How to make sulfuric acid by electrolysis of copper using an inert anode. Copper sulfate is very easy to obtain in large quantities at gardening and hardware stores and provides a convenient route to sulfuric acid if the appropriate anode can be obtained.
Warning: This should be done in a well-ventilated area as hydrogen gas build up is explosive. Copper sulfate is toxic and sulfuric acid is corrosive, wear gloves when handling them.
The procedure is extremely simple, just get a copper sulfate solution, insert two electrodes and run a current through them. The anode, the positive electrode, must be an inert material that can withstand extremely oxidizing conditions. Very few materials meet this condition, platinum, lead dioxide, and carbon among them. Other metals, even stainless steel, are quickly destroyed under these conditions and cannot be used. The cathode, the negative electrode, is exposed to reducing conditions so the metal requirements are must less stringent. Copper is the best choice here since it has high electrical conductivity.
When applying power, the current should be adjusted so that corrosion at the positive terminal and bubbling at the negative terminal are both minimized. The bubbling at the negative terminal is hydrogen production and that’s wasted energy that should have gone into reducing the copper sulfate.
After the solution has gone clear, filter off the particles and the clear filtrate is dilute sulfuric acid that can be boiled down to obtain concentrated sulfuric acid. It will have trace amounts of metals but for most purposes this is not an issue.
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