Lobular crystallization (methanol - ether), needle-like crystals (water - ethanol), m.p. 202 ℃ (rapid heating decomposition). At 25 ℃ dissociation constant Ka3.7 × 10-11, Kb1.7 × 10-10. Soluble in water, slightly soluble in hot ethanol, insoluble in organic solvents. Decomposes to form at a temperature above the melting point of pyrrolidone and water. Appearance: white crystal or crystalline powder.
White flake or needle-like crystals; slightly smelly, with deliquescence; easily soluble in water, slightly soluble in hot ethanol, insoluble in cold ethanol, ether and benzene; decomposition point of 202 ℃; LD50 (rat peritoneal) 5400mg / kg.