Study of Sb‐doped SnO2 Gray Ceramic Pigment with Cassiterite Structure

In this study, Sb_xSn_1?xO₂ (0 ≤ x ≤ 0.5) compositions were synthesized by the ceramic method from Sb₂O₃‐SnO₂ and Sb₂O₅‐SnO₂ mixtures and characterized by Differential thermal analysis (DTA) and thermogravimetric analysis (TG), X‐ray diffraction, UV‐V‐NIR spectroscopy and CIE L*a*b* (Commission Internationale de l'Eclairage L*a*b*) parameters measurements. Solid solutions with cassiterite structure were obtained at 1300 °C. These solid solutions are stable into glazes. From Sb₂O₃, light gray coloured materials were obtained. From Sb₂O₅, bluish gray coloured materials were obtained at 1300 °C/6h when x ≥ 0.3. Sb_xSn_1?xO₂ with 0.3 ≤ x < 0.5, T = 1300 °C and Sb₂O₅ might be established as compositional range, fired temperature and antimony precursor to obtain gray ceramic pigments in this system.     

Vanadium determination in rat tissues and biological reference materials by neutron activation analysis

Vanadium was determined in adrenal gland, brain, ileum, kidney, liver, lung, muscle, myocard, skin, spleen, gonads, thyroid, and tibia of rats fed with normal diet and exposed to high vanadium doses in drinking water. Both radiochemical neutron activation analysis (RNAA) and instrumental neutron activation analysis (INAA) were employed. The RNAA procedure consisted in dry ashing samples prior to irradiation and vanadium separation from the irradiated samples by extraction with N-benzoyl-N-phenylhydroxylamine (BPHA) in toluene from 5 mol·l^–1 HCl. Vanadium accumulation as a function of a type of the tissue, exposure time, sex of rats, and administration of V(IV) or V(V) was studied. For quality assurance purposes, the biological (standard) reference materials NBS SRM 1571 Orchard Leaves, NBS SRM 1577a Bovine Liver, IAEA H-4 Animal muscle, and Bowen's Kale were analyzed.Presented at the 2nd Balkan Conference on Activation Analysis and Nuclear-Related Analytical Techniques, Bled, 4–6 October, 1989.     

Analytical applications of the o-dianisidine-persulfate reaction: Kinetic determination of silver and cobalt

A kinetic method for the silver determination based on the catalytic effect of Ag(I) on the oxidation of o-dianisidine by persulfate at pH = 4.5 in the presence of 1,10-phenanthroline is proposed. Ag(I) can be determined by measuring the absorbance of the reaction product at 450 nm, using the fixed time method. Co(II) does not have a catalytic effect in the reaction, but in the simultaneous presence of silver and cobalt the reaction shows an induction period the length of which is related to the Ag/Co molar ratio. As a consequence, two new methods for the determination of cobalt and silver using the induction period method are proposed. The two methods for silver are applied to the determination of silver in lead.     

Determination of iron and calcium impurities in magnesium oxide by atomic absorption

Summary An atomic absorption method has been developed for the determination of iron and calcium impurities in magnesium oxide. The effect of the magnesium matrix has been eliminated by the addition of hydroiodic acid and hydrogen peroxide to generate iodinein situ. The relative standard deviations were 0.5% for iron and between 0.5 and 1.5% for calcium.

---

Die Bestimmung von Eisen- und Calcium-Verunreinigungen in Magnesiumoxid mit Hilfe der Atomabsorption

Zusammenfassung Zur Bestimmung der Eisen- und Calcium-Verunreinigungen in Magnesiumoxid wurde die Atomabsorptionsspektroskopie herangezogen. Der Einfluß der Magnesiummatrix wurde durch Zugabe von Jodwasserstoffsäure und Wasserstoffperoxid, d. h. durch Freisetzung von Jod in situ beseitigt. Die rel. Standardabweichung für Eisen betrug 0,5%, für Calcium 0,5–1,5%.

     

Exchange of halogen bonded on aromatic core. Heterogeneous catalysis—I : Reaction mechanism of iodine exchange in o-iodobenzoic acid

Reaction mechanism of halogen exchange between arylhalogenide and halogenide anion is studied in a case when the aromatic core is inactivated with respect to the S_NAr substitution by other substituents. The exchange of iodine between o-iodobenzoic acid and ¹³¹I labelled NaI serves as a modelling reaction. The reaction was found to proceed heterogeneously on a glass surface. In the case of a rapid course of the surface reaction the reaction mechanism is more complicated and the equation derived by McKay cannot be applied for expressing the time dependence of the degree of isotopic exchange. Reaction mechanism was proposed for this reaction and compared with experimental data.     

Palladium-catalyzed electrophilic allylation reactions via bis(allyl)palladium complexes and related intermediates

The synthetic scope of the allyl-palladium chemistry can be extended to involve electrophilic reagents. The greatest challenge in these reactions is the catalytic generation of an allyl-palladium intermediate incorporating a nucleophilic allyl moiety. A vast majority of the published reactions that involve palladium-catalyzed allylation of electrophiles proceed via bis(allyl)palladium intermediates. The eta(1)-moiety of the bis(allyl)palladium intermediates reacts with electrophiles, including aldehydes, imines, or Michael acceptors. Recently, catalytic electrophilic allylations via mono-allylpalladium complexes were also presented by employment of so-called "pincer complex" catalysts.     

Di-2-pyridylmethylamine-based palladium complexes as new catalysts for Heck,Suzuki, and Sonogashira reactions in organic and aqueous solvents

A new palladium-dipyridylmethylamine complex is an excellent catalyst for C-C bond-forming processes such as the Heck, Suzuki, and Sonogashira reactions in organic and aqueous solvents under homogeneous conditions. [reaction: see text]     

Characterisation of Tokaj wines based on free amino acids and biogenic amines using ion-exchange chromatography

Summary Tokaj wines (Szamorodni and Aszu wines) of Hungarian origin were investigated on the basis of free amino acids and biogenic amines. The separation and determination of these compounds was performed by an amino acid analyser equipped with an ion-exchange resin column. The total amount of free amino acids and biogenic amines was higher in Aszu wines than in Szamorodni wines. The main amino acids were proline and arginine, while the major biogenic amines were tyramine and putrescine. The free amino acid and biogenic amine content of Aszu wines depended on the vineyards the wines originated from. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001     

Reactions of substituted furo[3,2-<Emphasis Type="Italic">b</Emphasis>]pyrrole-5-carboxhydrazides and their biological activity

The reactions of substituted furo[3,2-b]pyrrole-5-carboxhydrazides 1 with 5-arylfuran-2-carboxaldehydes 2, 4,5-disubstituted furan-2-carboxaldehydes 3 and thiophene-2-carboxaldehyde 4 has been studied. The advantage of microwave irradiation on some of these reactions was reflected in the reduced reaction time and increased yields. Reactions of 1 with 4-substituted 1,3-oxazol-5(4H)-ones 11 led to diacylhydrazines 13 or to imidazole derivatives 14 depending on the temperature. 1,2,4-Triazole-3-thione 17 was synthesized by two-step reaction of 1 with phenylisothiocyanate and subsequent base-catalyzed cyclization of thiosemicarbazide 16. The effects of hydrazones 5–10 on inhibition of photosynthetic electron transport in spinach chloroplasts and chlorophyll content in the antialgal suspensions of Chlorella vulgaris were investigated.