The FeVO4-MoO3 system

A phase diagram of the FeVO₄-MoO₃ system has been constructed from the results of DTA and X-ray analysis. The components of the system form a compound FeVMoO₇. This compound melts incongruently at 680±5 °C, with separation of the solid Fe₄V₂Mo₃O₂₀.     

Texture of zirconia obtained by forced hydrolysis of ZrOCl2 solutions

The structure and surface properties of ZrO₂ strongly depend on its preparation. In the present work the impact of prolonged aging at basic conditions (pH = 9, T = 100°C, t = 48 h), on the phase composition and textural properties, obtained by calcination of the precipitate, was investigated using several techniques conjointly (DTA/TG, DSC, XRD, porosimetry). The thermal effects accompanying the ZrO₂·xH₂O gel formation, the coalescence of the particles and crystallization were evaluated and discussed in terms of the structural differences between the aged and non-aged samples. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phase equilibria in the V2O5-FeVMoO7 system

The progress of the reactions of water with brownmillerite (C₄AF⁺) and its mixtures with gypsum (C¯SH₂) and calcium sulphoaluminate (C₄A₃¯S) was investigated by means of calorimetric measurements in situ and X-ray diffractometry to determine the reaction heat and the conversion of the solid reactants as functions of time up to 50 h. The rapid reaction of C₄AF with water and the modifying effect of sulphates on the composition of the hydrated phases were confirmed. The presence of sulphates causes the induction period during the reactions of aluminium and iron-containing clinker phases with water. These phenomena are important technologically too, especially in cements with increased contents of C₄AF and of sulphate-yielding phases (C¯SH₂ and C₄A₃¯S).

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Zusammenfassung Der Verlauf der Hydratation von Brownmillerit Ca₄AF^* bzw. seinen Mischungen mit Gips (C¯SH₂) und Calcium-sulfat-aluminat (C₄A₃¯S) wurde durch kalorimetrische Messungen in situ und Röntgendiffraktometrie verfolgt, um die Abhängigkeit der Reaktionswärme und des Umsatzes der festen Reaktanden von der Zeit (bis 50 h) zu bestimmen. Die schnelle Reaktion von C₄AF mit Wasser und der modifizierende Effekt der Sulfate auf die Zusammensetzung der hydratisierten Phase wird bestätigt. Die Anwesenheit von Sulfat bewirkt eine Induktionsperiode bei der Reaktion von alumimum- und eisenhaltigen Klinkerphasen mit Wasser. Diese Erscheinungen sind von technischer Bedeutung, insbesondere für Zemente mit erhöhtem Gehalt an C₄AF und sulfatbildenden Phasen wie C¯SH₂ und C₄A₃¯S.

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(4 · l23 · Fe2O3) (4 · 3l23 · SO3) ( 50 ). . - . , , - .

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Dedicated to F. Hanic, D. Sc. on the occasion of his 60th birthday     

Reactivity of FeVO4 towards MgMoO4 in the solid-state

A compound of the formula Fe₃Mg₂Mo₂V₃O₂₀ has been obtained as a result of a reaction between FeVO₄ and MgMoO₄ taken at a molar ratio of 3:2. This compound crystallises in the monoclinic system and its unit cell parameters are the following: a=0.6971 nm, b=0.9055 nm,c=1.2542 nm, g=102.00°, Z=2. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evaluation of antioxidants in Dong quai (Angelica sinensis) and its dietary supplements

The antioxidant activity (AA), total phenolic content (TPC) and total flavonoids content (TFC) in Dong quai (DQ, Angelica sinensis) raw materials and dietary supplements (DS) containing this plant were determined using the CUPRAC, FRAP and fluorescence methods. The antioxidant activity for DQ aqueous extracts revealed by CUPRAC was (1330.45 ± 1.30) μmol Trolox equivalent (TE) per 100 g of dry mass (DM), whereas the antioxidant activity as determined by FRAP was (1813.9 ± 2.0) μmol of TE per 100 g of DM. Lower values were noted for the fluorescence method than for CUPRAC and FRAP (ranging from (35.96 ± 0.3) to (304.6 ± 1.4) μmol of TE per 100 g of DM). The highest TPC values were determined for an aqueous extract of DQ ((3330.3 ± 2.3) μmol of TE per 100 g of DM), while TFC for ethanolic extracts of DQ was ((146.50 ± 0.5) mg of quercetin equivalent (QE) per 100 g of DM). Cinnamic acid, isomers of benzoic acid and derivatives of quercetin were analysed by HPLC-PDA. The ferulic acid concentration in an ethanolic extract of DQ was (21.83 ± 0.07) mg per 100 g of DM. Of the flavonols detected, rutin exhibited the highest concentration in ethanolic extract of DQ ((3.32 ± 0.13) mg of QE per 100 g of DM). Other phytochemicals (alkaloids, saponins, flavonoids, anthraquinones, tannins, steroids, etc.) were identified by phytoscreening colour reaction. The results were analysed by principal component analysis (PCA), cluster analysis and one-way ANOVA tests.     

Bestimmung von Mikromengen Schwefel nach Aufspaltung des S8-Ringes in Indium-, Blei-, Antimonund Wismutsulfiden mit Hilfe einer induzierten Reaktion von Natriumazid mit Jod

Zusammenfassung Die Bestimmungsmethode für Mikromengen elementaren, in Sulfiden enthaltenen Schwefels mit Natriumazid und Jod wurde modifiziert. Der Analyse geht die Aufspaltung des S₈-Ringes voraus, die man dank der nukleophilen Wirkung von N₃ ^– in DMF-Lösung erreicht. Diese Methode wurde auf die Bestimmung des Schwefels in Indium-, Blei-, Antimon- und Wismutsulfid angewandt. Sie ist einfach und empfindlich. Ihre Fehlergrenze liegt bei ± 4%.

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Determination of microamounts of sulfur after cleavage of the S₈ king in indium, lead, antimony and bismuth sulfides by means of an induced reaction of sodium azide with iodine

Summary The determination of microamounts of elemental sulfur contained in sulfides using sodium azide and iodine was modified. The analysis was preceded by cleavage of the S₈ ring, which is achieved by virtue of the nucleophilic action of N₃ ^– in DMF solution. This method was applied to the determination of sulfur in indium, lead, antimony and bismuth sulfides. It is simple and sensitive. Its limit of error is ±4%.

     

Determination of microgram amounts of azide by gas chromatography

Azide ions (5–120 μg) are oxidized by cerium(IV) in an acidic medium. The nitrogen evolved is displaced by helium carrier and quantified by gas chromatography with a thermal conductivity detector. The relative standard deviation is <5%. Many sulphur anions, cyanide and some metal ions which form azide complexes do not interfere.     

Application of isotachophoretic and conductometric methods for neomycin trisulphate determination

Determination of neomycin trisulphate (NMS) in a dosage form (Neox and Neosol) was carried out by capillary isotachophoresis (cITP) with conductometric detection. The following electrolytes: leading: 10 mmol dm⁻³ sodium acetate + 0.08 % hydroxyethylcelulose (HEC) and acetic acid to pH = 5.5, and terminating: 10 mmol dm⁻³ β-alanine were tested for isotachophoretic separation of NMS. The calibration curve was linear over the range of 10.00 mg dm⁻³ to 100.00 mg dm⁻³ with LOD = 5.69 mg dm⁻³ and LOQ = 18.96 mg dm⁻³. The results were compared to the conductometric determination of NMS with: ammonium molybdate (VI), silver nitrate (V) and Reinecke salt. Good accuracy was obtained from conductometric titration of NMS with Reinecke salt, the recoveries being as follows: 100 % (RSD = 1.99 %); 96.17 % (RSD = 2.10 %) and 95.22 % (RSD = 1.55 %) for NMS in pure form, Neosol and Neox, respectively.     

Localized Visualization of Chemical Cross-Talk in Microsensor Arrays by Using Scanning Electrochemical Microscopy

 An investigation of an array of four Pt microband electrodes 25 μm wide and spaced 25 μm apart was performed with the scanning electrochemical microscope (SECM). Where possible the SECM measurements were confirmed with conventional electrochemical measurements. It is shown how the sensiti- vity of the SECM recycling current to the activity of the underlying surface can be used to probe the homogeneity of enzyme-modified microelectrodes. The diffusion of H₂O₂ between these micro enzyme- electrodes and unmodified electrodes was investigated and it was demonstrated how the SECM can be a powerful tool in the elucidation of the properties of these electrodes. Received June 8, 1998. Revision November 12, 1998.     

Studies on the System AIVMoO7-V2O5

The phase equilibria in the system AlVMoO₇-V₂O₅ were investigated over the whole component concentration range up to 1000°C. A phase diagram was constructed from the results of DTA and XRD methods. This revised version was published online in July 2006 with corrections to the Cover Date.