Neues zum chemischen Transport von CuO und Cu2O

New Results on the Chemical Transport of CuO and Cu₂O The preparation of CuO crystals by chemical transport reactions with HCl is already well known, a comparison with other transport agents based on the principal of thermodynamic equilibrium and also the rate of transport was missing up to now. We report about experiments with the transport agents HgCl₂, Cl₂, I₂, Nh₄Cl, or CuCl; the quantitative evaluation was made by means of the cooperative transport model on the basis of the free energy function. By this way it is possible to find favourable experimental conditions for the suitable transport agents at the outset. It turned out that HgCl₂ is an appropriate transport agent which can easily be weighed. Also I₂ is useful, whereas the effect fo transport with Cl₂ (1 atm/298 K), CuCl, or NH₄Cl is very small. We investigated the chemical transport of Cu₂o and the conditions for the change of its direction of transport.     

Beiträge zum thermischen Verhalten von Sulfaten. VII [1, 2]. Zum chemischen Transport von ZnSO4 und Zn3O(SO4)2

Contributions on the Thermal Behaviour of Sulfates. VII. On the Chemical Transport of ZnSO₄ and Zn₃O (SO₄)₂ A powder of anhydrous ZnSO₄ can be prepared by heating ZnSO₄ · 7H₂O in air or in an argon atmosphere. In the same way it is possible to get a powder of Zn₃O(SO₄)₂. But up to now, it was difficult to get crystals of ZnSO₄ and there was no method known to synthesize crystals of Zn₃O(SO₄)₂. Investigations concerning chemical transport reactions of anhydrous heavy metal sulfates showed, that it is possible to get well formed crystals of ZnSO₄ and Zn₃O(SO₄)₂ by deposition from a vapour phase. Cl₂, HgCl₂, HCl, NH₄Cl and PbCl₂ were tested as transport agents and found suitable. If halides are used as transport agents, it is significant, that SO₃ can oxidize them to the halogens which are then the true transport agents. By use of PbCl₂ as a very effective transport agent, PbSC₄ will appear as an additional condensed phase. Thermodynamical considerations made it possible to understand the transport processes in these systems and to choose suitable conditions for our experiments.     

Beiträge zum thermischen Verhalten von Oxoniobaten der Übergangsmetalle. IV. Zum Chemischen Transport von CoNb2O6 mit Cl2, NH4 und HgCl2. Experimente und Modellrechnungen

Contributions on the Thermal Behaviour of Oxoniobates of the Transition Metals. IV The Chemical Vapour Transport of CoNb₂O₆ with Cl₂, NH₄Cl, or HgCl₂. Experiments and Calculations Well shaped crystals of CoNb₂O₆ were obtained by CVT using Cl₂ (added as PtCl₂), NH₄Cl or HgCl₂ as transport agents (1020°C → 960°C). As a result of thermodynamic calculations the evaporation and deposition of CoNb₂O₆ in the presence of Cl₂ can be expressed by the heterogenous endothermic equilibrium (1). The endothermic reaction (2) is responsible for the CVT of CoNb₂O₆ if NH₄Cl is used as transport agent: The unfavourable site of the equilibrium (3) causes the small transport effect using HgCl₂ as transport agent. Assuming Δ_BH°₂₉₈(CoNb₂O_6,s) = ?524.7 kcal/mol a satisfying agreement between thermodynamical calculation and experimental results can be reached.     

Chemischer Transport von Mischkristallen im System CuMoO4/ZnMoO4

Chemical Vapour Transport of Solid Solutions in the CuMoO₄/ZnMoO₄ System Two solid solutions exist in the system CuMoO₄/ZnMoO₄: Cu_1‐xZn_xMoO₄ with x=0 to x=0.15 and x=0.20 bis x=1, respectively. Single crystals of Cu_1‐xZn_xMoO₄ were obtained by chemical vapor transport in the temperature gradient 973K→873K using Cl₂, Br₂ or NH₄Cl as transport agents. No difference of the Cu/Zn ratio between source and sink was observed for the transport agents Cl₂ and NH₄Cl. A slight shift to higher Zn amounts was observed for single crystals of Cu_1‐xZn_xMoO₄ grown using Br₂ as transport agent. The experimental results were compared with results of model calculations.     

Crystal structure determination of complexes of monomethylammonium chloride and mercury(II) chloride: CH3NH3HgCl3, (CH3NH3)2HgCl4, and CH3NH3Hg2Cl5

The crystal structures have been determined of CH₃NH₃HgCl₃, (CH₃NH₃)₂HgCl₄, and CH₃NH₃Hg₂Cl₅. In (CH₃NH₃)₂HgCl₄ the Hg^II atom is tetrahedrally coordinated by four Cl atoms with Hg? Cl bond lengths of 2.464 to 2.478 Å. In the other two compounds the Hg^II atom is involved in two short covalent Hg? Cl bonds, forming a pseudo HgCl₂ molecule and two much longer bridging Hg? Cl bonds. The methylammonium groups are connected by hydrogen bonds to the chlorine atoms. The nature of the hydrogen bonding scheme probably causes disorder of the methylammonium groups.     

Beiträge zum thermischen Verhalten von Oxoniobaten der Übergangsmetalle. V. Zum Chemischen Transport von NiNb2O6 mit Cl2 und NH4Cl. Experimente und Modellrechnungen

Contributions on the Thermal Behaviour of Oxoniobates of the Transition Metals. V. Chemical Vapour Transport of NiNb₂O₆ with Cl₂ or NH₄Cl. Experiments and Calculations Well shaped crystals of NiNb₂O₆ were obtained by CVT using Cl₂ (added as PtCl₂) or NH₄Cl as transport agents (1020°C → 960°C). As a result of thermodynamic calculations the migration of NiNb₂O₆ in the temperature gradient in the presence of Cl₂ can be expressed by the heterogenous endothermic equilibrium (1). Assuming Δ_BH(NiNb₂O_{6, s}) = ?524.4 kcal/mol a satisfying agreement between thermodynamical calculation and experimental results can be reached. NH₄Cl is less suitable as transport agent, because Ni²⁺ is partly reduced to the metal by NH₃. The additionally H₂O produced by this reduction leads to a less favourable equilibrium position of (2) and to low deposition rates. .     

Beiträge zum thermischen Verhalten von Sulfaten. VIII. Zum chemischen Transport von FeSO4 mit NH4Cl und von von Fe2(SO4)3 mit Cl2 oder NH4Cl. Experimente und Modellrechnungen

Contributions on the Thermal Behaviour of Sulfates. VIII. The Chemical Vapour Transport of FeSO₄ with NH₄Cl and Fe₂(SO₄)₃ with Cl₂ or NH₄Cl. Experiments and Calculations Well shaped crystals of FeSO₄ and Fe₂(SO₄)₃ can be grown by CVT (T₁? 650°C). We investigated the dependence of the transport rate on the concentration of the transport agent (Fe₂(SO₄)₃/Cl₂ and Fe₂(SO₄)₃/NH₄Cl) as well as on the temperature (FeSO₄/NH₄Cl and Fe₂(SO₄)₃/Cl₂). Using Δ_fH(FeSO₄) = ?220 kcal/ mol, C^p(T) = 30.1 + 9.9 · 10^?3 ×T and Δ_fH(Fe₂(SO₄)₃) = ?615.4 kcal/mol a satisfying agreement between thermodynamical calculations and experimental results can be reached     

Kristallzucht und Strukturverfeinerung von Quecksilber(II)‐amidchlorid – HgClNH2

Crystal Growth and Refinement of the Crystal Structure of Mercury(II) Amide Chloride – HgClNH₂ Single crystals were prepared by recrystallization of HgClNH₂ from aqueous NH₃/NH₄⁺ solution at 160 °C. They were used for a single‐crystal X‐ray structure redetermination. The previously reported [W. N. Lipscomb, Acta. Crystallogr. 1951 , 4, 266.] structural topology determined on basis of X‐ray powder diffraction data is now confirmed. However, a higher symmetry is found: Space group type Pmma (instead of Pmm2), a = 6.709(1) Å, b = 4.351(1) Å, c = 5.154(1) Å, Z = 2. The crystal structure contains zig‐zag‐chains [Hg(NH₂)_2/2]⁺. Four Cl atoms complete the coordination sphere of Hg to a distorted octahedron. These share common faces and edges in layers [HgCl_4/4(NH₂)_2/2]. These layers are connected via hydrogen bonds N–H…Cl.     

Korrosion von Messing und Bronze durch Ammoniumhalogenide

Corrosion of Brass and Bronze by Ammonium Halides The intermetallic phases brass (Cu/Zn) and bronze (Cu/Sn) are corroded by ammonium fluoride and chloride, NH₄F and NH₄Cl, through selective oxidation of the less noble component zinc and tin, respectively. Copper is recrystallized as cube‐like or tabular single crystals under the respective influence of fluoride and chloride. Zinc and tin are incorporated in complex compounds of which (NH₄)ZnF₃, (NH₄)₂ZnF₄, Zn(NH₃)₂Cl₂ and (NH₄)₃SnF₇ were detected by X‐ray powder diffraction.     

Isotype Strukturen einiger Hexaamminmetall(II)-halogenide von 3d-Metallen: [V(NH3)6]I2, [Cr(NH3)6]I2, [Mn(NH3)6]Cl2, [Fe(NH3)6]Cl2, [Fe(NH3)6]Br2, [Co(NH3)6]Br2 und [Ni(NH3)6]Cl2

The Structures of some Hexaammine Metal(II) Halides of 3 d Metals: [V(NH₃)₆]I₂, [Cr(NH₃)₆]I₂, [Mn(NH₃)₆]Cl₂, [Fe(NH₃)₆]Cl₂, [Fe(NH₃)₆]Br₂, [Co(NH₃)₆]Br₂ and [Ni(NH₃)₆]Cl₂ Crystals of yellow [V(NH₃)₆]I₂ and green [Cr(NH₃)₆]I₂ were obtained by the reaction of VI₂ and CrI₂ with liquid ammonia at room temperature. Colourless crystals of [Mn(NH₃)₆]Cl₂ were obtained from Mn and NH₄Cl in supercritical ammonia. Colourless transparent crystals of [Fe(NH₃)₆]Cl₂ and [Fe(NH₃)₆]Br₂ were obtained by the reaction of FeCl₂ and FeBr₂ with supercritical ammonia at 400°C. Under the same conditions orange crystals of [Co(NH₃)₆]Br₂ were obtained from [Co₂(NH₂)₃(NH₃)₆]Br₃. Purple crystals of [Ni(NH₃)₆]Cl₂ were obtained by the reaction of NiCl₂ · 6H₂O and NH₄Cl with aqueous NH₃ solution. The structures of the isotypic compounds (Fm3 m, Z = 4) were determined from single crystal diffractometer data (see “Inhaltsübersicht”). All compounds crystallize in the K₂[PtCl₆] structure type. In these compounds the metal ions have high-spin configuration. The orientation of the dynamically disordered hydrogen atoms of the ammonia ligands is discussed.     

Beiträge zum thermischen Verhalten von Oxoniobaten der Übergangsmetalle. II [1, 2]. Zum Chemischen Transport von MnNb2O6 mit Cl2 und NH4Cl. Experimente und Modellrechnungen

Contributions on the Thermal Behaviour of Oxoniobates of the Transition Metals. II. The Chemical Vapour Transport of MnNb₂O₆ with Cl₂ or NH₄Cl. Experiments and Calculations Crystals of MnNb₂O₆ were obtained by chemical transport reactions in a temperature gradient (1020°C → 960 °C) using Cl₂ (added as PtCl₂) or NH₄Cl as transport agent. As a result of thermodynamic calculations the evaporation and deposition of MnNb₂O₆ in the presence of Cl₂ can be expressed by the endothermic equilibrium (1). The endothermic reaction (2) is responsible for the migration of MnNb₂O₆ if NH₄Cl is used as transport agent. Assuming ΔH°₂₉₈(MnNb₂O_{6, s}) = ?567.6 kcal/mol a satisfying agreement between thermodynamic calculations and experimental results can be reached.     

Die relative Unterkühlung an Quarzglasoberflächen und anderen Substraten beim chemischen Transport fester Stoffe über die Gasphase

The Relative Undercooling on Silica Glass Surfaces and other Substrates during the Chemical Transport of Solids via the Vapor-phase . The relative undercooling on etched surfaces of silica glass at the chemical transport of ZnS in a stream of gaseous iodine at 652–854°C is found to be ΔT = 37–43°. Scrapers on silica glass lead to a substantial smaller undercooling. During the deposition of ZnS (made from “pure” components) in a temperature gradient one finds a remarkable fractionation. In closed (etched) silica glass ampoules the relative undercooling is determined for the systems ZnS/I₂, ZnSe/I₂, ZnS/HCl; ZnS/H₂, CdS/I₂, CdSe/I₂, Al₂S₃/I₂ and Nb₂O₅/NbCl₅ using a special furnace, The region free of nuclei (or crystals) for instance at T₂ ≈ 800°C depending on the system (and T₂) is ΔT ≈ 13–45°. The variation of the substrates showed: for fire polished silica surfaces for ZnS/I₂ is ΔT ≈ 56°; for the different quartz-faces and ZnS/I₂ is ΔT ≈ 13–35°. Generally, on different substrates (broken pieces, fragments) one finds for ZnS/I₂ ΔT ≈ 20–28°. Using another way for the systems MoO₃/Cl₂, MoO₃/Cl₂, Ar, MoO₃/Cl₂, O₂ and MoO₃/HgCl₂ with T₂ a strongly decreasing value of ΔT is found.     

Synthese und Struktur von Ammin- und Amidokomplexen des Iridiums

Synthesis and Structure of Ammine and Amido Complexes of Iridium The reaction of (NH₄)₂[IrCl₆] with NH₄Cl at 300 °C in a sealed glass ampoule yields the iridium(III) ammine complex (NH₄)₂[Ir(NH₃)Cl₅], which crystallizes isotypically with K₂[Ir(NH₃)Cl₅] in the orthorhombic space group Pnma with Z = 4, and a = 1350.0(2); b = 1028.5(3); c = 689.6(2) pm. The reaction of (NH₄)₂[IrCl₆] with NH₃ at 300 °C, however, gives the already known [Ir(NH₃)₅Cl]Cl₂ beside a small amount of [Ir(NH₃)₄Cl₂]Cl₂. In pure form [Ir(NH₃)₅Cl]Cl₂ is obtained by ammonolysis of (NH₄)₂[Ir(NH₃)Cl₅] at 300 °C with NH₃. [Ir(NH₃)₄Cl₂]Cl₂ crystallizes triclinic (P1, Z = 1, a = 660,2(3); b = 680,4(3); c = 711,1(2) pm; α = 103,85(2)°, β = 114,54(3)°, γ = 112,75(2)°). The structure contains Cl^– anions and [Ir(NH₃)₄Cl₂]²⁺ cations with a trans position of the Cl atoms. Upon reaction of [Ir(NH₃)₅Cl]Cl₂ with Cl₂ one ammine ligand is eliminated yielding [Ir(NH₃)₄Cl₂]Cl, which is transformed to orthorhombic [Ir(NH₃)₄(OH₂)Cl]Cl₂ (Pnma, Z = 4, a = 1335,1(3); b = 1047,9(2); c = 673,4(2) pm) by crystallization from water. In the octahedral complex [Ir(NH₃)₄(OH₂)Cl]²⁺ the four ammine ligands have an equatorial position, whereas the Cl atom and the aqua ligand are arranged axial. Oxidation of (NH₄)₂[Ir(NH₃)Cl₅] with Cl₂ at 330 °C affords the tetragonal Ir^IV complex (NH₄)[Ir(NH₃)Cl₅] (P4nc, Z = 2, a = 702.68(5); c = 912.89(9) pm). Its structure was determined using the powder diagram. Oxidation of (NH₄)₂[Ir(NH₃)Cl₅] with Br₂ in water, on the other hand, gives (NH₄)₂[IrBr₆] crystallizing in the K₂[PtCl₆] type. Oxidation of (PPh₄)₂[Ir(NH₃)Cl₅] with PhI(OAc)₂ in CH₂Cl₂ affords the Ir^V amido complex (PPh₄)[Ir(NH₂)Cl₅].     

Über Kupfer(I)-sulfat Cu2SO4. Darstellung und thermische Eigenschaften

Preparation and Thermal Properties of Copper(I) Sulfate Cu₂SO₄ Copper(I) sulfate Cu₂SO₄ can be prepared in high purity by reaction of Cu₂O with dimethyl sulfate (CH₃)₂SO₄ at 160°C in an argon atmosphere. Using an extremely fine grained Cu₂O, as obtained by reduction of cupric acetate with hydrazine, and a reaction time of 10 minutes a Cu₂SO₄ is obtained that contains less than 1% Cu₂O. Longer reaction times lead to partial decomposition of the Cu₂SO₄ to Cu(met.) and CuSO₄. In a closed system Cu₂SO₄ melts at about 400°C, however, the melt rapidly decomposes to Cu and CuSO₄, solidifying simultaneously. When heated in a thermoanalyzer in flowing argon or in a vacuum, Cu and CuSO₄ react under liberation of SO₂. Increasing the temperature leads to CuO in three steps, which converts to Cu₂O when heated to 1000°C. The question of formation of Cu₂SO₄, occasionally mentioned in the literature, being responsible for the liquid phases observed in the system Cu? S? O at temperatures below 500°C, is discussed.     

Zwei Mercuri‐Ammin‐Komplexe: [Hg(NH3)2][HgCl3]2 und [Hg(NH3)4](ClO4)2

Two Mercuric Ammoniates: [Hg(NH₃)₂][HgCl₃]₂ and [Hg(NH₃)₄](ClO₄)₂ [Hg(NH₃)₂][HgCl₃]₂ ( 1 ) is obtained by saturating an equimolar solution of HgCl₂ and NH₄Cl with Hg(NH₂)Cl at 75 °C. 1 crystallizes in the orthorhombic space group Pmna with a = 591.9(1) pm, b = 800.3(1) pm, c = 1243.3(4) pm, Z = 2. The structure consists of linear cations [Hg(NH₃)₂]²⁺ and T‐shaped anions [HgCl₃]^—. The coordination sphere of mercury is ?effectively”? completed to compressed hexagonal bipyramids and distorted octahedra, respectively. Single crystals of [Hg(NH₃)₄](ClO₄)₂ ( 2 ) are obtained by passing gaseous ammonia through a solution of mercuric perchlorate, while the solution was cooled to temperatures below 10 °C. 2 crystallizes in the monoclinic space group P2₁/c with a = 791.52(9) pm, b = 1084.3(2) pm, c = 1566.4(2) pm, β = 120.352(1)°, Z = 4. The structure consists of compressed [Hg(NH₃)₄]²⁺ tetrahedra and perchlorate anions. The packing of the heavy atoms Hg and Cl is analogous to the baddeleyite (α‐ZrO₂) type of structure.     

Two Mercury Chloro Thiocyanate Complexes: NH4[HgCl2(SCN)] and NH4[HgCl(SCN)2]

Single crystals of NH₄[HgCl₂(SCN)] ( 1 ) and NH₄[HgCl(SCN)₂] ( 2 ) are obtained by slow evaporation of ethanol solutions of HgCl₂ and NH₄SCN or Hg(SCN)₂ and NH₄Cl. 1 crystallizes in the monoclinic space group P2₁ (a = 9.297(1), b = 4.171(1), c = 9.198(1)Å, β = 92.827(5)°). The structure consists in HgCl₂(SCN) linear chains, extending along the twofold axis, connected through the ammonium ions. 2 crystallizes in the monoclinic space group C2/c (a = 7.088(1), b = 19.986(2), c = 5.958(1)Å, β = 100.718(5)°). The structure consists of HgCl(SCN)₂ molecules connected through the ammonium ions. The second order non linear optical properties of 1 are discussed.     

Structural and Spectroscopic Studies of Halocuprate(I) and Haloargentate(I) Complexes [M2XnX′4−n]2−

The complexes [Cu₂Br₄]^2?, [Cu₂I₄]^2?, [Cu₂I₂Br₂]^2?, [Cu₂I₃Cl]^2?, [Ag₂Cl₄]^2? have been characterized as their isomorphous bis(triphenylphosphoranylidene)ammonium ([Ph₃PNPPh₃]⁺ = PNP⁺) salts by single crystal structural determinations. All anions show the centrosymmetric doubly halogen‐bridged forms [XM(μ‐X)₂MX]^2? with three‐coordinate metal atoms that have been observed in [M₂X₄]^2? complexes with other large organic cations. In [Cu₂I₂Br₂]^2? the iodide ligands occupy the bridging positions and the bromide the terminal positions, while in [Cu₂I₃Cl]^2?, obtained in an attempt to prepare [Cu₂I₂Cl₂]^2?, two of the iodide ligands occupy the bridging positions with the third iodide and the chloride ligand occupying two statistically disordered terminal positions. In [Ag₂Cl₄]^2? the distortion from ideal trigonal coordination of the metal atom is greater than in the copper complexes, but less than in other previously reported [Ag₂Cl₄]^2? complexes with organic cations. The ν(MX) bands have been assigned in the far‐IR spectra, and confirm previous observations regarding the unexpectedly simple IR spectra of [Cu₂X₄]^2? complexes.     

Darstellung und Kristallstruktur von (NH4)2[V(NH3)Cl5]. Die Kristallchemie der Salze (NH4)2[V(NH3)Cl5], [Rh(NH3)5Cl]Cl2 und M2VXCl5 mit M = K,NH4, Rb,Cs und X = Cl,O

Preparation and Crystal Structure of (NH₄)₂[V(NH₃)Cl₅]. The Crystal Chemistry of the Compounds (NH₄)₂[V(NH₃)Cl₅], [Rh(NH₃)₅Cl]Cl₂, and M₂VXCl₅ with M = K, NH₄, Rb, Cs and X ? Cl, O (NH₄)₂[V(NH₃)Cl₅] crystallizes like [Rh(NH₃)₅Cl]Cl₂ in the orthorhombic space group Pnma with Z = 4. The compounds are built up by isolated NH₄⁺ or Cl^? and complex MX₅Y ions. The following distances have been observed: V? N: 213.8, V? Cl: 235.8–239.1, Rh? N: 207.1–208.5, Rh? Cl: 235.5 pm. Both structures differ from the K₂PtCl₆ type mainly in the ordering of the MX₅Y polyhedra. The compounds M₂VCl₆ and M₂VOCl₅ with M = K, NH₄, Rb, and Cs crystallize with exception of the orthorhombic K₂VOCl₅ in the K₂PtCl₆ type. The ordering of the MX₅Y polyhedra in the compounds (NH₄)₂[V(NH₃)Cl₅], [Rh(NH₃)₅Cl]Cl₂ and K₂VOCl₅ enables a closer packing.     

Studies on thermal oxidation of chalcopyrite from Chitradurga,Karnataka State,India

When chalcopyrite is heated in air, up to 350? there is no marked change. Between 350 and 440?, surface material is oxidised to iron sulphate, CuSO₄ and Fe₂O₃, while in regions not accessible to oxygen the formation of Cu₅FeS₄, FeS and S takes place. From 440 to 500? oxidation and sulphation phenomena occur. Stable compounds between 500 and 650? are iron sulphate, CuSO₄ and Fe₄O₃, with a minor amount of 6CuO.Cu₂O indicated at 650?. After the decomposition of iron sulphate, CuSO₄ decomposes, first to CuO.CuSO₄ and then to CuO. By 750? the sulphur has been totally lost from all compounds, while the oxides of copper and iron partly react to form CuFe₂O₄. Final products of oxidation between 800 and 850? are CuO, CuFe₂O₄ and Fe₃O₄.     

Der chemische Transport von Cu,Ag, Au,Ru, Rh,Pd, Os,Ir, Pt unter Mitwirkung von Gaskomplexen. Al2Cl6, Fe2Cl6 oder Al2J6 als Komplexbildner

The Chemical Transport of Cu, Ag, Au, Ru, Rh, Pd, Os, Ir, Pt in the Presence of Al₂Cl₆, Fe₂Cl₆ or Al₂I₆, Causing Complex Formation Chemical transport experiments show, that the title elements (with exception of Os) in the presence of halide forming agents (HCl, Cl₂ or I₂ resp.) and of complex forming agents (Al₂Cl₆, Fe₂Cl₆ or Al₂I₆ resp.) give gaseous complex compounds with a remarkable stability. This leads to novel possibilities for the chemical transport of the elements and their compounds. The effect of complex formation can be predicted on the basis of qualitative thermodynamic considerations. The corrosion of the wall of the quartz ampoule at temperatures above 600°C by Al₂Cl₆/AlCl₃ is avoidable by the usage of Fe₂Cl₆/FeCl₃ instead of Al₂Cl₆/AlCl₃. Experiments in the system Pd/I₂, Al₂I₆ lead to the formation of crystals of Pd₂Al.