Hello, I'm new to this and definitely not a chemist and I cant seem to get my head round why we cement silver from silver nitrate with copper, melt that into shot to use for the silver cell electrolysis. Couldn't I just use the silver nitrate for electrolysis to grow the crystals and miss out the cementing and shot steps?
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Electrochemistry Cementing silver and electrolysis
- Thread starter DrMunns
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The silver cell is not a "batch" process. At first, only the silver will deposit on the cathode and it will be quite pure. However, after a short period of time, the silver in the solution will decrease to the point that copper will start co-depositing with the silver. The purity of the silver crystal is directly related to the ratio of silver to copper in the solution. A high ratio will provide pure crystal. A low ratio produces impure crystal.DrMunns said:
The silver cell is a "continuous" process. To maintain the silver crystal purity, the silver in solution must be kept at a high enough level so that only silver will deposit. In most cases, the lowest level is about 30-40g/l. This is usually maintained by continually dissolving silver from a high-silver content anode.
The purpose of dissolving/cementing the silver is, primarily, to raise it's purity so that the cell solution will last longer before the copper level reaches a point where it will co-deposit no matter how much silver is in the solution - this point is about 75g/l of copper. For example, the copper content in sterling silver is about 8-10%. By dissolution and cementation, the copper can be reduced to less than 1% and the solution will, therefore, last about 10 times longer before one has to do something about the copper content.
