In Las Palmas de Gran Canaria, tap water is chlorinated. In an Internet forum, someone claims that in 2008 the water had a chlorine concentration of 0,5 - 1mg/l. On the official site of Emalsa, the water provider, I couldn't find any information about chlorine concentration. I tried contacting them online, but the contact form is broken.
In another forum, I read that ascorbic acid (vitamin C) can be used to neutralize the chlorine: My taste buds say it works!
How much ascorbate/l do I need to neutralize the above amount of chlorine?
Answer
This is just a very short explanatory note on the article suggested by Greg E..
The reaction between ascorbic acid and hypochlorous acid is as follows: $$ \ce{C5H5O5CH2OH + HOCl → C5H3O5CH2OH + HCl + H2O}$$ so for 1 mole of hypochlorous acid you need 1 mole of ascorbic acid. This can be recalculated into a mass ratio by the use of their molecular masses:
$$M(\ce{C5H5O5CH2OH})=176\;\text{g/mole}$$ $$M(\ce{HOCl})=52.5\;\text{g/mole}$$ From this we can see that if the molar ratio is $1:1$, the mass ratio is $176:52.5$ which is $3.3:1$ somewhat higher than the article claims.
I am not exactly sure of the reason, it could be that there is some side reaction of ascorbic acid that also removes some additional hypochlorous acid although I wouldn't know which. Perhaps the article is talking about the amount of ascorbic acid you need to get a concentration which you don't taste anymore?
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