Specific heat measurements were made over the range 12° to 330° K on a sample of synthetic rubber GR-S (Buna S) by means of a n adiabat ic vacuum-ty pe calorimeter. A D ebye specific he["t function was used to calculate values below 15 0 K . At about -61 0 C the material undergoes a transition of the second order, the specific heat increasing rapidly by about 40 percent. From -50 0 to +60 0 C, the specific heat values can be calculated to within 0.1 percent by the equation C. = 0,4346 + 7.029 X

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... lO-' t+ 1.156 X 10-a t2 in calories gram-I degree Kelvin -I. At 25 0 C the specific heat is 1.894 internat ional joules gram-1 degree Kelvin-I (0.4528 calorie gram-1 degree K elvin -I). The increase in entropy from 0° to 298.16 0 K is calculated to be 1.824 internations.l joules gram -I degree Kelvin -I (0.4359 caloriE' gram -I degree K elvin -I). Values of specific heat, and increases of entropy, enthalpy , and free energy are tabuls.ted at 5-degree intervals. The experimental data indicate that values below the transition are dependent upon the thermal history of the ~ample . This phenomenon, as well as the temperature drifts observed, ca n be explained on the theory that the transition results from an increasingly slow s.pproach to the equilibrium state at temperatures in the transition region and below.