Figure 4
From: Crystal structure and characterization of pyrroloquinoline quinone disodium trihydrate
Powder X-ray diffractometry (XRD) of PQQ disodium trihydrate in air . The type I trihydrate crystal changed to the type II trihydrate crystal at150°C, which in turn changed to the type III crystal at 180°C. The crystal formed at 120°C is a mixture of type I and type II crystals. 2θ = type I: 9.1, 10.3, 13.8, 17.7, 18.3, 24.0, 27.4, type II: 11.4, 13.5, 18.0, 18.7, 26.0, 28.5, type III: 7.0, 11.5, 12.0, 17.4, 18.7.