# What dangerous gases could electrolysis with water and sodium carbonate produce?

My friend was very nervous when he noticed that I'm performing electrolysis in a room that we've just been residing. (it was under open window to let $\ce{H2}$ out) After a sharp argument, he made me shut it down, though I still thought that it was safe.

I'm using $\ce{Na2CO3}$ as electrolyte and as far as I know, it doesn't get electrolysed. I use normal pipe water. Such water surely contains some minerals however in really small amount. My friend pointed out that it also contains chlorine and that's what he's afraid of. He would disregard my notice that he's drinking this water often.

I'm using copper electrodes, producing copper hydroxide and copper carbonate. I failed to find out whether these compounds are hazardous. They're in solid state anyway.

From what I've said you can see that I'm very sure that the reaction is not hazardous. But I'm not chemist. There could be something I didn't think of in which case I've been poisoning myself for quite a while.

Could you make me sure or warn me?

My friend pointed out that it also contains chlorine and that's what he's afraid of.

The amount is laughable at. However, using distilled (deionized) water is recommended for other reasons.

I failed to find out whether these compounds are hazardous. They're in solid state anyway.

They are reasonably harmless. Of course, eating them is not recommended, but copper compounds have low toxity. Move to graphite or platinum electrodes is still recommended.

• For what other reasons is distilled water recomended? Jul 2 '14 at 18:06
• @TomášZato Because it is unknown what other compounds and in what amounts are present in tap water. Since deionized water is reasonably free available at reasonable price (<\$2/liter in my city), using it is recommended. Jul 3 '14 at 2:06
• If you're using hard water you might still end up creating a reasonable amount of chlorine, it's still worth distilling the water first. Apr 9 '20 at 14:13

Copper salts are toxic, which means the water you use would not be healthy after a while and be careful on disposing of it.

The minerals you have are probably in small amounts, and you can check this measuring the conductivity of the water.

You can make the gases pass through a filter of CaCO3 that will absorb any chlorine.

There is also the answers to this question for details on what is happening.

• Any chlorine coming from where? Does electrolysis cause dissolved chlorine to evaporate from water faster than when you're, for example, washing yourself? Jul 1 '14 at 22:42
• What do you mean by that second question? If there's say, NaCl, in the water, you could produce chlorine gas. But if you're doing it right next to an open window and in small amounts (which it appears you are), there should really be no worries. Jul 2 '14 at 4:17
• You said that I could filter the chlorine. So I asked if the electrolysis causes chlorine (which is dissolved in freshly poured water) to quickly leave the water. As I've said, I don't use salt because of the toxic products it creates. Jul 2 '14 at 18:08
• There could be some chlorine produced by the electrolysis but from what you say it isn't much and would stay in the water. The use of deionized water is so you don't have ions to consider. The idea of the filter is to tranquilize your friend. The oxygen isn't much either.
– f p
Jul 2 '14 at 18:21