The Analysis of Water Hardness by Automated Titration

The fully automated and PC-controlled water analysis system based on the 836 Titrando and the 815 Robotic USB Sample Processor XL from Metrohm. In particular it contains the new quick aliquoting device 6.9958.007, an overflow burette allowing quick and precise dosing of 100 mL sample after conductivity measurement, necessary for alkalinity determination and the water hardness titration. The MATi 1 has all it takes to perform 59 water determinations fully automated and includes all necessary accessories and sensors. It is a ready-to-use system that fulfills the following requirements: conductivity, pH, p-and m-value, hardness (Ca/Mg), quick aliquoting device with a high sample throughput and it is PC controlled.

The water analysis involves the determination of alkalinity and water hardness The Aquatrode Plus electrode is used as indicator electrode for the alkalinity determination; the water hardness titration is indicated by a Ca-ISE combined with the reference system of the Aquatrode Plus. The conductivity measurement is carried out with the 712 Conductometer by means of a conductivity cell installed on the second tower. The signal supplied by the conductivity meter is evaluated by the 836 Titrando. The standard rack used accommodates 59 beakers with a volume of 120 mL.

The samples are stirred by an 802 rod stirrer. The new overflow burette transfers the sample to the external titration vessel using the built-in pumps of the 815 Robotic USB Sample Processor XL. After the titration the membrane pumps of the 815 Robotic USB Sample Processor XL guarantee efficient aspiration of the spent solution and thorough rinsing of the titration equipment.