Generation of pressure

Polymerizations of methacrylic acid and derivatives are very energetic (MAA, 66.1 kj/mol MMA, 57.5 kJ/mol = 13.7 kcal/mol). The potential for the rapid evolution of heat and generation of pressure presents an explosion hazard if the materials are stored ia closed or poorly vented containers. 

Basic concepts discussed here are atmospheric pressure vacuum gage pressure absolute pressure Boyle s law or pressure/volume relationship Charles law or temper-ature/volume relationship combined effects of pressure, temperature and volume and generation of pressure or compression. 

Polythene containers holding the diisocyanate may harden and burst in prolonged storage, because of slow absorption of water vapour through the wall leading to urea deposition from hydrolysis and generation of pressure of liberated carbon dioxide. 

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... 

The excellent reproducibility that can be achieved in repetitive separations carried out over long periods of time, due in part to the stability of the various stationary phases to many aqueous mobile phase conditions. Thus, it is not uncommon with the current generation of pressure-stable HPLC sorbents for little change in the resolution to arise after more than 1000 repetitive analytical separations. 

Resonance combustion is defined as the generation of pressure maxima in the combustion chamber and the consequent irregularity of the burning rate these maxima originate from the interaction between the gas stream and the flame and become apparent as a kind of vibration. 

The idea behind this seems to be of a quantity of heat being transferred from burning coal to the boiler, and then through the engine to the condenser, while at the same time there is a parallel generation of pressure and transfer of force from the cylinder to the machines being driven. The transfer of force must bear a fixed relationship to a particular flow of heat - but no statement by any British experimenter at this time sheds any more light on the problem.54... 

By using high stirring rates It Is possible to operate under conditions In which the kinetics of the reaction can be studied In a regime not controlled by mass transfer limitations. Figure 1 shows a typical curve of the generation of pressure with time In a well mixed system. In this experiment t-butyl chloride was added to an 0.1 M emulsion of methylcyclopentane and the acid being stirred at 1000 rpm. 

The generation of pressure-dependent thermal rate coefficients from such microcanonical rate coefficients involves some averaging over a collision induced distribution. This averaging can once again reduce some of the errors due to the neglect of vibrational anharmonicities. In particular, at fairly high pressures, the distribution function is close to Boltzmann. In the calculation of thermal rate coefficients the errors in the distribution function then cancel with those in the microcanonical rate coefficients, just as in the high pressure limit. 

This one-step expression for the reaction rate is adequate for a demonstration of some of the general principles involved in the generation of pressure pulses. The equations are used to show the effects of the temperature gradient around a hot spot and the volumetric heat release rate there upon the propagation of autoignition. 

Pressure-driven systems are preferred compared to vacuum-driven systems for two reasons (a) Generation of pressures over 1 atm is important when viscous polymer networks are used for size separations and (b) interface to the mass spectrometer is simpler. 

Pure pentaborane(9) in dry glass ampuls may be stored for long periods at room temperature. The presence of impurities will result in the generation of pressure by formation of lower boranes and hydrogen. 

The solubility of gases in liquids is increased and that of solids is usually decreased by raising the pressure. Therefore, the solid solute of a saturated solution may precipitate during the generation of pressure and is no longer accessible for the reaction. The viscosity of liquid increases approximately twice every kilobar. This effect is particularly important for reactions containing diffusion-controlled steps. Finally, the compressibility of liquids is usually small compared to that of... 

The requirements for liquid chromatographic pumps include (I) the generation of pressures of up to 6000 psi (Ib/in. ), or 414 bar. (2) pulse-free output, (3) (low rates ranging from 0.1 to 10 mL/min, (4) flow reproducibilities of 0.5% relative or better, and (5) resistance to corrosion by a variety of solvents. The high pressures... 

This rapid production of gases from the decomposition of an explosive results in the formation of a high-pressure zone in the area where decomposition is taking place. This is an important concept to understand because this generation of pressure is one of the things... 

Typical fuel assembly, present generation of pressurized water reactors. 

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