Silver nitrate to silver - comparision

[arie_pk]

I received a batch of sterling silver ignots, and decided to do some tests to find the best way to purify..
1. I started with 119 grams of sterling using the copper method. After first purification, i got 97 gram. I started with those 97 grams from the beginning, (nitric and then copper bars) and on second purification i got 90 gram out of 97grams.

2. Second test i started with 81 grams sterling from the same batch. From silver nitrate i used salt and got the chloride. I used 8% sulphuric acid and iron. After a day I washed and melted and got 77g. I started all over again with those 77grams, and final result was 75g out of the 77g.

3. The worst results were with the lye/syrop method. I started with 72g of sterling. After adding the lye to the silver nitrate, i could see specks of white inside the silver oxide. I added more lye, and even poured out the first batch of water/lye, added fresh water and fresh lye. I left it overnight, and next morning added the syrop. The final result was 46g out of 72. I skipped out the second purification stage because io like my silver too much.

Does it make any sense guys? Or i did something wrong here

 

[peter i]

You are loosing a lot of silver somewhere!

Silver is easy to work with, and recovery should be better than 99% in all cases.

In the chloride method you have a recovery of 97% in the second run, and even that is lousy regarding that precipitation as chloride is a well established gravimetric method for silver analysis.


Did you test all water phases before throwing anything away? A drop of the solution and a drop of hydrochloric.... white precipitate means money is still in there!

When you precipitate as chloride, you must stir thoroughly, let settle and then add more chloride and see that nothing precipitates. It is far better to add the chloride as brine or hydrochloric acid, than as dry salt.


When working with noble metals, sloppy or incorrect procedures are expensive!

 

[Juan Manuel Arcos Frank]

Arie:

You are doing it well,I am sure you can do it better,here is my advice to you:

About the copper method you have got to use distilled water and boil the nitric acid solution,ingots are hard to dissolve.Once the ingot is dissolved you have got to dilute the acid solution with distilled water in proportion 1:5,then dip the copper slabs until precipitate all the silver.

About the salt method probably you do not precipitate all the silver chloride from the nitrate solution,the precipitation is completed once you add salt and does not form white clumps.

The time needed for iron process seems very long to me,you have got to stirr hard the solution and it does not take more than 15 minutes.

About the lye/syrup you have got to dilute the acid solution with distilled water before adding lye.

I suggest you this process:

First make your ingots to shot,then dissolve the shot in a solution of concentrated nitric acid and distilled water in proportion 1:1,do it outside because brown fumes of toxic nitrogen dioxide will form...boil the solution for 15 minutes,let cool and setlle down.Pour off the liquid,wash the mud (if any) in the filter with distilled water.

Add to the liquid common salt and continue adding until no more white clumps are formed,let settle down,now check if all the silver nitrate has converted to silver chloride.Take some liquid in a cristal glass and add some grains of salt...if you see small white clumps then you need to add more salt to the nitric solution.If the salt grains remain without change then it means that there is no more silver nitrate in the solution.Then wash the white mud 5 times with tap water.

To the white mud add sodium hydroxide until all the mud changes to black color,if you see some white grains continue adding sodium hydroxide and stirr well.Wash 3 times with tap water and then add Karo syrup...you will get pure silver without lose.

I hope it helps.

Best regards

Manuel

 

[goldsilverpro]

1. I started with 119 grams of sterling using the copper method. After first purification, i got 97 gram. I started with those 97 grams from the beginning, (nitric and then copper bars) and on second purification i got 90 gram out of 97grams.

The copper cementation method should give you very close to a 100% yield, assuming you dissolved the silver completely and then tested the solution to make sure that all the silver had been cemented out. One of the only places to get a loss would be if silver were still attached to the copper bars. Also, you could have some in the filter paper. If you torch melted too hot, you could have a sizable loss.

3. The worst results were with the lye/syrop method. I started with 72g of sterling. After adding the lye to the silver nitrate, i could see specks of white inside the silver oxide. I added more lye, and even poured out the first batch of water/lye, added fresh water and fresh lye. I left it overnight, and next morning added the syrop. The final result was 46g out of 72. I skipped out the second purification stage because io like my silver too much.

When you did the Karo/NaOH method, you used it directly on the silver nitrate solution. I suppose you could do it that way, but the copper and nitric in the solution could complicate the situation. For example, if there was any free nitric left in the solution, it would react with the NaOH.

The Karo/NaOH method should be used on silver chloride. Never let the silver chloride dry out or it will be difficult to get a complete conversion. For each 100 grams of silver that you started with, it will take at least 64.1 grams of NaOH, 42.7 ml of light Karo syrup, and about 430 ml of water for 100% conversion. I usually add 10% extra of each of the chemicals. Don't guess on the amounts. Stir vigorously when making the additions. I would first dissolve the NaOH in the water and then add the moist AgCl. Stir well for a few minutes and then add the Karo. Continue stirring for 5 minutes.

 

[SilverNitrate]

Silver Oxide/Hydroxide is soluble to more of a degree in excessive lye and heat. So generally solutions shouldn't be dumped, but rather treated as a single batch with the aldose/syurp

 

[Helian]

If you have silver nitrate and simply want to turn it into pure silver, put a few drops of nitric acid (that's right, just a few drops) in distilled water, dissolve the silver nitrate in it, and stir with a pure copper sheet. The silver will drop out as a coarse powder as it contacts the copper. I suspect that virtually no copper will drop out with the silver when you use this method, because it's recommended in a book I have on Inorganic analysis published in the 30's, and the author was very careful about such things.

 

[goldsilverpro]

helian,

With copper cementation, no copper will drop out. However, slivers of copper can fall off and contaminate the silver. Also, it takes a lot of rinsing to get the copper solution out of the silver. All in all, 99% pure silver is about all you can expect from copper cementation.

 

[Helian]

In any case it takes quite a bit of stirring to get all of the silver to drop. It's probably easier and faster to just convert to silver chloride and go the usual route.

 

[goldsilverpro]

Use about 6-8 pieces of buss bar and it won't take long at all. Speed is proportional to the surface area of the copper.

 

[Harold_V]

In any case it takes quite a bit of stirring to get all of the silver to drop. It's probably easier and faster to just convert to silver chloride and go the usual route.

Unless you have a purpose for dealing with silver chloride, no one in their right mind does so any more than is necessary. Cementing with copper is the way to go unless you have no source of copper.

Copper will recover all of the silver, along with any traces of PGM, with no attention whatsoever. Give it a day in a bucket with a supply of copper and walk away. You can recover your silver almost instantly if you have enough copper present, as GSP suggested.

Harold

 

[peter i]

And if you have pure silver nitrate, it is worth more than the pure silver it contains, and could just as well be used for a plethora of other nice jobs.