Investigations were made of the effects of frequency, temperature, intensity and gases on the rate of sonochemical dissociation of carbon disulfide. Application of 900 kHz ultrasound did not produce any noticeable change. When carbon disulfide was irradiated with 20 kHz, the liquid formed a heterogeneous mixture of black particles in a yellow solution. The rate of dissociation decreased with increasing temperature, in agreement with most sonochemical reactions. The rate also decreased with decreasing area of the horn tip, keeping total power constant. This dependence on the horn tip area, as well as that on the frequency, is in opposition to the dependence for the formation of iodine from the sonication of aqueous potassium iodide solution [See Part II, Ultrasonics Sonochemistry 3 (1996) 19]. The X-ray spectrum of the black particles and the yellow residue obtained after evaporation showed the presence of amorphous carbon and monoclinic sulfur. The rate of sono-dissociation of carbon disulfide in the presence of different gases is in the order He > H2 > Air > Ar > O2 > CO2.

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Sonication at two frequencies (20 and 900 kHz) was carried out on dilute (220 ppm) aqueous solutions of chlorobenzene. The formation of chloride ions was followed using ion chromatography. The solutions became more colored with time; the absorbance maximum was around 270 nm. Some of the compounds remaining in the solution could be identified; they were chlorinated phenols, chloronaphthalene, mono and dichlorobiphenyls, etc. At the same acoustic power, the rate of chloride formation with 20 kHz ultrasound was greater when a probe with a larger tip area was used, but significantly less than the rate with 900 kHz. The use of ultrasound for conversion of chlorine in organic compounds in water to chloride can thus be performed more efficiently using a higher frequency and with a lower intensity (power per area). There is, however, a possibility that the toxicity of the aqueous solution is increased by such treatment.

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