How to make copper sulfate

07.06.2011

Warning: This experiment produces moderately toxic copper sulfate. Do not dump more than a small amount down the sink. Do not drink the solution or eat the crystals.

This article will detail the process of creating a dirt-cheap impure form of copper sulfate using these simple household substances: copper wire, magnesium sulfate (Epsom salts), a container, and a 12VDC power supply.

Dissolve the magnesium sulfate in warm water to make a concentrated solution. Strip two lengths of copper wire (stranded is better than solid) and immerse them in the magnesium sulfate electrolyte. Attach them to the 12VDC power supply. They should not be near each other. Turn the power supply on.

At once, large quantities of hydrogen bubbles should be seen coming from the negative electrode (cathode), while small quantities of oxygen come from the positive electrode (anode). A white flaky solid should form at the cathode, and a light blue solution should start forming at the anode. Remove as much of the white flaky solid, a magnesium hydroxide precipitate, as you can. This will prevent it from redissolving and stopping the copper sulfate from forming. When the white precipitate starts becoming bright blue, stop the electrolysis and remove the copper wires. What you have is a solution of copper sulfate mixed with a large quantity of magnesium sulfate. The copper wire functioning as an anode should be somewhat corroded, and the other wire should be unchanged. Evaporate the blue solution. It should become bluer and eventually slushy blue crystals should start precipitating. After a while of being exposed to air, they will turn a dirty green because the copper sulfate has lost part of its water of hydration.

If you want pure copper sulfate, just buy it. Making it will require purchasing sulfuric acid and electrolytically oxidizing the copper in a sulfuric acid bath (some copper may plate out again at the cathode). Making it is not very economical.