Analytical techniques specific gravity

Hydrocarbon gases are amenable to analytical techniques, and there has been the tendency (and it remains) for the determination of both major constituents and trace constituents more than is the case with the heavier hydrocarbons. The complexity of the mixtures that are evident as the boiling point of petroleum fractions and petroleum products increases makes identification of many of the individual constituents difficult, if not impossible. In addition, methods have been developed for the determination of physical characteristics such as calorific value, specific gravity, and enthalpy from the analyses of mixed hydrocarbon gases, but the accuracy does suffer when compared with the data produced by methods for the direct determination of these properties. 

Polyurethanes are characterised by the conventional analytical and spectroscopic techniques in the same way as other polymers. The standard techniques used for detennining physical properties such as viscosity, specific gravity, drying time, hydroxyl value and isocyanate value (by butyl amine method) have been discussed in earUer chapters. Structural confirmation, molecular weight detennination, rheological behaviour and thermal characterisation are generally carried out by spectroscopic techniques such... 

The analytical chemistry of alcoholic beverages, of which the determination of ethanol is only one facet, continues to develop. However, several methods of analysis for ethanol are available and tradition, government legal requirements, and convenience, taken together or separately, usually govern the choice of method. These methods include (1) distillation and specific gravity measurement, (2) gas-liquid chromatography, (3) IR spectrometry, (4) headspace techniques, (5) enzyme methods, (6) chemical (colorimetric) methods, and (7) refractometry. These methods are now considered in turn. 

Figure 9 illustrates the deviations between experimental and predicted fraction properties. The differences in fraction yields (TBP) are well within the reproducibility of the method ASTM D2892. The rest of the properties of the fractions (specific gravity, sulfur and kinematic viscosity) also present differences close to the accuracy of their analytical techniques, if we consider the propagation of TBP reproducibility error to the physical properties. 

If T, the TBP temperature, can be expressed as a mathematical function of V, the integral may be evaluated analytically. More commonly, the integration is done based on some sort of curve fitting technique. Once the pseudocomponents are generated, their properties are estimated from correlations that are functions of the components boiling points and specific gravities. 

The specific fluidic system involved, while not the main topic of this entry, is closely linked to the detection system and warrants a brief explanation. Separation techniques such as CE and HPLC utilize channels or columns that pass a fluidic medium carrying the analytes of interest. Bulk flow is actuated using either gravity or pressure, in the case of LC, or electroosmotic forces, in the case of CE. Separation of analytes occurs due to physical or chemical interactions with what is incorporated into the column (a packing material that completely fills the column or is... 

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