New insights on the crystalline forms in binary systems of n-alkanes: Characterization of the solid ordered phases in the phase diagram tricosane + pentacosane

X-ray diffraction analyses of the pure components n-tricosane and n-pentacosane and of their binary mixed samples have enabled us to characterize the crystalline phases observed at “low temperature.” Contrary to what was announced in literature on the structural behavior of mixed samples in odd-odd binary systems with Δn = 2, the three domains are not all orthorhombic. This work has enabled us to show that two of the domains are, in fact, monoclinic (Aa, Z = 4), and the other one is orthorhombic (P_{ca2₁}, Z = 4). The conclusions drawn in this work can easily be transposed to other binary systems of n-alkanes.