Vapour + liquid) equilibrium (P-x-y) data are reported at three isotherms for the (propane + decafluorobutane), and (1-butene + decafluorobutane) binary systems. The range of temperatures extended from 312.92 K to 342.94 K. An apparatus based on the "static-analytic'' method, which had two electromagnetic ROLSI (TM) samplers, for repeatable and reliable equilibrium phase sampling and handling, was used to undertake the measurements. The experimental values were correlated with the "PR-MC-NRTL-WS'' model which comprised the Mathias-Copeman alpha function, Wong-Sandler mixing rule, and NRTL local composition model which were incorporated into the Peng-Robinson equation of state. Maximum pressure azeotropy is observed for both systems at all investigated temperatures. Liquid-liquid immiscibility was not observed over the range of temperatures studied. (c) 2013 Elsevier Ltd. All rights reserved.