In present paper potassium alums with chromium dopant were investigated. Crystals were grown by evaporation techniques. These crystals were analyzed via powder diffractometer Shimadzu XRD-7000 for the purpose of measuring unit cell parameter of grown crystals. Using atomic-emission spectrometer with inductively coupled plasma Varian 720-ES, elemental composition of samples was investigated. Finally, the plot of unit cell parameter as a function of part of chromium in crystals was obtained.