Refraction Index and Optical Absorption in Black and Green Liquors

Abstract

We presents the results of measuring concentration and temperature dependences of the refraction index in i) black liquors for soluble solid residue concentrations up to 70% within a temperature range of 10 - 90°C, and ii) in green liquors at a total alkali of 0 - 250 g/liter within the same temperature range. Interpolation expressions for laboratory calibration of commercial sensors are given. Absorption spectra in the solutions and their mineral carriers are obtained. The main components that determine formation of fundamental electronic absorption bands in black and green liquors are considered. Spectrophotometry of the ultraviolet wavelength range is shown to be a simple and effec tive method of industrial monitoring of the total alkali of liquors at a stage of caustization.