Diamond coatings of 0.1 to 1 mm thickness on silicon disks, used as electrodes in electrochem. reactors or systems like a DiaCell have shown outstanding properties in oxidn. of org. and inorg. compds. This reactivity can be assocd. with the prodn. of hydroxyl radicals, which may also be responsible for the prodn. of chlorine or ozone in naturally mineralized water. By addn. of a small amt. of supplementary NaCl to poolwater (250 to 900 ppm), it is possible to produce up to 10 g/h of chlorine. With the help of a newly developed online and direct measuring-free chlorine amperometric sensor, the loop-controlled prodn. of chlorine can easily be maintained in the range of 0.2 to 0.4 ppm free chlorine and guarantee the perfect disinfection of the poolwater. The simultaneous prodn. of even more powerful oxidants also helps to destroy incorporated org. materials in swimming pools. [on SciFinder (R)]