Chemical equilibrium constants by differential ultrasonic absorption

In 1953 Kurtze and Tamm observed a reduction of sound absorption in $MgSO4$ solutions upon the addition of NaCl. From this reduction it is possible to determine the concentration of $(NaSO4)$ ion pairs. A new equilibrium dissociation constant K_D=0.073 is obtained, considerably lower than the accepted value of K_D=0.019. The differential ultrasonic absorption technique is a new independent approach to the study of chemical equilibria that has proved to be very useful for the study of a difficult unsymmetrical electrolyte. Two recent experimental papers using independent techniques, electrical conductance and potentiometric measurements, support the new value. The technique should be useful for the study of many other equilibria. [This paper represents results of research sponsored by the Office of Naval Research and the National Science Foundation Grant GA 18763.]