Effect of mixed electrolytes on the temperature of sound velocity maximum of water

Abstract

Effect of mixed electrolytes (KCl + KBr), (KCl + KI) and (KBr + KI) on the temperature of sound velocity maximum (TSVM) of water, T_w, has been studied by determining the ultrasonic velocity with an accuracy of ± 0.003% using single crystal variable path interferometer working at 3 MHz. The velocity measurements were carried out at ; 2°C intervals over a range of 5°C on either side of TSVM of the solution. The accuracy in fixing TSVM is ± 0.2°C. The structural contribution to the shift in <i style="">T</i>_w of pure water due to the addition of mixed electrolytes, <img src='/image/spc_char/delta.gif' border=0><i style="">T</i>_str, has been found to be negative and increasing with concentration of mixed electrolytes. At any given concentration <img src='/image/spc_char/delta.gif' border=0><i style="">T</i>_str of (KCl + KBr) > (KCl + KI) > (KBr + KI). <img src='/image/spc_char/delta.gif' border=0><i style="">T</i>_str is also found to vary linearly with ionic strength of the mixed electrolyte solutions, and at any given ionic strength <img src='/image/spc_char/delta.gif' border=0><i style="">T</i>_str of (KCl + KBr) > (KCl + KI) > (KBr + KI). The results are explained in terms of enhancement in the structure breaking nature of Cl^-, Br^- and I^- due to K⁺ and is found to be in the order of I^- > Br^- > Cl^-.