Vapor pressure determination methods

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. 

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

Determination of Molecular Weight. The number average molecular weight (TEi) was measured by the vapor pressure equilibrium method with a Hitachi Molecular Weight apparatus (Model 117). 

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... 

For a measure of amount of water relevant to stability concerns, vapor pressure, or its related thermodynamic parameters, is more relevant. Determination of vapor pressure uses methods developed from thermodynamic roots, though if the product is not at true equilibrium, the measured quantity is not a thermodynamic descriptor of the product, although it is still a measure of a product characteristic. Water mobilities are often inferred from spectroscopic measurements of relaxational phenomena. Many workers attempt to identify different classes of water characteristic of different ranges of water content and water partial vapor pressure. Spectroscopic measurements, too, are often interpreted in terms of populations of water molecules with similar characteristics. 

The isopiestic (isothermal distillation) method for the determination of molecular weights is closely related to the vapor pressure depression method.10 A weighed amount of standard is introduced into one leg of an apparatus and a weighed portion of the unknown is placed in the other leg. Solvent is introduced into the apparatus, which is then evacuated and thermostated. The solvent will distill from one solution to the other until the vapor pressures (and therefore mole fractions) of the two have equalized. If the solutions are ideal, or if the deviations from ideality are similar, equilibrium will occur when the mole fraction of the known equals that of the unknown. 

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. 

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. 

The inspection assay tests discussed above are not exhaustive but are the ones most commonly used and provide data on the impurities present as well as a general idea of the products that may be recoverable. Other properties that are determined on an as-needed basis include, but are not limited to, the following (1) vapor pressure (Reid method) (ASTM D-323, IP 69, IP 402), (2) total add number (ASTM D-664, IP 177), and chloride content (ASTM D-4929, IP 244). 

Adonyi (50) developed a method in which the Derivatograph could be used for vapor-pressure determinations. The method is similar to that discussed by Ashcroft (48). 

DIN EN 12-93. Petroleum products. Determination of Reid vapor pressure. Wet method. 

ISO 3007-99. Petroleum products and crude petroleum - Determination of vapor pressure - Reid method. ASTM D 2879-96. Standard test method for vapor pressure-temperature relationship and initial... 

Miscellaneous methods. Some other techniques, such as dielectric constant measurements , conductimetry , mass spectrometry , and electronic spectroscopy are used less frequently but can also be useful. Change in vapor pressure determined with a manometric device can be used when the reaction mixture contains a volatile compound such as ethylene oxide... 

This test method covers the determination by means of a glass hydrometer of the API gravity of crude petroleum and petroleum products normally handled as liquids and having a Reid vapor pressure (Test Method D 323) of 26 psi (180 kPa) or less. Gravities are determined at 60 F (15.56 C), or converted to values at 60 F, by means of standard tables. These tables are not applicable to nonhydrocarbons or essentially pure hydrocarbons such as the aromatics. 

Tbe ASTM D 323 standard describes a method for determining the vapor pressure employing two chambers, A and B the volume of chamber A is four times that of chamber B. 

Various methods are available for estimation of the normal boiling point of organic compounds. Lyman et al. review and give calcula-tional procedures for the methods of Meissner, Miller, and Lydersen/ Forman-Thodos. A more recent method that has been determined to be more accurate is the method of Pailhes, which reqmres one experimental vapor pressure point and Lydersen group contributions for critical temperature and critical pressure (Table 2-385). 

Table 8-10 gives pertinent data for the Menschutkin reaction of triethylamine with ethyl iodide. These reactant molecules are volatile, so their transfer free energies were determined by a gas chromatographic variation of the vapor pressure method. For this reaction Eq. (8-57) is written... 

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