Binary Phase Diagrams of Some Molecular Compounds—I

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Abstract
The naphthalene-anthracene and naphthalene-d-camphor phase diagrams have been determined by calorimetric measurements and optical microscopy in order to establish the extent of the terminal solid solutions. The manner in which the solid solubility is affected by the crystal symmetry and molecular volumes of the components is considered. In the naphthalene-camphor system, in which the crystal symmetries and molecule volumes of the components are different, a eutectic is formed at 39 mole pct naphthalene and 304.5 K with terminal solid solubilities of 12.0 mole pct naphthalene in camphor and 6.0 mole pct camphor in naphthalene. In the naphthalene-anthracene system even though the crystal symmetries of the components are the same, the differences in molecular volumes results in a miscibility gap in the solid and the formation of a eutectic at 6.2 mole pct anthracene and 350.8 K. The terminal solid solubility is limited to 2.9 mole pct naphthalene in anthracene with practically no solid solubility in the reverse case. These experimental results are considered in conjunction with those for the anthracene-carbazole system, the phase diagram of which has been published previously.