Benzocaine-picric acid

Fig. 4.9 (See also color plate section.) Photographs of the microscope shde Kofler preparations showing the various phases of the benzocaine picric acid (BC PA) binary system. Top (a) the photomicrograph of the recrystalhzed contact preparation of BC and PA at 25 °C. The interference colours are due to the use of crossed polarizers. The pure compounds are at the extremities of the preparation, while in the region where the original compounds have merged a number of different areas may be observed, due to the formation of different crystalline species combining the two components. Heating this preparation on the hot stage microscope...

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