Which one of the following method is used for the estimation of the chlorine demand of water ?

Ans. is 'b' i.e., Horrock's apparatus o Chlorine demand of water can be estimated by Horrock's apparatus. o Chlorine demand of water is the amount of chlorine that is needed to destroy bacteria, and to oxidize all the organic matter and ammoniacal substances present in water. o It is the difference between the amount of chlorine added to the water, and the amount of residual chlorine remaining at the end of a specific period of contact (usually I hr), at a given temperature and pH of water.