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Effect-Dilution Average Ratio

Effect-Dilution Average Ratio Index (EDAR)... [Pg.237]

Dimensions Of Rings And Chains In DUute Solution By Small Angle Neutron Scattering. Theoretical predictions of the z-average mean-square radii of gyration (z,c=o) for flexible linear and cyclic polymers with the same number of skeletal bonds in dilute solution at the 6-point, which are unperturbed by excluded volume effects, predict a ratio of 2,c=o / = 2.0 [42] [43] [44] (where 1 refers to... [Pg.52]

An important criticism of the use of combustion trains is that combustion is not site specific, that is all atoms in the analyte end up in the gas transferred to the IRMS. For studies of carbon isotope effects this is invariably C02. The question is especially important for carbon isotope analysis because analyte molecules of interest usually contain several different kinds of carbon atoms and therefore combustion methods average or dilute the IE s of interest. Should site specific isotope ratios be required another method of sample preparation (usually much more tedious) is necessary. Combustion methods, however, are frequently used to study nitrogen and sulfur IE s because many organic molecules are singly substituted with these atoms. Obviously, oxygen isotope effects cannot be determined using combustion trains because external oxygen is employed. Rather some type of pyrolytic sample preparation is required. [Pg.222]

Fig. 10.8 Effect of fermentation on meadowfoam seed meal composition, in the absence (a) and presence of 10 mM FeS04 (b). Methods meadowfoam seed meal (12 g) and untreated meadowfoam seed (cv. Ross) were ground together in a ratio of 100 1 in a coffee grinder for 1 min. Ground mixture (10 g) was mixed with 30 mL of either water or 10 mM FeSOa, vortexed for 1 min, and sonicated for 1 min. At several time points after mixing, 0.1 mL ahquots of the liquid layer were taken and immediately diluted with 0.9 mL methanol, vortexed, centrifuged at 13,000 rpm for 10 min, and analyzed by HPLC as described in Fig. 10.7. Data points represent averages of duplicate incubations... Fig. 10.8 Effect of fermentation on meadowfoam seed meal composition, in the absence (a) and presence of 10 mM FeS04 (b). Methods meadowfoam seed meal (12 g) and untreated meadowfoam seed (cv. Ross) were ground together in a ratio of 100 1 in a coffee grinder for 1 min. Ground mixture (10 g) was mixed with 30 mL of either water or 10 mM FeSOa, vortexed for 1 min, and sonicated for 1 min. At several time points after mixing, 0.1 mL ahquots of the liquid layer were taken and immediately diluted with 0.9 mL methanol, vortexed, centrifuged at 13,000 rpm for 10 min, and analyzed by HPLC as described in Fig. 10.7. Data points represent averages of duplicate incubations...
Table I summarizes comparisons between asphaltenes derived from bituminous coal liquefaction and those derived from petroleum crudes. The molecular size and atomic H/C ratios suggest a molecular profile quite different for the two asphaltenes. The ranges represent, as best as could be found, reasonable extremes for each of the properties. We are well aware that the number-average molecular weight of petroleum asphaltenes has been influenced by aggregate formation. To overcome this effect, molecular weight determinations should be made in dilute noninteracting solvents (e.g., methylene chloride), and solutions should be filtered or ultracentrifuged in helium-degassed solvents. Table I summarizes comparisons between asphaltenes derived from bituminous coal liquefaction and those derived from petroleum crudes. The molecular size and atomic H/C ratios suggest a molecular profile quite different for the two asphaltenes. The ranges represent, as best as could be found, reasonable extremes for each of the properties. We are well aware that the number-average molecular weight of petroleum asphaltenes has been influenced by aggregate formation. To overcome this effect, molecular weight determinations should be made in dilute noninteracting solvents (e.g., methylene chloride), and solutions should be filtered or ultracentrifuged in helium-degassed solvents.
In an experimental study of mixed iron-silica colloids we found the opposite phenomenon, stabilization of colloids of iron hydroxide by silica colloids, which is manifested very clearly in undialyzed iron hydroxide sols of average concentration with a ratio of Fe203 SiOj = 1 3. Colloidal iron in mixed solutions proved to be more resistant to the action of electrolytes than in isolated sols of iron hydroxide. Only colloidal silica shows any stabilizing effect on sols of iron hydroxide dilute solutions undersaturated with Si(OH)4 are not stabilizers. It is characteristic that colloidal silica is capable of stabilizing colloidal iron in the same pH ranges in which pure silica sols are stable in acid (pH < 4) and alkaline (pH > 8) environments. In slightly acid environments (pH = 5-6) iron-silica sols are unstable and decompose to form mixed sediments, which sometimes are not uniform due to different rates of coagulation and deposition. [Pg.134]

Effect of Sample Size on Response. The response of the dual detectors was checked for linearity by analyzing the vacuum gas oil sample at various dilutions. Results are presented in Table I. The data indicate that the response for both detectors is essentially linear over a 25-fold range in concentration. Over this range, the ratio of the response for the aromatics with respect to that for the saturates is constant for both detectors to within several percent average deviation. Also, these data... [Pg.298]

Here, the notation MW refers to the molecular weight of solute i and the effective average molecular weights of the extract and raffinate phases, as indicated by the subscripts. For dilute systems, K" IQ (MW a(r ,ai/MWearaa)- Fot theoretical stage or transfer unit calculations, often it is useful to express the partition ratio in terms of mass ratio coordinates introduced by Bancroft [Phys. Rev., 3(1), pp. 21-33 3(2), pp. 114-136 and 3(3), pp. 193-209 (1895)] ... [Pg.1708]

This semigrand partition function approach as phrased in the context of KB theory thus allows one to obtain average structural information from thermodynamic data. We have made some series truncation approximations and so we must ask to what extent the success of the method depends on our assumptions. To consider this we turn to simulation and calculate some of the quantities we have derived. Simulation is, of course, always model dependent but this gives an otherwise independent view of the success of our low-order activity series theory. In particular, by using the ratio of partition functions as parameters in an activity series expansion for quantities such as N2) we must address whether these are the real coefficients or effective coefficients, which have considerable contributions or take up the slack from higher-order terms in the series. So for instance, at infinite dilution we can write... [Pg.318]


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See also in sourсe #XX -- [ Pg.234 , Pg.237 ]




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