Untersuchungen zur Trennung der Seltenen Erden durch Ionenaustausch, 2. Mitt.: Ionenaustauschgleichgewichte in Gegenwart von Acetat

Zusammenfassung Messungen der Verteilungskoeffizienten für die Ionenaustauschgleichgewichte S.E.³⁺–NH₄ ⁺ (S.E.=Y, La, Pr, Nd, Sm und Eu) in Gegenwart von Acetat (Ac) bestätigen die bei relativ niedrigen Acetatkonzentrationen aufgefundene Elutionssequenz. Bei höheren Konzentrationen ergeben sich Überschneidungen der K _v–c _Ac-Kurven. Es wird gezeigt, daß bei Betrachtung ausschließlich des Einflusses der Komplexbildung wegen der komplizierten Stöchiometrie im Falle einzähniger Liganden, wie des Acetations, Verschiebungen zu erwarten sind, falls die Differenzen entsprechender Stabilitätskonstanten verschiedenes Vorzeichen haben. Der Einfluß der Austauschaffinitäten wird insoferne berücksichtigt, als nur solchen Änderungen mögliche Realität zugestanden wird, weleho Verschiebungen in Richtung auf die normale, durch die Ionengrößen bedingte Sequenz darstellen.Mit 1 Abbildung     

Hexagonal high pressure phase of copper(I)tetraiodomercurate (Cu2HgI4)

Summary Using a high pressure X-ray camera Cu₂HgI₄ was subjected at room temperature to pressures up to about 8 GPa. A hexagonal high pressure phase (a=8.28 (2) Å,c=3.40 (0) Å, space group P lm,Z=1) could be detected. This phase shows a reversible transformation with pressure hysteresis. The transition occurs at 7 GPa when the pressure is increased but at 6 GPa when the pressure is decreased.

---

Hexagonale Hochdruckphase von Kupfer(I)tetraiodomercurat (Cu₂HgI₄)

Zusammenfassung Cu₂HgI₄ wurde in einer Hochdruckkamera bei Raumtemperatur mit einem Druck bis zu 8 GPa belastet. Dabei bildete sich eine hexagonale Hochdruckmodifikation (a=8.28 (2) Å,c=3.40 (0) Å, Raumgruppe P lm,Z=1). Für diese Phase wurde eine reversible Umwandlung mit Druckhysterese festgestellt. Mit steigendem Druck findet die Umwandlung bei 7 GPa mit sinkendem Druck jedoch bei 6 GPa statt.

     

Über die Auflösung der Seltenerdoxide in methanolischen Ammoniumacetatlösungen und die Darstellung von Verbindungen des TypsLn(OAc)3. 3NH4OAc. 1H2O bzw.Ln)OAc)3. 1 NH4OAc. 1H2O

Zusammenfassung Die Oxide der Lanthanide und des Yttriums lösen sich beim Erhitzen in methanol. Ammoniumacetatlösungen. Aus den Lösungen konnten Verbindungen vom TypLn(OAc)₃·3 NH₄ OAc· ·1 H₂O (Ln=La, Ce, Pr, Nd, Sm Eu, Gd, Tb, Dy, Ho) bzw. Ln(OAc)₃ 1 NH₄OAc 1 H₂O (Ln=Er, Yb, Y) isoliert werden.Die höheren Oxide PrO_1,83 und TbO_1,75 lösen sich nur unvollständig unter Valenzdisproportionierung. Der Löserückstand besteht aus PrO₂ bzw. TbO₂.

---

The oxides of the lanthanides and yttrium are dissolved in the heat by methanolic ammonium acetate solutions. From the obtained solutions compounds of the typeLn(OAc)₃·3 NH₄ OAc· ·1 H₂O (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho) andLn(OAc)₃·1 NH₄OAc·1 H₂O (Ln=Er, Yb, Y), respectively, could be isolated.The higher oxides PrO_1,83 and TbO_1,75 react incompletely and disproportionation of valence is observed. The residues consist of PrO₂ and TbO₂, respectively. *** DIRECT SUPPORT *** A3615112 00028

     

BIOSYNTHESIS OF PTERIDINES IN Neurospora crassa,Phycomyces blakesleeanus AND Euglena gracilis: DETECTION AND CHARACTERIZATION OF BIOSYNTHETIC ENZYMES*,†

Abstract— Occurrence, biosynthesis and some functions of tetrahydrobiopterin (H₄biopterin) in animals are well known. The biochemistry of H₄biopterin in other organisms than animals was hitherto not widely investigated. Recently H₄biopterin was found in the phytoflagellate Euglena gracilis, in the zygomycete Phycomyces blakesleeanus and in the ascomycete Neurospora crassa. In Euglena, Neurospora and Phycomyces the enzymatic activities of GTP cyclohydrolase I, 6-pyruvoyl tetrahydropterin synthase and sepiapterin reductase are detectable and the biosynthesis follows the same steps as were shown for animals. The biosynthetic enzymes, however, show a much lower sensitivity to those inhibitors that act on vertebrate enzymes. 2,4-Diamino-6-hydroxypyrimidine as inhibitor of GTP cyclohydrolase I and N-acetylserotonin or N-methoxyacetylserotonin as inhibitors of sepiapterin reductase can decrease pteridine biosynthesis significantly, in vitro and in vivo. The apparent K_mvalues are in general higher when compared with the respective animal enzymes. In Neurospora, the conversion of GTP to dihydroneopterin triphosphate was closely associated with subsequent production of 6-hydroxymethyl-7, 8-dihydropterin due to the high activity of dihydroneopterin aldolase, different from all other tested organisms. Investigations involving inhibition of pteridine synthesis might be a useful tool for evaluating the hypothesis that pteridines in fungi and plants are co-chromophores of various blue light-dependent, flavin-containing phototrcptors.     

Farbe und Konstitution bei anorganischen Feststoffen, 14. Mitt.: Die Lichtabsorption des zweiwertigen Kupfers in oxidischen Wirtsgittern

Zusammenfassung Um die Beziehungen zwischen der Lichtabsorption des zweiwertigen Kupfers nach isomorphem Einbau in ein oxidisches Wirtsgitter und dessen Konstitution aufzufinden, wurde Cu²⁺ in oktaedrischer (Cu _x Mg _1–x TiO₃, Cu _x Cd _1–x TiO₃, Cu _x Mg _1–x CaSiO₄, Cu _x Mg _1–x CaGeO₄, Cu _x Mg _2–x SiO₄, Cu _x Mg _2–x GeO₄) und tetraedrischer Koordination (Cu _x Zn_2–x SiO₄, Cu _x Mg _1–x Cr₂O₄) spektralphotometrisch untersucht. Die Farbkurven besitzen mindestens 2 Absorptionsbanden (Kristallfeldbanden) im längerwelligen und eine oft gut ausgeprägte Elektronenübergangsbande (charge transfer) im kürzerwelligen Spektralbereich. In einigen Fällen ist noch eine zweite Elektronenübergangsbande als Schulter zu erkennen. Es wurden auch Cu-haltige 2,3- und 2,4-Spinelle spektralphotometrisch untersucht (Cu _x Mg _1–x Al₂O₄, Cu _x Mg _1–x Ga₂O₄, Cu _x Cd _y Zn _1–x–y Al₂O₄, Cu _x Mg _2–x SnO₄, Cu _x Mg _2–x TiO₄, Cu _x Zn _1–x MgTiO₄, Cu _x Mg _1–x Cd _y TiO₄). Es zeigte sich, daß Cu²⁺ immer auf Tetraeder- und Oktaederlücken verteilt ist. Eine Aufweitung des Wirtsgitters durch isomorphen Einbau größerer Kationen bewirkt nicht immer eine IR-Verschiebung der Banden, sondern in einigen Fällen (Spinellphasen) auch eine UV-Verschiebung. Eine Sonderstellung nimmt das ägyptisch-Blau CuCaSi₄O₁₀ ein, da hier das Cu²⁺ von 4 O_2– in planarer Anordnung umgeben ist. Die Farbkurve weist 3 Maxima auf im Einklang mit der Kristallfeldtheorie.

---

In order to find out relations between the lightabsorption of bivalent copper isomorphously incorporated into an oxidic host lattice and the constitution of this lattice, the spectrum of Cu²⁺ has been investigated in octahedral (Cu _x Mg_1–x TiO₃, Cu _x Cd _1–x TiO₃, Cu _x Mg _1–x CaSiO₄, Cu _x Mg _1–x CaGeO₄, Cu _x Mg _2–x SiO₄, Cu _x Mg _2–x GeO₄) and tetrahedral coordination (Cu _x Zn _2–x SiO₄, Cu _x Mg _1–x Cr₂O₄). The colour curves show at least 2 absorption bands within the region of longer wave length and a charge transfer band often well developed in the range of shorter wavelength. In some cases also a second charge transfer band becomes conspicuous as a shoulder. Copper containing 2,3- and 2,4-spinels have been also investigated (Cu _x Mg _1–x Al₂O₄, Cu _x Mg _1–x Ga₂O₄, Cu _x Cd _y Zn _1–x–y Al₂O₄, Cu _x Mg _2–x SnO₄, Cu _x Mg _2–x TiO₄, Cu _x Zn _1–x MgTiO₄, Cu _x Mg _1–x Cd _y Zn _1–y TiO₄). From the colour curve one can infer that Cu²⁺ occupies in the spinels always tetrahedral as well as octahedral interstices. A widening of the lattice does not effect always a shifting of the absorption bands towards IR but in some cases (spinel phases) also the inverse shifting will occur. An exceptional case represents the egyptian blue CuCaSi₄O₁₀ since in this lattice the Cu₂₊ are surrounded by four O^2– in a coplanar arrangement. The colour curve shows three absorption bands in agreement with the crystal field theory.

---

---

Mit 20 Abbildungen     

Pore Development during the Carbonization Process of Lignin Microparticles Investigated by Small Angle X-ray Scattering

Application of low-cost carbon black from lignin highly depends on the materials properties, which might by determined by raw material and processing conditions. Four different technical lignins were subjected to thermostabilization followed by stepwise heat treatment up to a temperature of 2000 °C in order to obtain micro-sized carbon particles. The development of the pore structure, graphitization and inner surfaces were investigated by X-ray scattering complemented by scanning electron microscopy and FTIR spectroscopy. Lignosulfonate-based carbons exhibit a complex pore structure with nanopores and mesopores that evolve by heat treatment. Organosolv, kraft and soda lignin-based samples exhibit distinct pores growing steadily with heat treatment temperature. All carbons exhibit increasing pore size of about 0.5–2 nm and increasing inner surface, with a strong increase between 1200 °C and 1600 °C. The chemistry and bonding nature shifts from basic organic material towards pure graphite. The crystallite size was found to increase with the increasing degree of graphitization. Heat treatment of just 1600 °C might be sufficient for many applications, allowing to reduce production energy while maintaining materials properties.     

Formation of a Special Intermediate during Phase Transformation of Zeolite NaA to Nepheline

In the process of phase transformation of zeolite NaA to nepheline under hydrothermal conditions a special intermediate occurs. This is due to the high reaction rate of nepheline formation in the presence of water molecules. Consequently, the usually observed amorphous material with high condensed silica does not occur as separate phase. – The intermediate which is formed due to the destruction of the long-range order of zeolite is significantly short-range ordered. The phase transformation process starts at the outer surface of zeolite crystals, thus generating a diffusion barrier for sorption uptake processes.     

3D-shaping of biodegradable photopolymers for hard tissue replacement

Continuously increasing life expectancy results in a rising number of bone diseases and fractures. Replacements from natural sources are not only limited in their availability, they also have some serious disadvantages such as possible immunological reactions or transmission of diseases. New synthetic biodegradable materials based on photopolymers could be an alternative solution. In these investigations an acrylate-based monomer formulation has been developed, consisting of a biodegradable basis monomer which is derived from gelatin, different reactive diluents, an appropriate photoinitiator and filler materials. For the three-dimensional shaping process stereolithography is the method of choice because of its capability to produce cellular structures with high resolutions.