<prompt> Chlorine demand of water is measured byChlorimeterBerkfield filterDouble pot methodHorrocks apparatus  <response>: Ans. is d i.e. Horrocks apparatus Ref: Park 20e, p 637 19e, p 577, 18e, p 5301Chlorine 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 ammonical 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.Berkefield 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. 