Phase diagram measurements by Heat-flux DSC and thermodynamic calculations of the mixture of the Esters Ethyl undecanoate (C13H26O2) and Ethyl tridecanoate (C15H30O2)

In this report a phase diagram is determined by heat flux DSC of the binary mixture Ethyl
undecanoate and Ethyl tridecanoate. Our hypothesis for equilibrium phase behaviour is that
the components Ethyl undecanoate and Ethyl tridecanoate do have the same crystal form and
they have restricted miscibility in that form. However, the results of the DSC measurements
are complex and are not unambiguous. We determined a simple phase diagram and calculated
it with the program Winifit. The calculated phase diagram with the program shows good
similarity with the one obtained by the experiments. The excess Gibbs energy parameters of
the solid state are determined with Winifit, being A = 5000 J.mol-1 and B = 0,1. The mole
fraction of the critical point XC is calculated as XC =0,43. The critical temperature C T at XC
=0,43 is also calculated, being C T = 307,2 K. For better understanding the crystal structures
have to be examined in greater detail. On the left-hand side and on the right-hand side of the
phase diagram they have to be the same.