Supersonic Measurement of the Heat Capacity of Propylene

An apparatus designed for (1) a general study of acoustical dispersion in gases, and (2) measurement of gaseous heat capacities has been used to measure the heat capacity of propylene between 273 and 490°K. The general methods used are outlined and discussed. The measured heat capacity values agree well with those calculated from the frequency assignment as given by Wilson and Wells, and an assumed potential restricting rotation of about 2000 cal./mole, but deviate from the values calculated from Pitzer's frequency assignment and an 800-cal./mole potential. The measurements on propylene also have the value of serving as a test of the usefulness and practicality of the supersonic method of heat capacity determinations.