Refining of silver chloride to silver metal
A discussion started in 2003 but continuing through 20192003
Q. CAN ANYONE HELP ME OUT IN GETTING SILVER METAL FROM SILVER CHLORIDE? THIS SILVER CHLORIDE WAS OBTAINED AS A RESULT OF SILVER CYANIDE TREATMENT WITH 5% NaCl SOLUTION AND GETTING ELECTROLYZED. [This] GENERATES FREE CHLORINE, AND DECOMPOSES CYANIDE TO CYANATE. PLEASE DON'T ASK ME TO ADD KCN TO THIS AgCl -- I WANT TO GET RID OF CYANIDE AND AT THE SAME TIME GET SILVER METAL AS A PRODUCT.
fashion jewelry mfgr.
A. Dear Panjala,
There are several excellent books available on precious metal refining available from International Precious Metal Institute (IPMI) as follows; "Refining Precious Metal Wastes" [link is to info about book at Amazon] by C.M.Hoke, and "Small Scale Refining of Jewellers' Waste" [link is to product info at Amazon] by Roland Loewen.
To convert silver chlorides to metallic silver you will need to use dry caustic soda (sodium hydroxide)and dextrose (corn syrup can be used).
Rinse the silver chlorides well with water to remove any residual copper. Place the wet silver chloride sludge in a suitable container 1/3 silver chloride with about 2/3 free board. leave about 4 cm of water on top of the silver chloride. Wear goggles [paid link to product info at Amazon] and rubber Protective Gloves [paid link to product info at Amazon]. Slowly add the dry sodium hydroxide a scoop at a time, stirring well. The reaction is exothermic as the silver chloride is converted to silver oxide. Some people like to add the dextrose along with the sodium hydroxide as it has a defloccing effect on the silver chloride. The dextrose converts the silver oxide to a metallic form. The dextrose can be added a scoop at a time after the sodium hydroxide has reacted with the silver chlorides. When no more reactions with the sodium hydroxide or dextrose occur the process is complete. The resulting silver is rinsed well, dried and melted. The purity of the silver will be 98% to 99% pure and electrolytic refining should be done for optimum purity. For rough calculations by volume of silver chloride - liters of silver chloride X .30 kilos sodium hydroxide - liters of silver chloride X .15 kilos dextrose.
Be aware that this process should be done wearing proper safety equipment as the hot caustic solution can cause severe burns.
Good Luck & Best regards,Jim Sivertsen
- Alden, New York
A. You might try the simple method of converting your silver chloride to silver metal via mixing an equal weight amount of 0000 steel wool [linked by editor to product info at Rockler].Joseph Cummins
- Mineral Bluff, Georgia
Q. This is the only helpful article I have found so far and I honestly do not have time to continue searching. I attempted this process myself (only using sucrose rather than dextrose) and I was wondering if I did it correctly... my product was a silvery-gray powder. Is this what the silver is supposed to look like when the sugar/silver oxide reaction is finished? This method of retrieving silver has been attempted several times by another student at my school with varying results, none the same as mine, and I was wondering what the heck this stuff is supposed to look like if you do it right? Can anyone describe it to me or post a picture?
- Martinsville, Virginia
February 9, 2009
A. I have used this process in the past to recover laboratory silver residues.
By redissolving the silver hydroxide in 50% nitric acid, re-precipitating as the chloride and then reducing to the metal with Sodium Hydroxide and Dextrose (you can use sucrose), you will obtain a purer silver end product.
The end product is a silver-gray or bluish-black powder that is made up of tiny crystals of pure silver.
Fuse in a closed crucible rather than open in order to prevent loss of the fine silver powder.
- Holsworthy, Devon, UK
May 21, 2009
A. There is a very simple way to convert Silver Chloride to metallic silver that doesn't require you to buy a bunch of hard to get expensive chemicals.
Wash your Silver Chloride real good and put it in a container large enough for you to work in. Measure the water you use. Cover the Silver chloride with water to where you have about as much water over it as it is deep in the container. Then add 1/10th as much Sulfuric Acid as you have water. (400 ML of water = 40 ML of Sulfuric Acid.) Then just stir the Silver Chloride with something that is made out of iron. As the weak Sulfuric acid dissolved the iron and comes into contact with the Silver Chloride it will convert to metallic Silver. It will be a dark gray fluffy powder when finished.
The Sulfuric Acid is plain Auto battery acid and can be bought at about any Auto parts store. Add it to the Water and Silver Chloride slowly so it doesn't boil over or over heat your container. Surely you can find a piece of scrap iron to stir it with.
- Greenwood, Arkansas, USA
September 21, 2010
Q. Saw on the answer page a suggestion of adding an equal amount of 000 steel wool to the silver chloride. Is this done with both substances dry or in water, if so how much H20?
Reading about the sulphuric acid treatment of silver chloride, it says that the result is a dark gray powder, which is the silver. I have obtained silver chloride from x-ray film and it is already a gray color. How can I tell when the process is complete? Is there a great difference in the color or can I just take a good guess.Marc Mosse
hobbyist - Davenport, Iowa USA
October 10, 2010
A. Go with the Tollens reaction.
Dissolve your silver chloride in 28% ammonium hydroxide. It will form a coordination complex and dissolve, even as the chloride.
Stick a piece of silver wire in the tank, to seed the nucleation; otherwise, the silver will deposit along the edges of the container.
Add formaldehyde or any other available aldehyde you have. This will reduce the silver ions to silver metal, and they'll attach to the wire. You'll end up with a pretty nice looking ingot of the stuff.
- Toledo, Ohio
August 28, 2011
A. Making Silver Powder from Silver Chloride
Reducing Silver Chloride to Silver Powder - Iron method
Clean Cast Iron Skillet or Cast Iron Dutch Oven
PH test papers or pH meter
5 Coffee Filters
2 - 5 Liter glass beaker or rugged glass container
Strong, flexible Teflon Spatula
Prepare using the following proportions:
100 grams Silver Chloride
350 ml Water - (Tap water is O.K. - else use Distilled Water)
87 ml Sulfuric Acid - H2SO4 (96% - 18 Molar)
Yield: 75.21 grams Silver Powder for every 100 grams of Silver Chloride.
Grind the Silver Chloride to as fine a powder as possible. The finer the better.
Using sandpaper, sand the interior of a cast iron skillet or dutch oven to expose fresh iron metal.
Rinse the cast iron container thoroughly under running water.
Add the Silver Chloride, Water and Sulfuric Acid to your cast iron container.
1 - Warm the cast iron container to about 60° C (140° F - like coffee water temperature).
2 - Stirring with a spatula, dissolve as much as the Silver Chloride as possible (~30 mins).
3 - Pour off the entire liquid and powder into a clean 2-5 Liter glass jar.
4 - Rinse/Drain with very hot tap water until the ph of the water is 7.
5 - Add enough Ammonia (28% - very strong!) to cover the Silver Powder.
6 - Stir often, wait till any undissolved Silver Chloride is dissolved (~30 mins).
7 - Rinse/Drain with very hot tap water until the ph of the water is 7.
8 - Add enough HCL (Hydrochloric Acid - 37%) to cover the Silver Powder.
9 - Stir often, wait for any iron to be dissolved (~30 mins).
10 - Rinse/Drain with very hot tap water until the ph of the water is 7.
Stack 5 Coffee Filters together, pour out your powder into this sturdy filter packet.
Dry your filter/powder for at least 24 hours at room temperature. (break up lumps every 12 hours)
- Bulgaria Sofia
December 22, 2011
A. Dry well the silver chloride and add 70% sodium carbonate anhydrous and 10% carbon and melt using clay bonded crucible you will get pure silver. if you add 40% borax your output silver will be 995.0 or above.PONNUKALAI muthukalai
- Hyderabad, India
March 31, 2017
A. I concur with Mr. Muthukalai's advice.
Consultant - The Bronx, New York
June 13, 2012
This is a question more than an answer: HOW DO I REFINE THE SILVER AFTER A CHEMICAL RECOVERY CARTRIDGE? I'm talking about photographic residues, I have a Chemical Recovery Cartridge filled with iron wool and I don't know how to get silver from sludges, can any one help me?
- Guadalajara, Jalisco, Mexico
March 22, 2013
Q. I used a food grade sodium hydroxide and got a heavy waxy substance all over the silver during melting. Purity was also lower than using a lower grade drano or red devil lye as well. I do not know what happened. Any answers out there?Erik Keefer
- Grand Junction, Colorado, USA
March 23, 2013
Q. How do you convert a 1 pound bottle of Reagent Grade Silver Cyanide into metallic silver. Is the process similar to the one mentioned for converting silver chloride into silver?
Can one convert silver cyanide into silver chloride by adding hydrochloric acid to the silver cyanide powder?
I know the reaction liberates hydrogen cyanide gas a very deadly gas!! But is this the fastest way to convert the material to a chloride? Can one convert the resulting solution to metallic silver by adding reagent grade pure zinc dust to the solution and have the silver going into an ion exchange mode producing metallic silver as a precipitate?
- Goodyear, Arizona
Precipitating silver from Aqua Regia by adding copperNovember 9, 2014
Q. Adding copper powder to AR will precipitate silver?
Refinery - Astoria, New York, U. S.
November 10, 2014
"Adding copper powder to AR will precipitate silver?"
A. When an alloy containing less than about 8-10% silver is dissolved in aqua regia, the silver is immediately converted to the solid silver chloride. If the silver content exceeds 8-10%, the silver chloride will heavily coat the surface of the object and will prevent the other metals in the alloy from being dissolved.
In other words, if the silver is low enough so that the rest of the metals in the alloy dissolve in AR, most all the silver present will already be automatically precipitated as silver chloride (with the HCl). There will be essentially no silver dissolved in the AR. Therefore, the addition of copper will do nothing as far as the silver is concerned, since there is essentially no silver in the solution for the copper to precipitate.
Actually, in full strength AR, silver chloride is slightly soluble - I would say about 1 gram per liter, at most. When diluted (3 to 1 with water) or chilled, most all of this dissolved silver chloride will precipitate.
- Nevada, Missouri, USA
November 13, 2016
A. Instead of Sodium Hydroxide and Dextrose add some Mild Steel washers. Rinse well with the wet Silver Chloride. The washers can be allowed in the composition for the period of one day. The Chlorine will react with the ferrous and be converted to ferrous chloride in liquid form. Then remove the remaining washers and wash the metal powder (now you got only pure Silver powder) well with distilled water (for the entire process use only distilled water not chemically treated drinking water or any soft water. Rain water,if harvested properly, can be used. And dry the powder. Then melt it. You will get 99.5% pure silver powder.Irulappan Rajasekar
Free lance - Madurai, Tamilnadu, India
March 30, 2017
Q. Hi sir can you please help me?
When I add sodium hydroxide (flakes ) to silver chloride it's turning orange-brown. It's normal? Should I just need to keep on stirring and add sodium hydroxide and sugar?
- AZILAL, morocco
March 21, 2018
Q. I have silver powder from rock. How can I check & test it, and how do I convert it to metalSyed Hassan
- Karachi Pakistan
April 25, 2019
Q. I also have a question on this. Above, Mr.PONNUKALAI muthukalai mentioned a method for which I could be involved with in.
What temperature range would this be most effective with?
What effects can occur if the recipe of sodium carbonate and borax is not as above (could it result in higher melt loss for instance?).
With the amounts of Sodium Carbonate and Borax would there always be a large amount of slag generated on such melts?
Analysis - Liverpool UK
August 30, 2019
A. In fact reduction can be done with calcium carbonate. Adding 50 percent weight of dried silver chloride and 5 percent weight of carbon powder. Heating up to 1070 °C produces pure silver and very little slag. But using sodium carbonate will reduce silver chloride fast but eat away the clay-bonded graphite crucible. To avoid this we can add borax. Borax also acts as a collecting agent. But this process is easy and reaction is fast and working temp.is around 1000 °C
India - hyderabad india