Volatilization vapor pressure

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. 

The second ramp portion of this cure cycle is critical from a void nucleation and growth standpoint. During this ramp, the temperature is high, the resin pressure can be near its minimum, and the volatile vapor pressure is high and rising with temperature. These are the ideal conditions for void formation and growth. 

An appreciation of the importance of hydrostatic resin pressure must be developed to understand void growth fully. Because of the load-carrying capability of the fiber bed in a composite layup, the hydrostatic resin pressure needed to suppress void formation and growth is typically only a fraction of the applied autoclave pressure. The hydrostatic resin pressure is critical because it is the pressure that helps to keep volatiles dissolved in solution. If the resin pressure drops below the volatile vapor pressure, then the volatiles will come out of solution and form voids. 

Void formation and growth in addition curing composite laminates is primarily due to entrapped volatiles. Higher temperatures result in higher volatile pressures. Void growth will potentially occur if the void pressure (i.e., the volatile vapor pressure) exceeds the actual pressure on the resin (i.e., the hydrostatic resin pressure) while the resin is a liquid (Fig. 10.9). The prevailing relationship, therefore, is ... 

Synonyms ethanal, acetic aldehyde Formula CH3CHO MW 44.05 CAS [75-07-0] used in the production of acetic acid, acetic anhydride, and many synthetic derivatives found in water stored in plastic containers colorless mobil liquid fruity odor when diluted boils at 20.8°C solidifies at -121°C highly volatile vapor pressure 740 torr at 20°C density 0.78 g/mL at 20°C soluble in water, alcohol, acetone, ether, and benzene highly flammable... 

The solvent industry has made significant strides in developing newer grades and blends of solvents for a variety of applications. Safety solvents are being developed that are low in volatility (vapor pressure), low in toxicity, and biodegradable. However, these newer solvents are finding commercial acceptance mainly as cleaning solvents rather than as a dilution medium for epoxy resins. For adhesives, rather than replace the solvent, the trend has been to develop waterborne emulsions. 

Easily vaporized liquids are called volatile liquids, and they have relatively high vapor pressures. The most volatile liquid in Table 13-4 is diethyl ether. Water is the least volatile. Vapor pressures can be measured with manometers (Figure 13-12). 

Commercial Propane-Butane mixtures are produced to meet particular requirements such as volatility, vapor pressure, specific gravity, hydrocarbon composition, sulfur and its compounds, corrosion of copper, residues, and water content. These mixtures are used as fuels in areas and at times where low ambient temperatures are less frequently encountered. Analysis by gas chromatography is possible (ASTM D-5504, ASTM D-6228, IP 405). 

The vaporization and combustion characteristics of liquefied petroleum gas are defined for normal applications by volatility, vapor pressure, and, to a lesser extent, specific gravity. 

For natural gasoline, the primary criteria are volatility (vapor pressure) and knock performance. Determination of the vapor pressure (ASTM D-323, ASTM D-4953, ASTM D-5190,ASTM D-5191) and distillation profile (ASTM D-216, IP 191) is essential. Knock performance is determined by rating in knock test engines by both the motor method (ASTM D-2700, IP 236) and the research method (ATSM-2699, IP 237). The knock characteristics of liquefied petroleum gases can also be determined (IP 238). 

Under the conditions of its use, the concentrations of ethrane in air should be too low to produce any adverse health effects on humans. However, it should be borne in mind that this compound is highly volatile [vapor pressure 175 torr at 20°C (68°F)] and its concentration in air can go up from a spill or improper handling in confined space. 

Colorless liquid with a pleasant sweet odor sweet taste volatile, vapor pressure 158 torr at 20°C (68°F) density 1.484 at 20°C (68°F) boils at 61.2°C (142°F) solidifies at —63.5°C (—82°F) slightly soluble in water (0.82 mL/100 mL water at 20°C (68°F)), miscible with organic solvents sensitive to light. 

A. Carbon disulfide is highly volatile (vapor pressure 297 mm Hg), and inhalation is a major route of exposure. The OSHA permissible exposure limit (PEL) is 10 ppm (100 ppm, 30-minute peak), while the NIOSH recommended expo-... 

Weigh 1.5 g of iodine, I2, directly into a 50-mL or larger beaker using a beam balance. Do not let iodine touch the weighing pan or an aluminum weighing dish because iodine may react with aluminum on contact. Cover the beaker with a watch glass so that iodine vapor does not diffuse readily into the air. CAUTION Iodine can also be an irritant and cause systemic difficulties however, this is seldom a problem because of its low volatility (vapor pressure, 1 mmHg at 38.7°C). 

Esters and salts of 2,4-D are used as Insecticides and can have higher volatility (vapor pressure) toxicity simitar to that of 2,4-D (or 2.4-DP). Solvent contained in commercial products often presents a greater danger than active substance. Alcohol consumption increases toxic effects. The measures on tMs card also apply to 2,4-DP melting point 118 C. 

Organic volatile Vapor Pressure of volatile at -22°F (mmHg) Volatile retention in systems containing specified carbohydrate (g volatile per 100 g solid) ... 

MTBE is a volatile (vapor pressure 26.8 kPa at 20°C boiling point 55.3°C) flammable, and colorless liquid at room temperature with a terpene-like odor. Reported Henry s law constant varies from 59 to 305 Pa m mol but is usually less than 100. It is miscible with gasoline and is soluble in water, alcohol, esters, and ethers. It forms azeotropic mixtures (constant temperature-constant composition boiling mixture) with some solvents such as me anol. It... 

Liquid + vapor Dilference in volatilities (vapor pressure) Concentration of fruit juices 40... 

Vapor pressure is the plasticizer physical property that determines volatility. Vapor pressures (Pascals at 25°C) from the chemical literature [2,3] are shown below. 

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