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Is chlorine in there that accumulates (at the anode) and emerge out as chlorine gas? I was worried since I added a pinch of salt to the steamer in order to hasten the heating of tap water when I caught a cold (I should've just boiled a pot of water on the stove). I'm worried since chlorine gas is bad for the respiratory system. Also I'm curious to know what is this brown precipitate under the solution - hydroxides or cupric-oxides from the electrode?

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    $\begingroup$ Yes, it is possible to generate chlorine gas in an aqueous solution containing chloride ions. Further, I wonder why adding a salt will "hasten" the heating of tap water, since we typically teach that addition of solutes results in the boiling point elevation of solvents. $\endgroup$ – bobthechemist Aug 24 '13 at 1:49
  • $\begingroup$ Yes, but the conductivity increases and you didn't mention if it was dangerous. $\endgroup$ – Python Student Aug 24 '13 at 5:48
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    $\begingroup$ Yes, inhaling chlorine gas is dangerous. As for the conductivity of the solution, why does this matter if you are trying to boil it rather than electrolyze it? $\endgroup$ – bobthechemist Aug 24 '13 at 12:41
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So if I understand the question correctly, you heated up water with some salt by performing electrolysis.

If so, you would also generate chlorine gas. However, the heat capacity of water is really large, so I doubt that you would even be capable of bringing water to a boil by just jolting current through it.

To answer your question: Yes, when performing electrolyzation of any solution you should apply the usual precautionary measures, such as working in an open space or under a fume hood. Under no circumstances should it be possible for you to inhale the gases produced.

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  • $\begingroup$ "However, the heat capacity of water is really large, so I doubt that you would even be capable of bringing water to a boil by just jolting current through it." Despite the high heat capacity of water, generating steam results from more energy added (over time) than is lost. $\endgroup$ – Keith Reynolds Jun 23 '15 at 16:10
  • $\begingroup$ Some chlorine is is evolved but much more of the chlorine will react with the sodium hydroxide forming sodium chlorate (NaOCl), which is how a bleach is made, unless your using a membrane to keep the ions separate. $\endgroup$ – Keith Reynolds Jun 23 '15 at 16:22
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Your question is not very clear. Did you just heat the salt water? Or you have put electrode to electrolysis water? What material is your electrode? Copper?

Let me assume you are using copper electrode to electrolyze brine. Then you will have the following reactions:

Cathode: $$\ce{Cu - 2e -> Cu^2+}$$

Anode: $$\ce{2H2O + 2e -> H2 + 2OH-}$$

Over all: $$\ce{Cu + 2H2O -> Cu(OH)2 + H2}$$

So, when copper is your electrode, you will have no $\ce{Cl2}$ gas for sure. You will only breath in hydrogen gas.

If you use graphite as the electrode, you will get overall reaction: $$\ce{NaCl + 2H2O -> NaOH + H2 + Cl2}$$ It is possible to have the $\ce{Cl2}$ gas. However, if the amount of $\ce{Cl2}$ is not really big, it will be absorbed by water especially when it is basic. $$\ce{Cl2 + 2OH- -> ClO- + Cl- + H2O}$$ And over all: $$\ce{NaCl + H2O -> NaClO + H2}$$ No gas emitted. Electrolysis of water is actually one way to make bleach.

The conclusion is: it is safe to inhale unless you are using extremely big battery.

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  • $\begingroup$ Some Chlorine gas will likely evolve from the solution but your right in that your really making bleach. $\endgroup$ – Keith Reynolds Jun 23 '15 at 16:24
  • $\begingroup$ Your also make a decent point that it will require a lot of energy to make appreciable unsafe amounts, but i would recommend against inhaling bleach and chlorine gas if you can avoid it. On a further note, the fact that steam is being created implies that a fair amount of energy is being added. Not knowing the applied voltage leaves us not knowing how efficent the electrolysis was versus resulting in waste heat. $\endgroup$ – Keith Reynolds Jun 23 '15 at 16:30
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Electrolysis:

Your question "Is it dangerous to inhale the steam coming from electrolysis of salt-water solution?"

The answer short answer is: It is not safe.
The long answer involves relative safety, and depends on a few things.

First thing to understand is that chlorine is produced at the anode and sodium hydroxide produced at the cathode. Most of the chlorine will combine with sodium hydroxide producing NaOCl, in other words bleach. But, some chlorine gas may evolve from the anode because sodium hydroxide has not yet migrated to the anode in sufficient quantity. Either way, it is not safe to breath bleach or chlorine.

The relative danger depends on:

  • How efficient is the electrolysis: Higher voltages though causes more current to flow, are less efficient at electrolysis because it produces more heat than actual electrolysis for each unit of energy applied. More heat, thus steam more steam per electrolysis product, is comparatively less harmful.
  • Quantity of salt: Adding only a pinch of salt means that either very little bleach or even less chlorine gas will be produced; In such low concentrations either product is likely to remain dissolved in the water rather than evolve.

Steamers:

On the other hand, you mentioned adding a pinch of salt to a steamer. Conventional steamers do not perform electrolysis. Instead, electricity is passed through a restive load with the only product being heat. Adding a pinch of salt may raise the boiling point, and thus requires more heat to make steam, but it would be completely harmless, except for the dangers of heat from the steam.

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