UR-spektroskopische Untersuchungen an zeolithischen Heptagermanaten

Zusammenfassung Der direkte Nachweis von H₃O⁺-Ionen bzw. OH^–-Ionen in zeolithischen Germanaten wird durch UR-spektroskopische Untersuchungen erbracht. Hydronium-Ionen liegen vor beiM(I)₃HGe₇O₁₆·nH₂O sowie bei Ba- und Pb-Zeolithen der FormM(II)_2–x H_2x Ge₇O₁₆·nH₂O, während man in Ba- und Pb-Zeolithen der ZusammensetzungM(II)_2+x Ge₇O₁₆(OH)_2x ·nH₂O Hydroxyl-Ionen beobachtet.

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By IR-spectroscopic investigations of zeolitic germanates of formulaM(I)₃HGe₇O₁₆·nH₂O as well as of Ba- and Pb-zeolites of formulaM(II)_2–x H_2x Ge₇O₁₆·nH₂O the presence of H₃O⁺-ions can be detected. On the other hand inM(II)_2+x Ge₇O₁₆(OH)_2x ·nH₂O (M=Ba, Pb) hydroxyl ions are observed.

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Mit 2 Abbildungen     

Chemie der Seltenerdmetalle, 26. Mitt.: Tartrate der Seltenen Erden des TypsLn 4 T 3·xH2O und ihre Reaktion mit HCl

Zusammenfassung Nachstehende Verbindungen wurden hergestellt: Pr₄ T ₃·13 H₂O, Nd₄ T ₃·12 H₂O, Sm₄ T ₃·12 H₂O, Gd₄ T ₃·12 H₂O, Tb₄ T ₃·13 H₂O, Dy₄ T ₃·12 H₂O, Ho₄ T ₃·14 H₂O, Er₄ T ₃·14 H₂O, PrH₂ TCl·3 H₂O, NdH₂ TCl·3 H₂O, SmH₂ TCl·3 H₂O, GdH₂ TCl·4 H₂O, TbH₂ TCl·3 H₂O, DyH₂ TCl·2 H₂O, HoH₂ TCl·3 H₂O, ErH₂ TCl·3 H₂O. Die Präparate wurden mit Thermoanalyse, IR-Absorptionsspektren, Röntgenstreuung und hinsichtlich Löslichkeit weiter untersucht.

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Chemistry of the rare earth metals, XXVI: Tartrates of the rere earths of the types Ln₄T₃·xH ₂ O, and their reaction withHCl

The above series of compounds has been prepared and further characterized by thermal analysis, IR spectra, X-ray diffraction, and solubility.

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Ln=Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er.

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H₄ T=C₄H₆O₆.     

Lanthankomplexe mit 2,2′-Bipyridin-N,N′-dioxid

Compounds of the composition La(bpyO₂ ^*)₄Cl₃·4H₂O, La(bpyO₂)₃Cl₃·5H₂O, La(bpyO₂)₂Cl₃·3H₂O, La(bpyO₂)Cl₃·3H₂O, La(bpyO₂)₄Br₃·4H₂O, La(bpyO₂)₃Br₃·8H₂O, La(bpyO₂)₂Br₃·7H₂O, La(bpyO₂)Br₃·4H₂O, La(bpyO₂)₄I₃·3H₂O, La(bpyO₂)₃(NO₃)₃·2H₂O, La(bpyO₂)₂(NO₃)₃·2H₂O, La(bpyO₂)₄(SCN)₃·3H₂O, La(bpyO₂)₃(SCN)₃·2H₂O, La(bpyO₂)₂(SCN)₃·2H₂O were isolated. They were investigated by means of thermoanalysis, I.R. spectroscopy, X-ray diffraction and molar conductivity.     

Vanadyl phosphate dihydrate,a solid acid: the role of water in VOPO4·2H2O and its sodium derivatives Na x (VIV x VV 1−x O)PO4·(2−x)H2O

Sodium-containing intercalates having as general formula Na _x VOPOP₄·(2–x)H₂O (0.25x<0.50) have been obtained and characterized. Orthorhombic phases, which essentially maintain the structure of the layered oxide hydrate VOPO₄·2H₂O result. Intercalated sodium ions act as pillars. The presence of H₃O⁺ ions in the parent VOPO₄·2H₂O and also in some reduced phases, is detected. The understanding of the structural role of the water molecules is advanced and the topotactic dehydration/rehydration processes are studied. The formation of a new metastable VOPO₄·H₂O phase is established.     

Ion-Exchange Properties of Alkali-Metal Redox-Intercalated Vanadyl Phosphate

Ion exchange of alkali metals in M_xVOPO₄·yH₂O (M=H, Na, K, Rb, Cs) is reported. The role of valence, size, and affinity of the cations in the exchange process is discussed. The interlayer distance in the H_1-xK_xVOPO₄·yH₂O system is discussed in terms of finite layer rigidity theory. Different behavior is observed for K_xNa_1-xVOPO₄·yH₂O dependening on the starting compound used. When potassium in KVOPO₄·H₂O is exchanged for Na⁺, one phase compound is formed. In contrast, K_xNa_1-xVOPO₄·yH₂O formed from NaVOPO₄·H₂O and K⁺ is a multiphase system. Ion exchange does not proceed when exchanging ions differ distinctly from each other in size, e.g., sodium and cesium.     

Capacitive and textural characteristics of manganese oxide prepared by anodic deposition: effects of manganese precursors and oxide thickness

The influence of manganese precursors on the deposition rate of hydrous manganese oxide in the amorphous form (denoted as a-MnO_x·nH₂O) and the effect of oxide thickness on the electrochemical properties of a-MnO_x·nH₂O, for application as electrochemical supercapacitors, were systematically investigated in this work. The results showed that Mn(CH₃COO)₂·4H₂O is a more promising precursor because of its high deposition rate at much lower potentials in comparison with MnSO₄·5H₂O, MnCl₂·4H₂O, and Mn(NO₃)₂·4H₂O. The capacitive characteristics of a-MnO_x·nH₂O were found to be independent of precursors, probably due to the fact that the mean oxidation state of Mn is not significantly affected by changing the anions of manganese precursors (from the XPS results). The capacity of oxide deposits was found to be proportional to the charge density of deposition (i.e., loading) of a-MnO_x·nH₂O when it was equal to or less than a critical value (ca. 3.5 C cm^–2), while poorer capacitive behavior with a lower capacity was clearly found beyond this critical value. The a-MnO_x·nH₂O deposit with 3.5 C cm^–2, exhibiting an acceptable capacitive performance, showed the highest capacity of energy storage for supercapacitors.     

Tetraalkylammonium fluorooxoperoxovanadates

Summary Compounds crystallizing from theMOH-HF-V₂O₅-H₂O₂-H₂O (M=N(CH₃)₄, N(C₂H₅)₄, N(C₄H₉)₄) system have been characterized by elemental analysis, vibrational spectra, and X-ray powder patterns. Besides [N(CH₃)₄]₂[VO(O₂)₂F]·2H₂O (1) and [N(CH₃)₄]₃[V₂O₂(O₂)₄F] (2) which correspond to the known compoundsM ₂[VO(O₂)₂F] (M=K, NH₄, Cs) and (NH₄)₃[V₂O₂(O₂)₄F]·2H₂O, respectively, complexes of two new types have been obtained: [N(C₂H₅)₄]₂[V₂O_5–x (O₂) _x F₂]·H₂O(x0.25,3) and the first trinuclear peroxo complex of vanadium(V), [N(C₄H₉)₄]₂[V₃O₃(O₂)₄F₃]·6H₂O(4).

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Tetraalkylammonium-Fluorooxoperoxovanadate

Zusammenfassung Aus dem SystemMOH-HF-V₂O₅-H₂O₂-H₂O (M=N(CH₃)₄), N(C₂H₅)₄, N(C₄H₉)₄) kristallisierende Verbindungen wurden mittels Elementaranalyse, Schwingungsspektroskopie und Röntgendiffraktion charakterisiert. Neben [N(CH₃)₄]₂[VO(O₂)₂F]·2H₂O (1) und [N(CH₃)₄]₃][V₂O₂(O₂)₄F] (2), welche den bekannten VerbindungenM ₂[VO(O₂)₂F] (M=K, NH₄, Cs) und (NH₄)₃[V₂O₂(O₂)₄)F]·2H₂O entsprechen, wurden zwei neue Typen von Komplexen erhalten: [N(C₂H₅)₄]₂[V₂O_5–x (O₂) _x F₂]·H₂O (x0.25,3) und der erste dreikernige Peroxokomplex von Vanadium(V), [N(C₄H₉)₄]₂[V₃O₃(O₂)₄F₃]·6H₂O (4).

     

Neutron diffraction study on protonated and hydrated layered perovskite

A layered perovskite compound with Na⁺, D₃O⁺ ions (H₃O⁺) and D₂O molecules (H₂O) in the interlayer, D_xNa_1−xLaTiO₄·yD₂O, has been prepared by an ion-exchange/intercalation reaction with dilute DCl solution, using an n=1 Ruddlesden-Popper phase, NaLaTiO₄. Its structure has been analyzed in order to clarify the interlayer structure by Rietveld method, using powder neutron diffraction data. The structure analysis revealed that the layered structure changed from the space group P4/nmm-I4/mmm after the ion-exchange/intercalation reaction, and it induced the transformation of perovskite layers from staggered to an eclipsed configuration. The D₂O molecules and D₃O⁺ ions loaded in the interlayer statistically occupied the sites around a body center position of rectangular space surrounded by eight apical O atoms of TiO₆ octahedra in upper and lower layers.     

Synthesis, structure and properties of CsHSi3O7, a layered silicate with a chiral structure

The chiral layered silicate CsHSi₃O₇ has been synthesized by hydrothermal techniques, and its structure determined by single crystal X-ray diffraction. The compound crystallizes in the space group P2₁2₁2₁. The silicate single layer consists of both four- and three-connected SiO₄ tetrahedra and may be considered as a member of a series of layer structures with the general formula (Si₄O₉)_m(Si₂O₅)_n. Strong hydrogen bonds occur between the terminal OH⁻ and O²⁻ ions of neighboring layers. The Cs⁺ cations can be ion-exchanged by protons to give a phase of composition H₂Si₃O₇·H₂O with a water molecule occupying the original Cs position, as confirmed by single crystal X-ray diffraction data. The water molecule in H₂Si₃O₇·H₂O can be readily removed without collapse of the crystal structure. Both CsHSi₃O₇ and H₂Si₃O₇·H₂O show SHG (second harmonic generation) efficiencies comparable to that of quartz, and both are not phase-matchable materials.     

Effect of intercalation of metal ions on the colloidal and solid properties of vanadium pentaoxide hydrate,V2O5 nH2O

The colloidal stability of V₂O₅ nH₂O was studied on the basis of the measurements of critical flocculation concentration (CFC) by metal ions, amount of ions exchanged (or intercalated), and -potential. In total, the CFC values obeyed the Schulze Hardy law and strong Hofmeister's series was found in the systems including alkaline ions. The sequence of colloidal stability of V₂O₅ nH₂O in the electrolyte solutions was related to the intercalation of metal ions in the interlayer spaces of the solid. The largest CFC value for Li⁺ (87 mmol dm^–3) was explained by smaller affinity of Li⁺ to be intercalated in V₂O₅ nH₂O as well as smaller Hamaker constant of the intercalated solid compared to the other systems.Effect of intercalation of metal ions on the crystalline properties of the materials was measured by use of XRD and electron microscope. Under highly dehydrated condition the ions whose radii are smaller than 0.1 nm are captured in the structure of V₂O₅ nH₂O without changing interlayer distances, while those larger than 0.1 nm increase the interlayer distance. In a saturated H₂O vapor interlayer distances increased with increasing charge of intercalated ions. However, when intercalated with ions carrying the same valency the interlayer distances of the sample decreased with decrease in the hydration property of ions. Hydrolyzable Cr³⁺ gave exceptionally larger interlayer distances, both in a vacuum and in H₂O vapor.     

Structural and thermal interpretation of the synergy and interactions between the fire retardants magnesium hydroxide and zinc borate

The mechanism of cooperative action of commercial fire retardants is interpreted as resulting from specific chemical reaction and phase changes. This investigation focuses on the thermally initiated interactions between two forms of commercially available fire retardant compounds. The fire performance of a polyolefin with a metal hydroxide fire retardant, magnesium hydroxide, can significantly reduce the heat release rate through absorption of heat during conversion to its metal oxide. Formation of water, followed by vaporisation, decreases heat and dilutes volatiles from polymer degradation. The second form of fire retardant compounds are zinc borates (2ZnO·3B₂O₃·3H₂O and 4ZnO·B₂O₃·H₂O), that undergo dehydration with increasing temperature. Differential thermal analysis and wide-angle X-ray spectroscopy indicated that various structural changes occurred during heating. Endothermic transitions were observed for all components, while zinc borate (2ZnO·3B₂O₃·3H₂O) showed an exothermic crystallisation transition at relatively high temperature. The exotherm was modified by the development of a new crystalline phase, magnesium orthoborate (3MgO·B₂O₃) that formed on reaction with magnesium oxide (MgO) at temperatures greater than 500 °C. Formation of crystalline zinc oxide (ZnO) was also detected. From zinc borate (4ZnO·B₂O₃·H₂O), ZnO was primarily formed. No new crystalline phases were observed in the presence of MgO over the temperature range investigated.     

Relationship between interlayer hydration and photocatalytic water splitting of A′1−xNaxCa2Ta3O10·nH2O (A′=K and Li)

Partial replacement of alkaline metals in anhydrous KCa₂Ta₃O₁₀ and LiCa₂Ta₃O₁₀ was studied to control interlayer hydration and photocatalytic activity for water splitting under UV irradiation. A′_1−xNa_xCa₂Ta₃O₁₀·nH₂O (A′=K and Li) samples were synthesized by ion exchange of CsCa₂Ta₃O₁₀ in mixed molten nitrates at 400 °C. In K_1−xNa_xCa₂Ta₃O₁₀·nH₂O, two phases with the orthorhombic (C222) and tetragonal (I4/mmm) structures were formed at x?0.7 and x?0.5, respectively. Upon replacement by Na⁺ having a larger enthalpy of hydration (ΔH_h⁰), the interlayer hydration occurred at x?0.3 and the hydration number (n) was increased monotonically with an increase of x. Li_1−xNa_xCa₂Ta₃O₁₀·nH₂O showed a similar hydration behavior, but the phase was changed from I4/mmm (x<0.5, n∼0) via P4/mmm (x∼0.5, n∼1) to I4/mmm (x∼1.0, n∼2). The photocatalytic activities of these systems after loading 0.5 wt% Ni were quite different each other. K_1−xNa_xCa₂Ta₃O₁₀·nH₂O exhibited the activity increasing in consistent with n, whereas Li_1−xNa_xCa₂Ta₃O₁₀·nH₂O exhibited the activity maximum at x=0.77, where the rates of H₂/O₂ evolution were nearly doubled compared with those for end-member compositions (x=0 and 1).     

Lanthantartrate im neutralen und alkalischen Bereich

Zusammenfassung Die Substanzen LaHT ^*·4 H₂O, La₄ T ₃·14 H₂O, KLaT· ·3 H₂O, K₂LaTOH·4 H₂O, K₂LaH₃ T ₂·4 H₂O, K₃LaH₂ T ₂· ·4 H₂O und K₄LaHT ₂·5 H₂O wurden isoliert und durch Thermoanalyse, IR-Absorptionspektren und Röntgenstreuung näher charakterisiert. Es wurde auch ihre Löslichkeit in Wasser bestimmt.

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The following compounds where isolated, and characterized by means of thermal analysis, I. R. spectroscopy and X-ray diffraction. Their solubilities in aqueous solution were determined: LaHT·4 H₂O, La₄ T ₃·14 H₂O, KLaT·3 H₂O, K₂LaTOH· ·4 H₂O, K₂LaH₃ T ₂·4 H₂O, K₃LaH₂ T ₂·4 H₂O, K₄LaHT ₂· ·5 H₂O.

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Mit 7 Abbildungen     

Synthesis and characterization of one- to three-dimensional compounds composed of paradodecatungstate-B cluster and transition metals as linkers

Three new extended frameworks built from paratungstate and transition metals have been synthesized and characterized. In the compound Na₈[{Cd (H₂O)₂}(H₂W₁₂O₄₂)]·32H₂O (1), two neighboring paratungstate-B ions [H₂W₁₂O₄₂]¹⁰⁻ are linked by [Cd(H₂O)₂]²⁺ units, leading to the formation of infinite one-dimensional (1D) anion chain [{Cd(H₂O)₂}(H₂W₁₂O₄₂)]_n⁸ⁿ⁻. The anion [{Co(H₂O)₃}{Co(H₂O)₄}(H₂W₁₂O₄₂)]_n⁶ⁿ⁻ of the compound Na₆[{Co(H₂O)₃}{Co(H₂O)₄}(H₂W₁₂O₄₂)]·29H₂O (2) shows a layer-like (2D) structure in which paratungstate-B units are linked by CoO₆ octahedra, while the anion [{Co(H₂O)₃}₃(H₂W₁₂O₄₂)]_n⁴ⁿ⁻ of the compound (H₃O⁺)₃[{Na(H₂O)₄}{Co(H₂O)₄}₃(H₂W₁₂O₄₂)]·24.5H₂O (3) is a three-dimensional (3D) anionic polymer that consists of paratungstate-B units linked by CoO₆ octahedra. Compound 3 can reversibly adsorb and desorb water molecules leading to the color reversibly change from pink to violet. The preliminary magnetic measurement and electrochemical properties of compounds are performed. The crystal structure of unexpected product Na₄[NiW₆O₂₄H₆]·13H₂O (4) is described here for the rare report of crystal structure information on the Anderson-type polyoxotungstate which has nickel as a heteroatom.     

Hydrothermal Synthesis and Structural Characterization of a Tubular Arsenic-Vanadate: [CoII(2,2′-bpy)2]2[AsIII8VIV14O42(H2O)]·H2O

The hydrothermal reaction of VOSO₄, As₂O₃, CoC₂O₄·2H₂O and 2,2-bipy yields a novel arsenic-vanadate [Co^II(2,2-bpy)₂]₂[As^III₈V^IV ₁₄O₄₂(H₂O)]·H₂O (1), which is characterized by IR, elemental analysis, TGA, magnetic susceptibility and single crystal X-ray diffraction analysis. X-ray diffraction shows that compound 1 is the first example of tubular arsenic–vanadium cluster containing infinite {[Co(2,2-bpy)₂]₂[As₈V₁₄O₄₂(H₂O)]} chain constructed from [As₈V₁₄O₄₂(H₂O)] clusters interconnected through [Co(2,2-bpy)]²⁺ units. Crystal data: 1, orthorhombic, P 2₁2₁2₁, a=12.1401(2) Å, b=15.8722(1) Å, c=39.9533(5) Å, Z=4.Graphical Abstract: A novel polyoxoarsenicvanadate, [Co^II(2,2-bipy)₂]₂ [As^III₈V^IV ₁₄O₄₂(H₂O)]·H₂O, is depicted along with a tubular hybrid solid with a rhombic tube formed within the chain.     

Benzylammonium,imidazolium and pyridinium polyvanadates — Synthesis and characterization

Summary From the reaction systems,B-V₂O₅-HClO₄-H₂O andB-V₂O₅-H₂O, whereB is benzylamine (Bz), imidazole (Im) or pyridine (Py), eight new compounds were synthesized: at 20°C, the metavanadate and decavanadates of composition (BzH)VO₃, (BzH)₆V₁₀O₂₈·3H₂O, (ImH)₆V₁₀O₂₈·2H₂O, (PyH)₆V₁₀O₂₈·2H₂O, (ImH)₄H₂V₁₀O₂₈·2H₂O and (PyH)₄H₂V₁₀O₂₈·3H₂O, and at 60°C, the hexavanadates of composition (ImH)₂V₆O₁₆·H₂O and (PyH)₂V₆O₁₆·H₂O. ThepH ranges of solutions the polyvanadates can be isolated from, were estimated. The compounds prepared were characterized by chemical analysis and IR spectroscopy. The synthesis of deuterated analogues allowed to assign the IR bands corresponding to vibrations of water in the spectra of deca- and dihydrogendecavanadates and to V-OH vibrations in the spectra of dihydrogendecavanadates.

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Benzylammonium-, Imidazolium- und Pyridinium-Polyvanadate. Synthese und Charakterisierung

Zusammenfassung Aus dem ReaktionssystemB-V₂O₅-HClO₄-H₂O undB-V₂O₅-H₂O [B=Benzylamin (Bz), Imidazol (Im) oder Pyridin (Py)] wurden acht neue Verbindungen synthetisiert: bei 20°C entstanden die Metavanadate und Decavanadate der Zusammensetzung (BzH)VO₃, (BzH)₆V₁₀O₂₈·3H₂O, (ImH)₆V₁₀O₂₈·2H₂O, (PyH)₆V₁₀O₂₈·2H₂O, (ImH)₄H₂V₁₀O₂₈·2H₂O und (PyH)₄H₂V₁₀O₂₈·3H₂O, bei 60°C entstanden die Hexavanadate (ImH)₂V₆O₁₆·H₂O und (PyH)₂V₆O₁₆·H₂O. DiepH-Bereiche, innerhalb derer Polyvanadate isoliert werden können, wurden abgeschätzt. Die Verbindungen wurden mittels chemischer Analyse und IR-Spektroskopie charakterisiert, wobei die Synthese deuterierter Analoga die Zuordnung von Banden unterstützte.

     

Thermoanalytical characterization of vanadium-chromium oxide compounds prepared by 'soft chemistry' method

Summary Hydrated microcrystalline compound, V_1-xCr_xO_y·nH₂O, where x<0.063 and 4.4<n<8 and hydrated amorphous phases, CrVO₄·H₂O and Cr₂V₄O₁₃·4H₂O have been prepared using peroxo-polyacids of vanadium and chromium. The transformations of these hydrated phases upon heating were studied by TG-DTA and XRD techniques and led to three crystalline anhydrous compounds: (i) phase V_1-xCr_xO_y, which is closely related to the orthorhombic V₂O₅, (ii) Cr₂V₄O₁₃ and (iii) monoclinic CrVO₄-M. The ranges of coexistence of phases in equilibrium were also determined.     

Synthesis,structure and magnetism of a one-dimensional silicotungstate array: K3H4Cu0.5{Cu[Cu7.5Si2W16O60(H2O)4(OH)4]2} · 9H2O

A structurally distinct, multi-copper(II)-substituted silicotungstate K₃H₄Cu_0.5{Cu[Cu_7.5Si₂W₁₆O₆₀(H₂O)₄(OH)₄]₂} · 9H₂O (1) has been synthesized and characterized by FT-IR spectroscopy, elemental analysis, variable-temperature magnetic measurements, electron spin resonance, and X-ray diffraction. Green crystalline plates of 1 were obtained by the reaction of K₈[γ-SiW₁₀O₃₆] · 12H₂O with 8 equiv. of Cu(II) in a 50% ethylene glycol solution. A cationic copper center connects the terminal oxygen atoms of neighboring polyanions, resulting in a one-dimensional structure. Magnetic susceptibility measurements indicate weak ferromagnetic superexchange between the Jahn–Teller-distorted S = 1/2 Cu(II) centers.     

Crystal Structure of the Mixed-Valence Neptunium Compound Na6[(NpVO2)2(NpVIO2)(MoO4)5] · 13H2O

The crystal structure of the mixed-valence Np(V) and Np(VI) compound Na₆[(Np^VO₂)₂(Np^VIO₂)(MoO₄)₅] · 13H₂O was determined. The structure is built of the anionic layers [(Np^VO₂)₂(Np^VIO₂)(MoO₄)₅] ^6n- _n with the Na⁺ cations and crystal water molecules between them. The Np(V) and Np(VI) atoms in the anionic layers are ordered. The motif of the anionic layer is close to that found in Mg₂[(UO₂)₃(SeO₄)₅] · 16H₂O. The isostructural mixed-valence Np(V) and U(VI) compound was also synthesized.     

Mixed insoluble acidic salts of tetravalent metals VI. Crystalline mixed zirconium-titanium arsenate and hafnium-titanium arsenate

Mixed crystalline zirconium-titanium arsenates Zr_xTi(_1–x) (HAsO₄)₂·H₂O and harnium-titanium arsenates Hf_xTi(_1–x) (HAsO₄)₂ H₂O (where x=0–1) of various compositions with different Zr/Ti or Hf/Ti ratios have been prepared. The compounds have been characterized by X-ray, thermal analysis, chemical analysis, and pH-titrations. For powder X-rays, the compounds appear to be homogeneous crystalline materials with structures similar to -ZrP, -TiP or -ZrTiP. The thermograms show a loss of approximately two moles of H₂O, followed by a small loss of O₂ with probable formation of ZrO₂, As₂O₃, HfO₂, As₂O₃, ZrO₂, As₂O₅, HfO₂, As₂O₅ from which As₂O₃ and As₂O₅ are practically sublimed in two steps. The exchange capacities at r.t. are generally similar to -ZrP and -TiP but are found to be much lower in value.