Composition determinative curves

The spectra illustrated in fig. 5.15 show that absorption maxima of all spin-allowed CF bands move to longer wavelengths with increasing iron content of the orthopyroxene, forming the basis of composition determinative curves (Hazen et al., 1977b Adams, 1974) and enabling this pyroxene structure-type to be identified in telescopic reflectance spectra of surfaces of the Moon (Pieters etal., 1985 Bums, 1989a). 

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

In order to validate the HPLC method, three separate determinations of the standard curve were performed. The data collected for each amount for all three curves (i.e. nine data points per amount) were averaged and replotted to yield a composite standard curve for salvinorin A. 

Polymerization Results. A batch polymerization of MMA-MAA comonomer was analyzed for the determination of the reactivity ratios of the two monomers. The change in the ratio of the copolymer composition determined by GC was plotted against conversion as shown in Figure 1. Similarly, the calculated curves for some assumed reactivity ratios are also shown in the same Figure. The optimum values of the reactivity ratio for the emulsion poly-... 

In order to determine the extent of propagation of this correlated motion, the T s of hexadecanediol were obtained (Table VIII). The results indicate that the motional characteristics responsible for field dependent relaxation are present to C-16 at 75°. This behavior disappears between 80° and 95°. Although it is desirable to extend these measurements to longer alkyl chains, even for HDD, resolution of C-5 through Cn 3 is not possible, and only composite relaxation curves are obtained. 

Figure 10.5. The 1 pm versus 2 pm pyroxene spectral determinative curve widely used to identify compositions and structure-types of pyroxenes on planetary surfaces (from Adams, 1974). Circles refer to room-temperature data. Numbered squares (orthopyroxene En86Fs14) and triangles (clinopyroxene Wo42En51Fs7) represent spectral data obtained at the temperatures (1) 80 K (2) 173 K (3) 273 K (4) 373 K and (5) 448 K (modified from Singer Roush, 1985).

The contrasting temperature-induced shifts of the pyroxene 1 and 2 pm bands could lead to erroneous estimates of the composition and, to a lesser extent, structure-type of a pyroxene-bearing mineral assemblage deduced from the remote-sensed reflectance spectrum of a hot or cold planetary surface if room-temperature determinative curves, such as that shown in fig. 10.5, are used uncritically. For example, remote-sensed spectra of planets with hot surfaces, such as Mercury and the Moon, would lead to overestimates of Fe2+ contents of the orthopyroxenes and underestimated Fe2+ contents of the clinopyroxenes (Singer and Roush, 1985). Planets with cold surfaces, such as Mars and the asteroids, could produce opposite results. On the other hand, the room-temperature data underlying the pyroxene determinative curve shown in fig. 10.5 may impose constraints on the compositions of pyroxenes deduced from telescopic spectra of a planet with very high surface temperatures, such as Mercury. 

Despite these successes, important process parameters, like bath agitation, bath constituents and particle type are disregarded. The constants k, 0 and B inherently account for these constants, but they have to be determined separately for every set of process parameters. Moreover, the postulated current density dependence of the particle deposition rate, that is Eq. (2), is not correct. A peak in the current density against the particle composite content curve, as often observed (Section III.3.H), can not be described. The fact that the peak is often accompanied by a kink in the polarization curve indicates that also the metal deposition behavior can not be accounted for by the Tafel equation (Eq. 4). Likewise, the (1-0 term in this equation signifies a polarization of the metal deposition reaction, whereas frequently the opposite is observed (Section 111.3,(0 It can be concluded that Guglielmi s mechanism... 

This composite calibration curve for seawater demonstrates the applicability of the cold-trap pre-concentration technique to low concentration ranges of mercury. Approximately 0.2 ng of mercury can be determined with a 25x scale expansion. Since the response depends on the vaporization and elution of trapped mercury from the column, the calibration curves were similar for other aqueous media including acidified (nitric acid) distilled deionized water. Therefore, this cold-trap procedure appears to separate effectively reducible mercury species from interfering substances that might be associated with differing solution matrices. 

To complete the construction of the Y-X diagram from simulation results, the feed line must be drawn. The intersection with the diagonal of a straight line drawn through the feed composition determines one point on the q-line. One other point is determined by the feed equilibrium vapor and liquid compositions at the feed tray conditions. If the feed is a saturated liquid, the equilibrium liquid composition is the same as the feed composition, and the equilibrium vapor composition is the bubble point composition on the equilibrium curve. In this case the q-line is vertical. For a saturated vapor feed, the equilibrium vapor composition is the same as the feed composition, the equilibrium liquid composition is the dew point composition, and the q-line is horizontal. For a mixed-phase feed, the c/ line slope is determined by the feed thermal condition (Section 5.2.2). Note that, for a multi-component mixture, the feed equilibrium vapor and liquid compositions from the simulation output may not lie exactly on the equilibrium curve because of the discrepancies resulting from lumping the light components in one pseudocomponent. 

The C02 sorption isobar measurement at ambient pressure yielded a monotonic desorption curve with a saturation point at approximately -80 °C. (Fig. 3.4.12(a)) The saturated quantity of 3.0 molecules per Rh2 unit at -80 °C agrees well with the composition determined from the single-crystal X-ray diffraction data at -180 °C (Figs. 3.4.11 and 3.4.12). The DSC measurements repeatedly revealed exo- and endothermic phase transitions in a C02 atmosphere. (Fig. 3.4.12(b)) The temperatures where the sets of cyclic DSC peaks occur shift to lower values as the concentration of C02 (partial pressure) decreases, demonstrating that the observed crystal phase transition is gas-adsorption induced. The estimated value indicates that the a crystal can include no more than one C02 molecule under the current a-saturation condition and subsequently transforms to the inclusion crystal, which can include up to three C02 molecules per Rh2 unit in the channels (Fig. 3.4.12(c)). 

Chu et al. [96] heated PS/PVME above 139°C for 30 min and quenched it at 0°C. Tip relaxation values of component polymers were observed through well-resolved peaks. By comparing these values to Tip of non-heated blends at various composition determined experimentally, they estimated the coexistent compositions at various heat-treatment temperatures and a LCST phase diagram was obtained. Asano et al. analyzed relaxation curves of PC/PMMA [92] and PS/PVME [52] by using Equation (10.9). 

A recent analytical study stresses the growing need, prompted partly by l islatory requirements, to differentiate polymorphs and to quantify polymorphic mixtures in pharmaceutical production [126]. The compounds benzil and benzoic add were chosen as a model system for the development of an XRD protocol which could be extended to the quantification of mixtures of drug polymorphs. The study involved the evaluation of sample thickness, the determination of preferred orientation effects, optimum milling conditions and the construction of diffraction intensity-composition calibration curves for mixtures of benzil and benzoic acid. Since the composition of such mixtures can be accurately determined by an independent method, namely HPLC, vaUdation of the quantification of mixtures by the XRD protocol was possible. It was concluded that the protocol is accurate for the model system to within a few percent. It is desirable that the general validity of the approach suggested be tested on a range of real polymorphic systems. 

The crystal structure and chemical composition of curved micas have been studied in comparison with flat micas in glass-ceramics, both of which had the same composition as shown in Table 3-1. The flat crystals were formed at 1040°C and the curved ones at 960°C. The chemical composition of the crystals has been determined with electron microprobe analyses (Holand et al., 1983). 

In a binary mixture, if two of the loop curves intersect, i.e., if the vapor curve of one crosses the liquid curve of the other, then the two compositions determine a vapor-liquid equilibrium point. This is due to the fact that, for a binary system of two phases, the phase rule allows two degrees of freedom. However, the value may not be unique, t.e., in the higher pressure region, particularly very near the critical, it is possible for a given vapor to have two possible equilibrium liquids of different compositions. These two conditions can be at the... 

In deterrrrirration of phase diagrams, the binodal curves, which permit to establish concerrtration range of phase separation, are considerably better docrrmented than the eqrrilibrittm ctrrves (tie-line compositions). This results from the fact that analytical procedures to obtain binodal points are less complicated than those used to determine the equihbrium compositions. Binodal curves and tie-line compositions were represented with various different correlations having two or three adjustable parameters [202-209]. 

The functional relationship of composition and pressure has in it all the information about a solid-gas reaction - deciphering it, however, may be a problem. The solid consists of a three-dimensional array of atoms. At equilibrium at any composition there will be a certain deployment of species characteristic of the solid and the locus of these equilibrium states determines the composition-pressure curve. A phase of variable composition will have defects present at varying concentration and the nature of the defects themselves will be a function of their concentration. All this will be revealed in the functional relationship of temperature, pressure and composition. 

The data from temperature rising elution fractionation are obtained as a disfribution of polymer concentration as a function of elution temperature. These data ean be eonverted into a composition distribution curve if the relationship between braneh concentration and elution temperature is known. Such calibrations can be determined experimentally from well-defined narrow composition disfribution samples, or they can be calculated theoretieally [9]. A sehematic representation of a eomposition distribution plot is shown in Figure 4. 

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