In these images, the white areas represent the distribution of the unknown phase; a comparison of the global diffraction pattern with the respective phase is shown in Figure . It can clearly be observed that there is a small quantity of this phase in the fresh tablets, but the aging has caused a significant increase throughout the tablet. It is reasonable to assume from the extent of observation that it is related to either the glycolide or the MCC content based on the initial weights in the tablet. Considering MMC initially, the diffraction pattern shows that Cellulose I is present as a mixture of the two different polymorphs, Iα and Iβ. The unknown phase has a sharper diffraction pattern from a more crystalline product indicating conversion to either one of the two polymorphs. Cellulose Iβ is the more likely choice due its higher stability (approx. 8 kJ/mol ) and the pair of Bragg reflection above 2ϴ = 16° and those above 2ϴ = 20° which are somewhat more discriminatory (Figure ). Conversion of MCC during storage has not been observed during stability studies and the only transition reported from Iα to Iβ was after an annealing process at 260°C using NMR as a probe hence it is unlikely that the new material has its origin from MCC.