of it
as i add s,bisulfite gold wont come down ,heated to a boil a bowl of hot water add the participant then add the acid with gold ,and still nothing

any ideas

precious metals

 

[lazersteve]

Did you add urea until the fizz was gone?

 

[PRECIOUS METALS]

yes plus added a little extra just to make shore

 

[lazersteve]

Here's a snapshot of the silver chloride after it has dried. Tomorrow I'll attempt to turn this back into silver metal powder on video. Notice how the light has changed the color of the Silver Chloride.

Steve

P.S. I've posted an update to the previous post on Filtering in the Tutorial Questions Section.

 

[PRECIOUS METALS]

wow yea i got lots of that ,i filter my aqua regia before participating to get the silver cloride out ,would love to see the video how to tern it into silver .

 

[goldsilverpro]

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.

 

[lazersteve]

Thank you for the great suggestions. I had previously made note of the chunks problem in the follow up text. You are correct the chunks did not fully convert as expected and had to be rerun. I did those the day after the video was made.

I have posted the theorectical calculations for the amount of NaOH to use when prompted by another poster for the information. It worked out to right at 12 grams and I used 17 for good measure.

I had no clue about the exact amount of karo to use and will incorporate your figures into my future work.

Thank you again,

Great post. It's always nice to get things right working as a team. Your vast experience with silver will come in handy to the forum in future posts I'm sure.

Steve

 

[Harold_V]

My choice for converting silver chloride to elemental silver required almost no effort on my part aside from washing the chloride well before the conversion. I kept a jar of chloride at the ready, to which I'd add more as it accumulated. When I had enough to convert, usually about a quart, I washed it well a few times with tap water, to eliminate any traces of copper, then once or twice with hot water, to remove any lead nitrate that may have been carried to the pot. Instead of pouring off solutions, I used a small hose and did all my transferring by that method. It avoids stirring up the chloride, which tends to go all at once when you pour.

Once well washed, the chloride was placed in a large Pyrex handled vessel, where it was covered with a 10% solution of HCL and tap water. Pieces of scrap aluminum were then introduced to the chloride, and stirred occasionally. Given enough time, there's a complete conversion of chloride to elemental silver. After the conversion is complete, pieces of aluminum are removed, and a wash with HCL and water cleans the silver. Wash and decant, then filter with a Buchner funnel. This silver is ready * to be melted, then run in the parting cell.

Harold

An added note: It makes no sense to dry silver chloride. It does not handle well, and serves no real purpose. Keep it wet at all times by leaving the last solution poured in until you need to add more. Decant when you need more room, always keeping the chloride covered with solution.

Edit: * removed the word "for" which made no sense.

 

[lazersteve]

Harold,

Your hands on experience is the best in the land! Thank you. I'll try it your way and post a video for everyone to see how you do it! Check your PM's.

Great Stuff,

Steve

 

[lazersteve]

Hello Again,

I tried my first shot at inquarting and cornflaking my percipitated silver with the gold from my electrolytic cell. The melted gold weighed 11.5 g and the assumed silver powder weighed 29.5 g.

When I began melting the silver powder, I ran into the exact situation that Chris pointed out in his comment on my silver percipitation tutorial... a translucent milky film. There was a lot more than I expected, so as he said, my silver did not fully convert from the chloride. I went ahead with the inquarting and ended up with this after cornflaking the mix:

The cornflakes weigh 28.5 grams total so I figure I had quite a bit of unconverted silver chloride ( 12.5 grams!!! ). I guess this shows I need a little more practice myself when it comes to converting silver chloride to silver.

:idea: I learned that Chris and Harold are right on the money when it comes to silver chloride:
Never dry the chloride out, leave it submerged in water after dropping it from the nitric solution. Rinse it well and always convert the chloride wet.

Thanks for all the great tips guys, don't give up hope on me yet, I'll get the hang of the purification steps soon enough.

Any and all advice will be greatly appreciated (like how do I get the melted silver chloride out of the melting dish ).
Steve

 

[Harold_V]

Any and all advice will be greatly appreciated (like how do I get the melted silver chloride out of the melting dish ).
Steve

Here's a good case for using soda ash. While I don't recommend you reduce silver chloride with a torch, especially in a dish, if your dish is so contaminated, get everything molten, then introduce soda ash and get it in the mix. You'll see silver prills form before your very eyes.

Remember how I told you to clean melting dishes? Soda ash is a reducer, which will convert the silver chloride to elemental silver, the only problems being it's not exactly a fast conversion, and it dissolves your melting dish as it works. If you save your flux and dishes, and eventually end up with a ball mill and furnace, you'll recover the values when you can allow the flux mix to "cook" for the prescribed amount of time. That tilting furnace I posted some time ago was used in that capacity. Truth be told, if you'll follow my advice and store this stuff instead of converting it to ready cash, you'll have one of the best retirement funds you could imagine. You can't spend it the way it is, and it adds up quite quickly. Were it not for my waste materials, which I stored for about 20 years, I'd not have been able to retire at age 54.

Harold

 

[lazersteve]

Good News,

Luckily I poured the molten silver chloride off into a second dish and it didn't stick to the second dish! I went out to the garage after making the above post and the cooled silver chloride flaked right off the dish all in one big piece... no problems.

Thanks for the repeat on the soda ash tip. I used the advice once already and it worked pretty well. I'll keep it in mind for future snafus!

Steve

 

[lazersteve]

Harold,

I processed the once molten left over silver chloride as you described with the soda ash. I got another 6 grams of silver out of it, but that still leaves me 6.5 grams shy. There is still a lot of very free flowing liquid that has to be poured off when the dish is hot. Is this stuff still silver chloride? How much soda ash does it take to convert this stuff back to silver. I worked on it for nearly half an hour to get the 6 grams back. How do I know when there is no more silver in the molten residues? When I heat the dish intensely I get white smoke and a free flowing liquid. If I add soda ash to this I get a gray-green crusty substance that melts and becomes free flowing again.

Steve

 

[Harold_V]

Steve,

I wish I had answers for you. I never processed silver chloride by that method, although I reduced quite a bit of it from my waste materials in similar fashion, which was by design. Unfortunately, I had no idea of the amount of chloride in the mix. The source was from filters after filtering gold chloride, and any filters that may have been used in processing silver by other means. My purpose in this case was to use silver as a collector of greater values. For that, it was exceedingly successful, with my final flux being of such low value that it wasn't acceptable at a refinery that goes after trace values with litharge. Based on that, I was more than comfortable that I was extracting the values to a point where any further effort would have been wasteful of not only my time, but of resources as well. Cooking reducing charges such as those I used were very hard on furnace lining, necessitating frequent patching and quite often a complete reline. They would be worse, by far, on melting dishes due to their makeup. My furnace lining was 94% alumina.

While I appreciate your scientific approach to your learning curve, you may just have to get used to losing trace amounts. Some of the previous handling could very well have been the source of some of your loss, which, in reality, is quite small. Not withstanding, I'm sure it irritates you no end that you can't account for the missing metal.

I've always had a saying. As long as you don't toss anything, it's not lost, although it may be tied up in something. That, of course, would have to include filters from a fume hood. For all I know, when you heat silver chloride with an open flame, some of it may volatize and be lost. I simply don't know! Perhaps Sue can lend his thoughts in this instance. He claims to be a chief metallurgist, where I have no training aside from hands-on refining.

As a last resort, it wouldn't hurt to introduce more soda ash to the dish to see if more metal forms. If so, that may provide you with some guidelines on how much is required to reduce the chloride.

Also, if you'd be interested, I can provide the recipe I used for flux in the tilting furnace when I reduced my waste materials. It was of my own design after considerable research----with a requirement of reducing silver chloride being of uppermost importance to the operation.

You may recall that when reducing silver chloride for the sake of recovering the silver (not when needed as a collector), my method was to reduce it with scrap aluminum. I don't recall ever having any problems with less than total recovery, although if I did, the slag from melting it would have been further processed in my tilting furnace, at which time I'd extract any values that may have slipped past me.

Unlike GSP, I was never enamored with silver, although I processed a large quantity of it and appreciated having it as a savings account. In truth, were it not a necessity in processing gold, I wouldn't have processed silver at all. When it was put in terms of dollar value, I handled, easily, twenty times more in gold, and my reserves reflected that very thing, considering I did all my refining on a percentage basis. I could process one hundred ounces of gold much faster than I could 100 ounces of silver, with very little difference in chemical costs, if any. As they say-----do the math!

Harold

 

[lazersteve]

Harold,

Thank you for the reply. I tried more soda ash and still no results. The main thing I notice is that if I increase the torch heat I get a white smoke. The residue which produced the additional 6 gms of silver is now a greenish white color and turns into a very flowing liquid with minimal heat. The missing weight exactly equals the remaining substance. It cools into a hard greenish white smooth mass that doesn't stick to whatever you dump it on when it's molten. It's not glassy like borax, but is brittle. The melting dish is very clean now. 8)

I've tried another batch of silver following the modified directions given by you and Chris and this batch had little if any of the flowing substance after melting. I did notice something different about the second batch. As the button cooled for a second or two it began discharging a gas which formed a rough nugget like appearance on the top of the silver button. Do you know what that may have been? I figured it was some flux trapped under the button venting thru the silver as it cooled. Here's what it looks like:

I'm interested in your flux recipie if you wish to share it with me, either publicly here or privately via PM.

Thanks Again,

Steve

 

[Harold_V]

As the button cooled for a second or two it began discharging a gas which formed a rough nugget like appearance on the top of the silver button. Do you know what that may have been?

Most assuredly, it's nothing more than oxygen. As you study silver, you'll come to understand that it has a tremendous affinity for oxygen, which it will absorb at the rate of nine times its own volume, but expels as the metal solidifies. Silver and oxygen do not readily mix with one another. When the oxygen is expelled a crabby surface with tiny "volcanoes" is not uncommon. The presence of other elements in the metal (copper, for example) seriously interfere with the absorption of oxygen, so you don't see that characteristic when melting dirty silver, or alloyed silver. You can use that as a measure, of sorts, to determine if your silver is near being pure.

I'm interested in your flux recipie if you wish to share it with me, either publiclly here or privately via PM.

I'll go to the file where I have it stored and copy the information and post it here. Mean time, please check your PM's.

Harold