Studies on the effect of chlorides of magnesium, calcium, strontium and barium on the temperature of the sound velocity maximum of water

The effect of chlorides of magnesium, calcium, strontium and barium on the temperature of the sound velocity maximum (TSVM) of water, Tw, has been studied by determining the ultrasonic velocity using a single crystal variable path interferometer working at 3 MHz. The accuracy in ultrasonic velocity measurement is ± 0.05 m s− 1. The ultrasonic velocity measurements were carried out at ≃ 2 °C intervals over a range of 5 °C to either side of TSVM of the solutions. The accuracy in fixing TSVM is ± 0.2 °C. The shifts in TSVM of water due to the addition of MgCl2 and CaCl2, (ΔTobs), are found to be positive at low concentrations becoming maxima around the weight fraction w ≃ 2.3 × 10− 2 for MgCl2 and w ≃ 3.8 × 10− 2 for CaCl2 and becoming negative around w ≃ 5.6 × 10− 2 for MgCl2 and w ≃ 3.8 × 10− 2 for CaCl2. (ΔTobs) for MgCl2 > CaCl2 > SrCl2 > BaCl2 indicating that the strength of the structural interactions in modifying the hydrogen-bonded structure of water is in the order Mg2+ > Ca2+ > Sr2+ > Ba2+. The results are explained in the light of the structural properties of the anions and cations in the solutions in modifying the three dimensional hydrogen-bonded structure of water.