Thermodynamic properties were predicted for two groups of pure fluids, along the saturation curve and in the single-phase region: IUPAC pure fluids (propylene, chlorine, oxygen and nitrogen) and halogenated hydrocarbons (R11, R12, R21, R22, R152a). A new form of equation GEOS, named GEOS3C, was used. A wide comparison with Literature recommended data, as well as with results of other six cubic equations of state (Soave-Redlich-Kwong, Peng-Robinson, Stryjek-Vera, Schmidt-Wenzel, Freze et al, and Salim and Trebble) was made. The GEOS3C equation has three parameters estimated by matching three points on the saturation curve (vapor pressures and the corresponding liquid volumes). The three fixed temperatures are the triple point, the boiling point and the reduced temperature T-r = 0.7. The GEOS3C equation leads to the best results in predicting vapor pressure and volumes at saturation. It also gives reasonable deviations for the other thermodynamic properties in the saturation range, but this do not lead necessarily to similar best predictions of all properties in the single-phase region.