High-resolution molar volume data for 4-cyano-4'-n-octylbiphenyl (8CB) are presented as a function of temperature near the nematic to isotropic (NI) phase transition. Close to the NI transition the volume was measured at 10 mK temperature steps and at two different pressures. From the data an isobaric thermal expansion coefficient, alpha(p)(T), and isothermal compressibility coefficient, beta(T)(T), were calculated. Fitting the V(T) and beta(T)(T) data according to a tricritical hypothesis with the critical exponents alpha = alpha' = (1)/(2) allowed one to find the spinodal temperatures, T* and T**, on both sides of the first-order phase transition. A universal ratio (T-NI - T*)/(T** - T-NI) is compared with the theoretical mean field value. The measured volume jump at the transition, DeltaV(NI), is related to the enthalpy jump, DeltaH(NI), which was obtained from the very precise calorimetric measurements by other authors.