We have made PVTξ measurements of R115 and R114 at temperatures from 296 to 443 K, pressures from 0.4 to 9.8 MPa, and densities from 153 to 1387 kg·m−3, for four compositions, namely, 25, 50, 75, and 100 wt% R115. The data were obtained along isochores. The uncertainties in temperature, pressure and density are less than ±8 mK, ±2.2 kPa and ±0.1%, respectively. Using the experimental measurements on 100 wt% R115, we have validated our experimental apparatus and measurements. Furthermore, from the PVTξ measurements for 75wt% R115, 50wt% R115, and 25wt% R115, we have determined dew points and bubble points enabling us to construct the dew- and bubble-point curves for each composition. Our measurements also yield the critical point of R115 and R114 as a function of the concentration of the mixture.