Vapors density

Vapor density is a measure of the relative weight of vapor compared to the weight of air. Published data on the characteristics of petroleum products usually include the vapxir density. The value of 

For this reason, while responding to a spill or leak, we must consider environmental and topographical features of the surroundings, such as wind direction, the slope of the ground, and any natural or artificial barriers that may channel the liquid or vapors. It is critical in a non-fire incident, such as a spill or leak, to determine the type of petroleum liquid present and its source. Information about the material s vapor density enables us to make reasonable predictions as to the possible behavior of the emitting vapor. These factors may influence the route of approach, the positioning of firefighting apparatus and personnel, the need for and the route of evacuation, and the boundaries of the potential problem area. It is essential that no apparatus or other motor vehicles or personnel be located in the path that a vapor cloud will most likely follow. 

As a rule of thumb one should approach a hydrocarbon spill (non-fire situation) under the assumption that the liquid is vaporizing (the vapors will be invisible) and that the liberated vapors are heavier than air unless proven otherwise. The expected conduct of a heavier-than-air vapor is for it to drop and spread at or below ground level much as a liquid would. The big difference is that a liquid will be visible and its boundaries well defined. One can expect that the invisible heavier-than-air vapor will settle and collect in low spots such as ditches, basements, sewers, etc. As the vapor travels, it will be mixing with the air, thus some portions of the cloud may be too rich to burn, other sections too lean, and still others well within the explosive range. Some typical vapor densities for petroleum products are 3 to 4 for gasoline, 2.5 for naphtha, and 1.1 for methanol. For comparison, the vapor density for hydrogen gas is 0.1. 

With their low specific gravity, most petroleum liquids, if spilled onto a pool of water, have a tendency to spread quickly across the water s surface. Unless the fluid contacts an obstacle. 

Some specific gravities of common petroleum liquids are 1 to 1.1 for asphalt, 0.8 for gasoline, and 0.6 for naphtha. 

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Increasing the pressure of irreversible vapor-phase reactions increases the rate of reaction and hence decreases reactor volume both by decreasing the residence time required for a given reactor conversion and increasing the vapor density. In general, pressure has little effect on the rate of liquid-phase reactions. 

Vapor density increases, giving a smaller column diameter. 

Vapor Density. Substitution of the Antoine vapor-pressure equation for its equivaient iog P in the ideai gas equation gives... 

The vapor density of acetic acid suggests a molecular weight much higher than the formula weight, 60.06. Indeed, the acid normally exists as a dimer (4), both in the vapor phase (5) and in solution (6). This vapor density anomaly has important consequences in engineering computations, particularly in distillations. 

Mercuric Chloride. Mercuric c Aon.d.e.[7487-94-7] HgCl2, is also known as corrosive sublimate of mercury or mercury bichloride. It is extremely poisonous, and is particularly dangerous because of high (7 g/L at 25°C) water solubiUty and high vapor pressure. It sublimes without decomposition at 300°C, and has a vapor pressure of 13 Pa (0.1 mm Hg) at 100°C, and 400 Pa (3 mm Hg) at 150°C. The vapor density is high (9.8 g/cm ), and therefore mercuric chloride vapor dissipates slowly (5). 

AH ammonium haUdes exhibit high vapor pressures at elevated temperatures, and thus, sublime readily. The vapor formed on sublimation consists not of discrete ammonium haUde molecules, but is composed primarily of equal volumes of ammonia and hydrogen haUde. The vapor densities are essentiaHy half that expected for the vaporous ammonium haUdes. Vapor pressures at various temperatures are given in Table 2 (11). Latent heats of sublimation, assuming complete dissociation of vapors and including heats of dissociation are 165.7, 184.1, and 176.6 kJ /mol (39.6, 44.0, and 42.2... 

Solvent name PEL, ppm Flash point, °C LEL, vol % UEL, vol % Evaporation b rate Autogenous ignition temperature, °C Vapor density... 

Physical Properties. Sulfur dioxide [7446-09-5] SO2, is a colorless gas with a characteristic pungent, choking odor. Its physical and thermodynamic properties ate Hsted in Table 8. Heat capacity, vapor pressure, heat of vaporization, density, surface tension, viscosity, thermal conductivity, heat of formation, and free energy of formation as functions of temperature ate available (213), as is a detailed discussion of the sulfur dioxide—water system (215). 

Arsenic pentafluoride (arsenic(V) fluoride), AsF, is a colorless gas that condenses to a yellow Hquid its dielectric constant is 12.8 at 20 °C. It is formed by reaction of a mixture of bromine and antimony pentafluoride with arsenic trifluoride. The molecule is a trigonal bipyramid and is somewhat dissociated as indicated by vapor density measurements. 

Bismuth Trichloride. Bismuth(III) chloride is a colodess, crystalline, dehquescent soHd made up of pyramidal molecules (19). The nearest intermolecular Bi—Cl distances are 0.3216 nm and 0.3450 nm. The density of the soHd is 4.75 g/mL and that of the Hquid at 254°C is 3.851 g/mL. The vapor density corresponds to that of the monomeric species. The compound is monomeric in dilute ether solutions, but association occurs at concentrations greater than 0.1 Af. The electrical conductivity of molten BiCl is of the same order of magnitude as that found for ionic substances. 

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