Solid-Liquid Equilibria of Simple Eutectic Systems

Solid-Liquid Equilibria of Simple Eutectic Systems 

Following Eq. (8.10), in the case of simple eutectic systems the solubility of a solid compound in the liquid phase can be calculated for a given temperature, if besides the enthalpy of fusion and the melting temperature information about the real behavior, that is, the activity coefficient, is available. Following Eq. (8.10), even similar compounds, as for example, anthracene and phenanthrene, can show 

In this case, for the calculation of the solid solubilities xi additional information about the transition temperature Ttrs and enthalpy of transition A trs is required. 

Calculate the solubility of anthracene and phenanthrene in benzene at 20 C. For the calculation it should be assumed that the binary systems show ideal mixture behavior (y, = 1). 

From the results it can be recognized that the solubilities of the chemically very similar compounds anthracene and phenanthrene differ by more than one order of magnitude. The much lower solubility of anthracene is thereby caused by the higher melting temperature and larger enthalpy of fusion (lower standard fugacity 

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