The main X-ray diffraction data (crystal system, polymorph modification, indices hkl, elementary cell parameters, space group, etc.) were obtained and defined for a series of n-fatty acids ÑnÍ2nÎ2 with even (n = 12, 14, 16, 18, 20, 22, and 24) and odd (n = 19) numbers of carbon atoms in molecules. Double compounds were synthesized within two binary systems of even n-fatty acids. The double compounds are new acids constructed of combined dimers. In case of the system Ñ12Í24Î2–Ñ14Í28Î2, a half of the dimer is molecule Ñ11H23ÑOÎÍ (laurinic acid) and its other half is molecule Ñ13H27ÑOÎÍ (miristinic acid). In case of the system Ñ14Í28Î2–Ñ16Í32Î2, a half of the dimer is molecule Ñ13H27ÑOÎÍ (miristinic acid) and its other half is molecule Ñ15H31ÑOÎÍ (palmitinic acid). Combined dimers have not got center of symmetry unlike “ordinary” dimers of even n-fatty acids.