Determination of composition

Marin, D. Mendicuti, F. Polarographic Determination of Composition and Thermodynamic Stability Constant of a Complex Metal Ion, /. Chem. Educ. 1988, 65, 916-918. 

PECULIARITIES OF DETERMINATION OF COMPOSITION OF THE SOLID SOLUTIONS OF THE BIVALENT METALS HYDRATED DIPHOSPHATES... 

Questions of the analytic control of maintenance of the bivalent metals cations to their joint presence in materials of diverse fixing always were actual. A simultaneous presence in their composition of two cations with like descriptions makes analysis by sufficiently complicated process. Determination of composition still more complicates, if analyzed object is a solid solution, in which side by side with pair of cations (for example, Mg " -Co ", Mn -Co, Zn -Co ) attends diphosphate anion. Their analysis demands for individual approach to working of methods using to each concrete cations pair. 

The actual Russian standards allow presentation of hydrocarbon components of UGC as individual compounds only for C -C hydrocai bons. The rest is described as pseudo-compound C,, although its content may reach 60 % m/m. Apparently, the detailed determination of composition of hydrocarbons C, in UGC allows essentially to raise quality of both its processing and its record. The best method for the determination of heavy hydrocai bons is capillary gas chromatography. Typical approach is based on preliminary sepai ation of UGC samples to gaseous and liquid phases. 

In X-Ray Fluorescence (XRF), an X-ray beam is used to irradiate a specimen, and the emitted fluorescent X rays are analyzed with a crystal spectrometer and scintillation or proportional counter. The fluorescent radiation normally is diffracted by a crystal at different angles to separate the X-ray wavelengths and therefore to identify the elements concentrations are determined from the peak intensities. For thin films XRF intensity-composition-thickness equations derived from first principles are used for the precision determination of composition and thickness. This can be done also for each individual layer of multiple-layer films. 

The principle application of XRF thin-film analysis is in the simultaneous determination of composition and thickness. The technique has been used for the routine analysis of single-layer films since 1977 and multiple-layer films since 1986. Two main sources of publications in the fields are the annual volumes of Advances in X-Ray Analysis by Plenum Press, New York, and the Journal of X-Ray Spectrometry by Heyden and Sons, London. Typical examples on the analysis of single-layer films and multiple-layer films are used to illustrate the capabilities of the technique. 

Determination of Compositional Sequences. In the copolymerization of MMA and MAA or TBTM, compositional dyads and triads are generated. These sequences are determined by the relative concentration of monomers as well as by their relative reactivity. These compositional sequences characterize the material and allow predictions of activity based on structure by comparison with field tested polymers. 

Finally, NMR relaxometry has also been used in the determination of composition of meat and meat products. Correlations between relaxation parameters and fat content in minced meat and meat emulsions,115 117 protein content in fresh meat115,118 and moisture content in sausages119 have been demonstrated results from fat determinations are summarised in Table 3. 

Determination of compositions of melts segregated from peridotite using aggregates of diamond. Earth Planet. Sci. Letters, 114, 477-89. 

Asami, K. Hashimoto, K. Shimodaira, S. (1978) XPS determination of composition of alloy surfaces and surface oxides on mechanically polished iron chromium alloys. Corrosion Sci. 18 713-723... 

Ganguly J., Bhattacharya R.N., and Chakraborty S. (1988) Convolution effect in the determination of compositional profiles and diffusion coefficients by microprobe step scans. Am. Mineral. 73, 901-909. 

Since the polymer-filler interaction has direct consequence on the modulus, the derived function is subjected to validation by introducing the function in established models for determination of composite modulus. The IAF is introduced in the Guth-Gold, modified Guth-Gold, Halpin-Tsai and some variants of modified Halpin-Tsai equations to account for the contribution of the platelet-like filler to Young s modulus in PNCs. These equations have been plotted after the introduction of IAF into them. 

A most important and promising use of TLC in polymer chemistry is undoubtedly the determination of compositional distribution curves for statistical copolymers. 

Their examination procedures may be divided into two parts physical testing and chemical analysis. The former determines its value as an explosive from a purely physical standpoint, whereas the latter includes determination of composition and of certain physical characteristics having a direct relation to one of the ingredients of the explosive mixture... 

The metal/ligand ratios in the complexes listed in Table 2 are obviously related to the proportions of vertices, edges and faces of the various metal polyhedra. The charges of the metals and ligands need not balance in these compounds. There is, however, another set of complexes (MX)f or (RMXR )p with no net charge, where the thermodynamics of solvation rather than symmetry might appear to be the primary determinant of composition and structure. In these cages the structure must adapt to the fixed M/X ratio. 

In this section, we describe time-resolved, local in-situ measurements of chemical potentials /, ( , f) with solid galvanic cells. It seems as if the possibilities of this method have not yet been fully exploited. We note that the spatial resolution of the determination of composition is by far better than that of the chemical potential. The high spatial resolution is achieved by electron microbeam analysis, analytical transmission electron microscopy, and tunneling electron microscopy. Little progress, however, has been made in improving the spatial resolution of the determination of chemical potentials. The conventional application of solid galvanic cells in kinetics is completely analogous to the time-dependent (partial) pressure determination as explained in Section 16.2.2. Spatially resolved measurements are not possible in this way. 

One of the first breaks from traditional analytical chemistry was the addition of microchemical methods. These methods essentially extended macro-scale techniques so that lliey could be applied for determinations involving very small (milligram) quantities of samples. These methods required fully new approaches or extensive modifications of macroscale equipment. Consequently, the apparatus usually was sophisticated, relatively costly, and required, greater manipulative skills. Nevertheless, microchemical methods opened lip entirely new areas of research, making possible the determination of composition where the availability of samples, as in many areas of biochemistry, was confined to very small quantities. 

Identification of fulleranes by Raman spectroscopy and XRD is difficult due to complexity of obtained mixture. Precise determination of composition for white colored fullerane samples was performed using APPI FT-ICR mass spectrometry. 

The information includes location of double bonds In fatty acids, indentlficatlon of components in complex lipids, determination of compositions of anionic and cationic surfactants, and identification of long-chained alkyl substituents on phosphonium and ammonium ions. 

The chapters in this volume have been collected in order to chart a course toward a more holistic, thus more realistic, view of mineral reactivity than can be garnered from equilibrium modeling. Spectroscopies are the tools by which structure, dynamics, and reactivity can be most directly examined. Examples include numerous means of mineral spectroscopy applied to numerous ends, such as determination of composition, purify, interaction with energy, characterization of chemically and spectroscopically special (active) centers, and adsorbate interactions. Coverage of both spectroscopy and minerals is intended to be illustrative, not exhaustive. 

Another review [36] discusses the determination of composition and structure, including tacticity, branching and end groups for diene polymers with the help of IR spectroscopy. 

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