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

Estimation of chlorine demand of water (or dose of bleaching powder required for disinfection of water) is done by 'Horrock's apparatus'. 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. Is the amount of chlorine added to water minus amount of residual chlorine remaining at the end of specific period of contact (1hr). - Also remember, Free chlorine level in water is estimated by CHLOROSCOPE.