Sciencemadness Discussion Board

de-chlorination byproducts

Traveller - 17-2-2013 at 14:53

It is a well known fact that adding ascorbic acid to chlorinated bath water will neutralize the effects of chlorine in bath water.

What is the byproduct created from this reaction?

bahamuth - 17-2-2013 at 15:35

Well, a 20 second online search yielded the desired result for me, you should try it..:P

Also, "well known fact" statements usually is frowned upon, by me at least. Provide a reference so others which do not know this "fact" can join in. (Also I suspect you would find the answer to your question if you bothered search for a reference to the reaction in question)





PS. A search hint in the spirit of spoonfeeding, enter this into Google: "dechlorination of water by ascorbic acid"

Traveller - 17-2-2013 at 15:45

If you don't want to give someone an answer, why even bother posting? Does it boost your ego to act this way?

bahamuth - 17-2-2013 at 16:24

Quote: Originally posted by Traveller  
If you don't want to give someone an answer, why even bother posting? Does it boost your ego to act this way?


No it does not, but is intended to shame you a little bit so that you may learn to UTFSE as the rest of us.

If you wanted to know this particular piece of information search for it, not post a semi-vague question on a science forum and wait until someone spoonfeeds you the whole textbook answer.

For the sake of keeping this a thread on a science forum, a collection of knowledge so to speak, I will quote my findings below.
Quote:

VITAMIN C DECHLORINATION
Vitamin C is a newer chemical method for neutralizing chlorine. Two forms of vitamin C, ascorbic acid and sodium ascorbate, will neutralize chlorine. Neither is considered a hazardous chemical. First, vitamin C does not lower the dissolved oxygen as much as sulfur-based chemicals do. Second, vitamin C is not toxic to aquatic life at the levels used for dechlorinating water. Although ascorbic acid is mildly acidic and, in large doses, will lower the pH of the treated water, sodium ascorbate is neutral and will not affect the pH of the treated water or the receiving stream. Both forms of vitamin C are stable, with a shelf life of at least 1 year in a dry form if kept in a cool, dark place. Once it is placed in solution, however, vitamin C degrades in a day or two.

Ascorbic Acid
One gram of ascorbic acid will neutralize 1 milligram per liter of chlorine per 100 gallons of water. The reaction is very fast. The chemical reaction (Tikkanen and others 2001) of ascorbic acid with chlorine is shown below:

C5H5O5CH2OH + HOCL → C5H3O5CH2OH + HCl + H2O

Ascorbic acid + Hypochlorous acid → Dehydroascorbic acid + Hydrochloric acid + water



Approximately 2.5 parts of ascorbic acid are required for neutralizing 1 part chlorine. Since ascorbic acid is weakly acidic, the pH of the treated water may decrease slightly in low alkaline waters.

Sodium Ascorbate
Sodium ascorbate will also neutralize chlorine. It is pH neutral and will not change the pH of the treated water. Sodium ascorbate is preferable for neutralizing high concentrations of chlorine. If a large amount of treated water is going to be discharged to a small stream, the pH of the treated water and the stream should be within 0.2 to 0.5 units of the receiving stream.

The reaction (Tikkanen and others 2001) of sodium ascorbate with chlorine is shown below:

C5H5O5CH2ONa + HOCL → C5H3O5CH2OH + NaCl + H2O

Sodium ascorbate + Hypochlorous acid → Dehydroascorbic acid + Sodium chloride + water



Approximately 2.8 parts of sodium ascorbate are required to neutralize 1 part chlorine. When vitamin C is oxidized, a weak acid called dehydroascorbic acid forms.

Several studies have evaluated the use of ascorbic acid and sodium ascorbate to neutralize low levels of chlorine—less than 2 milligrams per liter. Only one study (Tacoma Water Utility Report) evaluated the use of ascorbic acid to neutralize high levels of chlorine—up to 100 milligrams per liter. The Tacoma, WA, Water Utility Engineer recommends against using ascorbic acid to neutralize high levels of chlorine in large volumes of water because it lowers the pH of the treated water. The Tacoma Water Utility engineer recommends using sodium ascorbate instead.





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