Abstract: The effect of ultrasound on reactive crystallization is studied by measuring the induction time when nucleation is predominantly homogeneous. Barium sulphate is used as the working substance precipitated by mixing aqueous BaCl2 and Na2SO4 solutions. The experiments were carried with various energy inputs.

The effect on heterogeneous nucleation is investigated and compared with the effect on homogeneous nucleation by determining quantitatively the influence of ultrasound on the diffusion coefficient (DAB) together with the contact angle (è) and geometric correction factor(f). Additionally, the ultrasonic effect on the critical supersaturation ratio, where predominant nucleation mechanism changes from homogenous nucleation to heterogeneous nucleation, is measured and compared with the result obtained from classical nucleation theory.