Über den Einfluss der Sekundäranregung und der Streuung auf die Röntgenfluoreszenzintensitäten bei der Lösungs-RFA

For solution techniques, X-ray fluorescence intensities are-besides primary excitation-primarily influenced by scattering processes, and on a small rate by secondary excitation when compared with scattering. An increase of solved matter causes an increase of the secondary contribution and a decreasing scattering influence. This should be taken into account for selecting reference solution concentrations as well as for considering the accuracy of the method.     

Statistische methoden zur ermittlung der verteilung der molekülgrössen in hochpolymeren systemen aus experimentalergebnissen der fraktionierten fällung. IV. Berücksichtigung der polydispersität der fraktionen

The relation between the most important statistical parameters of the number frequency h(P) determining the kinetics of polymerization and the molecular weight distribution H(P) is explained. The polydispersity g_w of H corresponds to the non-uniformity of H(= U). For calculating g_w, a correction formula (22) is derived which takes into account the averaged polydispersity α of the fractions. By this means, the asymmetry of h is also calculated. As explained in an earlier investigation, it is possible to determine the type of distribution function in the SWN step diagram. If this type is known, it is furthermore possible to calculate the correction quantity α according to the equilibrium theory of G. V. Schulz. The α unequivocally depends on the distribution function, the volume quotient φ of the sol and the gel, and on the parameter k of the function type, if the number X of the fractions lies between 5 and 20 and the single fractions show approximately the same mass. As an example, it is shown that then the quantity k, which is characteristic for the type of the reaction, can be calculated from the experimental data with an error of only a few per cent, and α² has a value below 0.1. Although, with a fractionation column, α² generally shows lower values, in favorable cases even down to 0.03, the uncertainty in the determination of the parameter k is, for many practical reasons, generally not lower compared with the uncertainty observed in precipitation fractionations using our new method.