A practical method of calculating Z(eff) was developed for the coherent to Compton scattering ratio and the method is applicable for any material with known weight percentages of different elements in the compound. The coherent to Compton scattering ratio depends only on the mixture under study and provides a measurement of certain complicated functions of the atomic number Z and Z(eff). In order to measure the effective atomic number of Sb2O3, BaO, La2O3, CeO2 and Nd2O3, the linear differential scattering coefficients of 59.5 keV gamma-rays have been studied using a high-resolution Si(Li) semi-conductor detector. The coherent to Compton scattering ratio R is taken from the linear differential scattering coefficients mu(E, q). The results obtained have been compared with relativistic (RT) and non-relativistic (NRT) theoretical values. (C) 2005 Elsevier Ltd. All rights reserved.