The standard applies to all types of water with a sulphate content of at least 3 mg/l. At concentrations up to 7.5 g/l NaCl, a SO42~ content of 3 to 100 mg/l can be easily determined. Ca2+ bothers. It must be removed in advance by an ion exchanger. Above 5 mg/l, Fe3+ influences the color change of the indicator. It is also removed when an ion exchanger is used. The interference due to phosphate can be corrected, provided that the phosphate content is not higher than the sulphate content (see note 7). Note Dis urbing amounts of organic matter or too strong an inherent color of the water to be tested can in most cases be removed, for example by filtration after adding activated carbon.
NEN 6487-1982 history
1982NEN 6487-1982 Water - Titrimetric determination of the sulphate content