Hydrocarbons defined

Aranow, Witten and Andrews (1958) have considered the entropy of fusion of long chain hydrocarbons defined by the equation... 

Diesel fuels are complex mixtures of hydrocarbons defined by physical and chemical properties. Petroleum diesel fuels are based on molecules with 9 to 20 carbon atoms and a boiling range between 170°C and 350°C (10). These fuels are produced by sequential chemical treatments and refining of heavy petroleum oils followed by distillation. In general, specifications for fuels are inclusive so as not to exclude compositions with similar operational characteristics. However, environmental concerns regarding toxic emissions from diesel engines have led to legislation that has forced manufacturers to modify diesel fuel chemistry (11). 

My friend Leszek Stolarczyk remarked on still another kind of symmeby in chemistry (in an impublished paper). Namely, the alternant hydrocarbons, defined in the Hueckel theory, despite the fact that they often do not have any spatial sjfmmetry at aU, have a S)mimetric energy level pattern with respect to a reference energy. We meet the same feature in the Dirac theory, if the electronic and positmiic levels are considered. This suggests a underlying, not yet known, internal reason common to the alternant hydrocarbons as viewed in the Hueckel theory and the Dirac model, which seems to be related somehow to the notion of supersymmetry. 

There are several fundamental type-hydrocarbons, defined by the substituents at C-atoms 10, 13 and 17 and latterly, according to the 1989 nomenclatural recommendations, at C24 (Table). Each of these hydrocarbon types is divided into two sub-types on the basis of the way in which adjacent rings are fused to each other. There are two possible methods of fusion... 

There are several criteria used to define solvent power. Chemical analysis is ideal because it can indicate the proportion of hydrocarbons known to be good solvents in particular, the aromatics. 

In France, bitumen belong to a category of products called "hydrocarbon binders . They are defined and classified in the French Standard, NF T 65000. The hydrocarbon binders comprise ... 

Structural maps display the top (and sometimes the base) of the reservoir surface below the datum level. The depth values are always true vertical sub sea. One could say that the contours of structure maps provide a picture of the subsurface topography. They display the shape and extent of a hydrocarbon accumulation and indicate the dip and strike of the structure. The dip is defined as the angle of a plane with the horizontal, and Is perpendicular to the strike, which runs along the plane. 

The resistivity log can also be used to define oil / water or gas / water contacts. Figure 5.53 shows that the fluid contact can be defined as the point at which the resistivity begins to increase in the reservoir interval, inferring the presence of hydrocarbons above that point. 

Recall that the recovery factor (RF) defines the relationship between the hydrocarbons initially in place (HCIIP) and the ultimate recovery for the field. 

The economic lifetime was introduced in Section 13.3, and was defined as the point at which the annual cashflow turned permanently negative. This is the time at which income from production no longer exceeds the costs of production, and marks the point when decommissioning should occur, since it does not make economic sense to continue to run a loss-making venture. Technically, the production of hydrocarbons could continue beyond this point but only by accepting financial losses. There are two ways to defer decommissioning ... 

It has been pointed out [138] that algebraically equivalent expressions can be derived without invoking a surface solution model. Instead, surface excess as defined by the procedure of Gibbs is used, the dividing surface always being located so that the sum of the surface excess quantities equals a given constant value. This last is conveniently taken to be the maximum value of F. A somewhat related treatment was made by Handa and Mukeijee for the surface tension of mixtures of fluorocarbons and hydrocarbons [139]. 

We began this section with an inquiry into how to define the size of a polymer molecule. In addition to the molecular weight or the degree of polymerization, some linear dimension which characterizes the molecule could also be used for this purpose. For purposes of orientation, let us again consider a hydrocarbon molecule stretched out to its full length but without any bond distortion. There are several features to note about this situation ... 

Because of the wide variation in the composition of natural gas as it is recovered at the wellhead and because natural gas can be used over a wide range of hydrocarbon contents, any specification for natural gas is usually broadly defined. However, the natural gas obtained at the wellhead usually undergoes some type of treatment or processing prior to its use for safety, economic, or system and material compatibiUty reasons. 

Most hydrocarbon resins are composed of a mixture of monomers and are rather difficult to hiUy characterize on a molecular level. The characteristics of resins are typically defined by physical properties such as softening point, color, molecular weight, melt viscosity, and solubiHty parameter. These properties predict performance characteristics and are essential in designing resins for specific appHcations. Actual characterization techniques used to define the broad molecular properties of hydrocarbon resins are Fourier transform infrared spectroscopy (ftir), nuclear magnetic resonance spectroscopy (nmr), and differential scanning calorimetry (dsc). 

Natural Products. Various methods have been and continue to be employed to obtain useful materials from various parts of plants. Essences from plants are obtained by distillation (often with steam), direct expression (pressing), collection of exudates, enfleurage (extraction with fats or oils), and solvent extraction. Solvents used include typical chemical solvents such as alcohols and hydrocarbons. Liquid (supercritical) carbon dioxide has come into commercial use in the 1990s as an extractant to produce perfume materials. The principal forms of natural perfume ingredients are defined as follows the methods used to prepare them are described in somewhat general terms because they vary for each product and suppHer. This is a part of the industry that is governed as much by art as by science. 

Open-chain saturated hydrocarbons have the generic names alkanes and paraffins. In this article, terms such as hexanes, heptanes, and octanes are synonymous with C, C, and Cg alkanes, respectively, and do not refer to the straight chains of 6 carbons, 7 carbons, and 8 carbons, as defined in the lUPAC system. 

JSlonhydrocarbon and Oxygenated Solvents. Most kidustrial solvents that are not hydrocarbons are pure chemical compounds. As such, they have sharp boiling pokits and weU-defined properties. Specifications for these solvents focus mosdy on impurities such as water and other contaminants. This also means that a solvent from one manufacturer should perform the same as the same solvent from another manufacturer any differences are probably the result of impurities, stabiLker content, etc, rather than the properties of the overall solvent. 

Tar sand has been defined as sand saturated with a highly viscous cmde hydrocarbon material not recoverable in its natural state through a well by ordinary production methods (2—8). Technically the material should perhaps be called bituminous sand rather than tar sand because the hydrocarbon is bitumen, ie, a carbon disulfide-soluble oil. 

Asphalt [8052-42-4] is defined by the American Society for Testing and Materials (ASTM) (1) as a dark brown to black cementitious material in which the predominating constituents are bitumens that occur in nature or are obtained in petroleum processing. Bitumen is a generic term defined by ASTM as a class of black or dark-colored (soHd, semisoHd, or viscous) cementitious substances, natural or manufactured, composed principally of high molecular weight hydrocarbons, of which asphalts, tars, pitches, and asphaltites are typical. 

Bitumen Soluble in Carbon Disuffide (ASTMD4). Asphalt is defined as a mixture of hydrocarbons that are completely soluble in carbon disulfide. Trichloroethylene or 1,1,1-trichloroethane have been used in recent years as safer solvents for this purpose. The procedure for these and other solvents for asphalt with Htde or no mineral matter are described in ASTM D2042. 

Ground turbine fuels are not subject to the constraints of an aircraft operating at reduced pressures of altitude. The temperature of fuel in ground tanks varies over a limited range, eg, 10—30°C, and the vapor pressure is defined by a safety-handling factor such as flash point temperature. Volatile fuels such as naphtha (No. 0-GT) are normally stored in a ground tank equipped with a vapor recovery system to minimise losses and meet local air quaUty codes on hydrocarbons. 

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