Reflectance Spectra and Color of Potassium and Silver Chromates in Various Matrices

Abstract

The matrix influence on the diffuse reflectance spectra of K₂CrO₄ and Ag₂CrO₄ has been studied spectroscopically and colorimetrically. Oxide matrices (MgO, BaO, Li₂CO₃) were found to be inert towards the studied compounds. In halide matrices, the symmetry decrease of the tetrahedral CrO₄²⁻ ion was observed through the appearance of the symmetry-forbidden transitions and intensity reversal. A bathochromic shift of the bands, in comparison to the results for K₂CrO₄, was found in the Ag₂CrO₄/Ag₂SO₄ system. It is explained under the assumption of strong cationanion interaction in the latter. On the basis of the color parameters, the halide matrices can be ordered according to their inertness towards K₂CrO₄. The quantitative relationship between the matrix effect and the molecular size of the host lattice components is given for K₂CrO₄.