This nitrogen heterocycle is useful as an intermediate in the synthesis of drugs and polymers. It is prepared by the action of nitric acid on o-phenylenediamine. Explosions have been reported during vacuum distillation to purify the chemical. When recrystallized from the melt, benzotriazole will slowly crystallize, forming beautiful spherulite crystals. The time-lapse movie was made using a modified version of the Intel Play QX3 microscope equipped for polarized light illumination with a full-wave (first order) retardation plate.