Fractionated volatilization

As a result of volatilization, significantly elevated indoor air levels of trichloroethylene can occur in homes that use water supplies contaminated with trichloroethylene (Andelman 1985a). The transfer of trichloroethylene from shower water to air in one study had a mean efficiency of 61% which was independent of water temperature (McKone and Knezovich 1991). The study authors concluded that showering for 10 minutes in water contaminated with trichloroethylene could result in a daily exposure by inhalation comparable to that expected by drinking contaminated tap water. Another study using a model shower system found that, in addition to shower spray, shower water collecting around the drain could be an important source of volatilized trichloroethylene, and the fraction volatilized could be affected by spray drop size and flow rate (Giardino et al. 1992). 

Determination of the various elements collected in the cryogenic trap can be done by fractional volatilization followed by AAS24. 

Statistical Results from the Analysis Methods. Continuous time vs. relative intensity curves were made spectrometrically for each of 11 elements in seven different coal ash samples. The results showed that peak intensities for all the elements in each sample were generally reached between 50 and 60 sec after initiation of the arc. This behavior helps to explain why using iron as the variable internal standard was successful for the normally wide range of volatilities represented. The large dilution factor involved or a possible carrier distillation effect of barium nitrate might explain the almost complete absence of fractional volatilization. 

Electric power loss Accumulation of noncondensibles Failure of automatic controls Loss of heat in series fractionation Volatile material entering system Heat exchanger tube failure... 

The volatile fraction is also defined by the measurement technique. As covered in the section on the determination of the dissolved fraction, the methods used for removing carbonate carbon must result in the loss of some fraction of the organic material present. This fraction is customarily considered as the volatile fraction, and it is different if it is lost by acidification and evaporation at 60 °C or by acidification followed by freeze-drying. In any case, the volatile fraction is not the fraction volatile at normal surface ocean temperature and pH but rather the fraction volatile at a pH low enough to permit the carbonate removal. In our laboratory, hydrocarbons, ethers, aldehydes, ketones, and some alcohols and acids can be removed by these techniques. 

The heat conductance through the sample and in the plasma is responsible for the fact that with the Nd YAG lasers available today, the crater diameters are still much wider than the values determined by the diffraction limitations. When using conventional lasers with pulses in the ns and ps range the plasma shields the radiation, whereas with the femtosecond lasers that are now available a free expanding plasma is obtained, where the heating of the plasma appears to be less supplemented by the laser radiation. This leads to less fractionated volatilization of the solid sample and differences in crater shape, which need to be investigated further [229]. 

Guyot B., Cros E. and Vincent J.C. (1982) Caracterisation et identification des composes de la fraction volatile d un cafe vert arabica ain et d un cafe vert arabica puant. Cafe, Cacao, The 26, 279-90. 

Characterization of Volatile Fraction. Volatile organic compounds found in oily wastewaters consist primarily of lower-molecular-weight aliphatic and aromatic hydrocarbons. Because of its relatively high vapor pressure, this fraction is quite often lost during analysis of oily wastes. For this reason a separate procedural step was incorporated into the overall scheme for analysis of the volatile fraction. An unfiltered sample of oily waste is used in this determination. The volatile fraction is separated from water by means of nitrogen sparging and collected in an activated carbon absorption column. The collected compounds are desorbed into carbon disulfide and analyzed by GC. 

The kinetics of volatilization of polymers have been discussed in detail by Doyle (71, 84). If w is the apparent residual mass fraction calculated on the initial mass, the apparent mass fraction volatilized, v. is... 

For a particular volatilization step, however, the appropriate residua) mass fraction is the true one, h, calculated on the total fraction volatilized during the step, rather than on the total initial mass... 

Pyrolysis-gas chromatography-mass spectrometry (PY/GC/MS) of the asphaltenes was achieved in the manner described elsewhere (14). The amount of the asphaltene fraction volatilized was determined by weighing the pyrolysis tubes after a sequence of experiments. 

EDPE/EVAc> 2 RT Argon X 100-160 k Gel fraction, volatile products, tensile strength, elongation at break. Shore ED hardness. Young s modulus, aging, crystallinity 20... 

Heavy fraction volatile at the pyrolysis tern -perature and nonvolatile at room temperature Total amount Volatiles in the sample, o]o... 

Heavy fractions volatile at the pyrolysis temperature and nonvolatile at room temperature 75 49.9 59.6 37.6... 

Variants of TVA are differential condensation TVA [903] and sub-ambient TVA or SATVA [910, 938]. In SATVA the condensable gases and volatile liquids are further fractionated volatile components are collected in gas cells and less volatile liquid fractions are separated and characterised by GC-MS. SATVA consists in the slow, controlled, distillation of the volatile products from the -196°C trap (where they have been collected) as it is heated up to room temperature. As they distil, MS or IR identifies the volatiles and at the same time they are collected in narrow fractions for further analysis. Continuous pressure monitoring during distillation is recorded as a SATVA curve [939]. McGill et al [940,941] have indicated that the very simple technique of trap-to-trap distillation of trace amounts of liquid-nitrogen condensable volatiles can be used for qualitative... 

TVA has been used mainly for the study of the basic degradation patterns of depolymerisation [910,942]. McNeill et al. [949] have studied thermal degradation of PS and PS/IDBPby means of TVA, SATVA and GC-MS. In the presence of 4,4 -isopropylidene-bis-(2,6-dibromophenol) (IDBP), the main products were similar, except for propiophe-none and phenylpropanoyl bromide in the presence of IDBP. Similarly, TG and TVA have been used to study the thermal stabilities of PET, PBT and PDMT [950]. In this case, the amounts of the main product fractions (residue, cold ring fraction, volatile products) have been determined quantitatively and the various materials present in the volatile and cold ring fractions have been separated and identified. McNeill et al. [939] also fractionated PVC/DOP by... 

Dry mineral matter-free (dmmf) Data are expressed in percentage of the coal assumed to be free of both moisture and mineral matter. This theoretical term is mainly used for coal classification and implies that mineral matter has a solid (ash) and gaseous fraction (volatiles originating from clays, carbonates, and oxidation of FeS2, see also Table 3.2). 

H2, CO, CO2, H2O, furan, fiirancarboxyaldehyde, methyUurans, acetone, hydroxypropanone, butenal, butanone, butanedione, levoglucosan Fixed gases (not identified), pentene, acetaldehyde, furan, propionaldehyde, acetone, acrolein, 2-methyUuran, butyraldehyde, methyl ethyl ketone, benzene, 2,5-dimethylfiiran, methyl vinyl ketone, 2,3-butanedione, toluene, crotonaldehyde, H2O, cyclopentanone, cyclooctatetraene, acetol, pyruvaldehyde, acetic add, furfural, formic acid, 5-methyl-2-furfural, furfuryl alcohol, butyrolactone, 2-hydroxy-3-methyl-3-cyclopenten-2-one, phenol, o-cresol, m-cresol, p-cresol, 2,5-dimethylphenol, 3,4-diinetfaylphenol, 5-hydroxymefhylfuifural Mainly H2O and CO 2, smaller amounts of CO, formaldehyde, methanol, acetic acid, ethanol and acetaldehyde, and very htUe tar Product fraction volatile at 25°C contains acetic acid, CO2, CO, CH4,... 

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