Enthalpies of formation of some phases present in the Y−Ba−Cu−O system by solution calorimetry

Enthalpies of some of the phases in the Y–Ba–Cu–O system were determined by solution calorimetry using a Calvet microcalorimeter. The standard enthalpies of formation for the phases were found to be YBa₂Cu₃O_6.60, –2627.9; YBa₂Cu₃O_6.77, –2641.8; YBa₂Cu₃O_6.90, –2652.0; YBa₂Cu₃O_6.99, –2659.3; Y₂Cu₂O₅, –2198.6; Y₂BaCuO₅, –2656.4; BaCuO_2.33, –788.6; and BaCuO_2.42, –796.2 kJ-mol^–1.     

Kinetics of Sulfur Oxide, Sulfur Fluoride, and Sulfur Oxyfluoride Anions with Ozone

Rate constants and product branching ratios were measured for eleven sulfur oxide, sulfur fluoride, and sulfur oxyfluoride anions reacting with O₃. The SO^– ₂ ion reacts rapidly to form –O^– ₃, SO^– ₃, and e^–. The temperature dependence of the branching ratio shows more reactive detachment and less SO^– ₃ formation at higher temperature. SO^– ₃ reacts with O₃, forming SO^– ₄ at 1/3 to 1/4 of the collisional rate from 200 to 500 K, respectively. At 300 K, SF^– ₆ charge transfers to O₃ at 20% of the collisional rate. F₂SO^– ₂ reacts with O₃ at a few percent of the collision rate, forming both O^– ₃ and FSO^– ₃; The ion F₃SO^– reacts slowly with O₃ to form F₃SO^– ₂. The ions SO^– ₄, SF^– ₅, FSO^– ₂, FSO^– ₃, F₃SO^–, and F₅SO^– are unreactive with O₃. A trend is noted relating the ion reactivity with the coordination of the central sulfur atom, i.e., the number of S–F bonds plus two times the number of S=O bonds. Only ions with a sulfur coordination of 4 or 6 are reactive, although the reaction rate constants are generally small. The reactivity trends appear to be partially explained by spin conservation. These reactions are all sufficiently slow, so O₃ reactions should not play a major role in SF₆/O₂ discharges. All ions studied have been found to be unreactive with O₂.     

Titration von Sulfid mit einer sulfidionensensitiven Elektrode

Zusammenfassung Eine Methode zur potentiometrischen Titration von Sulfid mit Natriumplumbat(II)lösung an einer sulfidsensitiven Membranelektrode wird beschrieben. Sie eignet sich zur Bestimmung von 10^–4% Sulfid in Gegenwart von Cl^–, Br^–, J^–, SCN^–, SO₃ ^2–, S₂O₃ ^2–

---

Titration of sulphide with a sulphide-ion sensitive electrode

A method is described for the titration of sulphide with sodium plumbate(II) solution using a sulphide-sensitive electrode. The method is suitable for the determination of 10^–4% of sulphide in the presence of Cl^–, Br^–, J^–, SCN^–, SO₃ ^2–, S₂O₃ ^2–.

---

---

Wir danken Herrn Dr. K. Obst für wertvolle Hinweise und Diskussionen.     

Quantitative chemical analysis on paper: Determination of phosphate in the presence of large quantities of other ions

Summary A rapid method has been developed for the determination of phosphate by means of filter paper impregnated with lead iodide. A sample is added to the impregnated filter paper by means of a capillary, and after irrigation to cause migration of the ions a white spot is obtained as the lead iodide is converted into the phosphate. The weight of the spot is dependent on the p_H and the quantity of phosphate present.The determination is possible in the presence of SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, I^–, IO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, succinic, citric and tartaric acids. The determination is impossible in the presence of C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2–, or CO₃ ^2–.The method permits the determination of 7–100g of phosphate with an accuracy of 2%.

---

Zusammenfassung Ein schnelles Verfahren zur Phosphatbestimmung wird besehrieben, bei dem man sich eines mit Bleijodid imprägnierten Filterpapiers bedient. Die Probe wird mit einer Kapillare auf das Papier aufgebracht. Man erleichtert die Ionenbewegung durch geeignete Befeuchtung und erhält einen weißen Fleck infolge Umsetzung des Bleijodids in -phosphat. Das Gewicht des Fleckens hängt vom p_H und von der Phosphatmenge ab.Die Bestimmung ist möglich in Gegenwart von SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, J^–, JO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, Bernsteinsäure, Zitronensäure und Weinsäure; sie ist nicht möglich bei Gegenwart von C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2– oder CO₃ ^2–. 7 bis 100g Phosphat können mit einer Genauigkeit von 2% bestimmt werden.

---

Résumé On a développé une méthode rapide pour le dosage des phosphates sur papier-filtre imprégné d'iodure de plomb. On dépose l'échantillon sur le papier-filtre imprégné, à l'aide d'un capillaire, et, après humidification pour provoquer la migration des ions, on obtient une tache blanche quand l'iodure de plomb est converti en phosphate. Le poids de la tache dépend du p_H et de la quantité de phosphate présent.Le dosage est possible en présence de SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, I^–, IO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, et des acides succinique, citrique et tartrique. Il est impossible en présence de C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2– ou CO₃ ^2–.La méthode permet le dosage de 7 à 100g de phosphate avec une précision de 2%.

     

Reactions of Neutral and Charged Molybdenum Oxide Clusters with Low-Molecular-Weight Alcohols in a Gas Phase Studied by Ion Cyclotron Resonance

A set of oxygen-containing molybdenum oxide clusters Mo _x O _y (x = 1–3; y = 1–9) was obtained with the use of a combination of a Knudsen cell and an ion trap cell. The reactions of positively charged clusters with C₁–C₄ alcohols were studied using ion cyclotron resonance. The formation of a number of organometallic ions, the products of initial insertion of molybdenum oxide ions into the C–O and C–H bonds of alcohols, and polycondensation products of methanol and ethanol were found. The reactions of neutral molybdenum oxide clusters Mo _x O _y (x = 1–3; y = 1–9) with protonated C₁–C₄ alcohols and an ammonium ion were studied. The following limits of proton affinity (PA) were found for neutral oxygen-containing molybdenum clusters: (MoO) < 180, (Mo₂O₄, Mo₂O₅, and Mo₃O₈) = 188 ± 8, PA(MoO₂) = 202 ± 5, PA(MoO₃, Mo₂O₆, and Mo₃O₉) > 207 kcal/mol.     

Study of the fluorite–pyrochlore–fluorite phase transitions in Ln<Subscript>2</Subscript>Ti<Subscript>2</Subscript>O<Subscript>7</Subscript> (Ln=Lu,Yb, Tm)

The ordering processes in Ln₂Ti₂O₇ (Ln=Lu, Yb, Tm) are studied by X-ray diffraction, thermal analysis, infrared absorption (IR) spectroscopy, and electrical conductivity measurements. The coprecipitation method followed by freeze-drying was used for Ln₂Ti₂O₇ synthesis. The region of low-temperature fluorite phase existence is 600 °C<T<740 °C. The low-temperature fluorite–pyrochlore phase transition in Ln₂Ti₂O₇ takes place at ~740–800 °C. Ln₂Ti₂O₇ (Ln=Lu, Yb, Tm) have the structure of disordered pyrochlore with antisite Ln–Ti defects at 800 °C<T<1,100 °C.The high-temperature pyrochlore–fluorite transformation takes place in Tm₂Ti₂O₇, Yb₂Ti₂O₇, and Lu₂Ti₂O₇ in air at T>1,600 °C. The conductivity values are 5·10^–3 S/cm for Tm₂Ti₂O₇, 6·10^–3 S/cm for Yb₂Ti₂O₇, and 10^–2 S/cm for Lu₂Ti₂O₇ at 740 °C. This order–disorder transition leads to a 2 orders of magnitude conductivity growth and a 10–30 times permittivity increase in Ln₂Ti₂O₇ samples obtained at 1,700 °C.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003     

The ESR Study of O2 – Radical Anion Formation during Adsorption of an NO + O2 Mixture and O2 on ZrO2 and (0.1–2.0)% MoO3/ZrO2

The influence of conditions of the preliminary thermal treatment of ZrO₂, ammonia and methanol adsorption, and MoO₃ supporting on O₂ ^– formation during the adsorption of an NO + O₂ mixture was studied. The interaction of O₂ ^– with different molecules was studied. Adsorbed ammonia and methanol, as well as supported Mo⁶⁺ ions, were shown to inhibit this reaction. The involvement of the Zr⁴⁺ and O^2– Lewis sites in the reaction was concluded. The interaction of ammonia and methanol with the O₂ ^– radical anions changed the g tensor parameters and decreased the thermal stability of O₂ ^– in the case of methanol. O₂ ^– radical anions were formed on the reduced (0.1–2.0)% MoO₃/ZrO₂ samples during the interaction of O₂ with the Mo⁵⁺ ions in the octahedral configuration. As in the case of O₂ ^– formation during NO + O₂ adsorption on ZrO₂, the radical anions were localized in the coordination spheres of the coordinately unsaturated Zr⁴⁺ ions. A change in the MoO₃ content of the samples from 0.1 to 0.5% led to an increase in the amount of O₂ ^–, whereas a change from 0.5 to 2.0% led to a decrease in the O₂ ^– amount due to the screening of the Zr⁴⁺ ions by oxo complexes and polymolybdates.     

The effect of carbonyl complexation on highly exothermic vanadium oxidation reactions

The effects of CO complexation on highly exothermic vanadium oxidation reactions is evaluated. We study the chemiluminescent (CL) reaction products formed when vanadium vapor entrained in Ar or CO is oxidized by O₃ or NO₂. The multiple collision V+Ar+O₃→VO^*(C ⁴Σ⁻, ⁴Φ, ²X)+Ar+O₂ reactive encounter yields two previously unreported VO excited states, whereas the V+Ar+NO₂→VO^*+Ar+NO reactive encounter populates states up to and including VO^* C ⁴Σ⁻. The multiple collision V+nCO+O₃ reactive encounter would appear to form a VOCO excited state complex, emitting in the region 420–560 nm, via the formation and oxidation of V(CO)₂ viz. V(CO)₂+O₃→VOCO^*+CO+O₂ and a relaxed VO excited state emitter via V+nCO+O₃→VO^*+nCO+O₂ where the VO excited state excitation is mediated by V–CO complexation. In complement, the much less exothermic V–NO₂ encounter displays an emission which, in concert with previous studies of CO complexation, suggests the formation of a VO(CO)₂ excited state complex viz. V(CO)₂+NO₂→VO(CO)₂^*+NO. The experiments characterizing CL are complemented by comparative laser-induced fluorescence studies of the VO X ⁴Σ⁻–CO and Ar interactions and their influence on the VO C ⁴Σ⁻–X ⁴Σ⁻ laser-induced excitation spectrum. These studies, in conjunction with further attempts to excite LIF in the 420–560 nm region, suggest that the observed complex emissions result primarily from VO excited state interactions. Complementary time-of-flight mass spectroscopy of vanadium and vanadium-oxide–carbonyl complex formation demonstrates the formation of V(CO), V(CO)₂, V₂(CO), and VOCO, the latter three of which demonstrate clear metastable-ion dissociation peaks for the processes VOCO⁺→V⁺+CO₂, V(CO)₂⁺→V⁺+2CO, and V₂(CO)⁺→V₂⁺+CO, suggesting that these vanadium complexes when formed in a reaction-based environment may be photodissociated with light in the visible and ultraviolet regions.     

Lactones ofFerula gigantea

The following substances have been isolated from an acetone extract ofFerula gigantea B. Fedtsch.: a coumarin — umbelliferone, C₉H₆O₂, mp 230–233°C; and sesquiterpene lactones — talassin A, C₂₅H₃₀O₇, mp 188–191°C; malaphyllinin, C₂₄H₂₄O₇, mp 231–235°C; malaphyll, C₂₉H₃₂O₉, mp 212–213°C; and malaphyllin, C₂₆H₂₈O₉, mp 216–218°C. Structures have been proposed for three new sesquiterpene lactones on the basis of an analysis of their spectral characteristics.All-Union Scientific-Research Institute of Medicinal Plants, Moscow. M. V. Lomonosov Moscow State University, Botanical Garden, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 490–495, July–August, 1979.     

Indirekte Quecksilberbestimmung mit dem Nickelsalz der Antipyrin-4-Dithiocarbonsäure

Zusammenfassung Eine indirekte, extraktionsphotometrische Methode zur Bestimmung kleiner Quecksilbermengen wurde angegeben. Sie beruht auf der Verdrängung des Nickels aus farbigen, chloroformischen Lösungen von antipyrin-4-dithiocarbonsaurem Nickel. Die Herabsetzung der Lichtabsorption solcher Lösungen bei 575 nm ist der jeweiligen Quecksilbermenge proportional. Gold, Silber, Kupfer, Quecksilber(I), Cyanid und ÄDTA verhindern die Bestimmung. Der Einfluß sonstiger Fremdionen wurde untersucht.

---

Summary An indirect extraction-photometric method of determining small quantities of mercury has been worked out; it is based on the displacement of nickel from (4-DTA)₂Ni. A fall of the absorption of the color of this solution after extraction with the test specimen is measured at=575 nm. The determination is not possible in the presence of Au(III), Ag(I), Cu(I), Cu(II), Hg(I) and S₂O₃ ^2–, SO₃ ^2–, CN_– ions and Complexon III. Therefore a study was made of the influence of Tl(I), Pb(II), Cd(II), Ni(II), Co(II), Cr(III), Mn(II), Fe(II), Fe(III), Zn(II), Bi(III), Al(III), as well as of C₂O₄ ^2–, C₄H₄O₆ ^2–, Cl^–, I^–, SCN^–, SO₄ ^2–.

---

Résumé On a mis au point un dosage photométrique indirect, par extraction, de petites quantités de mercure; il repose sur le déplacement du nickel du composé (4-DTA)₂Ni. On mesure la diminution de l'absorption de la coloration de cette solution après l'extraction par l'échantillon étudié à = 575 nm. La présence des ions Au-III, Ag-I, Cu-I, Cu-II, Hg-I et S₂O₃ ^2–, SO₃ ^2–, CN^–, complexone-III rend le dosage impossible. On a étudié également l'influence de Tl-I, Pb-II, Cd-II, Ni-II, Co-II, Cr-III, Mn-II, Fe-II, Fe-III, Zn-II, Bi-III, Al-III, ainsi que de C₂O₄ ^2–, C₄H₄O₆ ^2–, Cl^–, I^–, SCN^–, SO₄ ^2–.

     

Gas-phase reactions in plasmas of SF6 with O2 in He

Processes which occur in microwave discharges of dilute mixtures of SF₆ and O₂ in He have been examined using a flow reactor sampled by a mass spectrometer. Two classes of experiments were performed. In the first set of experiments, mixtures containing 6×10¹¹ cm^–3 SF₆, 6×10¹⁶ cm^–3 He, and O₂ in the range (0–3.6)×10¹³ cm^–3 were passed through a 20-W 2450-MHz microwave discharge. The gas mixtures arriving at a sample point downstream from the discharge were examined for SF₆, SF₄, SOF₂, SOF₄, SO₂F₂, SO₂, F, and O. In the second class of experiments, rate coefficients were measured for the reactions of SF₄ with O and O₂ and for the reaction of SF with O. The rate coefficient for the reaction of SF with O was found to be (4.2±1.5)×10^–11 cm^–3 s^–1. SF₄ was found to react so slowly with both oxygen atoms and oxygen molecules that only upper limits could be placed on the rate coefficients for these reactions. These values were 2×10^–14 cm³ s^–1 and 5×10^–15 cm³ s^–1 for reactions with O and O₂ respectively. The observed distribution of products from the discharged mixtures is discussed in terms of the measured rate coefficients.     

Porphyrins

The extended Hückel model is further developed to allow prediction of spin state and is applied to ferrous porphin complexes with H₂O, CO, O₂, N₂ and ferric porphin complexes with OH^–, F^–, Cl^–, CN^–. The model shows that if the iron atom lies in the porphyrin plane only low or intermediate spin states are possible, with the weakest ligands just producing low spin. The high spin (ionic) complex can only occur with iron displaced from the plane, in which geometry CO and CN^– are calculated to be low spin, OH^–, F^–, Cl^– high spin, and H₂O borderline between low and high. The model predicts that N₂ will not bond and that a stable O₂ complex is impossible if O₂ is perpendicular to the plane. Discussion is given of the ligand field, absorption spectra, soft X-ray spectra, and Mössbauer spectra.

---

Zusammenfassung Das erweiterte Hückelmodell wird in einer Weise ausgebaut, daß Aussagen über Spinzustände möglich werden. Das Verfahren wird auf eisen-(II)-haltige Porphyrinkomplexe mit H₂O, CO, O₂ und N₂ als Liganden und eisen-(III)-haltige Komplexe mit OH^–, F^–, Cl^– und CN^– angewendet. Dabei zeigt sich, daß nur Zustände mit niedrigem oder mittlerem Spin möglich sind, wenn das Eisenatom in der Porphyrin-Ebene liegt, und daß dabei die schwächsten Liganden den niedrigsten Spin ergeben. Komplexe mit hohem Spin (Ionenkomplexe) sind nur dann möglich, wenn das Eisen nicht in der Ebene liegt, und zwar haben dann der CO- und der CN^–-Komplex niedrigen, der OH^–-, F^–- und Cl^–-Komplex hohen und der H₂O-Komplex entweder hohen oder niedrigen Spin. Das Modell ergibt ferner, daß N₂ nicht gebunden wird und daß ein stabiler O₂-Komplex nur entsteht, wenn das O₂-Molekül senkrecht zur Bindungsebene steht. Zum Schluß werden Ligandenfeld, Absorptionsspektren, weiche Röntgenspektren und Mössbauerspektren diskutiert.

---

Résumé Le modèle de Hückel étendu est élaboré de manière á permettre la prédiction de l'état de spin et est appliqué aux complexes de la porphine ferreuse avec H₂O, CO, O₂, N₂ et de la porphine ferrique avec OH^–, F^–, Cl^–, CN^–. Ce modèle montre que, si l'atome de fer se trouve dans le plan de la porphyrine, seuls des états de spin bas et intermédiaires sont possibles, les ligands les plus faibles donnant seulement un spin bas. Le complexe à spin élevé (ionique) ne peut exister qu'avec le fer en dehors du plan, auquel cas on calcule un spin bas pour CO et CN^–, haut pour OH^–, F^–, Cl^–, et l'un ou l'autre pour H₂O. Ce modèle permet de prédire que N₂ ne se liera pas et qu'un complexe stable avec O₂ est impossible si O₂ est perpendiculaire au plan. On discute le champ des ligands, le spectre d'absorption, le spectre des rayons X mous et le spectre Mössbauer.

---

---

National Institutes of Health Pre-Doctoral Fellow.     

Thermal decomposition of lanthanide(III) and Y(III) 3,4,5-trihydroxybenzoates: Preparation, properties

Complexes of lanthanides(III) (La-Lu) and Y(III) with 3,4,5-trihydroxybenzoic acid (gallic acid) were obtained and their thermal decomposition, IR spectra and solubility in water have been investigated. When heated, the complexes with a general formula Ln(C₇H₅O₅)(C₇H₄O₅)·nH₂O (n=2 for La-Ho and Y: n=0 for Er-Lu) lose their crystallization water and decompose to the oxides Ln₂O₃, CeO₂, Pr₆O₁₁, and Tb₄O₇, except of lanthanum and neodymium complexes, which additionally form stable oxocarbonates such as Ln₂O₂CO₃. The complexes are sparingly soluble in water (0.3·10^–5–8.3·10^–4 mol dm^–3).This revised version was published online in November 2005 with corrections to the Cover Date.     

Geochemical and gamma spectrometric analysis of ores and hostrocks of the Kanawa uranium occurrence in NE Nigeria

The Kanawa mineralization is one of the numerous low grade U-occurrences in the Gubrunde horst, NE Nigeria. Eighty nine samples consisting of ore and host rocks have been analyzed for 12 elements and 3 isotopes by atomic absorption spectrometry, colorimetry and direct -spectrometric methods and the data described using multivariate statistical techniques. The results show an enhancement of U, Mn, P₂O₅, Fe₂O₃, CaO,²¹⁰Pb,²²⁶Ra and²³⁴Th in the ore zones. The element/isotopic associations (U–P₂O₅–²¹⁰Pb–²²⁶Ra–²³⁴Th), (Na₂O–K₂O–MgO), (Fe₂O₃–MnO–CaO–Cu) were established in the mineralized rhyolites, while (P₂O₅–²¹⁰Pb–²²⁶Ra–²³⁴Th), (Na₂O–K₂O–MgO–Zn) and Fe₂O₃–Mn–U) occur in the altered/unmineralized rocks. The variation in the pattern of association of Cu, U, Zn and CaO could be ascribed to their remobilization, depletion, enrichment or introduction in the ore zone by hydrothermal solutions. The elements/isotopes U, Zn, Cu, P₂O₅,²²⁶Ra,²¹⁰Pb,²³⁴Th or their ratios could in addition to Pb, Ba, Ce, Sm be used as pathfinder elements in prospecting concealed ores in NE Nigeria.     

By-product formation in spark breakdown of SF6/O2 mixtures

The yields of SOF₄, SO₂F₂, SOF₂, and SO₂ have been measured as a function of O₂ content in SF₆/O₂ mixtures, following spark discharges. All experiments were made at a spark energy of 8.7 J/spark, a total pressure of 133 kPa, and for O₂ additions of 0, 1, 2, 5, 10, and 20% to SF₆. Even for the case of no added O₂, trace amounts of O₂ and H₂O result in the formation of the above by-products. However, addition of O₂ significantly increases the yields of SOF₄ and SO₂F₂, while SOF₂ is only slightly affected. The net yields for SOF₄ and SO₂F₂ formation range from 0.18×10^–9 and 0.64×10^–10 mol·J^–1, respectively, at 1% O₂ content to 10.45×10^–9 and 7.15×10^–10 mol·J^–1, respectively, at 20% O₂ content. The mechanism for SOF₄ production appears to involve SF₄, an important initial product of SF₆, as a precursor. Comparison of the SOF₄ and SO₂F₂ yield from spark discharges (arc and corona) shows that the yields from other discharges (arc and corona) shows that the yields can vary by at least three orders of magnitude, depending on the type of discharge and on other discharge parameters.     

The support and characterization of C60 and MoO3 on Al2O3

A new type of catalyst from supporting C₆₀ on MoO₃ and Al₂O₃ has been prepared. The effect of different order of impregnation and calcination atmosphere on catalyst are investigated by the solution test in toluene, UV-VIS spectroscopy and temperature programmed reduction (TPR). The results show that when the catalyst was prepared by supporting MoO₃ on C₆₀/Al₂O₃ and calcined in N₂, there is a stronger interaction between C₆₀, MoO₃ and Al₂O₃, but when supporting C₆₀ on MoO₃/Al₂O₃, the interaction is relatively weak. We consider that in the former method a new complex, Mo–C₆₀–O–Al, is formed.     

Phase analysis of high-temperature superconductors by selective dissolution combined with ICP-AES

Summary An apparatus for the selective dissolution as a chemical method of phase analysis and its operating conditions are described. Using ICP-AES as determination method an example for the YBCO system is found in the phase YBa_2–0.04Cu_3+0.03O_x and a BSCCO system is found in three phases of 35.6% Bi₂(Sr,Ca)_4–0.08Cu_3–0.05O_x, 30.1% Bi₂(Sr,Ca)_3–0.09Cu_2–0.08O_x and 34.3% Bi₂(Sr,Ca)_2–0.07Cu_1–0.05O_x.     

Resorufin, Resazurin und einige ihrer Derivate als titanometrische und stannometrische Indicatoren

Zusammenfassung Resorufin, Resazurin und einige ihrer Derivate sind auf ihre Eignung als titanometrische und stannometrische Redoxindicatoren in stark salzsaurer Lösung untersucht worden. Als am besten geeignet erwiesen sich MethylÄtherresorufin, MethylÄtherresazurin, ÄthylÄtherresorufin und ÄthylÄtherresazurin, wobei die Fehler bei allen Bestimmungen unter ± 0,6% lagen. Mit 0,01 n TiCl₃-Lösung können in CO₂-AtmosphÄre die Ionen Fe³⁺, Au³⁺, Cr₂O₇ ^2–, [Fe(CN)₆]^3– und VO₃ ^–, mit 0,01 n SnCl₂ Lösung die Ionen Fe³⁺, Ir⁴⁺, Cr₂O₇ ^2–, [Fe(CN)₆]^3–, [PtCl₆]^2– und VO₃ ^– direkt titriert werden.

---

Summary Resorufin, resazurin and some of their derivates have been examined for their applicability as titanometric and stannometric indicators in hydrochloride acid medium. Methylether resorufin, methylether resazurin, ethylether resorufin and ethylether resazurin have been found to be most suitable, the error of all determinations being below ± 0.6%. By means of 0.01 N TiCl₃ solution Fe³⁺, Au³⁺, Cr₂O₇ ^2–, [Fe(CN)₆]^3– and VO₃ ^– can be titrated in CO₂ atmosphere, 0.01 N SnCl₂ solution can be applied to the titration of Fe³⁺, Ir⁴⁺, Cr₂O₇ ^2–, [Fe(CN)₆]^3– and VO^3–.

---

---

Ich danke Frau S. ujová für die technische Hilfe.     

Study of the equilibrium of formation of arsenic(iii) lacunar heteropolytungstates by Raman spectroscopy

The formation of lacunar heteropolyanions (HPA): [AsW₉O₃₃]^9–, [As₂W₁₉O₆₇(H₂O)]^14–, and [As₂W₂₀O₆₈(H₂O)]^10– in aqueous solutions was investigated by Raman spectroscopy at [Na₂HAsO₃]₀ = 0.1, [Na₂WO₄]₀ = 0.9 mol L^–1 and pH 9.4–1.6. The [AsW₉O₃₃]^9– HPA is characterized by the most intense band ns (W=O) at 948 cm^–1 retaining its position in the pH range from 8.9 to 7.5. Under these conditions, the equilibrium constant of [AsW₉O₃₃]^9– formation from H₂AsO₃ ^– and WO₄ ^2– ions was estimated (logK = 87.0±1.0). The asymmetrical band at 952 cm^–1 corresponding to H_x[As₂W₁₉O₆₇(H₂O)]^(14–x)– shifts to 960 cm^–1 as the pH decreases from 6.5 to 5.5, which is due to the change in HPA protonation. The [As₂W₂₀O₆₈(H₂O)]^10– HPA is formed at pH 3.1—1.6; it is characterized by a band at 972 cm^–1.