The standard applies to all types of water. After preliminary dis illation, contents from 0.5 µg/l can be determined by extraction with chloroform. For levels greater than 0.1 mg/l, a direct photometric determination can be carried out. Dis urbances caused by oxidizing substances can be eliminated by adding iron(II) sulphate. If oil or tar is present, this must be removed by alkaline extraction. Dis urbances caused by colored compounds, by sulfur compounds such as sulphite and sulphide, and by compounds that form precipitates in an alkaline environment. , are eliminated by dis illation from an acidic medium in the presence of copper sulphate. With sulphide contents higher than 10 mg/l, the sulphide with excess lead carbonate must be precipitated and filtered off. Note Phenols other than hydroxybenzene form compounds of different color and/or with the reagent. or color intensity. The measured contents may therefore differ from the actual contents.
NEN 6670-1982 history
1982NEN 6670-1982 Water — Photometric determination of the content of phenols volatile with water vapour