Sound absorption in aqueous mixtures of $MgSO4$ and HCl

Sound absorption measurements were made at 25 °C over the frequency range of 30–300 kHz for aqueous mixture of $0.02 M MgSO4$ and HCl, using a spherical resonator method. At 1 atm, the excess sound absorption measured for a mixture of 0.1 M HCl is negligible while that of 0.05 M HCl showed a maximum absorption, $(agr;λ)max × 106$⁠, of 9.49 ± 0.21 at 214 kHz and that of 0.01 M HCl, 68.90 ± 0.71 at 161 kHz. AT 307 atm the mixture of 0.05 M HCl showed a maximum absorption of 5.78 ± 0.14 at 205 kHz. These results will be discussed in terms of normal mode coupling Of $HSO4−$ and $MgSO4$ dissociation reactions. The observed decrease in absorption as HCl is added cannot be explained by ion‐pairing concepts alone.