# Can I boil off chlorine? Does it evaporate quickly at high temperatures?

Can I boil off chlorine? Does it evaporate quickly at high temperatures?

I am asking because I want to remove it from drinking water, and I don't want to wait 24 hours for it to evaporate naturally.

• Isn't it usually chloramine, rather than elemental chlorine, in drinking water? – David Richerby Mar 27 at 12:41
• @DavidRicherby Depends on the municipality. Some stick to the traditional molecular chlorine as a disinfectant, but others have indeed switched over to using chloramines, as they're more persistent. (And thus you don't lose disinfectant capability at the edges of your water distribution network.) -- If JMN hasn't already, they should check with their local water works about the type of disinfectant they use. (Most will happily provide information on this and other water quality metrics.) – R.M. Mar 27 at 14:43

Yes, solubility of chlorine decreases drastically as the temperature rises, and it's almost insoluble in boiling water. That's also the reason why in the areas where tap water is chlorinated, it advised to boil it before drinking.

Data from [1, p. 8]:

Figure 5. Solubility of chlorine in water, hy­drochloric acid (two concentrations), and so­dium chloride solutions (three concentrations) All percentages are weight percents.

In aqueous solutions, chlorine is partially hy­drolyzed, and the solubility depends on the pH of the solution. Below 10 °C chlorine forms hydrates, which can be separated as greenish-yellow crystals. Chlorine hydrate is a clathrate, and there is no definite chlorine: water ratio.

### References

1. Chlorine: Principles and Industrial Practice, 1st ed.; Schmittinger, P., Ed.; Wiley-VCH: Weinheim ; New York, 2000. ISBN 978-3-527-29851-8.
• Can you comment at what level of water chlorination "they" suggest you boil the water before drinking? – costrom Mar 27 at 14:15
• @costrom I cannot speak for the entire world, but in Russia there should be between $\pu{0.3 mg L-1}$ and $\pu{0.5 mg L-1}$ of residual chlorine according to the state sanitary and epidemiological standards. In general I guess it won't hurt to boil any tap water before drinking as it also reduces probability of infection and reduces water hardness. As they say, to make holy water, boil the hell out of it. – andselisk Mar 27 at 14:25
• Hmmm; boiling water also a way to make untreated water safe to drink. – Joshua Mar 27 at 18:40