Vapor pressure definition

The preceding definition is applicable to other characteristics such as MON, vapor pressure and volatility characteristics such as E70 and El00. 

A heat of immersion may refer to the immersion of a clean solid surface, qs.imm. or to the immersion of a solid having an adsorbed film on the surface. If the immersion of this last is into liquid adsorbate, we then report qsv.imm if tbe adsorbed film is in equilibrium with the saturated vapor pressure of the adsorbate (i.e., the vapor pressure of the liquid adsorbate P ), we will write It follows from these definitions... 

A saturated aqueous solution in contact with an excess of a definite solid phase at a given temperature will maintain constant humidity in an enclosed space. Table 11.4 gives a number of salts suitable for this purpose. The aqueous tension (vapor pressure, in millimeters of Hg) of a solution at a given temperature is found by multiplying the decimal fraction of the humidity by the aqueous tension at 100 percent humidity for the specific temperature. For example, the aqueous tension of a saturated solution of NaCl at 20°C is 0.757 X 17.54 = 13.28 mmHg and at 80°C it is 0.764 X 355.1 = 271.3 mmHg. 

Acentric Factor The acentric facdor of a compound (co) is primarily a measure of the shape of a molecule, though it also measures a molecules polarity. It is calculated from the reduced vapor pressure (P ) at a reduced temperature of 0.7 by the definition, Eq. (2-23). 

This is the definition of /ci for temperature T and for a pressure equal to the vapor pressure of the pure solvent Pi ... 

Cavitation occurs in a rapidly moving fluid when there is a decrease in pressure in the fluid below its vapor pressure and the presence of such nucleating sources as minute foreign particles or definite gas bubbles. As a result, vapor bubble forms that continues to grow until it reaches a region of pressure... 

Vapor pressure, which is the tendency of a liquid to release vapors to the surrounding area, goes down as MW increases but goes up as temperatures rise. By definition, the more volatile a liquid, the higher its vapor pressure and the lower its boiling point. Examples are ... 

The activities of the various components 1,2,3. .. of an ideal solution are, according to the definition of an ideal solution, equal to their mole fractions Ni, N2,. . . . The activity, for present purposes, may be taken as the ratio of the partial pressure Pi of the constituent in the solution to the vapor pressure P of the pure constituent i in the liquid state at the same temperature. Although few solutions conform even approximately to ideal behavior at all concentrations, it may be shown that the activity of the solvent must converge to its mole fraction Ni as the concentration of the solute(s) is made sufficiently small. According to the most elementary considerations, at sufficiently high dilutions the activity 2 of the solute must become proportional to its mole fraction, provided merely that it does not dissociate in solution. In other words, the escaping tendency of the solute must be proportional to the number of solute particles present in the solution, if the solution is sufficiently dilute. This assertion is equally plausible for monomeric and polymeric solutes, although the... 

Whenever the solute and solvent exhibit significant degrees of mutual attraction, deviations from the simple relationships will be observed. The properties of these nonideal solutions must be determined by the balance of attractive and disruptive forces. When a definite attraction can exist between the solute and solvent, the vapor pressure of each component is normally decreased. The overall vapor pressure of the system will then exhibit significant deviations from linearity in its concentration dependence, as is illustrated in Fig. 10B. 

The spectra in Figure 11.4 were recorded from headspace vapor either at room temperature (TNT, PETN) or elevated temperature (about 50°C for RDX). For TNT this corresponds to a saturated headspace vapor pressure of less than 10 ppb. At these levels strong signal is observed with relatively weak signal from room air. Explosives compounds that have been detected by the MS detector with high sensitivity include TNT, ADNT, DNT, NT, TNB, DNB, DMNB, RDX, HMX, EGDN, NG, PETN, and TATP. (see Explosive Definitions, page 329). 

Climatic Zone Definition Criteria [Mean Annual Temperatures Measured in Open Air (°C) and Mean Annual Partial Vapor Pressure (hPa)] Long-Term Testing Condition [Temperature (°C) and RH]... 

This relationship constitutes the basic definition of the activity. If the solution behaves ideally, a, =x, and Equation (18) define Raoult s law. Those four solution properties that we know as the colligative properties are all based on Equation (12) in each, solvent in solution is in equilibrium with pure solvent in another phase and has the same chemical potential in both phases. This can be solvent vapor in equilibrium with solvent in solution (as in vapor pressure lowering and boiling point elevation) or solvent in solution in equilibrium with pure, solid solvent (as in freezing point depression). Equation (12) also applies to osmotic equilibrium as shown in Figure 3.2. 

Nonflammable indicates that no flash point was observed by the ASTM test method D-3278-82 or D-56 below the boiling point of the solvent mixture or below 100°F, whichever is lower (this is the DOT, ANSI, and NFPA definition). The composition of liquid blends can vary from the originally supplied composition during use, owing to tile differing vapor pressures of the individual constituents. Care must be taken to avoid preferential loss of PFCs, which would result in flammable mixtures. 

In this study, a thermodynamic framework has been presented for the calculation of vapor-liquid equilibria for binary solvents containing nonvolatile salts. From an appropriate definition of a pseudobinary system, infinite dilution activity coefficients for the salt-containing system may be estimated from a knowledge of vapor pressure lowering, salt-free infinite dilution activity coefficients, and a single system-dependent constant. Parameters for the Wilson equation may be determined from the infinite dilution activity coefficients. 

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