Fig. 1.

Photo of the sonochemical setup (a). Schematic illustration of the setup indicating the different position of the hydrophone relative to the sonotrode: (b) under the sonotrode, (c) on the same level with the sonotrode tip. The illustrations (d, e) demonstrate the simplified schemes of the images (b, c) for Mg suspensions and liquids without particles and will be included next in the discussion. The question is: can generated hydrogen bubbles during ultrasonic treatment of magnesium particles participate in the evolution of stable or transient cavitation bubbles? (f).