A new method for an automated determination of hardness (calcium ions) in sugar factory juices was developed, based on a combination of the Clark method with a foam probe. Some uncertainties of the original method are eliminated through a well-defined foam generation by means of aeration and a precise course of a program. A cleaning step as a part of the cycle ensures a high reliability of the procedure. During the 2000 campaign, two prototypes worked without any trouble in two sugar factories over several months. Maintenance is confined to manually cleaning a gas distribution tube once a week, hence the equipment has low service requirement. Reagents of technical purity can be used, thus giving low running costs. Systematic errors of the Clark method as well as varying colors of juices have only a slight influence on the results of the automated method.
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