Vapor pressure determinations

The equilibrium vapor pressure above a confined liquid depends only on temperature. The fraction of the total pressure exerted by vapor pressure determines the composition of the vapor-air mixture. Thus when the total pressure is reduced, for example at high elevations or in vacuum tmcks, the vapor concentration in air increases. Since flash points are reported at a... 

Equilibrium vapor pressure determination, Pu-noble metal... 

Knudsen effusion technique and equation, vapor pressure determination. 100-101... 

Vapor Pressure Determination using DSC", A. Brozens, R.B. Cassel, C.W. Schaumann R. Seyler, Proceeding. N. Am. Therm. Analysis Soc. 22nd Conf. Denver, Colo. (1993). 

The assumptions inherent in the derivation of the Hertz-Knudsen equation are (1) the vapor phase does not have a net motion (2) the bulk liquid temperature and corresponding vapor pressure determine the absolute rate of vaporization (3) the bulk vapor phase temperature and pressure determine the absolute rate of condensation (4) the gas-liquid interface is stationary and (5) the vapor phase acts as an ideal gas. The first assumption is rigorously valid only at equilibrium. For nonequilibrium conditions there will be a net motion of the vapor phase due to mass transfer across the vapor-liquid interface. The derivation of the expression for the absolute rate of condensation has been modified by Schrage (S2) to account for net motion in the vapor phase. The modified expression is... 

Nelson, O.A., Senseman, C.E. (1922) Vapor pressure determinations on naphthalene, anthracene, phenanthrene, and anthraquinone between their melting and boiling points. Ind. Eng. Chem. 14, 58-62. 

Power, W.H., Woodworth, C.L., Loughary, W.G. (1977) Vapor pressure determination by gas chromatography in the microtorr range-anthracene and triethylene glycol di-2-ethyl butyrate. J. Chromatogr. Sci. 15, 203-207. 

Wiedemann, H.G. (1972) Application of thermogravimetry for vapor pressure determination. Thermochim. Acta 3, 355-366. 

Prepared by the method of Lindsay and Allen, Org. Syntheses, Coll. Vol. 3,710 (1955). The phenyl azide used had b.p. 41-43°/5 mm., d 5 1.5567. The boiling point deviates slightly from that given by Lindsay and Allen, namely 49-50°/5 mm. however, it agrees fairly well with the other value given by these authors, namely 66-68°/21 mm., and with the values of Darapsky,2 and the vapor pressure determinations by Carothers,3 as shown by a plot of log p vs. 1 /T. 

Fig. 35. Data processing for thermogravimetric vapor pressure determination...

Table 5. Input of measured TG-data, processing for vapor pressure determination, output of results... 

Basically, the vapor pressure determination involves the measurement of the saturation concentration or pressure of the solute in a gas phase [37-45]. It can... 

K, there is a significant increase in pressure and values of 30 bar (or higher) were recorded. Assuming that the water-R-22 interface temperature had to attain the superheat-limit value before an explosion occurred, these data are in remarkable agreement with in Table XVI. Also shown in Fig. 11 is the vapor pressure of R-22 calculated for the interface temperature between the water and the saturated R-22 (232 K). Essentially all measured pressures fall below this curve, and this suggests that the maximum pressure transient corresponds to the vapor pressure determined in this manner. (Another limit could be chosen as the critical pressure of R-22, 50 bars, but this value significantly exceeds any measured pressure.)... 

X 10 " at 25 °C (extrapolated from vapor pressures determined at higher temperatures, Pupp et ah, 1974)... 

Rothman. A.M. Low vapor pressure determination by the radiotracer transpiration method. Anal. Chem., 28(6) 1225-1228. 1980. 

That characteristic of a chemical called vapor pressure determines the quantity of that chemical that can be contained in a specific volume of air at a given temperature and pressure. Vapor pressures of the explosive chemicals of interest are strong functions of temperature. See Chapter 2. In fact, it has been shown [10] that, for the entire temperature range of interest, the vapor pressure of DNT is about 20 times that of TNT, but that the vapor pressures of both show similar temperature dependence. The vapor pressure of each increases by about a factor of 4 for each decade increase in temperature, from about 5°C to about 50°C. 

Physical Properties. The size, molecular weight, and vapor pressure determine the pore size necessary to trap and release a substance efficiently. Large molecules such as pesticides cannot be collected and recovered on molecular sieves nor will small molecules like gaseous hydrocarbons be retained well by porous polymers. 

There is considerable evidence, based on various physical measurements, that sugar-cation complexes exist in solution. Among these methods, reviewed extensively by Rendleman (I), are solubility, optical rotation, vapor pressure determination, and most importantly, electrophoresis. Whereas the sum total of this evidence establishes that at least... 

Li, X.-W, Shibata, E., Kasai, E., Nakamura, T. (2002) Vapor pressure determination for dibenzo-p-dioxin, dibenzofuran, octachlo-rodibenzo-p-dioxin and octachlorodibenzofuran using a Knudsen effiision method. Mater. Transact. 43, 2903-2907. 

Rordorf, B.F., Sama, L.P, Webster, G.R.B. (1986b) Vapor pressure determination for several polychlorodioxins by two gas saturation methods. Chemosphere 15, 2073-2076. 

Weber, J.B., Shea, P.J., Strek, H.J. (1980) An evaluation of nonpoint sources of pesticide pollution in runoff. In Environmental Impact of Nonpoint Source Pollution. Overcash, M., Davidson, J., Editors, Ann Arbor Science Publishers, Ann Arbor, Michigan. Wiedemann, H.G. (1972) Applications of thermogravimetry of vapor pressure determination. Thermochim. Acta 3, 355-366. Weidner, C.W. (1974) Degradation in ground water and mobility of herbicides. Report prepared for the Office of Water Research and Technology, U.S. Environmental Protection Agency, Washington DC. PB 239242. 

Rose, F L., Mclntire, C.D. (1970) Accumulation of dieldrin by benthic algae in laboratory streams. Hydrobiologia 35, 481. Rothman, A.M. (1980) Low vapor pressure determination by the radiotracer transpiration method. 7. Agric. Food Chem. 28,1225-1228. Ruelle, R, Kesselring, U.W. (1997) Aqueous solubility prediction of environmentally important chemicals from the mobile order thermodynamics. Chemosphere 34(2), 275-298. 

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