Silver cell

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Silver cell is a common name on the electrolytic silver refining cells. There are two major designs, the Moebius and the Thum cell. For other silver refining techniques see silver refining.

Contents

Chemistry

Electrolyte composition

Moebius cell

(Main article: Moebius cell)

Thum cell

(Main article: Thum cell)

Detecting and dealing with fouled electrolyte

(Main article Removing palladium from silver nitrate)

Sometimes the silver contains palladium and while some will end up in the anode slime, some of the palladium will dissolve and end up in the electrolyte. A sign of dissolved palladium is when the electrolyte turns green instead of blue from dissolved copper.

The best test for palladium is dimethylglyoxime, in acidic condition it will give a yellow precipitate and it is also a good way to remove the palladium from the electrolyte. Approximately 2.5g DMG will precipitate 1g palladium from the solution.

Basic plan for dealing with palladium.

  • Test if there is palladium in the electrolyte.
  • Prepare a DMG solution by dissolving DMG in a basic solution.
  • Take a sample and measure the volume.
  • Add enough nitric acid to the sample to keep it acidic even when adding the DMG solution.
  • Add the DMG solution until no more precipitate is created.
  • Calculate the amount of nitric acid and DMG solution needed
  • Add nitric and then the DMG solution
  • Filter off the yellow precipitate and wash it.
  • If needed, add more silver nitrate to the electrolyte.

The yellow precipitate can be turned into palladium metal by calcining or dissolved in aqua regia and turned into palladium chloride.

Patents

Cell voltage and contamination

References

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