ISO 2522:1974

The method specified determines only those phenols capable of reacting at the 2nd, 4th and 6th position (-OH = 1). The procedure consists in extraction of free phenols from a test portion with sodium hydroxide solution. Bromination of these phenols with potassium bromide-bromate solution in an acid medium and determination of the excess bromine after reaction with potassium iodide by titration with standard volumetric sodium thiosulphate solution.