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Structural and Energetic Behavior of Mixed Samples in the Hexacosane ( n‐ C 26 H 54 )/Octacosane ( n ‐C 28 H 58 ) System; Solid‐Solid and Solid‐Liquid Equilibria
Author(s) -
Rajabalee Fazil,
Métivaud Valérie,
Mondieig Denise,
Haget Yvette,
Oonk Harry A. J.
Publication year - 1999
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/(sici)1522-2675(19991110)82:11<1916::aid-hlca1916>3.0.co;2-d
Subject(s) - chemistry , eutectic system , monoclinic crystal system , phase diagram , orthorhombic crystal system , solid solution , isothermal process , thermodynamics , phase (matter) , polynomial , diffraction , crystallography , crystal structure , organic chemistry , microstructure , mathematical analysis , physics , mathematics , optics
The combination of the experimental (microcalorimetric and X‐ray diffraction) methods and thermodynamic analyses enabled us to determine the phase diagram of the system hexacosane ( n ‐C 26 H 54 )/octacosane ( n ‐C 28 H 58 ). Isothermal X‐ray measurements performed on mixed samples at `low temperature' ( T 308 K) revealed three crystalline forms: two monoclinic (M 011 and M dci ) and one orthorhombic (O p ). Four of the five rotator phases were observed at `high temperature': R I , R II , R IV , and R V . Fourteen solid‐solid and two solid‐liquid two‐phase regions were observed, as well as one peritectic, one eutectoid, one metatectoid, and five peritectoid three‐phase equilibria. The thermodynamic calculations of the phase‐equilibrium relations, carried out with the polynomial functions described in a previous paper and new ones given here, showed full consistency with the experimental data, evidencing the reliability of these polynomial functions.