Power ultrasound is applied for cooling crystallization to control and modify the particle size and crystal habit of an active pharmaceutical ingredient, phenacetin. Operating parameters including sonication intensity and duration, solution concentration, and cooling rate are studied and compared. With respect to mean particle size, the effect of sonication intensity is most significant. In addition, the crystal habit of recrystallized phenacetin is modified substantially and shows an elliptic shape. Recrystallized phenacetin also provides an enhanced dissolution rate compared with the original sample. These results prove that ultrasonic crystallization is an efficient tool for controlling the solid-state properties of an active pharmaceutical ingredient.

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