Reflectance and probe window contamination: Study of pulping solutions

The reflectance from industrial pulping solutions was investigated with the use of a reflectometer. It was observed that the reflectance is time-depen dent on the contamination of the probe window. The optical constants of the pulping solutions were calculated by using Fresnel's theory and the concep t of critical angle. A simple mathematical model, based on the random conta mination of the probe window, was observed to yield satisfactory agreement between the measurement and theory of reflectance. It is proposed that opti cal constants of pulping solutions can be estimated despite the contaminate d layer on the prism face.