Abstract
The paper presents Raman investigation of the nature of phonon motions in various organic solids and discusses chemical, physical as well as some practical applications of phonon studies. In order to characterize the nature of these motions. delocalization and relaxation of phonons are studied using the mixed crystal technique and temperature dependence of phonon spectra. The application of phonon spectra to investigate chemical perturbation of crystal structure in a group of closely related compounds is discussed. Some preliminary studies are presented on application of phonon spectra in solid state reactions. In regard to practical applications, it is shown that phonon spectra can be used to identify truly random solid solutions as well as various polymorphic forms of a given compound.