Thermal deformations and polymorphous transformations of solid solutions of paraffins in C₁₇-C₁₉, C₁₉-C₂₁, C₂₁-C₂₃, C₂₂-C₂₄, and C₂₃-C₂₄ systems are investigated by thermal X-ray diffractometry using a temperature step of several tenths of a degree. It is examined how the length of a molecular chain of a homolog (n) and the difference in length (Δn) between the chains as well as the molecular composition of a solid solution affect these transitions, and the data are compared with those for the individual homologs of paraffins.