Triboluminescent Crystals from the Microwave Oven

Anthranilic acid was acetylated in a microwave oven (1,000 W) by irradiating for one minute at full power in a 100 mL beaker fitted with a glass funnel as condenser. After cooling, yellow fluorescing crystals were often obtained; but, if not, recrystallization from 10% water–methanol yielded cubes that fluoresced brightly under 360 nm light. Crushing the crystals between two watch glasses in a darkened room demonstrated the triboluminescent effect (i.e., the production of bright blue sparks when the crystals are fractured).