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  • 1 Glaxo Wellcome Inc. Pharmaceutical Development Research Triangle Park NC 27709 USA Research Triangle Park NC 27709 USA
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This article provides a thermodynamic analysis of DSC data for acetaminophen polymorphic forms I and II by measurement of heat capacity. Form I is found to have lower heat capacity and free energy and hence better stability than Form II down to at least –30C. The transition temperature below which Form II becomes more stable was determined to be less than –120C. Form I is more stable than Form II as a consequence of its higher entropy, since its crystallographic packing arrangement is of larger energy.