The paper presents the results of a study phase behavior five n-alkanes C34H70 (n-tetratriacontane), C36H74 (n-hexatriacontane), C38H78 (n-octatriacontane), C40H82 (n-tetracontane) and C42H86 (n-dotetracontane) presented as an aqueous dispersion with characteristic particle size 100–200 nm. was carried out by new optical method. melting, crystallization rotator temperatures these were determined.