Crystal data for anhydrous theophylline

The powder data for anhydrous theophylline (1,3-dimethylxanthine), C₇H₈N₄O₂, are reported. It is orthorhombic, Pna2₁, with a = 24.628 (4), b = 3.833 (2), c = 8.501 (5) Å; U = 802.49 Å³; Z = 4; D_m = 1.478, D_c = 1.489 Mg m^-3.