Abstract: An apparatus is provided for identifying an unknown liquid by determining the speed of sound in the liquid. A pulse generator provides an excitation pulse to a first acoustic transducer which transmits an acoustic pulse in the liquid. The acoustic pulse is received by a second acoustic transducer at a distance from the first transducer measured by a displacement transducer. A gated clock is enabled by the excitation pulse and disabled when the acoustic pulse received by the second acoustic transducer reaches a predetermined threshold. The clock measures the time it takes the acoustic pulse to travel the distance between transducers. The temperature of the liquid is determined by indirect means and is provided as an input to a digital computer which computes the speed of the acoustic pulse by dividing the distance between the transducers, provided by the displacement transducer, by the elapsed time measured by the clock.