Polymorphism in Anthranilic Acid Crystals—Examination by DTA and DSC
- 1 December 1972
- journal article
- research article
- Published by Taylor & Francis in Molecular Crystals and Liquid Crystals
- Vol. 19 (2) , 133-140
- https://doi.org/10.1080/15421407208083859
Abstract
Crystalline anthranilic acid in modifications I and II has been prepared from aqueous, ethanolic and non-polar solvents, and examined by DTA to determine transition and melting temperatures and by DSC to give associated enthalpy and entropy changes. The transition I → II occurs at 352.2 K at a zero extrapolated heating rate. An additional endotherm occurs with modification II when the acid is obtained from buffered aqueous solutions within a narrow pH range. The low transition enthalpy occurring under these conditions indicates that the modification has a lower degree of lattice order than II obtained under more acid conditions or from ethanolic solution. I and II were confirmed by X-ray powder photographs. The morphology of the forms obtained is discussed briefly.Keywords
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