# why do I get chlorine gas production during electroetching?

I was electroetching stainless steel plates with table salt as electrolyte and the power supply was providing 5V, 6A when I placed the anode and cathode about .25 inches apart. I started smelling a swimming pool chlorine smell and when I pulled out the anode, it had a yellow film on it which smelled strongly of chlorine also, which I am guessing is some sort of chlorine precipitate. I thought that distinct smell came from chloramines though, not a chlorine gas, so I don't know exactly what compound I was smelling.

However when I returned the plates to .5 inches apart and heated the solution from about 15C to 35C, I was drawing 5V, 8A since the heat allows the reaction to happen more vigorously. However, I no longer smelled any chlorine even though there was a higher power consumption. What is going on here? Clearly the distance between the two plates affects this, but can someone give a chemical explanation as to why?

• Smaller distance means less inner resistance, ergo smaller voltage difference within the solution, and higher voltage difference at the electrodes (if both experiments are run at 5V total). I assume (or guess) you just passed the overvoltage for $\ce{2Cl- -> Cl2 + 2 e-}$. Also the change in temperature possibly lowers the overvoltage of chlorine production. – Karl Jan 17 at 2:23