ION-SELECTIVE ELECTRODES IN PROCESS CONTROL: WATER HARDNESS MEASUREMENT OF ION EXCHANGE TREATED WATER

摘要

A liquid, ion exchange, divalent measuring electrode has been used successfully to continuously monitor water hardness. It has sufficient sensitivity to distinguish between 0.5 and 1 ppm CaCO_3. This is important when treating water for high pressure boiler application. The divalent electrode has the advantage of being a direct potentiometric measurement without the necessity of adding a reagent.At the levels of interest, water hardness, hydrogen and sodium ions can present major interferences. A multi-electrode system using electrodes for sodium, pH and divalent ions has been employed in studying the response of the divalent electrode to give corrected hardness. When monitoring the performance of ion exchange units, only a water hardness electrode is necessary. System configurations designed to eliminate sensitivity to flow rate, static charges and air bubbles are also discussed.