This part of ISO 10359 specifies a method for the determination of dissolved fluoride in fresh, potable and low contaminated water, and some surface waters, using an electrochemical technique. The method is directly suitable for measuring fluoride concentrations from 0,2 mg/1 to 2,0 g/l. After the addition of a known amount of fluoride, concentrations as low as 0,02 mg/1 tan be detected (see 7.3). The method is not suitable for waste waters and industrial effluents; this determination will be the subject of ISO 10359-2.