The present study aims to investigate the effect of butyric acid used as an additive and its concentration ranging between 50 ppm and 250 ppm during the polymorphic phase transformation of beta-glycine to alpha-glycine. Analysis includes a continuous measurement of the ultrasonic velocity and periodically the X-ray diffraction (XRD) pattern. Morphological characterization shows that the alpha-glycine crystals obtained in pure media are smooth, prismatic shapes, and that butyric acid plays a major role in crystal shape change. SEM imaging and morphology analysis indicates that the presence of butyric acid to media results in shorter, rounded and aggregated crystals. Further analyses of Fourier Transform Infrared Spectroscopy (FTIR), zeta potential measurements, and elemental analysis reveals that butyric acid adsorbs on the crystals' surface and changes both the surface charge and the elemental composition of the crystals obtained. In addition, thermal decomposition behaviors of the crystals are investigated and the obtained data is modeled using the thermal decomposition kinetic models of FWO, KAS, and Tang. Based on the data of the FWO kinetic model, the average activation energy of the crystals obtained in butyric acid media is calculated as 118.8 +/- 17.0 kJ/mol, which is higher than that of crystals obtained in pure media. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.