Abstract: In this paper, an ultrasonic study has been made of the state of sulphuric acid in water. Ultrasonic velocity of sulphuric acid in water as a function of concentration has been measured using pulse-echo method in the temperature range 0~75℃ and various parameters such as molar sound velocity, specific acoustic impedance, adiabatic compressibility, intermolecular free length for the solution and the ultrasonic velocity of pure sulphuric acid have been computed from the measurement results. Excess ultrasonic velocity, excess adiabatic compressibility and excess intermolecular free length have also been calculated.