This International Standard specifies methods for determining the phenol index (3.2) in drinking waters, surface waters and waste waters. After a preliminary distillation, the test samples are analysed according to specific application as follows: method A (direct colorimetric method): this method is capable of measuring the phenol index in test samples that contain more than 0,10 mg/l in the aqueous phase (without chloroform extraction), using phenol as a standard; method B (chloroform extraction method): this method is capable of measuring the phenol index without dilution from about 0,002 mg/l to about 0,10 mg/l when the coloured end-product is extracted and concentrated in chloroform phase, using phenol as a standard. NOTES 1 The limits of detection achievable with both methods are insufficient for checking compliance with the limits given in the Directive 80/778/EEC for drinking water. 2) According to the results of a German interlaboratory trial using a method almost identical to method B, the lower limit of detection is 0,01 mg/l.