Weight-fraction sampling

It has been shown19,20) that under PAA complex formation with excess of partly quaternized PYP, the latter is quite effectively fractionated by composition, macromolecules of the copolymer enriched with nonalkylated units being selected in the polycomplex. It is of importance that the preliminary molecular-weight fractioned sample of P-4-VP is quarternized with ethyl bromide, i.e., under the conditions of an experiment it is possible to consider... 

Original weight Weight fraction Sample fraction PS, PS in Critical elongation... 

Weight-fraction Sampling of Primary Polymers Batch Reactor, Transfer to Polymer [48]... 

Taylorf carefully fractionated a sample of nylon-6,6 and determined the weight fraction of different n-mers in the resulting mixture. The following results were obtained ... 

Column 9. Aj/Aj j gives that fraction of the area under the entire curve which has accumulated up to the Nth class. Since the curve is a weight distribution, this is equal to the weight fraction of material in the sample having M < Mj. 

It may be shown that M > M. The two are equal only for a monodisperse material, in which all molecules are the same sise. The ratio MI /MI is known as the polydispersity index and is a measure of the breadth of the molecular weight distribution. Values range from about 1.02 for carefully fractionated samples or certain polymers produced by anionic polymerization, to 20 or more for some commercial polyethylenes. 

Example 1 Sample Quantity for Composition Quality Control Testing An example is sampling for quality control of a 1,000 metric ton (VFg) trainload of-Ks in (9.4 mm) nominal top-size bentonite. The specification requires silica to be determined with an accuracy of plus or minus three percent for two standard errors (s.e.). With one s.e. of 1.5 percent, V is 0.000225 (one s.e. weight fraction of 0.015 squared). The problem to be solved is thus calculating weight of sample to determine sihca with the specified error variance. 

However, Bengough and Varma [17,18] affirm that there is no systematic dependence between the rate of dehydrochlorination and molecular weight for samples obtained by fractionation of Geon III. 

Equation 1-5 was written for a sample containing a single element upon which monochromatic x-rays are incident. In so far as x-ray absorption is an atomic property, the mass absorption coefficients for other samples are additive functions of the weight-fractions of the elements, free or combined, that are present that is,... 

Suppose the weight-fraction Wes of element E in sample S is to be determined by measuring the intensity, Ies, of an analytical line. In the simplest case, we may assume that... 

The discussion preceding Equation 7-5 points to the weight-fraction as the logical unit for the x-ray emission spectrography of infinitely thick samples. Were all complications absent, one might expect proportionality between analytical-line intensity and weight-fraction such that... 

The relationship in Equation 7-12 is more likely to hold when E and St are both present at low weight-fractions in the samples because x-ray absorption by the sample is then least affected by variations in the weight-fraction of E or St. Then a calibration curve is conveniently established by varying We at constant Wst (7.14, especially Figure 7-8). 

Ia/Icu (/a = intensity of Ka for copper in the alloy Icu — corresponding intensity for pure copper) for alloys containing the following weight-fractions of copper 0.01 (0.0099) 0.04 (0.0373) 0.53 (0.504) 0.88 (0.867). This excellent agreement can be further improved by applying suitable corrections. There probably is no better way of analyzing metallic samples for which a point-to-point exploration on a minute scale is required. 

The weight fractions of the anatase and rutile phases in the samples were calculated from the relative intensities of the strongest peaks in XRD patterns corresponding to anatase and rutile as described by Spurr and Myers [4]. 

Given the following weight fractions in % for a sample of sand, plot your calculated data in terms of ... 

The chemical composition of caramel color is not yet fully understood but some compounds identified in the low weight fraction are considered caramel markers. All caramel classes contain 5-hydroxymethyl)-2-furaldehyde (5-HMF). In caramel classes in and TV, 4-methyUmidazole (4-MeI) has been detected, while 2-acetyl-4(5)-tetrahydroxybutylimidazole (THI) was found only in class HI caramel colors. The analysis of five caramel III samples by SPE/HPLC-MS revealed concentrations between 28.3 and 46.8 iglg THI and 73.3 to 187.8 for 4-MeP (see Figure 5.2.3). 

The molecular weight distribution of cell wall polysaccharides was estimated by gel filtration with a TOSOH TSK gel G4000 PWXL (7.8 x 300 mm) column equilibrated and eluted with 0.05 M sodium acetate, 0.01 M EDTA, 0.05 M NaCl (pH 5.0) in polyuronide and 0.05 M sodium citrate, 0.1 M NaCl (pH 5.5) in the hemicellulose fraction. Samples (1 mg/ml) of 100 ml were injected. The eluate was monitored by a refractive index detector (Shimadzu R1D-6A, Kyoto, Japan) and collected at the fraction size of 0.4 ml. 

It is important to use well-fractionated samples for the purpose of determining the value of in the manner set forth above. If the sample includes species covering a considerable range in molecular weight, then the nature of the averages of the measured quantities, ( y/2 required by Eq. (23) assumes mportance. It may be... 

Figure 11. Conversion vs. weight fraction styrene in monomer, styrene n-butyl methacrylate (samples as for Figure 10) ((------) ti = 0.68, r == 0.45 (------)...

If an amorphous phase is present in the sample, it is still possible to perform the quantitative analysis by introducing a small amount of crystalline powder with the known weight fraction 1 that will be the iV+ 1 phase in the sample, so the equation becomes ... 

So, when in a multiphase sample, it is possible to separate the contribution to the diffraction pattern of each phase (F j)). Relation (26) permits the evaluation of the relative weight fractions Wi if the chemical compositions of the phases and of the global sample are known ... 

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