What is Chlorine Demand test? what are it's application?

Answer 1

Funny you should ask. Some friends of mine developed a demand kit about 20 year ago.

Chlorine demand represents undesignated compounds in water than can react with chlorine. The test is to take a certain volume of the water in question and add a certain amount of chlorine and a color indicator. Usually, if the demand exceeds the chlorine, the mix will go colorless. If there is leftover chlorine (residual), the color will be less than the original level, and can be related to the conc of the residual chlorine by a color comparator. It is used in water treatment and wastewater treatment, and in pools to determine if the pool-water has a residual chlorine level.