Liquid NaOCl is subjected to a gradual decrease in concentration when it is
stored for a long period. Also light and high temperature have a negative
impact on the activity of the product. So it is advisable to check on regular
basis the activity of the product by titration. The titration of
OCl- is based on a neutralization reaction. Basically this means
that the strong oxydans will be neutralized by a reductans in the presence of a
colour indicator. In fact the same will happen as for the colour reaction; when
all the chlorine has been neutralized by the reductant the colour will change.
By measuring the amount of reductant that is needed to neutralize the chlorine
we can calculate the initial concentration of chlorine.
