Piston cylinder apparatus

Both of these in situ devices use substantially less solution (volumes of solution samples for each kinetic run are usually of the order of a few cm3) than a typical piston-cylinder apparatus. The pill-box cell method has the advantage that the cell can be filled in an appropriate glove box for oxygen-sensitive samples or for nonaqueous solvent-based systems that are sensitive to moisture. Temperature control is exerted by fluid circulating through the metal block. 

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. 

Doped ice V samples were prepared from solutions containing 0.01 M DCl in D2O. The solutions were frozen in a piston-cylinder apparatus precooled to 77 K, and the frozen doped ice heated isobarically at 0.5 GPa to 250 K. Thereafter, the samples were cooled from 250 K at 0.8 K min to 77 K, decompressed, and recovered under liquid nitrogen (cf. Figure 1). The transition to ice II on cooling at 0.5 GPa was never observed, which is in agreement with ref 16. 

In order to calculate in situ densities from the piston displacement data a reference density is required, which is in our case the density p(LDA)=0.92 0.02 g/cm at 125 K Furthermore, it is necessary to subtract the piston displacement obtained in a blind experiment, i.e., the same experiment, but without ice (bottom curve in Fig. la). This blind experiment was previously called indium correction . However, the correction functions d (p) recorded with 350 mg of indium and no ice (solid line) and the correction functions recorded with no indium and no ice (dashed line) shown in Fig. 2c indicate that the correction function is dominated by the compressibility of the piston-cylinder apparatus and the frame of the material testing machine, whereas the indium contribution is negligible. The in situ density p(p) can be calculated using the mass of ice m(ice H) and the cross-section of the bore A from the difference in piston displacement Ad(p) ( real experimenf d(p) minus blind experimenf d (p)) as... 

Beyond this range, the pressures are normally created by static pressure devices, such as piston-cylinder apparatus, solid state presses or anvil devices (opposed, tetrahedral and cubic anvil), when the sample is simply squeezed to create pressure up to 150 kbar (15 GPa) (Figure 4.9). These methods have allowed the synthesis of compounds which could not be created in any other way. However, only very small samples are produced (50 mg) in these expensive reactions, and so industrial applications of the materials produced are unlikely. 

Bohlen S. R. (1984) Equilibria far precise pressure calibration and a frictionless furnace assembly far the piston-cylinder apparatus. N. Jb. Mineral. Mh. 9, 404 412. 

A separate section will be devoted to covering the monitoring of reaction progress at high pressure by nuclear magnetic resonance (NMR) spectroscopy. Although there have been no reports to date, in principle for sufficiently slow reactions aliquot samples from a piston-cylinder apparatus could be followed by NMR spectroscopy however, such a procedure would not be viable because of the large solution volumes required if deuterated solvents were to be used. 

The modest pressures of 5 kbar (0.5 GPa) necessary to cause transitions to columnar phases in polymers make the design of apparatus using large specimens relatively straightforward and it is easy to accommodate associated characterization techniques such as thermal conductivity or nuclear magnetic resonance (NMR) probes. Much of the author s early work was with a piston-cylinder apparatus with a working length of 5 cm and a diameter of... 

While it is important to take proper precautions (see Appendix 2), properly built equipment offers few hazards if relatively small quantities of liquids are used under pressure. The energy stored in a compressed liquid is of the order of 0.2-0.5 kJ mor kbar" this is much less than in a gas. In the event of the catastrophic failure of a vessel, only around 10 per cent of the liquid would need to escape to reduce the pressure to the atmospheric value, and double-walled vessels are unlikely to suffer a failure of both cylinders. The author has experienced the failure of a piston-cylinder apparatus which led to nothing more than a sudden depressurization. On the other hand, hazards may arise from the low-pressure side, which is likely to be carrying oil at 500 bar or more a pin-hole jet at this pressure can penetrate the human body. The valve threads may become worn and the stems may then be forcibly ejected. So hose connections should be inspected and renewed regularly and, where possible, they should be shielded from personnel, the valves should be mounted with the stems pointing away from the operator, and the guidelines set out in the code of practice (see Appendix 2) should be followed. 

Piston-cylinder apparatus for the preparative scale to 20 kbar, and intensifiers, manganin gauges, valves, and fittings to 13 kbar... 

Hydrothermal- and carbonate-exchange techniques. The majority of available experimental fractionation data are for oxygen isotope fractionations involving minerals. Much of the data, particularly the early data, were obtained using water as the isotopic exchange medium. These experiments were either done at ambient pressure (typically synthesis experiments), or in cold-seal pressure vessels at pressures of 1 to 3 kbar (e.g. O Neil and Taylor 1967 O Neil et al. 1969 Clayton et al. 1972). Later experiments were done in a piston cylinder apparatus (at 15 kbar) to exploit the pressure enhancement of exchange rates (Clayton et al. 1975 Matsuhisa et al. 1979 Matthews et al. 1983a,b). 

Cohen el al. l74j described a piston-cylinder apparatus which could be... 

Figure 2.4 Schematic diagram of the double-headed piston-cylinder apparatus. To move the piston, any pressure imbalance between the methane and air chambers must overcome friction at the surfaces of contact between the piston heads and cylinder walls.

Consider a pure gas held in the cylinder of a piston-cylinder apparatus the cylinder is thermally insulated from its surroundings. We take the gas to be our system, which is initially at equilibrium at temperature T, volume V, and total number of moles N. Experiment shows that specifying these three quantities fixes the thermodynamic state of pure systems. From this initial state we place a single large weight on top of the piston, exerting a constant pressure changing its volume. The... 

Argon is held in a vertical piston-cylinder apparatus. The piston has a diameter... 

A liquid mixture of ethanol and water completely fills the cylinder of a piston-cylinder apparatus. The cylinder is closed to mass transfer, but its walls are thermally conducting and the piston can be moved. Determine values for V, Fg, and T, and explain what each of these quantities means. If the cylinder were insulated, which of your values change and which remain the same ... 

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