Volatile constituents

The conversion of coal to gas on an industrial scale dates to the early nineteenth century (14). The gas, often referred to as manufactured gas, was produced in coke ovens or similar types of retorts by simply heating coal to vaporize the volatile constituents. Estimates based on modem data indicate that the gas mixture probably contained hydrogen (qv) (ca 50%), methane (ca 30%), carbon monoxide (qv) and carbon dioxide (qv) (ca 15%), and some inert material, such as nitrogen (qv), from which a heating value of approximately 20.5 MJ/m (550 Btu/fT) can be estimated (6). 

Amyris Oil. Obtained by steam distillation of the wood of y m hakamijera L., the so-called West Indian sandalwood which is indigenous to northern South America, Central America, and the West Indies, amyris oil [8015-65-4] is a pale yellow to brownish yellow viscous oil with a slightly oily-sweet and occasionally peppery balsamic woody note. It finds use as a blender and fixative for soap fragrances. The volatile constituents, which are primarily hydrocarbon and oxygenated sesquiterpenes, are shown in Table 22 and Figure 5 (63). 

B. D. Mookherjee and R. W. TrenMe, "Volatile Constituents of Tiacture of Tonquia Musk," paper presented at the FTIIth International Congress of Essential Oils, Oct. 12—17, 1980, Cannes, Grasse, France. 

Extraction. Traditionally tea leaf is extracted with hot water either in columns or ketdes (88,89), although continuous Hquid soHd-type extractors have also been employed. To maintain a relatively low water-to-leaf ratio and achieve full extraction (35—45%), a countercurrent system is commonly used. The volatile aroma components are vacuum-stripped from the extract (90) or steam-distilled from the leaf before extraction (91). The diluted aroma (volatile constituents) is typically concentrated by distillation and retained for davoring products. Technology has been developed to employ enzymatic treatments prior to extraction to increase the yield of soHds (92) and induce cold water solubiUty (93,94). 

Fig. 1. Residua are obtained by removal of the volatile constituents of the feedstock at atmospheric pressure or at reduced pressure and can be converted to...

Distillation (ASTMD402). Approximate amounts of volatile constituents are deterrnined by this test which is particulady appHcable to cutback asphalt and road oils. 

Substitution using non-irritant resins and constituents, or less hazardous or less volatile constituents. 

Air emissions from refineries include fugitive emissions of the volatile constituents in crude oil and its fractions, emissions from the burning of fuels in process heaters, and emissions from the various refinery processes themselves. Fugitive emissions occur throughout refmeries and arise from the thousands of potential fugitive emission sources such as valves, pumps, tanks, pressure relief valves, flanges, etc. 

R. M. Smith and M. D. Buifoi d, Optimization of supercritical fluid extraaion of volatile constituents from a model plant matrix , 7. Chromatogr. 600 175-181 (1992). 

Evolution or volatilisation methods depend essentially upon the removal of volatile constituents. This may be effected in several ways (1) by simple ignition... 

Similarly, the rate of evaporation of materials depends on the vapor pressure, p, of the volatile constituent, which in turn varies directly as its molar concentration and the temperature ... 

Diffusion of a reactive component or a volatile constituent into or out of a material is also a temperature dependent rate phenomenon, as ... 

The theoretical treatment which has been developed in Sections 10.2-10.4 relates to mass transfer within a single phase in which no discontinuities exist. In many important applications of mass transfer, however, material is transferred across a phase boundary. Thus, in distillation a vapour and liquid are brought into contact in the fractionating column and the more volatile material is transferred from the liquid to the vapour while the less volatile constituent is transferred in the opposite direction this is an example of equimolecular counterdiffusion. In gas absorption, the soluble gas diffuses to the surface, dissolves in the liquid, and then passes into the bulk of the liquid, and the carrier gas is not transferred. In both of these examples, one phase is a liquid and the other a gas. In liquid -liquid extraction however, a solute is transferred from one liquid solvent to another across a phase boundary, and in the dissolution of a crystal the solute is transferred from a solid to a liquid. 

The more volatile constituent is transferred under the action of a concentration gradient from the liquid to the interface where it evaporates and then is transferred into the vapour stream. The less volatile component is transferred in the opposite direction and, if tlie molar latent heats of the components are equal, equimolecular counterdiffusion takes place. 

The enantioconvergent biohydrolysis of sterically demanding trisubstituted oxiranes has also been reported [189,190]. For instance, the enantioconvergent hydrolysis of a trisubstituted rac-epoxide (Figure 6.70) was a key step in the chemoenzymatic synthesis of a volatile constituent of the beer aroma [190]. 

Me3SiCl 14 (2.5 mb) is added to a solution of 2 g /9-ketoester 1412 in 20 mb dry CHCI3. The solution is cooled with ice-water and HCl gas introduced until saturation occurs. After 16 h at room temperature the volatile constituents are removed in vacuo and the residue distilled in a Kugelrohr apparatus to give 1.7 g (93%) 1413 as a slightly yellowish oil, b.p. 95 °C/0.2 Torr [4] (Scheme 9.49). 

Graddon, A. D., Morrison, S. D., and Smith, J. F. (1979). Volatile constituents of some unifloral Australian honeys. /. Agric. Food Chem. 27,832-837. 

Distillation is a suitable technique for the isolation of volatile organic compounds from liquid samples or the soluble portion of solid samples [24,27-30]. The physical basis of separation depends on the distribution of constituents between the liquid mixture and the vapor in equilibrium with that mixture. The more volatile constituents are concentrated in the vapor phase, which is collected after condensation. The effectiveness of the separation is dependent on the physical properties of the... 

Applications Conventional GC is a workhorse in the qualitative and quantitative analysis of polymer additives in complex mixtures and has found numerous applications. Both GC and auxiliary techniques are particularly useful for characterisation of (semi)volatile constituents and additives ranging from gases to hydrocarbon waxes (fatty acids and their... 

Major types of volatile constituents in polymers include unreacted monomers, nonpolymerisable components of the original charge stock, residual polymerisation solvents, and water. Frequently, complex nonpolymerisable mixtures are present. The concentration of these substances may need to be determined for various reasons, such as the effects on materials properties and the risk of tainting in foodstuff- and beverage-packaging grades. For this purpose various GC methods are in regular use ... 

Volatile constituents in alfalfa and red clover extracts, in Flavors and Fragrances A World Perspective, Lawrence, B. M. et al., Eds., Conference. Washington, D.C., 16-20 Nov. 1986, Elsevier Science Publishers, Amsterdam, The Netherlands, 1988. 

---