Benzoic acid vapor pressure

Selected physical properties of benzoic acid are given in Table 1, solubiHties in water in Table 2, solubiHties in various organic solvents in Table 3, and vapor pressures in Table 4. 

Colomina, M., Jimenez, P, Turrion, C. (1982) Vapor pressures and enthalpies of sublimation of naphthalene and benzoic acid. J. Chem. Thermodynamics 14, 779-784. 

Fig. 34. Vapor pressure of benzoic acid measured on a thermobalance with Knudsen effusion cell...

The observed ambient organic aerosol formation rates are also consistent with those estimated by extrapolation of smog-chamber kinetic data. Other heavy unsaturates, such as styrene and indene, are present in the atmosphere and may contribute, in part, to the formation of benzoic acid and homophthalic acid, respectively. Diesel exhaust and industrial emission are possible sources of such heavy unsaturates. Diolefins of C6+ are not present in gasolines and exhaust gases and have not been found in the atmosphere, and their possible role as precursors of the Cs-7 difiinctional acidic compounds is seriously challenged. Lower diolefins are emitted in automobile exhaust. Examination of vapor-pressure data indicates that the bulk of their expected photooxidation products remains in the gas phase, including most of the less volatile C3-4 dicarboxylic acids. 

Photolytic. A n-hexane solution containing /n-xylene and spread as a thin film (4 mm) on cold water (10 °C) was irradiated by a mercury medium pressure lamp. In 3 h, 18.5% of the p-xylene photooxidized into p-methylbenzaldehyde, p-benzyl alcohol, p-benzoic acid, and p-methylacetophenone (Moza and Feicht, 1989). Glyoxal and methylglyoxal were produced from the photooxidation of p-xylene by OH radicals in air at 25 °C (Tuazon et al., 1986a). The rate constant for the reaction of p-xylene and OH radicals at room temperature was 1.22 x lO " cmVmolecule-sec (Hansen et al., 1975). A rate constant of 7.45 x 10 L/molecule-sec was reported for the reaction of p-xylene with OH radicals in the gas phase (Darnall et al, 1976). Similarly, a room temperature rate constant of 1.41 x 10 " cm /molecule-sec was reported for the vapor-phase reaction of p-xylene with OH radicals (Atkinson, 1985). At 25 °C, a rate constant of 1.29 x lO " cmVmolecule-sec was reported for the same reaction (Ohta and Ohyama, 1985). 

Soil. The major soil metabolite is 2,6-dichlorobenzamide which degrades to 2,6-dichloro-benzoic acid. The estimated half-lives ranged from 1 to 12 months (Hartley and Kidd, 1987). Under field conditions, dichlobenil persists from 2 to 12 months (Ashton and Monaco, 1991). The disappearance of dichlobenil from a hydrosol and pond water was primarily due to volatilization and biodegradation. The times required for 50 and 90% dissipation of the herbicide from a hydrosol were approximately 20 and 50 d, respectively (Rice et al., 1974). Dichlobenil has a high vapor pressure and volatilization should be an important process. Williams and Eagle (1979) found... 

Equation 10.27 is generally known as Freundlich equation. Equation 10.27 with concentration replaced by pressure was also used to describe the adsorption isotherms of gases on solids, suggesting the incorrect idea that adsorption from solution by a solid could be paralleled with gas or vapor adsorption on the same adsorbents. Whereas in some cases the restriction to dilute solutions was imposed by the solubility of solids (e.g., benzoic acid in water or stearic acid in benzene) it was not imposed on the investigation of mixtures of completely miscible liquids, e.g., acetic acid in water. 

Table 4. Saturated Vapor Pressure, p, of o- and />Hydrox benzoic Acids ...

A 0.750-g sample of solid benzoic acid, C7H6O2, was placed in a 0.500-L pressurized reaction vessel filled with 02 at 10.0 atm pressure and 25°C. The benzoic acid was burned completely to water and C02. What were the final mole fractions of C02 and H20 vapor in the resulting gas mixture brought to the initial temperature The vapor pressure of water at 25°C is 23.8 torr. Neglect both the volume occupied by nongaseous substances and the solubility of C02 in water. The water pressure in the gas phase cannot exceed the vapor pressure of water, so most of the water is condensed to the liquid. 

Reported vapor pressures of benzoic acid at various temperatures and the coefficients for the vapor pressure equations... 

FIGURE 13.1.2.1.2 Logarithm of vapor pressure versus reciprocal temperature for benzoic acid. 

H. Dohse and M. Dunkel. J. Chem. Soc. 1930, 2409-10. Vapor pressure, cryoscopy AH, Kf benzoic, acetic acids. 

Physical Properties Chloropicrin is a colorless oil, bp of 112°C, and mp of 69°C, with apungent, stinging odor that has been described as anise-like. Its vapor pressure is approximately 20 mm/Hg at 20°C, and its molecular mass is 164 (Redeman et al., 1948). This liquid has a density of 1.66 g/mL and a vapor density of 5.6 relative to that of air. PS has low solubility in water (approximately 2 g/L), but is quite soluble in typical organic solvents (chloroform, acetone, ethyl acetate, etc.). Chloropicrin dissolves a variety of organic compounds including, for example, benzoic acid and various resins. 

A number of studies have explored ways in which partial vapor pressures may be obtained using TGA data, thereby allowing both prediction of vapor pressure under a range of circumstances and calculation of the constants associated with the approaches described previously. In particular, Price and Hawkins (12) have argued that the rate of mass loss for vaporization and sublimation within a TGA should be a zero-order process, and hence should be constant for any given temperature, subject to the important condition that the available surface area also remains constant. This means that the value of v from Equation 6.4 should be easily calculated from the TGA data. If one performs this experiment for materials with known vapor pressure and temperature relationships (the authors used discs of acetamide, benzoic acid, benzophenone, and phenanthrene), then the constant k for the given set of TGA experimental conditions may be found. Once this parameter is known, the vapor pressure may be assessed for an unknown material in the same manner. 

The small amount of benzoic acid that forms with the phthalic anhydride during the oxidation of naphthalene represents a waste when not recovered. Methods have been proposed for the separation of the two acids which depend on differences in solubility and vapor pressure. Thus, an aqueous dispersion of the two acids is subjected to the leaching action of a solvent for the benzoic acid, such as gasoline or benzene. The solvent is subsequently separated from the water layer and the acids recovered... 

The determination of the vapor pressure of various compounds was reviewed by Wiedemann (49). He discussed the determination of vapor pressure by TG techniques based on the Knudsen effusion method. The sample holder that was employed is illustrated in Chapter 3 (Figure 3.6). For some measurements, a Pyrex glass cell having a diameter of about 15 mm was used. Four organic compounds were studied p-chlorophenyl-AT. Af-dimethyl urea (Monuron. a herbicide), p-phenacetin, anthracene, and benzoic acid, in the temperature range of 250-400 K. The vapor-pressure curves of these compounds, in the range from 0 10 Torr, are shown in Figure 4.49. The AHs values calculated were Monuron. 27.4 p-phenacetin 27.6 anthracene, 20.1 and benzoic acid. 20.7 kcalmole. 

Dehydration of homoallylic alcohols. 0-Cholesteryl thiobenzoate (1, X ,ax 256, 288, and 420 nm) on irradiation in cyclohexane with a medium-pressure mercury vapor lamp for 12 min. is converted into 3,5-cholestadiene (2) and thio-benzoic acid in quantitative yield. Similar irradiation of O-cholestanyl thiobenzoate results merely in rearrangement to the thiobenzoic acid S-ester hence the elimination reaction appears to require some conjugation in the transition state of the newly formed bond. ... 

The acid form of benzoic acid has a relahvely low melting point and high vapor pressure, and this is used in test (b). 

The specificity of the test comes from two properties of benzoic acid its chemical stability and its vapor pressure. Benzoic acid does not char when treated with concentrated sulfuric acid, as many organic substances do. One reference mentions, however, that heat should be applied carefully since charring will otherwise initiate. ... 

Marshal JS, Palmer WM (1948) The distribution of rain-drops with size. J Atmos Sci 5 165-166 Mircea M, Stefan S, Fuzzi S (2000) Precipitation scavenging coefficient influence of measured aerosol and raindrop size distributions. Atmos Environ 34 5169-5174 Monte MJS, Santos LMNBF, Fulem M, Fonseca IMS, Sousa CAD (2006) New static apparatus and vapor pressure of reference materials naphthalene, benzoic acid, benzophenone, and ferrocene. J Chem Eng Data 51 757-766... 

As crystalline drugs generally have very low vapor pressure at room temperature, almost no drugs noticeably sublime except for volatile drugs such as naphthalene. However, when the drugs are mixed with porous powder, the capillaries can provide a sink condition for the diffusion of the drug molecules in the mixture. The rate of diffusion of benzoic acid was calculated for a mixture of 50 mg benzoic acid and 950 mg CPG at 300 K. The diffusion equation... 

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