Non Isomorphism and Miscibility in The Solid State: Determination of The Equilibrium Phase Diagram n-Octadecane C₁₈H₃₈ + n-Nonadecane C₁₉H₄₀

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

“…A triclinic form T p ͑P1, Z 1 3 ͒ is observed in the range 8 < n < 24, 1,2,22 while several monoclinic modifications M 011 , M 201 , M 012 , and M 101 are found in longer even alkanes as from C 26 . 23 All these forms have the same space group [4][5][6]23 ͑P 21/a , Z 2͒ but differ by the shift of adjacent molecules in the planes (b ‫ء‬ c for M 011 and M 012 and a ‫ء‬ c for M 201 and M 101 ) of a whole number of CH 2 units.…”

“…We have thus prepared mixed samples of C 28 with C 26 molecules behaving like impurities (in fact, we have studied the binary system C 26 1 C 28 which will be the subject, as said, in the introduction of another paper). Figure 6 also shows the diffraction patterns of some mixed samples C 26 1 C 28 rich in C 28 . We notice that the 00l lines of the M 011 form ͑᭞͒ diminish and finally disappear at the molar concentration of 0.85 in C 28 .…”

“…Polymorphism of n-alkanes (C n H 2n12 ; hereafter denoted by C n ) and determination of binary phase diagrams [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] in the alkane family have been reported on in recent years in numerous publications. The polymorphism of n-alkanes is rather well known where many solid-solid phase transitions have been observed as a function of temperature.…”

Review of Thermophysical Property Data of Octadecane for Phase-Change Studies

“…The majority of researchers have defined Te [21,22,23,24,25,26,27,28,29,30,31] or Tp [19,20,29,31,32,33,34,35,36,37,38,39,40,41] as the melting temperature. Temperatures T* with insufficient information about their determination have been reported for DSC measurements [42,43,44,45,46,47,48,49,50,51], for adiabatic calorimeters (AC) [52,53,54,55] and for results which have been achieved with other not classified (NC) techniques [6,56,57,58,59,60,61,62]. A summary of all available data on the melting temperature can be found in Table 1 (alongside with data on the enthalpy, described in the next section) and Figure 1a which shows the melting temperatures arranged according to the given temperature definitions and its mean values.…”

“…As for the melting temperature, there are numerous results for the melting enthalpy of octadecane available in the literature. Many of these results were also obtained from the heat flow signal of DSC measurements, but without giving information about the way of determining the peak area which is the measure for the melting enthalpy [19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,47,48,49,50,51]. The peak area depends on the integration limits and the type of the assumed baseline of the heat flow signal [18].…”