Optical determination of anionic charge in a process stream

A device for the optical measurement of the anionic charge of an aqueous stream in a vessel holding the stream, comprising:

• a dye supply unit, in connection with the vessel,
• means for measuring the light absorption or transmittance spectra of the stream, and
• means for processing the obtained light absorption or transmittance results, wherein the means for processing have been selected from mathematical processing steps of derivation, whereby the means for processing is adapted to apply the minimum or maximum value of the derivative at the maximum absorbance area of the dye in the calculations so that it correlates with the total charge of the stream,
• wherein the means for measuring the light absorption is adapted to measure the anionic charge of said aqueous stream directly from the flow in the vessel for holding the stream,
• wherein said aqueous stream comprises at least one of dissolved and colloidal substances,
• wherein the device further comprises a stream fractioning unit for separating the stream into fractions according to the particle size of any substances contained therein.