I want to make a high voltage variable capacitor by pumping the copper sulfate out of a 40 oz beer bottle leyden jar. But what kind of pump can I use to do this? I don't know if an aquarium pump could handle this. And I have to be able to pump the copper sulfate back in.
The major problem is a redox reaction between Copper and Iron. The Copper will fall out of solution and the Iron will decompose. This works quite dramatically with an iron nail and I suspect steel will probably corrode rather badly as well. This is relevant because the rotor shafts on most aquarium water pumps are steel. Although expensive, a peristalic pump might be a viable option. This sort of pump uses a set of roller bars to squeeze fluid through a flexible tube. It's the kind of pump surgeons use to pump blood around outside the body. Another option might be special industrial pumps used for highly corrosive acids and bases. They are piston driven, but all the internal pump parts are non reactive plastics like teflon. Another design uses a plastic coated magnet linked magnetically to an external magnetic rotor. The internal magnetic rotor is encased in plastic, so there is no reaction between the pump and what it is handling. One thing to concider is that industrial pumps are designed to be high volume, and are perhaps a bit overpowered for something like 40 ounces of fluid. In this respect, the peristalic pump might be a better option. FYI: Copper sulfate is a blue solution which is somewhat toxic but far less so than things like Arsenic and Cyanide. It is very toxic to plants however, which is why it is used to kill tree roots in septic lines. It will also stain masonry because Copper carbonate forms, a dull, chalky green pigment. Copper, Arsenic and Chromium are the three elements used to manufacture treated lumber. It is green because of the Copper. Nealy all Copper salts are either blue or green.
There are easier solutions than pumping. You can make a container that pivots with the plates on one side, so as it pivots more or less of the plates are uncovered. Or a larger container with the plates on one side and a solid piston on the other. The piston moves up or down, taking up more or less volume, and causing the plates to be more or less uncovered. .
