<prompt> Which one of the following method is used for the estimation of the chlorine demand of waterChlorometerHorrocks apparatusBerkfeld filterDouble pot method  <response>: Chlorine demand of water can be estimated by Horrocks 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.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 1 hr, at a given temperature and pH of water.InstrumentHorrocks ApparatusChlorinator ChloronomeChloroscopeUtilityChlorine demand estimationMixing or regulating dose of chlorineMeasuring residual level of chlorineBerkefield filter is a type of ceramic filter which is used for purifying water on small scale.The Double Pot Method provides a constant dose of chlorine to well water during periods of emergency. 