Isotopic techniques involving oxygen-18 have been used to study the processes involved in the sonochemical formation of hydrogen peroxide during cavitation in oxygen-saturated solutions. Both tracer and equilibration experiments were carried out in an all glass system with converging ultrasonic fields providing maximum intensities of 103 w/cm2 at frequencies of 600 and 800 kc/sec. In oxygen-saturated water, one-third of the hydrogen peroxide oxygen was found to be derived from the oxygen gas while in solutions containing 30% (by volume) methanol, all of the peroxide oxygen was derived from the oxygen gas. In both cases, the oxygen molecule appears to be incorporated as a unit in one peroxide molecule without formal cleavage of the O - O bond. Conditions associated with ultrasonically produced cavitation appear sufficient to dissociate water into H and OH and to rupture the C - H bond in organic molecules such as methanol but not sufficient to dissociate molecular oxygen. The oxygen molecule is involved in secondary reactions with hydrogen atoms, and hence, contributes to the formation of hydrogen peroxide. The experimental results can be explained most readily in terms of the large temperature rises which are presumed to occur within cavitation during compression but do not exclude electrical phenomena within the cavitation bubbles as a possible mechanism for the dissociation processes.

Del Duca, M., Yeager, E., Davies, M. O., & Hovorka, F. (1958). Isotopic Techniques in the Study of the Sonochemical Formation of Hydrogen Peroxide. The Journal of the Acoustical Society of America, 30(4), 301–307.