Ultrasonic and hypersonic properties of ionic hydrate melts

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Abstract
Ultrasonic and Brillouin scattering measurements have been used to establish the relaxation properties of zinc chloride, zinc nitrate, and calcium nitrate hydrate melts in the frequency range 5 MHz to 12 GHz. A distribution of relaxation times is observed for these melts which is generally much broader than for a single relaxation. The width of this distribution decreases with increasing temperature and water content. Deuteration of the hydrate melts produces a significant increment in the low frequency absorption and also an increment in the mean relaxation time. The experimental data have been compared with the Isakovich–Chaban and Montrose–Litovitz theories of viscoelastic relaxation. The mean relaxation times predicted by the I–C theory are generally longer than the experimental values, and the shape of the predicted distribution is different. The data can be closely fitted to the M–L treatment with proper choice of the two adjustable parameters in the theory. A multiple state chemical model is proposed for the hydrate melts. Under such circumstances this model can be reduced to a form which falls within the mathematical framework of the M–L treatment.

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