Relative vapor density

Relative vapor density is the ratio between the density of a gas or vapor (Dg) and the density of air (DJ at the same temperature and pressure conditions  

Vapor density of a chemical is directly proportional to its MW. The average MW of air is 29 amu. At 25°C and 1 atmospheric pressure, average air density is 1.19 kg/m. The vapor density of air is referred to as being 1 for the calculation of relative vapor density of other vapors. Any chemical with MW 29 amu would have a vapor density 1 under the same temperature and pressure conditions, according to the Ideal Gas Law. Hence, the vapor is heavier than air and it will tend to stay in or flow to low places. Vapor of chemicals with MW 29 amu have a vapor density of 1. These vapors would tend to migrate to higher places and will be easily diluted by air currents. The vapor densities of aU CWAs and TICs, except for a few chemicals such as hydrogen cyanide, carbon monoxide, diborane, and ammonia, are 1. 

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The relative vapor density (RVD) values in Table 18.9 have been calculated as the density of dry air saturated with the compound of interest at 20°C. This represents the weighted mean molecular weight of the compound-saturated air relative to the mean molecular weight of dry air, which is 29 g/mol. The RVD value may be calculated from Equation 18.23 ... 

VD Relative vapor density of the gaseous agent as compared to air. Unless otherwise indicated, these values are calculated based on the standard reference weight of air (i.e., 29). 

Spencer et al. (14) reported that the degree of reduction in vapor pressure in soil due to adsorption is dependent mainly upon soil water content, the nature of the pesticide, its concentration and soil properties, particularly soil organic matter content. The concentration of the desorbed pesticide in the soil water dictates the vapor density of the pesticide in the soil air in accordance with Henry s law. Hence, soil water adsorption coefficients can be used to calculate relative vapor densities in the soil atmosphere. 

Figure 1. Relative vapor density of dieldrin (HEOD) versus concentration in Gila silt loam as affected by soil water content.

Heat of vaporization (at boiling point) Relative vapor density (air = 1)... 

Molecule Tbp (K) Flammability Relative vapor density Water soluble... 

The vapor density is the mass of solvent vapor per cubic meter of air (kg/m ) that is in equilibrium with the liquid at 101.3 kPa. The vapor density thus corresponds to the solvent content in the atmosphere at saturation and is temperature dependent. The relative vapor density of solvents <4 is referred to the density of air and can be calculated according to ... 

In the ideal case, the relative vapor density is temperature independent. Relative... 

Relative density (water-1) 0.98 Relative vapor density (air-1) 3.S Relative density at 20 C of saturated mixture vapor/air(air-1) 1.03 Vapor pressure, mm Hg at 20 C 7.1 Solubirityinwater.g/IOOmI 16 Explosive limits, vol% incur 7-7 Rslativa molecular mass 100.1 LogPoetanol/water 2.1 Qrossformuia TLV-TWA not available ... 

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