The results of the X-ray diffraction and thermal X-ray diffraction studies of the paraffins C_nH_2n+2 are revised based on new principles asserting the existence of several types of rotator states of paraffins. Along with the known isomorphism factors, such as the parity (symmetry) of the starting components and the difference between the chain lengths of their molecules (Δn), there is a factor that is specific to paraffins: differences in the energy state of molecules entering solid solutions.