A method for determining the sonic velocity in a fluid as a function of pressure and temperature is described. The method used measures the time required for an expansion wave to travel a known distance through the test medium. The results of the sonic velocity measurements are presented for normal hydrocarbons from C6 to C16 for temperatures and pressures from 60 to 250 F and 0 to 5000 psig, respectively. The density of the hydrocarbons was also determined. The absolute viscosity of the test compounds was determined by use of a rolling-ball viscometer for pressures from 0 to 6000 psig in the temperature range given. Tabulated and graphical results are presented for adiabatic bulk modulus, density, and absolute and kinematic viscosity for the range of hydrocarbons tested.