Vapor pressure vaporization

Calorimetric Calorimetric Vapor Pressure Vapor Pressure Vapor Pressure... 

Equations for Hadacher vapor pressure, vapor heat capacity, saturated Hquid volume, and Hquid viscosity can be found in Refs. 34 and 41. 

Cavitation. The subject of cavitation in pumps is of great importance. When the Hquid static pressure is reduced below its vapor pressure, vaporization takes place. This may happen because (/) the main stream fluid velocity is too high, so that static pressure becomes lower than vapor pressure (2) localized velocity increases and static pressure drops on account of vane curvature effect, especially near the inlets (J) pressure drops across the valve or is reduced by friction in front of the pump or (4) temperature increases, giving a corresponding vapor pressure increase. 

The vapor pressure is an important property of the material to be thermally vaporized. In a closed container at equiUbrium, the number of atoms returning to the surface is the same as those leaving the surface, and the pressure above the surface is the equiUbrium vapor pressure. Vapor pressures are strongly dependent on the material and the temperature (Fig. 4). 

Substances with high vapor pressure evaporate rapidly. Those with low vapor pressure evaporate slowly. The impact of vapor pressure on the rate of evaporation makes vapor pressure a very important property in considering the tactical use and duration of effectiveness of chemical agents. A potential chemical agent is valuable for employment when it has a reasonable vapor pressure. One with exceptionally high vapor pressure is of limited use. It vaporizes and dissipates too quickly. Examples are arsine and carbon monoxide. On the other hand, mechanical or thermal means may effectively aerosolize and disseminate solid and liquid agents of very low vapor pressure. Vapor pressure and volatility are related. Translated into volatility, vapor pressure is most understandable and useful. 

Vapor Pressure Vapor pressure is a function of the substance and the temperature and is often used as a measure of how rapidly a liquid will evaporate. The pressure exerted when a solid or liquid is in equilibrium with its own vapor. 

Vapor pressure is exerted by a solid or liquid in equilibrium with its own vapor. All liquids have vapor pressures. Vapor pressure depends on temperature and is characteristic of each substance. The higher the vapor pressure at ambient temperature, the more volatile the substance. Vapor pressure of water at 20 0 is 17.535 torr. 

To understand vapor pressure, let s consider an empty jar that is partially filled with water and then covered with a lid. We will assume the space above the water in the jar contains only air when we screw on the jar s lid. After the lid is place on the jar, water molecules leave the liquid and enter the air above the liquid s surface. This process is known as vaporization. As time goes by, more water molecules fill the air space above the liquid, but at the same time, some gaseous water molecules condense back into the liquid state. Eventually, a point is reached where the amount of water vapor above the liquid remains constant. At this point, the rates of vaporization and condensation are equal, and equilibrium is reached. The partial pressure exerted by the water at this point is known as the equilibrium vapor pressure or just vapor pressure. Vapor pressure is directly related to the temperature, that is, the higher the temperature, the higher the vapor pressure. Table 9.4 gives... 

Vapor Pressure Vapor pressure of solution with nonvolatile solute is lower than that of solvent... 

Odor and appearance Odor threshold Specific gravity Vapor pressure Vapor density Evaporation rate Boiling point Freezing point pH... 

Duarte-Garza, H.A., Hwang, C.-A., Kellerman, S., Miller, R.C., Hall, K.R., Holste, J.C. (1997a) Vapor pressure, vapor density, and liquid density for Ll-dichloro-l-fluoroethane (R-141b). J. Chem. Eng. Data 42, 497-501. 

The vapor pressure, Pvp, of a liquid or solid is the pressure of the compound s vapor (gas) in equilibrium with the pure, condensed liquid or solid phase of the compound at a given temperature [5-9]. Vapor pressure, which is temperature dependent, increases with temperature. The vapor pressure of chemicals varies widely according to the degree of intermolecular attractions between like molecules The stronger the intermolecular attraction, the lower the magnitude of the vapor pressure. Vapor pressure and the Henry s law constant should not be confused. Vapor pressure refers to the volatility from the pure substance into the atmosphere the Henry s law constant refers to the volatility of the compound from liquid solution into the air. Vapor pressure is used to estimate the Henry s law constant [equation (2.4)]. 

Liquids are constantly evaporating at their surface. That is, the molecules at the surface of the liquid can achieve enough kinetic energy to overcome the forces between them and they can move into the gas phase. This process is called vaporization or evaporation. As the molecules of the liquid enter the gas phase, they leave the liquid phase with a certain amount of force. This amount of force is called the vapor pressure. Vapor pressure depends upon the temperature of the liquid. Think about a pot of water that is being heated in preparation for dinner. The water starts out cold and you do not see any steam. As the temperature of the water increases you begin to see more steam. As the temperature of the water molecules increases, the molecules have more kinetic energy, which allows them to leave the liquid phase with more force and pressure. You can then conclude that as the temperature of a liquid increases, the vapor pressure increases as well. This is a direct relationship. 

Melting point Boiling point Vapor pressure Vapor density Liquid density Conversion factor Odor... 

Once the PVT relationship has been proven satisfactory for representing a fluid, it may be used, together with the thermodynamic functions, to derive expressions for other properties such as vapor pressure, vapor-liquid equilibrium (VLE) relationships, enthalpy departure from ideal gas behavior, and so on. 

Vapor pressure Vapor density (relative to air) Volatility at 25°C... 

Low molecular weight isocyanates such as TDI have a high vapor pressure (vapor pressure of TDI = 2.3 x lO" mmHg at 25 °C) and are respiratory Irritants and lachrymators. Prolonged inhalation of TDI vapors may lead to symptoms resembling asthma. The maximum allowable vapor concentration has been reduced to 0.005 ppm. 

Vapor Pressure. Vapor pressure is one of the most fundamental properties of steam. Figure 1 shows the vapor pressure as a function of temperature for temperatures between the melting point of water and the critical point. This line is called the saturation line. Liquid at the saturation line is called saturated liquid liquid below the saturation line is called subcooled. Similarly, steam at the saturation line is saturated steam steam at higher temperature is superheated. Properties of the liquid and vapor conveige at the critical point, such that at temperatures above the critical point, there is only one fluid. Along the saturation line, the fraction of the fluid that is vapor is defined by its quality, which ranges from 0 to 100% steam. 

VAPOR PRESSURE - Vapor pressure denotes the lowest absolute pressure that a given liquid at a given temperature will remain liquid before evaporating into its gaseous form or state. 

Ap p is the vapor pressure deficit = saturated vapor pressure - vapor pressure of the air, N/m is the water efficiency coefficient, N/m ... 

Air/water Evaporation rate Solubility Vapor pressure Vapor density Dissociation constant Specific gravity Particle size... 

Air/soil Evaporation rate Soil adsorption constant Vapor pressure Vapor density Octanol/water partition coefficient Solubility Particle size... 

In summary, die decision for a special equipment depends to some extend on concentration, temperature and pressure ranges one is interested in. From the experience of the author, the combination of isopiestic vapor pressure/vapor sorption measurements for the determination of solvent activities with infinite dilution IGC for the determination of Henry s constants provides good experimental data and covers a temperature range that is broad enough to have a sufficient data basis for thermodynamic modeling. If one is interested in both solvent solubiUty and diffusion data, finite concentration IGC or piezoelectric sorption techniques should be applied. 

Lipophilic chemicals are absorbed most easily (for example, benzene). These can include liquid solvents or solvents having low vapor pressure. "" Vapors absorbed by dermal uptake can significantly contribute to the body burden as a result of the whole body exposure e.g. 1-2 %ofxylene or toluene, up to 5-10% l-methoxypropane-2-ol. For other substances, much higher skin absorption rates were measured after the whole body exposure 2-methoxyethanol up to 55 %, 2-ethoxy-eflianol up to 42 %. ... 

Pressure gradient Temperature gradient Vapor pressure Vapor pressure Pressure gradient Concentration gradient Gradient of electric potential Concentration gradient Pressure gradient and... 

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