Size distribution and geometry are key properties of crystal products

which can affect product quality and downstream processes of filtration

drying

storage and transportation. An on-line process analysis system

including ultrasonic particle size analyzer

attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR)

turbidity analyzer and two-dimensional imaging system

was developed to monitor crystallization of Aspirin ethanol solution at various stirring and cooling rates. The results show that lower cooling or faster stirring rate produces more amount of fine crystals and higher cooling rate yields product with larger mean size and higher aspect ratio (AR). Therefore

adjusting cooling and stirring rate is an effective technique to control particle size distribution and shape of Aspirin crystals.