## 2 Materials and Methods  
The Pressure-Specific Volume-Temperature, _PvT_ and Pressure-Specific Volume-Temperature-Composition, _PvT_z measurements for the low GWP refrigerants and their binary systems were performed using an isochoric apparatus. The triple points of pure fluids and the Solid-Liquid Equilibrium (SLE) of their blends were measured with an apparatus specifically built to reach temperatures down to about 100 K.  
The isochoric apparatus is formed by an AISI 304 stainless-steel isochoric sphere and two thermostatic baths that work at low temperatures (from 210 to 298 K) and high temperatures (from 303 to 390 K), respectively. A schematic view of the experimental setup is shown in Figure 1. For details of the setup, the measurement procedure and the uncertainties are given in previous works [16; 17] and only a summary of the information is reported in this section. The spherical cell (1) containing the refrigerant sample is connected to a differential diaphragm pressure transducer (4) coupled to an electronic null indicator (5). In the new setup, the transducer and sphere were placed vertically and a magnetic pump (3) for mixing the sample was connected to the sphere. Temperature is controlled by a PID device and measured with a calibrated resistance thermometer (8). The measured binary systems were prepared by a gravimetric method. To perform the experimental runs, the sample charged in the isochoric sphere was allowed to stabilize at the temperature set-point for an hour before the pressure measurements were taken. After recording the measured values, the set-point of the thermostatic bath was changed to the next set temperature. The measurement procedure was then repeated. The isochoric measurements have the following expanded uncertainties at the 95% confidence level (coverage factor of 2): 1.2 mg for the masses, 0.03 K for the temperature, 1 kPa for the pressure, 0.3 cm\({}^{3}\) for volumes, 0.001 for the mole fractions, and 0.005 m\({}^{3}\) kg\({}^{-1}\) for specific volumes. Figure 1: Schematic view of the isochoric apparatus. The experimental setup for the triple point temperatures and SLE measurements is based on the cooling curve method [18; 19] which is a dynamic technique of measurement and does not require the visual observation of phase behavior. Figure 2 shows the experimental setup. The detailed descriptions of the experimental setup and the testing procedure were reported in previous works [20; 21; 22]. Only summary information is included below. The apparatus includes a measuring cell (1) consisting of a stainless-steel cylinder. The cover of the cylinder has two holes that house two T-type thermocouples (2). To avoid any premature stratification of the sample and to ensure homogeneity during the sample liquefaction and crystallization, a stirrer (3) was placed inside the cylinder. The measuring cell is surrounded by a copper coil that exchanges heat with the cell through its contact surface and by means of a working fluid (air or liquid nitrogen). The cell and the copper coil are placed inside a thermally insulated Dewar flask (7). The apparatus has two separate circuits: a compressed air circuit and a liquid nitrogen circuit. One end of the compressed air circuit is connected to the dry air supplier (8). A mass flow control (9) was installed downstream  
Figure 2: Schematic view of the Solid-Liquid Equilibrium (SLE) apparatus. the dry air supplier to adjust the air flow rate, while a rotameter (10) measured the air flow rate. On the other end, the compressed air circuit is connected both to the thermally insulated liquid nitrogen Dewar tank (11) and to an external heating coil (13) that is connected to the copper coil surrounding the measuring cell. The two circuits allowed to carry out measurements in two operating modes: cooling and heating modes. During the cooling mode, a cooling curve is drawn in real time and the sample solidification results in a slope modification of the temperature trend in correspondence to the freezing point.