Addition of hydroxide to an isoelectronic series of bis-diazineplatinum(II) complex ions

Base hydrolysis of bis-bipyridylplatinum(II) occurs via a 1:1 intermediate adduct with hydroxide ion. The equilibrium constants for this 1:1 addition of hydroxide inwater to complex ions [PtL2]2+, where L=one of theisoelectronic set 2,2-bipyridyl (bpy); 2,2- bipyrazine (bpz); 3,3-bipyridazine (bpdz) and 2,2- bipyrimidine (bpym) are respectively (as log10K at 25°C): 4.23; 4.59; 3.82; 6.14. This result is rationalized in terms of addition at the 6–position of the ligand.     

Di- and tetranuclear copper(II) complexes of a novel binucleating tetrathioether-tetrathiol ligand

A novel bi-tetradentate polythioether ligand, 6,6-methylene-bis(5- mercapto-3-thiahexyl)-4,8-dithiaundecane-1, 11-dithiol (H4L) was synthesized, and its di- and tetranuclear copper(II) complexes were prepared, and characterized by elemental analyses, magnetic moments, 1H-n.m.r., i.r., and Uv/vis spectra. The i.r. data show that the ligand acts in a tetradentate manner and coordinates via one S atom of the thioether and thiol groups. The geometry of the metal chelates is discussed with the help of magnetic and spectroscopic measurements. The elemental analyses, stoichiometry, and spectroscopic data of the complexes indicate that the copper(II) ions are coordinated to the bi-dianion of the ligand. The function of the thiol ligand is to release protons to form copper(II) complexes, (Cu2L).     

中性红作试剂荧光光度法测定亚硝酸根

研究了在盐酸介质中ＮＯ＾－２与中性红的亚硝化反应。结果表明，在０．０４８ｍｏｌ／Ｌ的盐酸介质中，ＮＯ＾－２与中性红反应生成无荧光的物质，ＮＯ＾－２在４０－２４０μｇ／Ｌ，范围内与荧光猝灭程度成正比，常见的共存离子不干扰其测定。所拟方法用于水样中ＮＯ＾－２的测定，结果满意。     

Conductivities and silver electrode polarization resistance of solid electrolyte ceramics from ZrO2-Y2O3 powder synthesized in air plasma

Ceramic specimens have been obtained from the powder of ZrO₂-7.5 mol% Y₂O₃ having a specific surface area of 30 m²/g synthesized in air plasma. The novelty of this research lies in the fact that the plasma process makes it possible to prepare so-called nanopowders with a particle size less than 100 nm, possessing specific physical, chemical and technological properties. The sintered density of the specimens was 94–96% of the theoretical value, 6.001 g/cm³. The X-ray diffraction pattern of the specimens corresponded to a face-centered cubic lattice. Impedance in the frequency range of 100 Hz–15 MHz and d.c. polarization curves in a potential range of −10 to 10 mV were measured in the temperature range 200–850 °C in heating and cooling cycles. The intragrain, the grain boundary and the total bulk conductivities, the electrode polarization resistance and their activation energies were determined. The thermal stability of the studied system was proved in three measurement series up to 600–850 °C in heating and cooling cycles. The results obtained have shown that the conductivity of ZrO₂-7.5 mol% Y₂O₃ ceramics is not solely a function of temperature, but also depends on the previous thermal state of the ceramics. Received: 16 October 1997 / Accepted: 19 January 1998     

Electroanalytical end-point determination of hydrolytic precipitation titrations of sulphate and oxalate

Summary Electroanalytical End-Point Determination of Hydrolytic Precipitation Titrations of Sulphate and OxalateThe possibilities of application of biamperometric and bipotentiometric end-point determination by means of various indicator electrodes are described. Several titrants were used. Best results were obtained with quinhydrone electrodes. Interference levels of several anions were established. The lowest concentration of oxalate and sulphate that can be determined is 5×10^–4 M.

---

Zusammenfassung Die Anwendungsmöglichkeiten der biamperometrischen und bipotentiometrischen Endpunktbestimmung mittels verschiedener Indikatorelektroden wurden beschrieben. Es wurden einige Titranten benützt. Die besten Resultate wurden mit Chinhydronelektroden erhalten. Die störende Wirkung verschiedener Anionen wurde festgestellt. Die geringste bestimmbare Konzentration beider Anionen (Sulfat und Oxalat) ist 5·10^–4 M.

     

Analytical evaluation of the derivatives used in equilibrium calculations

The derivatives of the total concentrations and other measured quantities with respect to the formation constants are calculated in general by a numerical method using finite increments. It is shown in this paper that these values can be calculated analytically, whereby the disadvantages of numerical differentiation may be avoided. The use of this method gives the possibility of writing faster programs for the calculation of the stability constants, based on the SCOGS and LETAGROP principle, without as large a memory requirement as in the LEAST and MINIQUAD programs.     

Synthesis and 13C-NMR spectroscopic investigations of rhamnobioses

A convenient method has been developed for the synthesis of all mono- and di-O-benzyl ethers of methyl α-L-rhamnopyranoside applying a new stereoselective method for the hydrogenolytic ring-cleavage of benzylidene acetals. Using the prepared dibenzyl ethers as aglycones, the (1→2)-, (1→3)- and (l→4)-linked rhamnosyl-rhamnose derivatives (13–15) were synthesised. Hydrogenolysis of the latter compounds and subsequent acetylation gave the pentaacetates (16–18) of methyl dirhamnosides, which on saponification furnished the free methyl dirhamnosides (19–21). Acetolysis of 16–18 gave the corresponding dirhamnose-hexaacetates which were transformed into the three disaccharides by saponification. The structure of each product was investigated by ¹³C-NMR spectroscopy, and for the purpose of ¹³C-NMR studies the mono-O-methyl ethers of methyl α-L-rhamnopyranoside, the diacetates and di-O-benzyl ethers of the latter compounds, and, also the diacetates of methyl α-L-rhamnopyranoside were synthesised.It has been established that, for ¹³C-NMR investigations of oligosaccharides, the benzyl ethers of monosaccharides are more suitable model compounds than the currently used monosaccharide methyl ethers.     

Biamperometric neutralisation titrations in non-aqueous solvents applying tin electrode pair for the end-point detection

Summary Tertiary amines and salts of organic acids in acetic anhydride with 5% of acetic acid were titrated applying a biamperometric indicating system consisting of a polarised or unpolarised pair of tin electrodes by means of 0.1 N perchloric acid in glacial acetic acid. Amounts of 15.4–29.8 mg were analysed with average deviations of <0.6%, the results obtained being in a good agreement with those of potentiometry. The biamperometric end-point detection using an indicating system of polarised pair of tin electrodes can be applied for coulometric determinations of these bases with satisfying accuracy. By means of anodic generation of hydrogen ions in the presence of hydroquinone amounts of 0.5–1.0 mg were titrated with average deviations of < 1.3%. The results obtained were compared with those obtained of catalytic thermometric and photometric titrations.

---

Biamperometrische Neutralisationstitrationen in nichtwärigen Lösungsmitteln unter Anwendung eines Zinn-Elektrodenpaares als Indicatorsystem

Zusammenfassung Tertiäre Amine und Salze organischer Säuren werden in Acetanhydrid mit 5% Essigsäure durch Titration mit einer 0,1 N Lösung von Perchlorsäure in Essigsäure bestimmt. Das verwendete biamperometrische Indicatorsystem besteht aus einem Paar polarisierter oder nichtpolarisierter Zinnelektroden. Mengen von 15,4–29,8 mg wurden mit einer mittleren Abweichung von <0,6% analysiert. Die Ergebnisse stimmen gut mit denen von potentiometrischen Titrationen überein. Die biamperometrische Endpunkttechnik mit polarisierten Zinnelektroden kann für coulometrische Bestimmungen dieser Basen mit zufriedenstellender Genauigkeit benutzt werden. Durch anodische Erzeugung von Wasserstoffionen in Gegenwart von Hydrochinon wurden Mengen von 0,5–1,0 mg mit einer mittleren Abweichung von < 1,3% titriert. Die Ergebnisse wurden mit denen von katalytisch-thermometrischen und photometrischen Titrationen verglichen.