Reporting Vapor-Pressure Data

Many handbooks have tables of vapor pressures, as do more detailed tables like the steam tables [1—4]. The values shown there are not direct experimental measurements. Instead, they are computed from equations that have been fitted to the experimental data. In the computer age we wish to represent the experimental data by equations that our computers can manipulate. There are some strong limits on the forms those equations can take, which we will see in Section 5.4. 

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Our tests led us to disbelieve the reported vapor pressure data. 

Cole and Taylor (3) determined the vapor pressures of NaB02(g) by a dynamic method with dry N2 as carrier gas. Their vapor pressure data were taken over a flow-rate range where the apparent vapor pressure Increased with decreasing flow rate, and the data were then extrapolated to zero flow rate. The vapor species of the sample was also assumed to be monomeric NaB02(g). JANAP 3rd law analyses of their reported vapor pressure data over the liquid NaB02 In the temperature range 1150 C-1350 C yield (298.15 K) = 75.37 3.32 kcal mol and the drift -20.6 cal K mol . (The 2nd law enthalpy of vaporization Is A apH (298.15 K) - 107 kcal mol ). Using the 3rd law (298.15 K), we obtain A H (298.15 K) = -154.1 4 kcal mol... 

The equilibrium pressures for the reaction NH Cl(cr) = NHg(g) + HCl(g), at 320-636 K, have been measured by many investigators. Smits and de Lange ( ), using the densi-tensimeter, determined the vapor pressure of NH Cl(cr) and the density of the saturated vapor simultaneously. The results obtained indicate that within the range 527-626 K the saturated vapor completely dissociates into gaseous NHg and HCl. Based on this conclusion, the reported vapor pressure data were employed to evaluate the enthalpy of dissociation of NH Cl(cr) by both the 2nd and 3rd law methods. The results are presented as follows. 

The vapor pressures of ZrF (cr) in the temperature range 617-1150 K were determined by many investigators using various methods. Based on the reported vapor pressure data, the corresponding heats of sublimation are evaluated by the 2nd and 3rd law methods. Using the 3rd law Ag j H(298.15 K) and AjH"(ZrF, cr, 298.15 K) = -456.8 kcal mol", the enthalpies of formation at 298.15 K for ZrF (g) are evaluated. The results are presented in the table below. The values of AjH"(ZrF, g, 298.15 K), listed in the last column of this table are in excellent agreement which indicate that the estimated missing vibrational frequencies and... 

Silva and Weber (1993) reported vapor pressure measurements for the 1-ch oro-l,l-Difluoroethane (RI42b) and 1,1 -Difluoroethane (R152a) refrigerants. The data are given in Tables 3.5 and 3.6 respectively. Use Antoine s equation to correlate the data for R142b and the following equation for R152a (Silva and Weber, 1993)... 

Fig. 31. Vapor pressure data for glycerol. The solid line represents Eq. (109) with the constants reported by Tang and Munkelwitz (1991).

He (liq.). Vapor pressure data were reported by Dana and Onnes,1,2 Keesom, Weber, and Ngaard,1 Keesom, Weber, and Schmidt,1 Onnes,1,2 Onnes and Weber,1,3 and Spangenberg.1 We have utilized the data of Dana and Onnes.1,2. 

Ne (liq.). Vapor pressure data for liquid neon were reported by Cath and Onnes,1 Crommelin,5 Onnes and Crommelin,2 Crommelin and Gibson,1 Clusius,1 Verschaffelt,2 and Mathias, Crommelin, and Onnes.3... 

V = —2.31 at the boiling point, —151.0°. Other vapor pressure data were reported by Ramsey,1, 3 Ramsey and Travers,1 and Patterson, Cripps, and Whytlaw-Gray.1... 

I2 (g). Vapor pressure data on solid iodine were reported by Baxter and Grose,1 Baxter, Hickey, and Holmes,1 and Ramsay and Young.1 Haber and Kerschbaum1 measured the vapor pressure at low temperatures. Giauque2 critically reviewed the data, and deduced for the heat of sublimation, Fs= —16.069+0.0040 ( +273.1), which gives at 18°, —14.91. Earlier calculations were made by Wohl,3 Dewar,1 and Nernst.1... 

I2 (liq.). Vapor pressure data for liquid iodine were reported by Ramsay and Young,1 Stelzner and Niedersehulte,1 and Rassow.1 These data yield for the heat of vaporization, V— —12.75 + 0.0056 ( +273.1). Combination of this equation with that for the heat of sublimation gives for the heat of fusion of solid iodine, F= —3.3+0.0016 ( +273.1), or —4.0 at the melting point. See also Rideal.1... 

I hr vap.tr pressures up to the fouling point arc reported in the literature for all four compounds, 1VH, MM" Vapor pressure data up to the critical point ate available for furan.,w IMF and dioxane. The method of Miller was... 

The critical properties have been experimentally measured for bromobenzcnc, chlorobenzene, and fluorobcn-Mnc s.s.iuj.w Lydcrsen s method wus used U calculate the critical properties of benzyl chloride 1 Literature data arc reported for the vnpnr pressure ot bru-mobenzene, chlorobenzene, and fluorobcn/ertc up to the critical point, -1" 271 Stull has compiled the vapor pressure data on benzyl chloride up to its boiling point J Ashcroft pce cms data from 48T to I I C. 275 The vapor pressure above the boiling point was estimated ... 

Values of the heat of concentration and heat capacity of sea water near room temperature have been measured experimentally. The heat of concentration values compare favorably with those calculated from the vapor pressure data given by Arons and Kientzler by use of the Clapeyron equation. The heat capacity agrees with tne values reported by Cox and Smith. Calculated values for the heat of concentration and boiling point elevation from 77° to 302° F. at salinities up to 9% are presented in both tabular and graphical form. 

Sg (g), S6 (g), S2 (g). Sulfur gas is a mixture of S8 and its dissociation products. The gas in equilibrium with the liquid at 150° is practically all Sg. Vapor pressure data on liquid sulfur were reported by Ruff and Graf,1 Bodenstein,4 Gruener,1 and Mathies1 and these data were used by Preuner and Schupp1 to compute V = — 20.0150. The vapor pressure data of West and Menzies1 yield V — 20.5150. Awbery1 measured directly the heat of vaporization at the boiling point to be —202. 

S02 (liq.). Vapor pressure data were reported by Faraday,3 Young,2 Cardoso and Fiorentino,1 Henning and Stock,1 Mund,1, Mills,1 Bergstrom,2- 8 Burrell and Robertson,1 Regnault,7 Pictet,1 and Blumcke.1 See also Antione.8 The heat of vaporization of liquid sulfur dioxide was measured directly by Eucken,2-8 Estreicher and Schneer,1 Chappuis,2 Estreicher,2 Mathias,1 Schneer,1 Cailletet and Mathias,1- 2 and Smith.1 The last named found V= — 6.07 10. 

S02 (c). Vapor pressure data on solid and liquid sulfur dioxide were reported by Bergstrom,2- 8 Burrell and Robertson,1 and Steele and Bagster.1 These data yield for the heats of sublimation and vaporization of the solid and liquid near the melting point, —8.56 and —6.64, respectively whence F- —1.9 at the melting point. 

SOCl2 (g). Ogier6-7 reported —6.5 for the heat of vaporization of the liquid Arii,8 from vapor pressure data, deduced the value —7.56. 

N2Ob (g). Berthelot9 reported the heat of sublimation of solid nitrogen pentoxide to be —13.2. The vapor pressure data of Daniels and Bright1 yield —13.8. 

PC13 (g). Antoine2,3 and Andrews14 found the heat of vaporization of liquid PC13 to be —6.9 and —7.1, respectively. Vapor pressure data were reported by Regnault.4, 7. 

CO (liq.). Vapor pressure data on liquid carbon monoxide were reported by Olszewsky,7 8 Wroblewsky,1 5 2 Baly and Donnan,1 Clusius and Teske,1 Hoppel,1 Verschoyle,1 Crommelin, Bijleveld, and Brown,1 and Clayton and Giauque.1 The calorimetric data on the heat of vaporization of liquid carbon monoxide are Eucken,2 3 —1.414 at —190° Clayton and Giauque,1 —1.444 at —191.5°. 

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