Prediction of adsorption of organic component and water vapour mixture onto activated carbon

A simple isotherm equation is derived for the adsorption of an organic component onto activated carbon in presence of water vapour. The theoretical results are compared with experimental data for toluene-water vapour-activated carbon, which were published byRipperger andGermerdonk [10].

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Vorhersage der Adsorption einer organischen Komponente und Wasserdampf an Aktivkohle

Zusammenfassung Es wird eine einfache Adsorptionsisotherme abgeleitet, welche die gleichzeitige Adsorption eines organischen Stoffes und Wasser an Aktivkohle beschreibt. Die theoretischen Ergebnisse werden mit experimentellen Resultaten vonRipperger undGermerdonk [10] für Toluol-Wasser-Aktivkohle verglichen.

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Symbols a _i adsorbate concentration in adsorbent, kg/kg of carbon - a _0i monolayer capacity, kg/kg of carbon - b _i kinetic parameter of theLangmuir equation - E _j adsorption energy in thej-th layer - i i-th component (1 — water vapour, 2 — organic compound) - j j-th layer - m number of layers - n number of adsorbed components - p partial pressure, Pa - p* saturation partial pressure, Pa - p _C water vapour partial pressure at begining of capillary condensation, Pa - surface coverage     

Chains of spheres in shear and electric fields

Summary The behaviour of electrically formed linear chains of rigid conducting spheres of equal size suspended in a Newtonian, dielectric fluid was studied in simple shear at rateG and in uniform electric fields of strengthE _o directed across the planes of shear. At lowG (E _o = 0) the chains rotated as single rigid axisymmetric particles; at highG they broke up into smaller rigid fragments. WhenE ₀ 0, (G = 0), they became oriented with their axes parallel to the electric field direction. In combined shear and electric field they behaved either as rigid or as flexible particles depending on the interparticle gaps.The hydrodynamic and electric orientation constants of rigid chains of various lengths were determined experimentally and compared with those of rigid conducting spheroids of same geometric axis ratios. It was found that the electric orientation constants for chains of a given length depended upon whether or not the spheres were in electrical contact and reached maximum values when they all touched one another.Both touching and non-touching chains appeared to be held together in shear whenE ₀ = 0 by small amounts of polymerized suspending oil bridging the gaps between adjacent spheres. The polymerization was caused by dielectric breakdown resulting from the electric field intensification in the gaps between the approaching spheres during chain formation.The significance of these interesting observations is briefly discussed.

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Zusammenfassung Das Verhalten von elektrisch, geformten linearen Ketten aus festen, leitenden gleichgroßen Kügelchen in einer Newtonschen, dielektrischen Flüssigkeit wurde untersucht in einer einfachen Scherströmung mit StrömungsrateG und in einem gleichmäßigen elektrischen Feld mit FeldstärkeE ₀ senkrecht stehend zu den Strömungsebenen. Bei kleinemG(E ₀ = 0) rotierten die Ketten als feste, achsensymmetrische Teilchen; bei hohemG brachen sie auseinander in kleinere feste Bestandteile. BeiE ₀ 0 (G=0) orientierten sich die Ketten in die elektrische Feldrichtung. Bei gleichzeitig angelegter Scherströmung und elektrischem Feld verhielten sie sich einerseits als feste und andererseits als flexible Teilchen je nach Größe der einzelnen Kugelabstände innerhalb der Kette.Die hydrodynamischen und elektrischen Orientierungskonstanten fester Ketten verschiedener Länge wurden experimentell bestimmt und verglichen mit den entsprechenden Konstanten eines festen, leitenden Sphäroiden mit gleichem geometrischem Achsenverhältnis. Dabei ergab sich, daß die elektrische Orientierungskonstante abhängig war von den einzelnen Kugelabständen und maximale Werte annahm, wenn alle Kügelchen in der Kette sich genau berührten.Die Ketten mit oder ohne völlige Kugelkontakte wurden in der Scherströmung (E ₀ = 0) durch kleine Mengen von polymerisiertem Öl zusammengehalten. Die Polymerisation des Öls erfolgte während der Kettenformung in den einzelnen Kugelabständen auf Grund dielektrischer Kurzschlüsse, welche durch hohe elektrische Feldstärken bedingt waren.Die Bedeutung dieser interessanten Beobachtungen wird kurz erläutert.

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Nomenclature b sphere radius - c small number defined in [6] - E ₀;E ₀ ^c ;E ₀ ^f uniform electric field strength directed alongx ₂ axis; critical (minimum)E ₀ to cause dielectric breakdown between spheres;E ₀ at which chains were formed - f _n [8] etc. electrohydrodynamic field parameter defined in [8], etc. - G;G _e shear rate; critical (minimum)G to cause chains to break up forf _n 0 - ₃ (); ₃ ( _in) electric orientation function of a doublet; of chains ofn spheres - K dielectric constant of the suspending medium - n number of spheres in a chain - N histogram distribution (fig. 4) - O _in symbol for _in for touching chains - P(r _p) electric orientation function of a rigid conducting spheroid - r distance between centres of a doublet - r _e,r _e ^E ;r _p; r_e equivalent hydrodynamic and electric spheroidal axis ratios of a chain, resp.; geometric axis ratio of an axisymmetric particle; defined in table 2, note^e - t;t ^* time; dimensionless time = (8 ₀ KE ₀ ² /)t - T period of rotation of a chain about thex ₁ axis - u _i undisturbed flow velocity in thex _i direction (i = 1, 2, 3) - x _i Cartesian coordinates defined in figure 1 - error symbol - _i, _in dimensionless gaps between spheres of a doublet; between spherei andi+1 of a chain ofn spheres (i = 1 ton – 1) - ₀ permittivity of free space - viscosity of the suspending medium - _i, _i spherical polar angles with respect to thex _i axis - ₂ ⁱ , ₂ ^f initial and final ₂ before and after applyingE ₀ for a timet - density of suspending medium - specific electric conductivity of the suspending medium - ₁ stable steady orientation angle of chains forf _n 1 With 5 figures and 3 tablesThis work was supported by Grant MA-4012 from the Medical Research Council of Canada.     

Pneumatik in der Gras-Chromatographie

Zusammenfassung Es wird gezeigt, daß in der temperaturprogrammierten Gas-Chromatographie (PTGC) der Massenstrom des Trägergases sich kontinuierlich in der Kolonne ändert, auch wenn dieser Strom am Kolonneneingang konstant gehalten wird. Die Bedingungen, unter denen diese Änderung vernachlässigbar ist, werden aufgezeigt. Ein pneumatischer Widerstand W für den Massenstrom m des Trägergases einer gas-chromatographischen Kolonne wird definiert. Eine Näherungsformel wird abgeleitet, die die Änderung von W bei PTGC beschreibt. Es wird bewiesen, daß die zeitlich mittlere lineare Trägergasgeschwindigkeit bei PTGC mit konstantem Trägergasstrom zunimmt. Vier Prinzipien zur Konstanthaltung des Trägergasstroms werden kritisch geschildert. Der Einfluß des Totvolumens der Probenaufgabe und der Zuleitungen zur Kolonne bewirkt, daß der Trägergasstrom am Ausgang der Kolonne und im Detektor bei PTGC sich ändert, selbst wenn die üblichen genau arbeitenden Mengenregler verwendet werden. Der Regelfehler wird als Funktion der Heizrate, des Totvolumens und des Strömungswiderstands W der Kolonne für konkrete praktische Beispiele mit Hilfe einer Kenngröße A beschrieben und diskutiert. Besnders bei Capillarkolonnen wirkt sich dieser Regelfehler so aus, daß quantitative Analysen in der PTGC mit Wärmeleitfähigkeitszellen als Detektoren nur sehr schwer durchführbar sind. Die entsprechenden Fehlermöglichkeiten werden aufgezeigt. Ursache der schlechten Regelung des Trägergasstroms in der PTGC ist eine Zeitverzögerung, die völlig analog der bekannten elektrischen Zeitverzögerung mit RC-Gliedern ist. Eine mathematische Behandlung befindet sich im Anhang.

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Summary It is shown, that in programmed-temperature gas chromatography (PTGC) the mass-flow velocity m of the carrier gas in the column changes continuously, although the inlet mass-velocity is held constant. This change can be neglected within calculable limits. A pneumatical resistance W (for mass flow rate) is defined. An equation is derived describing approximatively the change of W in PTGC. Evidence is given for the growth of the time-averaged linear carrier-gas velocity with increasing temperature. Four principles are discussed to active constant mass-flow rate in PTGC. Using commercial mass-flow controllers in PTGC the dead volume V _T (before the column inlet) causes changes in m at the outlet of the column. The deviation of the flow-rate regulation is—amoung others-1. a function of the heating rate, 2. V _T and 3. W of the column and is discussed for practical examples with the help of a defined magnitude A. Practically it is impossible to analyse quantitatively with katharometers in PTGC using open tube columns because of the high W of these columns. Error possibilities are discussed. The difficulties of the mass-flow regulation in PTGC arise generally from the pneumatical time delay which is analogous to the electrical RC expression. In the appendix the mathematical treatment of the problems discussed above is given.

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Symbolverzeichnis a relative Änderung des Strömungswiderstands pro °C, definiert in Gl. (25) - c /RT - f 1 + P _i/P₀ = 1+P - i elektrischer Strom - j Martinscher Druckkorrekturfaktor - j Druckkorrekturfaktor, definiert in Gl. (10) - m Massenstrom eines Gases. (Durch einen Querschnitt in der Strömung tretende Masse Gas in der Zeiteinheit) - m m _k -m _i - p Druck in der Kolonne oder Druck im Totvolumen V _T - p/p p0/j = örtlich gemittelter Druck in der Kolonne - GDp=P _i -P ₀ Druckdifferenz an einem Strömungswiderstand - q freier Gasquerschnitt - r dT/dt = Heizrate - s 2L/Kq - t Zeit - u lineare Strömungsgeschwindigkeit, zurückgelegte Strecke pro Zeit - L/t ₀ = zeitlich gemittelte lineare Strömungsgeschwindigkeit - x Ortskoordinate in der Kolonne vom Eingang (x = 0) bis zum Ausgang (x = L) - A 1 +1/arc W ₁V_T = Kenngröße zur Beschreibung des Regelverhaltens bezüglich m _i, definiert in Gl. (32a) - C Kapazität eines Kondensators - F Volumenstrom. Durch einen Querschnitt in der Strömung tretendes Volumen pro Zeit bei dem dortigen Druck - K spezifische Permeabilität - L Kolonnenlänge - M Masse des Gases in der Kolonne bis zur Stelle V oder Masse des Gases in V _T - M ₀ Gesamtmasse des Gases in der Kolonne - P p _i/p₀ = dimensionslose Druckgröße - R Ohmscher Widerstand Gaskonstante des idealen Gasgesetzes - T absolute Temperatur - DT Temperaturerhöhung während eines Temperaturprogramms - V freies Gasvolumen der Kolonne bis zur Stelle x - V ₀ freies Gasvolumen der Kolonne insgesamt - V _t Totvolumen zwischen Mengenregler und Kolonneneingang - W Strömungswiderstand, definiert in Gl. (2) - PTGC Abkürzung für temperaturprogrammierte Gas-Chromatographie - Viscosität - Molmasse - Dichte - Index ₀ bezieht sich auf den Ausgang der Kolonne - Index _i bezieht sich auf den Eingang der Kolonne - Index _k bedeutet, daß die indizierte Größe konstant gehalten wird - Index ₁ bedeutet den Wert der indizierten Größe bei dem Start des Temperaturprogramms - Index ₂ bedeutet den Wert der indizierten Größe bei dem Ende des Temperaturprogramms Die Autoren möchten der Deutschen Forschungsgemeinschaft, Bad Godesberg, für die finanzielle Unterstützung danken, mit der diese Arbeit durchgeführt werden konnte. Herrn Dr. W. Schäfer von der Fa. Hartmann und Braun AG., Frankfurt a. M., danken wir für die fruchtbaren Diskussionen über das beschriebene Thema.Diese Arbeiten wurden am 4th International Symposium-Advances in Chromatography, 6–9. April 1967, New York, vorgetragen.     

Theory of ring formation in a reversible system: general solutions

The enumeration theory is extended in this work into a more general theory, taking back-reactions into consideration. The solutions may faithfully reproduce real processes from arbitrary starting points to a steady-state. Therefore, the presented theory includes the equilibrium theory by Jacobson-Stockmayer, the numerical solution by Gordon-Temple, and the irreversible theory by the present authors. The solutions are described first in general forms of transition probabilities {P}, and then explicitly with the aid of rate equations; simple proofs are given. The presented theory was applied to an experimental data: the distribution of cyclic species in poly(ethylene terephthalate). We shall show that agreement between theory and experiment is nearly perfect.AB model N ₀ Total number of units - V System volume - C ₀=N ₀/N _A ·V Initial concentration (N _A : Avogadro's number) - L _x AB type chain x-mer; (AB)_x - N _x Number of AB type x-mers - R _x Ring x-mer - N _Rx Number of ring x-mers - E Small molecule eliminated by bond-formation - N _E Number of small molecules eliminated by bond-formation - h _k Number of reacted functional units (f.u.) in statek - _k Number of reacted functional units (f.u.) in chains in statek - _k Total number of units in chains in statek - D=h _k /N ₀ Extent of reaction in statek - D ^*= _k / _k Extent of reaction in chains in statek - k _L Chain-propagation rate constant - k _Rx Cyclization rate constant of chain x-mers - k _B Bond breakage rate constant of chains - k _B,Rx Bond breakage rate constant of cyclic x-mers - <k _Rx > _k Mean cyclization rate constant in statek - g(x)=k _B,Rx /k _B Ring-opening factor of cyclic x-mers - P _Lx,k Probability that a chain x-mer will be formed in statek - {P} Set of transition probabilities per single jump in forward direction or reverse direction (see the text on individual transition probabilities) AB model M _A Total AA monomer unit number - M _B Total BB monomer unit number - M ₀=M _A +M _B Total particle number - _A,i =2M _A –h _i Unreacted A functional unit (f.u.) number in statei - _B,i =2M _B –h _i Unreacted B f.u. number in statei - _Ax Unreacted A f.u. number on x-mers - h _i Number of reacted A (or B) f.u. in statei - _i Number of reacted A (or B) f.u. in chains in statei - _A,i =2M _A –h _i + _i A f.u. number in chains in statei - _B,i =2M _B –h _i + _i B f.u. number in chains in statei - _i =2(M ₀–h _i + _i ) Total f.u. number in chains in statei - D=h _i /M ₀ Extent of reaction in statei - D _A ^* = _i / _A,i Extent of reaction of A f.u. in chains in statei - D _B ^* = _i / _B,i Extent of reaction of B f.u. in chains in statei - D ^*=2 _i / _i Extent of reaction in chains in statei - L _x (AA-BB)_x-1-AA type chain x-mer;x=1,2,3,... - L _x BB-(AA-BB)_x type chain x-mer;x=0,1,2,... - L _x (AA-BB)_x type chain x-mer;x=1,2,3,... - N _x Number of type x-mers - N _x Number of type x-mers - N _x Number of type x-mers     

The microrheology of colloidal dispersions VII. Orthokinetic doublet formation of spheres

Summary A theory is developed for the rate of doublet formation in dilute dispersions of spheres subjected to a simple shear flow of gradient G when Brownian motion can be neglected but taking account of both hydrodynamic and interparticle interactions. When Coulombic repulsive forces are negligible, the capture frequency is found to be approximately proportional toG ^0.82; when they dominate the van der Waals attractive forces, the capture frequency is zero. When both attractive and repulsive forces are important no simple relationship exists, but the capture frequency can be calculated numerically. Experiments are described which are in qualitative agreement with the theory. Hamaker constants for polystyrene in water calculated from the measured doublet formation agree with those calculated by means of the present theory from experimental data of other workers, but are somewhat higher than those obtained from perikinetic coagulation rates.

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Zusammenfassung Eine Theorie für Doppelkugelformationen in verdünnten Dispersionen, welche einer einfachen Scherströmung mit dem GradientenG ausgesetzt sind, bei dem die Brown'sche Molekularbewegung vernachlässigt werden kann, unter Berücksichtigung aber von hydrodynamischen und Zwischenkörper-Kräften, wird entwickelt. Wenn Coulomb'sche Abstoßungskräfte vernachlässigt werden können, ergibt sich die Einfanghäufigkeit mit ca.G ^0.82; wenn deren Größe aber die der Van der Waals Kräfte überschreitet, ist die Einfanghäufigkeit null. Bei Auftreten von anziehenden und abstoßenden Kräften existiert keine einfache Beziehung, sondern es kann nur eine numerische Berechnung durchgeführt werden.Experimente werden beschrieben, die in qualitativer Übereinstimmung mit der Theorie sind. HamakerKonstanten für Polystyrol in Wasser, errechnet von den gemessenen Doppelkugelformationen, stimmen mit den, mit Hilfe der bestehenden Theorie von anderen Forschungsergebnissen errechneten Werte überein, sind aber etwas höher als jene, die von perikinetischen Koagulationsmaßen erhalten wurden.

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List of Symbols A Hamaker constant - A(r*), B(r*), C(r*) functions introduced in [7] - b sphere radius - c, c _t volumefraction ofsingle spheres, total volume fraction - C _A ,C _R ratio of attractive and repulsive forces to hydrodynamic forces, resp. - d distance between top and bottom of tube - function introduced in [7] - F _attr,F _rep attractive and repulsive forces, resp - G, G _c shear rate, critical value - J; J ₈ capture frequency per particle; according toSmoluchowski - K dielectric constant of suspending medium - l; l* semi-axis ofcapture crosssection inX ₂-direction;l/b - N _o ;N _t number concentration of particles att=0; at timet - p (r* - 2)r - r;r* distance between sphere centers;r/b - R, R _o radial distance from tube center, tube radius - S;S ₁; S₂ ratio of singlets to doublets; at top of tube; at bottom of tube - t,t*;t* real and dimensionless time (Gt); average ofGt - u ₃ undisturbed fluid velocity in X₃-direction - x _i ;X _i ;X _i Cartesian coordinates;xi/b; coordinate axes - Z(x ₂);Z* (x ₂) boundary of capture crosssection; dimensionless value (Z(x ₂)/b) - ₀ orthokinetic capture efficiency, defined in [6] - o permittivity of free space - n suspending fluid viscosity - 0, polar coordinates - x reciprocal double layer thickness - ; xxx London wavelength; /2b - ratio of capture to collision cross-section - ; _c ratio of sphere radius and double layer thickness; critical value - ₀; ₀ ^c surface potential of sphere; critical value     

Synthesis and transformations of metallocycles

A novel regio- and stereoselective method for synthesizingthreo-2,3-disubstituted 1,4-dialumobutanes from -olefins and haloalanes (Et₂AlCl, (Et₂N)₂AlCl, (EtO)₂AlCl, Bu _i ² AlCl) with the participation of catalytic amounts of Cp₂ZrCl₂ or ZrCl₄ in the presence of magnesium metal was developed. The products of hydrolysis and deuterolysis of the dialuminum compounds obtained have athreo-configuration. The selective transformations of 1,4-dialumobutanes totrans-3,4-disubstituted tetrahydrothiophenes,trans-1,2-disubstituted cyclobutanes, and disubstituted ,-dienes were found to be possible.For Part 15, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1561–1567, August, 1995.This work was carried out with financial support from the Russian Foundation for Basic Research (Project No. 93-03-04136).     

Contribution to the thermodynamics of emulsions

Summary In this paper there are derived equations for thermodynamically stable emulsions of phase II in phase I in the presence of surfactants.

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Zusammenfassung In dieser Arbeit werden Gleichungen für thermodynamisch stabile Emulsionen einer Phase II in Phase I in Gegenwart oberflächenaktiver Stoffe abgeleitet.

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Notation A interfacial area between phase I and phase II - interfacial tension between phase I and phase II - ⁰ interfacial tension without presence of a surfactant - n _i number of moles = amount of componenti - C ₃ concentration of the surfactant = component 3 in phase I in mol/cm³ With 1 figure and 2 tables     

Farbe und Konstitution bei anorganischen Feststoffen, 15. Mitt.: Die Lichtabsorption des zweiwertigen Kobalts in Silikaten vom Olivintypus

Zusammenfassung Mischkristalle Co _x Mg_1-x CaSiO₄ (I) und Co _x Mg_2-x SiO₄ (II), in denen sich das Mg²⁺ vollständig durch Co²⁺ ersetzen läßt, wurden röntgenographisch und spektralphotometrisch untersucht, desgleichen Mischkristalle {CoCaSiO₄+y Co₂SiO₄} (III), <y0,1>. In I befindet sich das Co²⁺ in den triklin verzerrten OktaederpositionenM _i , in II und III außerdem in den monoklin verzerrten OktaederlückenM _s des Olivingitters (M _i M _s SiO₄).Beim Einbau von Co²⁺ in Mg₂SiO₄ werden die kleinerenM _i O₆-Polyeder bevorzugt besetzt und aufgeweitet. Die Absorptionsspektren des Co _s ²⁺ von II und III konnten ermittelt werden, indem man die überlagerte Lichtabsorption des Co _i ²⁺ durch ein Näherungsverfahren eliminierte. Beim Übergang Co _s ²⁺(II) Co _s ²⁺(III) wird eine beträchtliche IR-Verschiebung beobachtet; sie ist die Folge der Aufweitung derM _s O₆-Polyeder bei der Substitution von Mg²⁺ (bzw. Co²⁺ durch Ca²⁺.Folge der starken Verzerrung der Koordinationsoktaeder im Olivingitter, deren Konstitution ausführlich beschrieben wird, ist eine Verbreiterung und Aufspaltung der Absorptionsbanden. Während der Feldstärkenparameter für Co _i ²⁺ in den Co-haltigen Olivinphasen mit (Co²⁺) von Co _x Mg_1-x O vergleichbar ist. resultieren für Co _s ²⁺ auffallend niedrige -Werte.

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Mixed crystals Co _x Mg_1–x CaSiO₄ (I)<0,1x1,0>, Co _x Mg_2–x SiO₄ (II) <0,05x2,0>, and {CoCaSiO₄+yCo₂SiO₄} (III) –1). These phases crystallize in the olivine structure (M _i MM _s SiO₄) containing two differently distorted octahedral sites (M _i of triclinic andM _s of monoclinic symmetry).In I the Co²⁺ are incorporated in the intersticesM _i , in II and III in the intersticesM _s in addition. In II—for small values ofx—the smallerM _i O₆-polyhedra are occupied preferably by Co²⁺ and also widened. The spectra for Co _s ²⁺ of II and III could be obtained by eliminating the superimposed absorption of the Co _i ²⁺ using an approximative substraction method. Going from Co _s ²⁺(II) to Co _s ²⁺(III) produces a considerable shift of the absorption bands towards IR as a consequence of the expansion of theM _s O₆-polyhedra caused by the large Ca²⁺ in III.The considerable distortion of the coordination octahedra in the olivine lattice causes a broadening and splitting of the absorption bands. Whereas the ligand-field-parameter of Co²⁺ in theM _i -sites ofM _i M _s SiO₄ may be compared to (Co²⁺) of Co _x Mg_1–x O, remarkably low -values are observed for Co _s ²⁺.

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Mit 8 Abbildungen

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14. Mitt.:O. Schmitz-DuMont, H. Fendel, M. Hassanein undHelga Weissenfeld; Mh. Chem.97, 1660 (1966).     

A thermodynamic interpretation of the behavior of higher fatty alcohols and acids upon the chromatographic paper

An idea was presented of treating the chromatographed substance as a “solute,” and the chromatographic system, composed of the stationary and the mobile phase as a “solvent.” Moreover the concept of “local equilibrium” was introduced, allowing to regard a given chromatographic spot as a “binary solution.” Thus a possibility arose to apply the classical thermodynamic approach, normally used for binary solutions, and namely: μ_i = μ_i + RT ln x_iƒ_i, where μ_i—chemical potential of the “i”-th compound in the solution, μ_i—chemical potential of the pure “i”-th compound, x_i-molar fraction of the “i”-th compound, ƒ_i—its activity coefficient, in a modified form, suitable for the chromatographic purpose.     

Influence of magnetic dilution on the spin transition in the complex of iron(II) nitrate with 4-amino-1,2,4-triazole

Influence of magnetic dilution with Zn^II ions on the spin transition in the iron nitrate complex of 4-amino-1,2,4-triazole (AT) was studied by magnetochemistry, Mössbauer spectroscopy, and IR spectroscopy. In studies of the properties of solid phases of Fe _x Zn _1–x (AT)₃(NO₃)₂ (0.01x0.8), it was demonstrated that magnetic dilution results in a lowered spin transition temperature and an increased share of the high-spin form of the iron(II) complex.Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 6, pp. 145–151, November–December, 1993.Translated by L. Chernomorskaya     

Some theoretical aspects on morphology development in seeded composite latexes. I. Batch conditions below monomer saturation

In seeded emulsion polymerization, during the second stage, new interfaces appear and the surface area changes. A thermodynamic equilibrium approach is presented which predicts particle morphology of a whole range of non-spherical particles upon polymer conversion. Simulation takes into account swelling ratio, molar volumes and interfacial tension. As the particle geometry is complex, a new mathematical procedure is detailed.The computed data are useful to discuss either the stability or the instability of the particles morphology. These results must be compared with actual experimental structures.Abreviations and symbols G Gibbs' free energy - reduced Gibbs' free energy - _i interfacial tension - ₁₂ interfacial tension between polymer 1 and polymer 2 - _1w interfacial tension between polymer 1 and water - _2w interfacial tension between polymer 2 and water - r ₁ polymer 1 swollen by monomer 2 sphere radius - r ₂ polymer 2 swollen by monomer 2 sphere radius - r _i interfacial radius - h ₁ sphere 1 distance to minimal section - h ₂ sphere 2 distance to minimal section - h _i interfacial sphere distance to minimal section - sign ofh _i, positive when the interface sphere is on the side of the sphere 2, negative when the interface sphere is on the side of the sphere 1 - A ₁₂ surface between polymer 1 and polymer 2 - A _1w surface between polymer 1 and water - A _1w ⁰ surface between polymer 1 and water before polymerization - A _2w surface between polymer 2 and water - v ₁ volume of the polymer 1 swollen by monomer 2 - v _i volume of the polymer 1 swollen by monomer 2 before polymerization - v ₂ volume of the polymer 2 swollen by monomer 2 - V _p1 polymer 1 molar volume - V _p2 polymer 2 molar volume - V _m2 monomer 2 molar volume - n _p2 polymer 2 number of mole - n _p1 polymer 1 number of moles - n _m21 monomer 2 number of mole in the swollen polymer 1 - n _m22 monomer 2 number of mole in the swollen polymer 2 - n _m2 monomer 2 total number of mole - n _m2 monomer 2 number of mole before polymerization - TGn ₁ polymer 1 swelling rate - TGn ₂ polymer 2 swelling rate - TGn _i maximum number of mole of monomer 2 in polymeri by mole of polymeri - x polymer 2 conversion rate - K, p, q mathematical variables - D, r, a mathematical variables     

Magnetische Eigenschaften der ternären Phase (Co x Ni1−x )11Se8

The composition range of the ternary body-centered tetragonal phase (Co _x Ni_1–x )₁₁Se₈ extends fromx=0.03 tox=0.37 at 580°C. The magnetic susceptibilities and their variation with temperature and composition were investigated within the temperature range from 100 to 300 K using a magnetic balance. The temperature dependence of the magnetic suceptibilities was found to be consistent with theCurie-Weiss law from which magnetic moments were derived. Assuming the magnetic moments as spin-only values each cobalt atom contributes two unpaired electrons. Change in composition did not affect the magnitude of the magnetic moments. Based on crystallographic and magnetic data a simple model for the mutual distribution of cobalt and nickel atoms could be constructed.

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Mit 3 Abbildungen     

Mass transfer in the gas phase during top-blowing with plasma jets

Deoxidation of copper melts by hydrogen has been investigated experimentally by top-blowing with argon-hydrogen plasma jets. The course of the deoxidation process has been described mathematically using kinetic laws. The overall divided course of the process can be examined in live partial steps, which are hydrogen transport within the gas phase, hydrogen transport within the melt, oxygen transport within the melt, reaction between hydrogen and oxygen, and H₂O transport within the gas phase. Based on these five elementary processes, an equation for the velocity of deoxidation has been derived. The values of the rate of deoxidation resulting from this equation, in combination with the mass-transter coefficients valid for this process, have been compared to the experimental data. The results of this study verify those of former investigations on vaporization of elements out of copper melts. The mass-transfer coefficients are the same, when the local activity differences are used as the driving force for mass transport in a system. This means that the surface-renewal theory is valid, when mass-transfer coefficients are defined in this way. This is the case, at least, when metallic melts are subjected to top-blowing by plasma jets.Nomenclature a activity (a _i =x _{i i} ) - A _c (m²) effective mass-transfer area - D(m) characteristic length, such as diameter - D _r(m²/s) diffusion coefficient - H(Cu) oxygen dissolved in copper - k _g (mol/m²s) mass-transfer coefficient in the gas phase [k _g (i) mass-transfer coefficient for speciesi] - k _N (mol/m²s) mass-transfer coefficient in the melt phase - K _i = (x _i /y _i )_eq equilibrium coefficient (distribution coefficient) - n _N (mol) mole number of the melt phase - n _G (mol) mole number of the gas phase - n _i (mol/s) mole flow of speciesi - O(Cu) oxygen dissolved in copper - p(N) momentum flow - t(s) time - T (°C or K) temperature;T _G : in the gas,T _s : in the melt,T ^f : at the phase interface - x _i (mol/mol) concentration in the melt - y _i , (mol/mol) concentration in the gas phase - activity coefficient     

Kalorimetrischer und elektronenmikroskopischer Nachweis von Entmischungserscheinungen im pseudobinären System Dipalmitoyllecithin/ Dipalmitoyl-N-methyl-kephalin

By means of differential scanning calorimetry and electron microscopy the miscibility properties of the system dipalmitoyllecithin/dipalmitoyl-N-methyl-cephaline/ water (50 wt-% water) was studied. In theL _α-phase (high temperature phase) both phospholipids were completely miscible. On the other hand in the low temperature phases demixing occurs in the concentration range fromx _MPE?0.05 tox _MPE?0.35. The electron microscopy confirms these results. The electron microscopic pictures showed the ripple structure of theP _β phase.     

Extending the applicability of TG measurements to industry and to quality ensuring by dimensionless analysis

TheI _i=E _i/RT _i dimensionless evaluation is very suitable for describing the TG measurements according to theE _i/RT _i=lnA +n[ln(1–)_i]–ln(d/dr)_i equation. TheI _i andE _i functions make the comparison of the different TG measurements possible quantitatively in the case of more DTG peaks as well.TheI _i andE _i values as function of (1-)_i and 1/T _i open new way for further theoretical and practical studies by TG measurements. Such types of results are the quantitative determination of the effect of the measuring conditions, the measuring of the mechanochemical effect of grinding and among others the explanation of the self-hardening process of fly ashes of power stations.Strict connections exist between theI _i functions and the constants of the compensation effect (CE). These constants (tan, axis intersect) can be calculated directly from the average of the measured data of theI _i function making the introduction and theoretical and practical application of the idea of general activation energy (¯E) possible. The quantitative characterisation of the examined materials of the fine structure ofCE and of the thermal processes together proves the extending importance of TG measurements from industrial and material qualification aspects as well.The author thanks gratefully to Professor Márta Fehér mathematicien, Head of the Department of Philosophy at the Technical University of Budapest for the consultations and for the encouragements.     

Stoichiometry and conformation of the azacrown moiety in sodium complexes of azacrown ethers. A Raman/IR spectroscopic study. Part I: Complexes of 4,13-Diaza-18-crown-6

Three sodium complexes (bromide, iodide and thiocyanate) of 4,13-diaza-18-crown-6 were studied using Raman and IR spectroscopy and normal coordinate calculations to probe the stoichiometry of the complexes and the variation in the conformation of azacrown moiety on complex formation. complex formation is accompanied by characteristic shifts of the bands, especially of those in the 800–900 cm^–1 region. Complexes of both 11 and 21 stoichiometry were observed. Normal coordinate calculations showed the reduction of symmetry of azacrown moiety toC _i , in contrast to theC _2h symmetry known for the parent azacrown and potassium thiocyanate complex.     

MO-Berechnungen an Heterocyclen, 2. Mitt.: Die Anwendung verschiedener SCβ-Techniken auf pyrrol-und pyridinartige Heterocyclen

Zusammenfassung Die Übertragung der vonLonguet-Higgins undSalem entwickelten Beziehung zwischen _rs undp _rs ergibt von allen untersuchten SC-HMO-Verfahren die besten Resultate. Die Abhängigkeit der MO-Daten von der Größe der Bindungsalternation (Iterationsparameterx) einerseits und desCoulomb-integrals des Heteroatoms andererseits wird studiert. Es zeigt sich, daß einige Ergebnisse wie Superdelokalisierbarkeiten und Atomlokalisierungsenergien in kritischer Weise von diesen (bzw. einem dieser) Einflüssen abhängen. Berechnete Bindungslängen stehen in guter Übereinstimmung mit experimentellen Angaben. Dies ist ein direkter Hinweis auf die Möglichkeit der Verwendung einer einheitlichen Iterationsbeziehung für alle Bindungen.

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The application of an iteration relation between _rs andp _rs developed byLonguet-Higgins andSalem gives the best results of all investigated SC-HMO methods. The dependence of MO quantities from bond alternation (iteration parameterx) and theCoulomb integral of the heteroatom, respectively, is studied. It is shown, that the value of the iteration parameterx or (and) of theCoulomb integral critically influence some MO quantities such as atom localization energies and superdelocalizabilities. Calculated bond length are in fair agreement with experiment.

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Mit 2 Abbildungen     

Interfacial properties of mixtures of lecithin with a block copolymer surfactant at the water/air and water/oil interfaces

Surface pressure-area isotherms have been determined for both a pure lecithin (L, -dipalmitoyl phosphatidyl choline) and an impure lecithin (soya bean lecithin) at the water/air and water/oil interfaces. Equations of state have been applied and an equation of Gaines was found to be particularly successful in describing the isotherms. Mixed monolayers with an ABA nonionic block copolymer surfactant (A is poly(12-hydroxystearic) acid and B is poly(ethylene oxide)) were also investigated. The additivity rule was obeyed only at high surface pressures; inefficient packing was observed at low surface pressures. The polymer may promote a horizontal headgroup orientation in the lecithin, which gives rise to this effect. The presence of electrolyte up to very high concentrations in the aqueous phase (8.75 mol dm^–3 NH₄NO₃) was shown to expand the lecithin monolayer.Glossary of symbols W/A Water-air interface - W/O Water-oil interface - E/A Electrolyte-air interface - L-C Liquid-condensed - A _c Area per molecule obtained by conventional extrapolation of the -A isotherm at close-packing - A _e Experimentally determined area per molecule - A _t Theoretically predicted area per molecule - A _v Area per molecule obtained by vertical extrapolation of the -A isotherm at close-packing - A ₀ Head group area term - f _i Activity coefficient of water in surface region - i Constant - x _i Mol fraction of componenti - Z Compressibility factor=A/kT - Interfacial tension - Surface pressure - _i Partial molar area of component i     

Background elimination in three-dimensional spectroscopy using the intensian method

The method to eliminate background in the case of quantitative multidimensional spectroscopy, chromatography or any analytical 3-dimensional technique is shown. The 3-dimensional signal is required to be proportional to the concentration of determined substance and the additivity of signals should be obeyed. Eliminated background is assumed to be a low-order polynomial of two variables. The intensian method [1] is a generalization of the Beer-Lambert law, where a certain determinant called intensian replaces absorption and absorptivity. In practice there will be no need to use determinants, since usually they are replaced by expressions of few terms. Some details on the practical use of the method are given.Index of used symbols x, y UV, IR, GC, NMR or other scale. - A (x, y) intensity (absorption) of the 3-dimensional band of interest. - a (x, y) standard intensity (absorption) of the 3-dimensional band of interest. - B(x, y) intensity (absorption) of 3-dimensional background. - S(tx, y) intensity (absorption) of 3-dimensional multicomponent spectrum. - f (x, y) auxiliary function:f (x, y) =A (x, y), B(x, y), a(x, y), S(x, y). - (x _i, Yi) selected point,i positive integer number. - f(xi, yi) value off (x, y) in point (xi, yi). - S _i value ofS(x, y) in point (x _i, y_i). - b pathlength, measurement coefficient,c concentration. - , , , real numbers. - ij, _ij real coefficients of power expansions. - x ⁱy^j monomial of degree (i +j). - F(·) linear functional acting on 3-dimensional spectral functions. - J^3-dim(·) 3-dimensional intensian acting on 3-dimensional spectral functions. - J _n ^3-dim (·) 3-dimensionaln-points intensian. - d _i ith intensian coefficient, cofactor of expansion of J _n ^3-dim (f(x, y)) according to its first row (eq. (10)). - (.) absolute error. - r _i,, R random variables: eqs. (13) and (14). - G(.) (normal) distribution function. - z ordinate axis. - a - f , h abreviations for some arguments. - d _ijk,D _mnp abreviations defined in eq. (22).     

Bilayer studies in mixedn-decanol/n-tetradecanol complexes ofn-decylammonium beidellite

Complexes have been prepared by treatment ofn-decylammonium beidellite with mixtures ofn-decanol andn-tetradecanol with different concentrations. Measurements of the basal spacings of the obtained complexes have been performed in a wide range of temperatures. Three different bilayer phases have been established between (20 and 70°C: the _i(C₁₀) phases (=bilayers ofn-decyl chains); the _i(C₁₀/C₁₄) phases (=mixed bilayers ofn-decyl andn-tetradecyl chains in molar ratio approximately 1:1) and the _i(C₁₄) phases (=bilayer ofn-tetradecy 1 chains with then-decylammonium ions included). In all bilayer phases the chains stand perpendicular to the silicate interfaces. In definite concentration ranges two of the phases coexist, i.e., miscibility gaps occur, which disappear at temperatures higher than the temperature of the _i/ transition. The miscibility gaps are reversible with temperature. The composition of the intercalated bilayers has been studied by HPLC of the excess alkanol mixture separated from the beidellite complexes after the equilibrium has been reached. There is preferential adsorption of one of two alkanols from the mixture, which is in agreement with the observed miscibility gaps. The space filling problem as well as the structure of the three bilayer phases observed have been discussed.