Crystal structure studies of selected lithol red salts with the use of powder diffraction data

Abstract Lithol reds – azo compounds used as pigments in paintings and in the plastics and printing industries – were studied, with the result that the crystal structures of their salts with NH 4 + and Na + cations were determined from powder diffraction data. Moreover, the thermal stability and light-induced degradation of lithol reds were investigated. The obtained results were correlated with the disappearance of colours in the paintings of Mark Rothko.