The hardness and elastic modulus of some crystalline pharmaceutical materials

Abstract

The surface microhardnesses of single crystals of the following materials have been measured: aspirin, hexamine, sodium chloride, potassium chloride, urea, salicylamide and sucrose. A Leitz microhardness tester was used, with indentor loads of 25 g or less, in order to give indentations of less than 50 μm diagonal length and enable measurements to be made on single crystals. The compressive elastic modulus of some of the crystals was also determined using a “Techne” microtensile tester modified to work in compression. When the materials are listed in order of magnitude of Young’s modulus, this order is the same as when they are listed in order of magnitude for surface hardness.