AgCl to Ag without losses

[amesametrita]

Excuse me, friends.
I've promised not to write in public area about this forum misconceptions and obsolescence of Hoke's book.
But AgCl topic is very important for every silver refiner.

The only method I know which saves 100% Ag.

1) Mix AgCl slurry with Zn powder. After some delay violent reaction starts.
You convert 80-95% to metalic silver. Don't put too much powder. You'll recover the rest next time.
2) Quick wash
3) Dissolve all the zoo in diluted HNO3
4) Filter remaining AgCl for the next batch
5) Drop Ag from AgNO3 as you like.

Straightforward.

 

[lazersteve]

If I have silver chloride it's typically already clean and ready to be converted directly to silver metal without using any more nitric acid.

I can't understand why you would use the zinc method (at acidic pH) to convert the silver chloride to metallic silver, then digest in nitric acid, and start the whole process all over again? If you have a dirty silver nitrate solution, filter it 100% free of sediment, precipitate the silver chloride, wash with lots of hot water (test wash for presence of base metals in wash liquid for end point), and convert with any one of several well know methods for high purity silver (formic acid, sugar/lye, etc). Never let your silver chloride dry out.

If the silver chloride is dirty (contains solids other than silver) then the method outlined is simply a recovery method that Hoke outlines in detail and has been discussed here multiple times over the years. You may find this form of silver chloride when working with inquarted gold or gold filled scrap.

Here's a recent post where I discuss this exact method:

Using Zinc to Purify Dirty Silver Chloride

Steve

 

[amesametrita]

I can't understand why you would use the zinc method (at acidic pH) to convert the silver chloride to metallic silver, then digest in nitric acid, and start the whole process all over again?

1)
Because it's the only method without losses.
And much faster than "wash with lots of hot water" or "mix until you're dead".
At Hoke's time silver was cheap she asked every time a question "is it worth to recover it?"...
They even just melt silver chloride with soda ash that time.
2)
Why you think my method has something in common to your "zinc method (at acidic pH)"?
Do I use a bar?
Do I add dilluted acid?
You reduce Ag by hydrogen, I do it by Zn.

 

[Jeki rajput]

How to recover silver from silver chloride without any loss of silver??. Which method is best for fully recovery of silver from silver chloride??.means 75.5 gm of silver from every 100gm of silver chloride.PLEASE SOME ONE HELP ME.

 

[goldsilverpro]

Somewhere I have the original experiment sheet I used to determine the amount of light Karo corn syrup and NaOH it took to convert AgCl. This was done accurately in a lab. I did about 15 runs and, when enough of each of the 2 ingredients were used, in maybe 5 of the runs, there was 100% conversion of the silver. Not 99 or 99.5 - 100%.

Probably the largest lot I used this method on was about 9000 oz, in about 10 batches. I used a Lightnin' mixer, with a prop, in a plastic drum and stirred it for several hours. The AgCl had never been allowed to dry out. There was no AgCl visible after the melt cooled in a mold. The final yields were identical with the solution analysis before dropping the AgCl. For 31.1g of silver, or 41.3g or AgCl, it takes 13,3ml of Karo syrup and 20g of NaOH. I always use 10% extra, or a total of 14.6ml of syrup plus 22g of NaOH per 31.1g of silver. The silver was quite pure.

I used to work in a place that used formaldehyde and NaOH in about a 100gal tank with a mixer. Very fast conversion. All the copper had been well rinsed out and the silver was very pure.

 

[g_axelsson]

For more details about the conversion I recommend this post.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=53&t=120#p1497
It also contains advice on what to what to do if you have dried silver chloride and how to test how complete the conversion was.

Göran

 

[Lou]

While the aldose method works well for silver chloride, I have yet to find a more economical and cheap way of doing lots of the stuff than a large rubber lined concrete mixer, dilute sulfuric acid and scrap iron.

That material is tumbled and tested by removing a sample, rinsing with water until no more acid remains, and then rinsing with a strong solution of aqueous borax and carbonate. If no gold or PGMs are present in the silver, nitre can be added to the rinse solution to remove any other base metals. When that sample can be melted and the borax slag is dark but not metallic looking and no chloride fumes are given off, then the material is converted.

That material is dumped from the mixer into a large buchner, a strong magnet wrapped in plastic wrap removes the iron pieces (optional) where they can be hosed off to remove most of the cement silver. The silver is rinsed clean with tap water, then the liquid flux mixture as mentioned above. The material is packed wet into the crucible and melted.

I have had very good results with this. The only issue is high O content in the silver if nitre is used. The flip side is that the nitre removes pretty much everything but large amounts of Ni or any Au.