Multistate Dissociation and Sound Absorption in Sea Water

Abstract

At 75 kHz, the observed decrease of sea water sound absorption with increasing pressure is about twice that predicted from the multistep dissociation parameters selected by Eigen and Tamm [Z. Elektrochem. 66, 92–121 (1962)] to explain sound absorption in aqueous solutions of MgSO4 the salt responsible for sound absorption in sea water. To account for such a large pressure effect requires the equivalent of a single chemical reaction with a ΔV≃36 cm3/mole; for example, two successive chemical reactions each with a ΔV≃18 cm3/mole. The results are discussed in terms of three-step and two-step dissociation models. Included in our considerations are Millero's results [Geochimica et Cosmochimica Acta 35, 1089–1098 (1970)] obtained independently of acoustic data, which show only a small decrease with pressure for the concentration of MgSO4 ion pairs. [This paper represents results of research sponsored by the Office of Naval Research and the National Science Foundation.]