BINARY-MIXTURES OF N-ALKANES - PHASE-DIAGRAM GENERALIZATION - INTERMEDIATE SOLID-SOLUTIONS, ROTATOR PHASES

At ''low temperatures'', the binary mixtures of the consecutive [even- numbered: even-numbered]; [even-numbered: odd-numbered] and [odd-numbe red: odd-numbered] n-alkanes (19 < n < 27) do not form a continuous ho mogeneous solid solution. This study shows the existence of terminal s olid solutions which have the pure n-alkanes structures and many inter mediate solid solutions, denoted beta(n)' and beta(n) '' (n = 1 or 2): these intermediate phases have an orthorhombic cell as the odd-number ed n-alkanes, but they ate not isostructural with the pure n-alkanes n or with their terminal solid solutions. On the basis of powder X-ray d iffraction photographs, the phases beta(1)' and beta(2)' are indisting uishable in all the binary systems. The X-ray behavior of the phases b eta n '' is also identical. The succession of the solid solutions is d escribed when varying the concentration. With increasing temperature, the intermediate phases undergo the same solid-solid transitions as th e odd-numbered n-alkanes (n-tricosane), and the rotator phases appear at ''high temperatures'' below the solidus line. The phase diagrams of n-C-22: n-C-23, n-C-23: n-C-24, n-C-22: n-C24 and n-C-24: n-C-26 are presented.