Marginal electron density and density-difference functions

Summary For visual analysis of the density reorganization and distortion, the one-dimensional cut (x, y ₀,z ₀) and the two-dimensional cut (x, y, z ₀) of the three-dimensional electron density difference function (x, y, z) are frequently employed. However, these cut functions do not satisfy any sum rules in contrast to the original difference function (x, y, z). To avoid this difficulty, the use of the marginal electron density functions _x (x) and _xy (x, y) and their difference functions _x (x) and _xy (x, y) is proposed. The marginal densities are condensation of the three-dimensional density onto a particular plane or line of our interest, and they satisfy the sum rule (i.e., the conservation of the number of electrons) exactly. Some basic properties of the marginal electron density are clarified for typical diatomic molecular orbitals. An illustrative application is given for the bonding and antibonding processes in the H₂ system.     

Effect of thick fixed-charge layers on electrostatic interaction — a theoretical approach

The electrostatic interaction pressure of charged surface layers is considered qualitatively and quantitatively. In the case of mutual penetration of the surface layers in addition to Maxwell stress and osmotic resp. hydrostatic pressure an isotropic stress on the fixed charges carrying molecules of the surface layers has to be taken into account. The derivation of the pressure-distance equations is given starting from both thermodynamic/electrostatic and hydrostatic/electrostatic principles. A possible biological significance of the additional stress is discussed emphasizing its role in modifying the structure of surface layer molecules.List of symbols e ₀ elementary charge - k Boltzmann constant - n _i concentration of theith ionic species in the bulk solution - P hydrostatic pressure - P hydrostatic pressure in the bulk volume (× ) - P ^h integration constant, independent on ×:P ^h =P(h) - T absolute temperature - Z _i electrovalence of theith ionic species - thickness of the surface layer - , ₀ relative and absolute permittivities - II(×) osmotic pressure at position × - II osmotic pressure in the bulk solution (× ) - osmotic pressure in the symmetry plane of interacting identical surface layers (electric field strength equals zero) - integration constant, independent on ×: - _e ^h electrostatic component of the disjoining pressure _e ^h = _e (h) - (×) mobile charge density profile (cations and anions of the electrolyte) - (×) fixed charge density profile - ^t(x) total charge density profile ( ^t = +) - ¹(x) fixed charge density profile of one of the two surface layers ( ¹(×) 0 for 0×) - (×) electric potential profile     

Non-equilibrium rate coefficients and isotope effect with bimolecular ion-(polar) molecule reactions in xenon

Using the Fokker-Planck version of an approximate Boltzmann equation for the ion (translational) energy distribution function f _I the departure, k, of the non-equilibrium ion-(polar) molecule reaction rate coefficient k _non from its equilibrium value k ^(eq) is calculated. k enhances considerably with an increase of the dipole moment of the reacting molecular species (locked dipole reaction model). But the k-values, e.g. for reactions of H^–(D^–) and nitromethane in xenon enhance also with increasing ratio of the concentrations of CH₃NO₂ and Xe and decrease with enhancing gas temperature T. The reaction-induced (translational) non-equilibrium effect leads to a (non-equilibrium) kinetic isotope effect depending on and T. At T=300 K the example yields k _H /k _d =1.345(=5 · 10^–4),=1.409 (=10^–5) and=1.414–k _H ^/(eq) /k _D ^(eq) (10^–6).     

CPS K 843 Radiation-induced crosslinking: Effect on structure of polyethylene

Branched polyethylene irradiated (0–400 Mrad) with a Co⁶⁰ source at room temperature under vacuum was studied by density, wide- and small-angle X-ray scattering (WAXS and SAXS) measurements. The radiation effects on the structure of bulk, branched polyethylene are quite similar to those observed by others on single crystals or oriented preparations. These effects include changes in bulk density, crystallinity(w _c orv _c) and¯d ₁₀₀ and¯d ₂₀₀ spacings as a function of irradiation. A decrease in crystallinity is seen to begin at radiation dose 100 Mrad whereas lattice expansion indicating onset of an orthorhombic-hexagonal transition can begin as low as 10 Mrads. The decrease in crystallinity can be attributed to additional lattice distortions primarily introduced by the crosslinks occurring at the lateral grain boundaries, while lattice expansion can be associated with the same crosslinking mechanism which begins at the defects both within the crystals as well as those outside the crystals at the lateral grain boundaries. Strong evidence for a primary crosslinking-at-the-defects mechanism has also come from _c and _a data obtained in this study as a function of radiation dose. The same data have also led to an excellent correspondence between the measured density crystallinityv _c and the measured WAXS crystallinityw _c. Without consideration of the effects of crosslinks on _c and _a one would have obtained a divergence of the two crystallinities, especially at radiation doses greater than 100 Mrads.Dedicated Prof. Dr. R. Bonart on the occasion of his 60^th birthday     

Elastizitätsmodul und Dichte von kaltverstrecktem und druckbehandeltem Polyäthylen

Zusammenfassung Proben aus Polyäthylen hoher Dichte wurden bei Raumtemperatur mit verschiedenen Geschwindigkeitenv _ver auf einer Zugprüfmaschine verstreckt. Beiv _ver 10 mm/min beobachtet man eine fast isotherm verlaufende inhomogene Deformation, die zu Verstreckungsgraden=8–13 und mittleren Dichten = 0.80 g/cm³ in den verstreckten Probenbereichen führt. Die bei höherenv _ver bis zu 50 mm/min eintretende adiabatische Erwähnung ergibt höhere Verstreckungsgrade=13–18 und geringere Dichten = 0.64 g/cm³. Es existiert kein natürlicher Verstreckungsgrad. Der Dichteabfall mit zunehmendem kann durch eine Gerade repräsentiert werden; der ElastizitätsmodulE ergibt eine mit zunehmende Kurve.Nach einer Druckbehandlung der Proben mit 5600 bar bei Raumtemperatur erreichte ihre Dichte fast wieder den Anfangswert vor der Verstreckung, wobei keine Abhängigkeit von oder anderen Parametern zeigte. Der ModulE hatte zugenommen, aber nicht proportional zur Dichte. Der Vergleich von undE verstreckter Proben vor und nach der Druckbehandlung weist auf den Netzwerkcharakter von kaltverstrecktem Polyäthylen hin.Herrn Prof. Dr. K. Ueberreiter zum 70. Geburtstag gewidmet.     

Structure of casein micelles II. α s1-casein

Following the earlier study of the- and-casein micelle structure, we will now report results from the _s1-casein. Static and dynamic light scattering measurements were performed in a concentration range from 0.5 to 6.0 mg/ml atT=35 °C. A constant apparent molecular weight of 3.4×10⁶ daltons was found over the whole range. The apparent radii of gyration and the diffusion coefficients also show no detectable concentration dependence. The ratio of the two radiiR _g /R _H =2.78+0.21 is characteristic of extended rigid structures.R _g is the radius of gyration andR _H the hydrodynamic radius defined via the Stokes-Einstein relationship from the translational diffusion coefficient. This is in agreement with the analysis of the pronounced angular dependence of the scattered light, which leads to the conclusion that _s1-casein forms very long worm-like micelles. The contour length of one cylinder was found to beL1600 nm and the chains appear to be composed of about 12 Kuhn segments. At higher concentrations, lateral aggregation proportional to the concentration is observed. Beyond the overlap concentrationc ^* the asymptotic scattering curve changes its shape, which is interpreted as the beginning of a reversible gelation.     

Untersuchungen der Absolutintensität der Röntgenkleinwinkelstreuung an Polyäthylenterephthalat in Abhängigkeit von den Kristallisationsbedingungen

Zusammenfassung Es wurden Messungen der Dichte sowie der absoluten Intensität der Röntgenkleinwinkelstreuung an teilkristallinem Polyäthylenterephthalat durchgeführt. Aus den erhaltenen Resultaten wurden der Volumenanteil der Kristallite, die Dichte der Kristallitek und die Dichte der nichtkristallinen Bereiche _a berechnet. Bei Proben, die bei tiefer Temperatur kristallisiert worden waren, lagk unterhalb von 1,455 g/cm³, dem Wert, der aus den Abmessungen der Elementarzelle einer möglichst gut kristallisierten Probe bestimmt wurde. _a war bei allen Proben kleiner als die Dichte des völlig amorphen Stoffes. lag jeweils über dem Wert, der allein aus der Dichte in konventioneller Weise bestimmt wurde.

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Summary Measurements of the density and the absolute intensity of small angle X-ray scattering of semicrystalline polyethylenterephthalate were performed. From the results obtained the crystalline volume fraction, the density of the crystalsk and the density of the noncrystalline regions _a were calculated. With samples crystallized at lower temperatures,k lies below 1,455 g/cm³, the value obtained from the crystal unit cell dimension on a material crystallized as well as possible. _a is generally smaller than the density of a completely amorphous sample. For higher temperatures of crystallization, is larger than the values obtained simply from the density by conventional methods.

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Vorgetragen auf der Arbeitssitzung des Fachausschusses Physik der Hochpolymeren in der Frühjahrstagung Berlin 1971 vom 9. bis 13. März des Regionalverbandes Physikalische Gesellschaft zu Berlin.

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Wir danken Herrn Prof. Dr.E. W. Fischer für zahlreiche wertvolle Diskussionen. Unser Dank gilt ferner der Deutschen Forschungsgemeinschaft für die finanzielle Unterstützung dieser Arbeit, sowie der Fa. Kalle A. G., Wiesbaden, für die Überlassung der Folien.     

Bestimmung der molaren Masse und der Ladungszahl von Polymerelektrolyten mit der Ultrazentrifuge

Zusammenfassung In der vorliegenden Arbeit wird das Sedimentationsgleichgewicht der Systeme Na₆[H₂W₁₂O₄₀]—NaCI—H₂O und Na₆[H₂W₁₂O₄₀]—NaClO₄— H2O untersucht. Die scheinbare molare Masse Mapp des Natriummetawolframats wird in beiden Systemen als Funktion der Natriummetawolfrarnat-Anfangspartialdichte ₀ ^PX _z gemessen. Durch lineare Extrapolation der Funktion Mapp = Mapp (PP,, ) auf die Polymerelektrolyt-Anfangspartialdichte Null können die Grenzwerte der scheinbaren molaren Masse (Mapp)o ermittelt werden. Aus den (Mapp)o-Werten wird die Abhängigkeit der Größe (ln _PXz /m _BX ) _mPXz von der NaCI- bzw. NaClO₄-Molalität berechnet.Die Bestimmung der molaren Masse und der (stöchiometrischen) Ladungszahl eines Polymerelektrolyten aus den experimentell ermittelten (Mapp)o-Werten unter Anwendung der Lamm-Williams-Gleichung wird diskutiert. Zur Ermittlung der beiden Größen müssen mehrere Versuchsreihen mit zwei verschiedenen Fremdelektrolyten durchgeführt werden. Externe Messungen sind nicht erforderlich.Man erhält auf diese Weise verläßliche Werte so-wohl der molaren Masse als auch der (stächiometrischen) Ladungszahl.

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Summary The sedimentation equilibria of the systems sodium metatungstate-sodium chloride-water and sodium metatungstate-sodium perchlorate-water are investiated. In both systems the apparent molecular mass Mapp of sodium metatungstate (PX _z) is measured in dependence on partial density ₀ ^PX _z before centrifugation. By linear extrapolation of the function Mapp = Mapp ( ₀ ^PX _z the limiting value (Mapp)o for ₀ ^PX _z = 0 is obtained. The variation with sodium chloride and sodium perchlorate molality of the quantity (ln _{PX z} ^m _BX )mPX_z is calculated from (Mapp)o data.The determination of the molecular mass and the algebraic valency of a polymeric ion by means of the (Mapp)o values calculated by Lamm-Williams equation is discussed. In order to obtain these two quantities at least two series of experiments are required, each of which using a different supporting electrolyte. External measurements are not necessary. In this way reliable values for the molecular mass as well as for the stoichiometric valency are obtained.

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Mit 5 Abbildungen und 3 Tabellen     

Molekülordnung und Kristallinität in Polyhexamethylenadipamid

Zusammenfassung Kalorimetrische, röntgenographische und IR-spektroskopische Untersuchungen und Dichtemessungen ergaben für PA 66 eine bei anderen Polymeren unbekannte Anomalie. Die Abhängigkeit der Röntgenkristallinitätw _c und der kristallinitätsproportionalen Größen (experimentelle Schmelzwärme H ^*, IR-Bandenintensität) vom spezifischen Volumen ändert sich mit den Kiistallisationsbedingungen. Dies ist die Folge eines konformationsbedingten Übergangs zwichen zwei triklinen Modifikationen unterschiedlicher Dichte. Für aus der Schmelze, dem Glaszustand und verdünnter Lösung kristallisierte Proben treten bei allen drei Meßmethoden hinsichtlich der Abhängigkeit vom spezifischen Volumen drei Bereiche auf. Bereich I: Die Proben enthalten 1-Kristalle mit _c ^I =1,22 =1,22 gcm-³,H _M ^I =235 Jg^–1 und=1,095 gcm _u–3. Bereich II: Die Proben enthalten _II -Kristalle mit _cII=1,165 gcm^–3.H _M ^II =185 Jg _u ^–1 1 und pa =1,095 gcm^–3. Bereich III: Übergangsbereich, in dem sich das spezifische Volumen stärker ändert als we und H ^*, weil die Kristalldichte zwischen _c ^I und ell variiert.Die _c -Wertr wurden außer durch Extrapolation über dem spezifischen Volumen auch aus der Invarianten der Röntgenkleinwinkelstreuung bestimmt. In allen Fällen ist eine .röntgenographische Kristallinitätsbestimmung bei PA 66 willkürfrei und reproduzierbar möglich. Aus Dichte oder Schmelzwärme kannw _c unter Verwendung der ermittelten _c- und H_M-Werte nur bestimmt werden, falls die Proben den Bereichen I oder II angehören. Mit den üblichen Verarbeitungsmethoden erhält man jedoch meist Proben im Bereich III.

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Summary From the results of calorimetric, X-ray and infrared spectroscopic investigations and density measurements an anomaly is found for polyamide 66 which is not known for other polymers. The dependence of X-ray crystallinityw _c and other properties proportional to crystallinity (experimental heat of fusion H ^*, intensity of IR-absorptions) on the specific volume varies with the conditions of crystallization. This is due to a conformational transition between two triclinic modifications with different densities.Samples of polyamide 66 were isothermally crystallized from the melt, from dilute solution and from the glassy state at different crystallization temperatures. The results of each of the three experimental methods, when plotted versus specific volume, exhibit three sections Section I: The samples contain _I -crystals with _c =1.22 gcm^–3, H _M ^I = 235 Jg^–1 and _a =1.095 gcm^–3 Section II: The samples contain air-crystals with _c ^I =1.165 gcm-3, H _M ^II =185 Jg^–1 and ppa =1.095 gcm^–s; Section III: Transition range, where the change in the specific volume is greater than that inw _c and H ^*, because the crystal density varies continuously between _c ^I and _c ^II The crystal densities have been determined not only by specific volume extrapolations, but also from the mean square electron density fluctuation of the small angle X-ray scattering. In all cases it is possible to determine the crystallinity of polyamide 66 from X-ray measurements in an unequivocal and reproducible way. The calculation of crystallinity from density or heat of fusion is only possible, if the samples belong to section I or II. The usual processing methods, however, produce samples which belong to section III.

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Mit 15 Abbildungen und 2 Tabellen

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Herrn Professor Dr. Horst Pommer zum 60. Ge burtstag gewidmet.     

Simultaneous TG,DTG, DTA and EGA technique for the determination of carbonate,sulphate, pyrite and organic material in minerals,soils and rocks

A simultaneous TG, DTG, DTA and EGA method was developed for the determination of carbonate, sulphate, pyrite and organic material in minerals. The method is based on the selective direct determination of SO₃ and CO₂ evolved from the heated sample, and on the indirect determination of H₂O. The thermogas-titrimetric adapter of the derivatograph collects the liberated gases (CO₂, SO₃, SO₂) quantitatively, absorbs them in water, and titrates them continuously and automatically with NaOH titrant. The changes in the volume of titrant consumed are recorded as a function of the temperature. In two parallel examinations, one titration is performed at pH 4, and the other at pH 9.3. The former measurement yields only the amount of SO₃ (SO₂), while the latter gives the joint amount of SO₃ (SO₂) and CO₂.

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Zusammenfassung Autoren entwickelten eine Methode zur simultanen TG, DTG, DTA und EGA zur Bestimmung von Karbonaten, Sulfaten Pyrit und organischem Material in Mineralen. Die Methode basiert auf der selektiven direkten Bestimmung des beim Erhitzen der Probe entwickelten SO₃ bzw. CO₂ und der indirekten Bestimmung von Wasser. Die in Freiheit gesetzten Gase (CO₂, SO₃, SO₂) werden im gastitrimetrischen Adapter des Derivatographen gesammelt, in Wasser absorbiert und kontinuierlich und automatisch mit NaOH titriert. Das Volumen der verbrauchten Titrierflüssigkeit wird in Abhängigkeit von der Temperatur registriert. In zwei Parallelversuchen wird eine Titration bei pH 4, die andere bei pH 9.3 ausgeführt. Die erstere Messung ergibt nur die Menge an SO₃ (SO₂), während bei der letzteren die Gesamtmenge an SO₃ (SO₂) und CO₂ erhalten wird.

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, , ( ) , , . SO₃ CO₂, , . - (CO₂, SO₃, SO₂), . ë . : pH=4, - pH=9.3. SO₃(SO₂), — SO₃(SO₂) CO₂.

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The authors thank Prof. E. Pungor for valuable discussions, and Mrs. M. Kiss and Miss I. Fábián for their technical assistance.     

Gas permeability of block copolymers of styrene and butadiene

The permeability of styrene-butadiene block copolymer foils with different composition prepared by casting and pressing has been investigated for the gases Ar, CO₂, and CH₄ at pressure difference of 400 mbar and at the temperature range 298 T [K] 333.The permeation process can be described by the solution diffusion mechanism. The diffusion coefficients decrease in the sequence of the gases Ar, CO₂, and CH₄ and the solubility coefficients increase in the sequence Ar, CH₄, CO₂.The dependence of the permeability on the composition of the block copolymer can be interpreted by the help of percolation theory and the effective medium theory. It follows the critical volume fraction of the percolation of the transport phase _PB ^c (= 0,23) and the coordination numberz (= 4) giving an information concerning the multiphase structure of the block copolymer.Presented in part at the 33^rd Annual Meeting of the Colloid-Gesellschaft, Graz, Austria, September 14–16, 1987.     

A representation of the polarization term in the interaction energy between a molecule and a point-like charge

The interaction energy of a molecule M with a point-like charge q can be partitioned into simpler contributions, two of which can be expressed in terms of the charge distribution _M of the sole M. The first term, qV(r), represents the interaction of q with the undistorted charge _M ⁰ of M while the second q ² P(r) gives the additional contributions due to the polarization of _M ⁰ under the influence of the charge q placed at the point r. In this paper we investigate the possibility of getting an inexpensive and sufficiently accurate analytical representation of P(r) over the whole space outside the van der Waals volume of M.     

Kinetics and mechanism of the hydrolysis of sodium carboxymethylcellulose (Na-CMC) by a cellulase complex

TheSomogyi-Nelson colorimetric method is applied in a new manner more suitable for evaluating the kinetics of the enzyme hydrolysis of sodium carboxymethylcellulose (Na-CMC) catalyzed by the cellulase complex. By means of selective inhibition of a chosen enzyme from the cellulase complex it became possible to trace the effect of the other enzymes included in its composition.

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Kinetik und Mechanismus der Hydrolyse von Natriumcarboxymethylcellulose (Na-CMC) durch einen Cellulase-Komplex

Zusammenfassung Die kolorimetrische Methode nachSomogyi undNelson wird nach einem neuen Verfahren zur Verfolgung der Kinetik der hydrolytischen Spaltung von Natriumcarboxymethylcellulose (Na-CMC), katalysiert durch den Cellulase-Komplex, angewandt. Durch selektive Inhibierung eines bestimmten Enzyms des Cellulase-Komplexes kann man die Wirkung der anderen zu seiner gesamten Zusammensetzung gehörenden Enzyme verfolgen.

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Symbols Used E enzyme (E—cellulase;E—exo-cellobiohydrolase;E—-glucosidase) - [E] _w weight concentration of enzymeE - S substrate (Na-CMC—sodium carboxymethylcellulose) - [S]₀ weight concentration of substrateS - I inhibitor (I—lactose;I—calcium chloride;I—condurrite-B-epoxide) - P product (P—oligosaccharides;P—cellobiose;P—D-glucose) - P end product (K , K , K ) - DP degree of polymerization - DS degree of substitution - ES enzyme-substrate complex (E S, E S, E S) - EP enzyme-product complex (E P, E P) - EI enzyme-inhibitor complex (E I, E I, E I) - M _s molecular mass of substrateS - K _s substrate constant (K _s , K _s , K _s ) - K _I inhibitor constant (K _I , K _I , K _I ) - K _m Michaelis-Menten constant - k ₊₁,k ₊₂ (k ₊₂ ,k ₊₂ ,k ₊₂ ) forward rate constants - k _–1 reverse rate constant - ₀ initial rate of reaction - V maximal reaction rate - A change in absorbance - molar absorption coefficient - wavelength Herrn Prof. Dr.Hans Tuppy zum 60. Geburtstag herzlichst gewidmet.     

Spin density calculations in semiempirical restricted and unrestricted SCF MO methods

In the present paper spin densities are calculated by ten methods on chosen radical systems. - interaction parameters for the individual methods are determined by McConnel's relation a _i =Q _i and by that of Colpa-Bolton a _i =(Q+K _i ) _i and the correlation between the results of the individual methods is studied.

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Zusammenfassung In der vorliegenden Arbeit werden Spindichten anhand von zehn Methoden an ausgewählten Radikalsystemen ermittelt. Die --Kopplungsparameter für die einzelnen Methoden werden nach den McConnell a _i =Q _i - und Colpa-Bolton a _i =(Q+K _i ) _i -Beziehungen bestimmt. Die zwischen den Ergebnissen der einzelnen Methoden bestehende Korrelation wird untersucht.

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Résumé Dans ce travail les densitées de spin sont calculées par dix méthodes sur un système des radicaux choisis. On détermine des parametres - d'interaction pour les méthodes individuelles dans la relation de McConnell a _i =Q _i et celle de Colpa-Bolton a _i =(Q+K _i ) _i et étudie la correlation entre les résultats des méthodes individuelles.

     

Capillary rise of liquids in rectangular tubings

The capillary rise of liquids was investigated in square capillary tubings of different dimensions (e. g. 300 m · 300 m to 1000 m · 1000 m) in the temperature range 25° to 35°C.The data were fitted to an equation:=1/2 · ·g · (S · (C ·H/2 +C ·S)) where is the surface tension of the liquid,S is the side length of the square tubing,H is the capillary rise,C (= 1.089) is a capillary constant.     

Two-electron atomic wave functions which satisfy proportionality relations between one-and two-electron moments

Based on momentum- and position-space analyses of the moment operators for two-electron atoms, it is shown that there exists a family of two-electron wave functions which satisfy a proportionality relation, r/ ₁ ^v /r ₁₂ ^v =p/ ₁ ^v /p ₁₂ ^v =2^–v/2, between the one and two-electron moments in position and momentum spaces, where v is an arbitrary number for which the moments are well-defined.     

Thermal Expansion of Mixed Zirconium Phosphates

A series of framework phosphates with varied ratio of cations Na_5-2x B _x ^IIZr(PO₄)₃, B^II = Mg, Ca, Sr, Ba (0 x 2) and Na_5-3x Fe _x Zr(PO₄)₃ (0 x 1.33) were synthesized and studied under heating. The coefficients of thermal expansion along crystal axes _a and _c were calculated, and their dependences on the cationic composition (nature and concentration) and on the occupancy of out-of-framework structural positions were established.     

A kinetic method for the determination of nanogram amounts of cadmium (II) by its catalytic effect on the complex formation of manganese(II) withα,β,γ,δ-tetra-(p-sulf onatophenyl) porphine

Summary Cadmium(II) accelerates the complex formation reaction of manganese (II) with, , , -tetra(p-sulfonatophenyl)porphine (H₂TPPS₄). Cadmium(II) concentration as low as 10^–7 mol dm^–3 can be determined from the decrease in absorbance at 413 nm (_max of H₂TPPS₄) at a fixed time after the start of the reaction of manganese(II) with H₂TPPS₄. After the separation of lead(II) by coprecipitation of manganese(IV) oxide, the method is highly selective and is free from interference of most substances usually encountered. Sandell's sensitivity calculated from the calibration curve at 30 min after the start of the reaction is 1.43×10^–1 ng cm^–2.

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Eine kinetische Methode zur Bestimmung von Nanogrammengen von Cadmium(II) mit Hilfe seines katalytischen Effekts bei der Komplexbildung von Mangan(II) mit , , , -Tetra-(p-sulfonatophenyl)-porphin

Zusammenfassung Cadmium (II) beschleunigt die Komplexbildung von Mangan (II) mit, , , -Tetra-(p-sulfonatophenyl)-porphin (H₂TPPS₄). Konzentrationen bis zu 10^–7 Mol/l können durch Messung des Rückganges der Absorbanz bei 413 nm (_max von H₂TPPS₄) nach einer bestimmten Zeit gemessen werden. Nach Abtrennung von Blei(II) durch Mitfällung mit Mangan (IV)oxid ist die Methode sehr selektiv und frei von Störungen durch die meisten üblicherweise vorliegenden Substanzen. Die Empfindlichkeit nach Sandell, ermittelt aus der Eichkurve 30 min nach dem Start der Reaktion, beträgt 1,43×10^–1 ng/cm².

     

Crystal structure of the synthetic analog of radtkeite Hg<Subscript>3</Subscript>S<Subscript>2</Subscript>Cl<Subscript>1.00</Subscript>I<Subscript>1.00</Subscript>

The results of structural studies of the synthetic analog of the radtkeite mineral Hg₃S₂Cl_1.00I_1.00 are analyzed. The crystal structure of the compound has been refined; the unit cell parameters are a _m = 16.827(4) , b _m = 9.117(1) , c _m = 13.165(5) , = 130.17(2)°, V = 1543.3(8) ³, space group C2/m, Z = 8, R = 0.0527. A possible transition a ₀ = a _m; b ₀ = a _m + 2c _m; c ₀ = –b _m to the pseudo-orthorhombic F cell previously determined for radtkeite, where one of the angles ( ₀ ) is slightly different from 90° (89.55°), has been found. Each sulfur atom in the structure is bonded to three mercury atoms, forming SHg₃ umbrellas with distances 2.240(6) –2.474(8) and angles HgSHg 94.7(2)°–102.9(2)°. The SHg₃ fragments are linked through Hg vertices to form corrugated [Hg₁₂S₈] layers. The halogen atoms lie inside and between the [Hg₁₂S₈] layers; the distances are Hg-Cl and Hg-I 2.783(7) , 2.961(7) , and 3.083(4) –3.311(3) , respectively.Original Russian Text Copyright © 2004 by N. V. Pervukhina, S. V. Borisov, S. A. Magarill, D. Yu. Naumov, V. I. Vasiliev, and B. G. NenashevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 755–758, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Die Bedeutung der mittleren Probendichte für die quantitative Interpretation der Röntgenkleinwinkelstreuung teilkristalliner Polymerer

Zusammenfassung Die Bestimmung von überstrukturdaten polymerer Lamellenclustersysteme kann über Modellrechnungen der Röntgenkleinwinkelstreukurven erfolgen. Es wird gezeigt, daß in vielen Fällen die Modulation der Streukurve nicht allein durch die innere Struktur der Cluster bestimmt ist, vielmehr muß die mittlere Elektronendichte der Umgebung der Cluster mitberücksichtigt werden. An den Systemen HDPE, PP und iPS/PPO wird gezeigt, daß die Verwendung eines einfacheren Modells, in dem die kristalline Dichte _c = 1 und die amorphe Dichte _a = 0 gesetzt wird (schwarzweiß-Modell), für kleine Lamellenzahlen pro Cluster zu einer Scheinanpassung führt. Die BerÜcksichtigung der mittleren Probendichte fÜhrt zu abweichenden Anpassungsparametern bei der Berechnung der experimentellen Streukurve und damit zu anderen Über-rstrukturdaten. Der Einfluß der Umgebungsdichte wird vernachlässigbar klein, wenn die Zahl der lagekorrelierten Lamellen pro Cluster größer als 10 wird.

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Summary Superstructural parameters of polymeric material composed of clusters of lamella-shaped crystals can be obtained by model-calculations of their small-angle x-ray scattering curves. In this paper it has been demonstrated, that in many cases the modulation of the scattering curve is determined not only by the inner structure of the cluster but also dependent on the average (electron) density of the cluster environment, the mean sample density. Discussing the SAXS of the systems HDPE, PP and iPS/PPO it has been shown, that the use of a simpler ,black-white model, in which the crystalline density has been set _c = 1 and the amorphous density _a = 0, leads to a phony fit. The incorporation of the mean sample density into the model yields a different set of parameters. The mean sample density can be neglected as soon as the number of lamellae per cluster exceeds the value of 10.

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