Piston and cylinder apparatus

FIGURE 1 Cross section of simple piston and cylinder apparatus at high pressure. Original shape indicated by dashed lines. Distortions due to pressure are exaggerated. 

A sample consisting of 22.7 g of a nongaseous, unstable compound X is placed inside a metal cylinder with a radius of 8.00 cm, and a piston is carefully placed on the surface of the compound so that, for all practical purposes, the distance between the bottom of the cylinder and the piston is zero. (A hole in the piston allows trapped air to escape as the piston is placed on the compound then this hole is plugged so that nothing inside the cylinder can escape.) The piston-and-cylinder apparatus is carefully placed in 10.00 kg of water at 25.00°C. The barometric pressure is 778 torn... 

It is known that the enthalpy change for the decomposition of X, according to the reaction described above, is -1893 kJ/mol X. The standard enthalpies of formation for gaseous carbon dioxide and liquid water are -393.5 kJ/mol and -286 kJ/mol, respectively. The heat capacity for water is 4.184 J/°C g. The conversion factor between L atm and J can be determined from the two values for the gas constant R, namely, 0.08206 L atm/K mol and 8.3145 J/K mol. The vapor pressure of water at 29.5°C is 31 torn Assume that the heat capacity of the piston-and-cylinder apparatus is negligible and that the piston has negligible mass. 

The pressure limit of the piston and cylinder apparatus [39] was extended to allow commercial production of synthetic diamonds by designing the cylinder to accommodate pistons shaped as truncated cones. 

Let us examine the stresses and distortions that accompany the generation of pressure in this apparatus. In Fig. 1 the original (zero pressure) shapes of piston and cylinder are shown by dotted lines the distortions, shown by the solid lines, due to pressure are exaggerated. The bulging of the piston is most pronounced above the cylinder inside the cylinder the piston is supported by, and rubs on, the wall of the cylinder. The sharp change in radial bursting... 

To indicate the nature of reversible processes, we examine the simple expansion of a gas in a piston/cylinder arrangement. The apparatus is shown in Fig. 2.4, and is imagined to exist in an evacuated space. The gas trapped inside the cylinder is chosen as the system all else is the surroundings. Expansion processes result when mass is removed from the piston. To make the process as simple as possible, we assume that the piston slides within the cylinder without friction and that the piston and cylinder neither absorb nor transmit heat. Moreover, because the density of the gas in the cylinder is low and because the mass of gas is small, we ignore the effects of gravity on the contents of the... 

Blend Preparation Techniques—Techniques for the preparation and assay verification of calibration blends in the laboratory are described in Appendixes XI and X2. Also, a technique using a moving piston graduated cylinder apparatus, that is described in the calibration section of Test Method D 4468, can be used. However, some laboratories have found that the preparation of such blends is far from easy, and successful efforts require considerable knowledge and experience. 

Finally, compression-extrusion testing involves an extrusion cell commonly used for weakly structured, homogeneous food products. This apparatus consists of a piston that is forced into a cylinder open at one end and containing the product (Figure H2.2.5). Beyond the point of rupture of the food, the compressed material is forced to flow back through the annular space between the piston and the cylinder (Bourne, 1976 Edwards, 1999). The gap between the piston and the cylinder is called the annulus (Bourne, 1982). Variation in the annulus width results in variation in the force required for extrusion (Bourne, 1982). 

A reaction is carried out in a cylinder fitted with a movable piston, as shown here. The starting volume is V = 5.00 L, and the apparatus is held at constant temperature and pressure. Assuming that AH = —35.0 kj and AE = —34.8 kj, redraw the piston to show its position after reaction. Does V increase, decrease, or remain the same ... 

A cutaway drawing of the rotating-cylinder reactor is shown in Fig. 35. The mechanical aspects of the reactor system were designed to provide temperature control, fluid containment, and process measurements. The apparatus consists of a stainless steel (SS) holder and glass cylinder in which rides an SS piston, sealed by two Viton O-rings. Piston movements is monitored by a linear variable differential transformer (type 250 HCD, Schaevetz Engineering) attached to the piston and fixed relative to the cylinder. 

All high-pressure reactions were performed in a piston-cylinder apparatus, whose initial working volume is 10 ml. Details of this apparatus 39) are shown in Fig. 1 and explained below. 

A thermodynamic state is a macroscopic condition of a system in which the properties of the system are held at selected fixed values independent of time. The properties of the system are held constant by its boundaries and the surroundings. For example, a system comprising 2 mol helium (He) gas can be held in a piston-cylinder apparatus that maintains the system pressure at 1.5 atm, and the apparatus may be immersed in a heat bath that maintains the system temperature at 298 K. The properties of pressure (P) and temperature (T) are then said to be constrained to the values 1 atm and 298 K, respectively. The piston-cylinder and the heat bath are the constraints that maintain the selected values of the properties P and T. 

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