Abstract: The present invention relates to the field of wet chemical treatment of silicon substrates. The invention particularly relates to a method for the determination of the concentration of nitric acid in aqueous process solutions as being used for the treatment of substrates such as those made from silicon. The method is based on the determination of nitrate by means of UV spectroscopy/photometry with the aid of eliminating agents which effectively remove disturbing absorptions caused by other substances. Therein, the concentration of nitrate corresponds to that of nitric acid. According to the invention, a robust method is proposed by means of which the content of nitric acid in acid mixtures can be determined very precisely, and in fact likewise in fresh as well as in acid mixtures that have been used according to their intended purpose.

Abstract: A titration apparatus, which operated volumetrically and/or coulometrically, includes a basic apparatus with a control and actuation arrangement for the volumetric metering of reagents, a metering unit for the volumetric titration removably attached to the basic apparatus, and mechanical coupling elements for connecting the metering unit to the actuation device. Instead of the volumetric unit or in addition thereto, a coulometric titration cell may be connected with the basic apparatus directly or by an adapter unit, while using the same control device as the metering unit.