Studies on VLE for the binary difluoromethane (R32)+ propane (R290) system revealed the possibility of a liquid phase splitting at low temperatures. This was confirmed by successive measurements on the mutual solubility, and the upper critical solution temperature (UCST) was found at temperature T = 230 K. A similar phase behaviour was expected for the R32 + n-butane (R600) system. Experiments on the immiscibility of liquid phase system have been carried out at temperatures down to 220 K using a dedicated apparatus enabling the visual observation of the liquid phase split. The UCST was found at T = 246 K. The VLLE were correlated applying an equation of state. The present results are consistent with the VLE data measured at temperatures above the UCST within the estimated uncertainty of the experiment. The observed liquid phase split provides important new information on the fluid behaviour of HFCs + HCs systems and it is also important for engineering, due to its potential influence on the operation of refrigerating machines. (C) 2003 Elsevier Science B.V. All rights reserved.