STRUCTURAL EVOLUTION VERSUS TEMPERATURE OF THE BETA(0) PHASE OF THE N-EICOSANE N-DOCOSANE SYSTEM - ROTATOR TRANSITIONS/

The orthorhombic phase beta(0)[n-C20H42/n-C22H46] (Fmmm) determined by Gerson and Nyburg is isostructural with the orthorhombic Rotator phas e beta-RI (Fmmm), observed in n-tricosane (n-C23H48) and n-pentacosane (n-C25H52) and in the two binary systems: [n-C22H46/n-C24H50] and [n- C24H50/n-C26H54]. When the temperature increases, its b/a ratio change s progressively from 1.51 at 293 K to 1.73 at 309 K; it then transform s into the rhombohedral Rotator phase alpha-RII (R (3) over bar m) jus t below the solidus curve. These observations allow generalization of structural behaviour of two n-alkane mixtures (19 < n < 27), whose dif ference between carbon numbers is equal to 1 or 2.