Ueber die Best?ndigkeit von Cham?leonl?sungen

Ohne Zusammenfassung     

Anwendung von Sätzen über partielle Differentialgleichungen auf die Theorie der Orthogonalsysteme,insbesondere die der Ribaucour'schen cyklischen Systeme

Ohne Zusammenfassung     

Zur Theorie der Determinanten

Ohne Zusammenfassung     

On the Couette-Taylor instability in ferrohydrodynamics

A theory for the stabilizing influence of an axial external magnetic field on a magnetic colloid engaged in cylindrical Couette flow is presented. For the case of a narrow gap, analytical expressions which predict the magnetic field dependences of the critical wavelength and the critical Taylor number at the onset of cellular Taylor flow are obtained.     

Use of N-benzyl-2-naphthohydroxamic acid as a highly selective reagent for solvent extraction and spectrophotometric determination of vanadium(V)

N-Benzyl-2-naphthohydroxamic acid extracts vanadium(V) selectively and quantitatively into chloroform from 2-8.5M hydrochloric acid in the presence of Mo(VI), Zr(IV) and Ce(IV). The extraction takes place quickly and gives a stable reddish-violet extract which shows an absorption maximum at 505 nm with molar absorptivity of (5.34 +/- 0.05) x 10(3) 1.mole(-1).cm(-1). The optimum range for the determination is 2.2-7.4 ppm of vanadium(V) in the final solution. The method has been used for the determination of vanadium in steels.     

Liquid-liquid extraction of elements by antipyrine and diantipyrylmethane salts from non-aqueous solutions or in systems without an organic solvent

The liquid-liquid extraction method for inorganic compounds has been developed and further improved by using different types of multiphase systems involving pyrazolone derivatives. The degree of concentration of elements by use of three-phase liquid systems has been increased by 1-2 orders of magnitude, and a universal method for preconcentration of elements in non-aqueous media has been suggested. The development of extraction systems based on a single liquid component-water-and not requiring an organic solvent at all, has increased the safety of extraction methods and improved the working conditions. A new variant of spectrochemical analysis without mineralization of an extract has been developed. Its main advantage is that it reduces the analysis time by a factor of 6 or 8. The liquid-liquid extraction of elements in purely aqueous two-phase systems without an organic solvent can be combined with titrimetric, photometric and polarographic determination in hybrid analytical procedures.     

Determination of molecular-weight distribution and average molecular weights of block copolymers by gel-permeation chromatography

The problem of preparation of a block copolymer of precise molecular-weight distribution (MWD) and with heterogeneous composition on the basis of gel-permeation chromatography (GPC) data has been investigated. It has been shown that in MWD calculations the distribution f(p) of the composition p in individual GPC fractions should be taken into account. The type of the f(p) functions can be simultaneously established by an independent method, such as use of adsorption-column or thin-layer chromatography sensitive to the composition of the copolymer. It has also been shown that the actual f(p) may be replaced by a corresponding piecewise distribution, of simple form, without decrease in the precision of calculation of the MWD and average molecular weights of most known block copolymers.