Abstract
Crystals of riboflavin (natural, synthetic riboflavin and araboflavin) recrystallized from redistilled water are hexahedral and plate-shaped, and the interfacial angles of each pinecold and base are 90°. All these three are rhombic and optically negative. Natural and synthetic riboflavin are the same in respect to the fundamental optical constant. Araboflavin belongs to the same crystal system, but differs slightly in the fundamental optical constant.
