SF6 critical point apparatus

Qualitative observations • Liquid and gaseous state • Dynamic state during compression and expansion • Formation of the transition point at different temperatures Quantitative measurements • Representation of the critical point and critical temperature • Recording of isotherms on a PV diagram (according to Clapeyron) • Recording of isotherms on a PV-P diagram (according to Amegat) • Curves of saturated vapor pressure • Deviations of real gases from the ideal gas state Precision apparatus for studying the compressibility and condensation of a gas, determining the critical point, and recording the isotherms on the PV diagram (according to Clapeyron). Sulfur hexafluoride (SF6) is used as the test gas, which allows for easy setup with a critical temperature of 318.6 K (45.5°C) and a critical pressure of 3.76 MPa (37.6 bars). The device features a particularly compact and pressure-resistant transparent measuring cell. The volume of the cell is modified by the controlled rotation of a handwheel, and the volume change can be read on a fixed scale and a driven scale with a precision corresponding to 1/1000th of the maximum volume. The pressure is generated by a hydraulic system with castor oil of a quality approved for medical applications. The measuring cell and the hydraulic system are separated by a hat-shaped seal that coils up when the volume increases. Thanks to this design, the pressure difference between the cell and the oil compartment is practically negligible. Instead of measuring the gas pressure, a pressure gauge measures the oil pressure without dead volume in the cell. During the transition from the gaseous to the liquid state and vice versa, one can observe both the formation of the first liquid drop and the disappearance of the last gas bubble. The measuring cell is surrounded by a transparent water compartment. A circulation thermostat ensures a constant temperature with very high precision, and the temperature can be read and controlled using a thermometer. The good reading possibilities for volume, pressure, and temperature make it easy to record PV and PV-P diagrams and obtain high-quality results. By correcting the volume based on pressure and temperature, the quality of the results is comparable to values found in the literature.

The set includes: 1 hydraulic oil critical point device (castor oil), but without test gas (SF6), with connection fitting for MINICAN® gas canister and protection for gas connection 1 oil filling device 1 1.3 mm hexagonal screwdriver (for the set screw of the driven scale) 1 plastic tube, inner diameter 3 mm 1 tube connector for 1/8" (SW 11) 1 grease pump Other required equipment: Sulfur hexafluoride SF6 Required for possible degassing or filling of hydraulic oil: Castor oil Powerful vacuum pump