Surface Cleaning, Dispersive Effects, Emulsification

In order to obtain accurate and reproducible results, temperature and pressure should be carefully monitored. These mechanical effects tend to increase to a maximum and then decrease to zero with the upper limits defined by the boiling point of the solvent and a hydrostatic pressure at ambient equal to the peak acoustic pressure. This is also the normal pattern in sonochemistry [6,7,117,118], 

Several kinds of coating have been used in these studies [16] including  

Radioactive tracers which provide a simple, accurate, reproducible, and rapid method. 

Chemical coatings, e.g. zinc oxide which, when displaced from the surface, can be estimated by titration with dilute acid. 

Chemical dyes which can be estimated by colorimetry and provide a safe, rapid, and inexpensive method have been widely used, although they have proved slightly less accurate than radioactive tracers. 

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Class 3-Methods Based on Direct Mechanical Effects. These include the use of acoustical probes [57-71], acoustic impedance measurements [72—75], acoustic fluxmeter [76], the measurement of radiation forces [17,21,77—112], the distortion of liquid surface [ 113-115], surface cleaning, dispersive effects, emulsification [ 116-118], erosion [ 19,22,119-125], mass transfer measurements (electrochemical probe) [26,129], absorption methods [93,132], particle velocity measurements [132], and optical methods [133-141],... 

Ultrasonic cavitation has particularly important effects on biphasic systems, emulsification of immiscible liquid-liquids, particle breakage and dispersion, and surface cleaning in liquid-solid mixtures. These mechanical effects, even if sometimes oversimplified, appear to be understandable and predictable by nonexperts in the field, who exploited them in a variety of heterogeneous reactions. Sonochemistry of biphasic systems then developed rapidly, and synthetic applications were reviewed in recent articles. In many cases, the presence of a phase transfer catalyst becomes unnecessary, and sonication can be considered as a "physical substitute to PTC", according to the expression of Ando. a... 

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