Apparatus for determining the sound velocity of a liquid in a specimen having two walls between which the liquid is contained with one of the walls being deformable has a sensor including a transducer for transmitting ultrasonic energy signals between the specimen walls and apparatus for deforming the specimen wall by a known distance from a first to a second position relatively spaced from the transducer and an electronic circuit including a microprocessor for measuring first and second transit times of the signals through the liquid between the specimen walls for each of the specimen deformable wall first and second positions, and for calculating the sound velocity of the liquid based upon the known distance and the two measured transit times. Where blood is the liquid values of parameters such as glucose and hematocrit are obtained based on algorithms pre-programmed in the microprocessor.