This International Standard specifies two methods for the determination of the phenol index in waters of different origin (such as ground waters, surface waters, seep waters, and waste waters) in mass concentrations of 0,01 mg/l to 1 mg/l (in the undiluted sample). In particular cases, the range of application may be adapted by varying the operating conditions. Clause 3 describes the determination of phenol index (without distillation) after extraction, and in clause 4 the determination of phenol index (without extraction) after distillation is given.