Ask A Scientist Chemistry Archive

name         Heidi
status       student
grade        9-12
location     MD

Question -   How can one determine that there is more chlorine in 8oz
of tap water than in 8oz of distilled water? A simple experiment would be
best (other than test strips), but any suggestions are helpful.
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   Swimming pool stores have inexpensive, but accurate kits for
determining the chlorine content in swimming pools. These are much better
than "test strips" and pretty simple to use. There is also a procedure
using the reaction of  "available" chlorine (hypochlorite) to oxidize
iodide ion to I2 and measuring the color with a starch solution. Do a
"Google" search for "iodide method available chlorine" for details.
However, reducing the procedure to actual use will involve a lot more time
and effort. I would recommend the pre-packaged pool test kits.

Vince Calder
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Heidi,

Your question brings back memories as this is one experiment that I did
in high school chemistry.  You will have to do a bit of research on this
because I do not remember the reagents needed.  The test is similar to
testing pool water.  You take your sample, add a reagent and then test
the sample using a spectraphotometer.  The reagent produces a color
which is measured at a certain wavelength of light.  The more chlorine,
the darker the color and more light absorbed.  You start by creating a
graph using known concentrations of Chlorine.  Then you measure your
samples.

Have fun

Bob Hartwell
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