Figure 4.

Dissolution rate of BaSO₄ NM220 (green) and BaSO₄ IRMM381 (yellow). The SA/V is plotted against the dissolution rate k [ng/cm²/h]. The dashed line indicates the ramp down with decreasing flow-rate 3–0.1 mL/h and the solid line represents the ramp up with increasing flow-rate from 0.1 to 3 mL/h. The two different dashed green curves vary in initial mass. The dashed green curve with the square has an initial mass of 1.01 mg, whereas the curve with the round symbol has an initial mass of 0.14 mg. The two yellow solid curves vary from 1.42 mg initial mass for the square to 0.12 mg for the triangle. Both darker spots represent the dissolution rate for the dynamic dissolution with constant flow-rate for nano BaSO₄ NM220 yellow and BaSO₄ IRMM381 dark green.