A new method of K2CoxNi1-x(SO4)(2)center dot 6H(2)O mixed crystals growing was proposed. High-quality samples were synthesized from the water solution of K2SO4, NiCl2, and CoCl2. Transmission spectra of these crystals were investigated in the wavelength range of 200-900 nm. The bands that are responsible for the electronic transitions in octahedral complexes CoO6 and NiO6 are independently presented in these spectra. Infrared reflection was measured for these crystals in the range of 2.5-20 mu m. The identification of IR active mode frequencies was performed on the base of measured data. (C) 2009 Elsevier B.V. All rights reserved.