Coulometrische Wismutometrie

Zusammenfassung Durch elektrolytische Oxydation einer Bi-Anode in gesättigter NaCl-Lösung können Bi³⁺-Ionen in Lösung gebracht werden. Dieser Prozeß ermöglicht die coulometrische Bestimmung anwesender Anionen, die schwerlösliche Bi-Verbindungen bilden.Es wurden Semimikro- und Mikrobestimmungen von Phosphationen durch elektrolytisch erzeugte Bi³⁺-Ionen bei konstanter Stromstärke ausgeführt. Die Endpunktbestimmung erfolgte amperometrisch bei konstantem Potential mit einer Indikatorelektrode — tropfende Quecksilberelektrode — und mit einer gesättigten Kalomelelektrode als Bezugselektrode. Die coulometrische Wismutometrie bietet eine weitere Möglichkeit der coulometrischen Eichung volumetrischer Lösungen im Sinne des seinerzeitigen Vorschlags vonTutundi.

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Summary Bi³⁺ ions can be brought into solution through electrolytic oxidation of a Bi-anode in saturated NaCl solution. This process makes possible the coulometric determination of the anions present that yield difficulty soluble bismuth compounds.Semimicro- and micro-determinations of phosphate ions were made via Bi³⁺-ions produced electrolytically at constant current strength. The endpoint was determined amperometrically at constant potential with an indicator electrode-dropping mercury electrode-and with a saturated calomel electrode as reference electrode. The coulometric bismuthometry affords a further possibility of the coulometric standardization of volumetric solutions in the sense of the proposal previously advanced byTutundi.

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Résumé On peut utiliser les ions Bi³⁺ en solution par oxydation électrolytique d'une anode en bismuth, en solution de chlorure de sodium saturée. Ce procédé permet le dosage coulométrique des anions présents qui forment des composés peu solubles avec le bismuth.On a mis au point le dosage semimicro et micro des ions phosphates par les ions Bi³⁺ formés électrolytiquement sous intensité constante. On détermine par ampérométrie le point équivalent à potentiel constant à l'aide d'une électrode indicatrice — électrode de mercure à goutte pendante —et avec une électrode au calomel saturée comme électrode de référence. La «bismuthométrie» coulométrique offre de grandes possibilités pour l'étalonnage coulométrique de solutions volumétriques, suivant l'idée queTutundi a émise en son temps.

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Vorgetragen beim Symposium für analytische Chemie in Graz, 29. September bis 1. Oktober 1965.

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Wir danken Herrn Dipl.-Ing.Vladimir Pantovi für seine Hilfe bei unserer experimentellen Arbeit.     

A viscometric study of poly(methyl methacrylate) in 2-alkoxyethanols

θ-Conditions, the temperature coefficient of unperturbed dimensions of the macromolecules and the thermodynamic interaction parameters ψ and κ were determined for solutions of poly(methyl methacrylate) in 2-alkoxyethanols (methoxy, ethoxy and butoxy). The results for this series of solvents fit the data reported for other solvents and dln $\text{r}{}_0{}^2\text{/}\text{d}\text{T = 2.6 × 10}{}^{\mathrm{?3}}\text{K}{}^{\mathrm{?1}}$. The dependence of parameters ψ and κ exhibited deviations from the theoretical dependence, mainly near the limiting value ψ = 0.5.     

Partial Least-Squares Study of the Effects of Organic Modifier and Physicochemical Properties on the Retention of Some Thiazoles

JPC – Journal of Planar Chromatography – Modern TLC - Reversed-phase (RP) HPTLC with aqueous ammonia-organic modifier (acetonitrile, dioxane, acetone) mobile phases has been used to...     

Cadmium and zinc determination by neutron activation analysis and biochemical tests in tissues of workers professionally exposed to cadmium

Cadmium and zinc levels in urine, serum, hair obtained from workers professionally exposed to cadmium oxide dust and from a control, nonoccupationally exposed group were determined by neutron activation analysis. The study was completed by biochemical monitoring tests such as the ₂ (₂-MG) determination in urine and serum and the -aminolevulinic acid dehydratase (ALAD) determination in blood. Significantly increased levels of cadmium in urine, serum, and hair, ₂-MG in urine and serum, ALAD in blood and decreased levels of zinc in serum were found in the exposed group compared to the control group. The most distinct differences of the parameters studied were observed for cadmium in hair. Correlations among the parameters were preliminary evaluated, too. For quality assurance purposes, the cadmium and zinc concentrations were determined in biological (standard) reference materials NBS SRM-1577 Bovine Liver, Bowen's Kale, IAEA A-11 Milk Powder, and IAEA H-8 Horse Kidney.     

On distribution of molecular weight in anionic polymerizates of caprolactam

Measurement has been made of the dependence of the molecular weight distribution on the ratio of the catalytic system components and on the polymerization time for polycaprolactam obtained by anionic polymerization. A bimodal character of the curves was observed for products made using molar ratios of activator (N-benzoylcaprolactam) to initiator (sodium dihydro-bis(methoxyethoxy)aluminate) of 1:1 and 1:3, when the polymerization times were less than 1 hr. This course is explained by the influence of fast side-reactions, mainly condensations. For a ratio of 3:1 of the components of the catalytic system, smooth integral distribution curves are obtained, accounting for a very fast decrease in the strong base concentration in the initial stages of the polymerization.     

Flow injection analysis : Part VI. The determination of phosphate and chloride in blood serum by dialysis and sample dilution

The rapid determination of chloride and inorganic phosphate in blood serum based on continuous flow spectrophotometry was adapted to Flow Injection Analysis by applying dialysis as well as differential dilution of the injected samples. In addition to the manual injection procedure, an automated microsampling unit was developed and used. By continuous dialysis, chloride could be determined reproducibly at a sampling rate of 125 samples per hour at sample volumes of 60 μl or less. A similar sampling rate and high precision were obtained for the determination of inorganic phosphate by using differential dilution.     

Flow injection analysis. principles,applications and trends

The basic principles of Flow Injection Analysis are outlined. The parameters governing the dispersion of the injected sample zone in the system are discussed, and it is demonstrated how these parameters can be manipulated in order to suit the requirements of an individual analytical procedure. A number of examples illustrating the practical application of f.i.a. are described, comprising the use of automated, stopped-flow, merging-zones, extraction techniques as well as f.i.a. scanning and methods based on intermittent pumping. Updated lists on f.i.a. procedures published and species that can be determined by f.i.a. are included.     

Stereochemistry of cyclic ether formation—II : Intramolecular cyclisation of secondary aliphatic alcohols to tetrahydrofuran-type ethers

The mechanism and stereochemistry of δ-C atom functionalisation in the reactions of secondary straight-chain aliphatic alcohols with lead tetraacetate, ceric ammonium nitrate, and heavy metal (Pb⁴⁺, Hg²⁺, Ag⁺) salts (AcO)^?1, O^2?, CO₃^2?-halogen (I₂, Br₂, Cl₂) combinations are discussed. By demonstrating the intermediacy of 5-bromo-2-hexanol, it was confirmed that the dark silver oxidebromine induced cyclisation of 2-hexanol (and alcohols in general) involves (as the other hypohalite reactions) intramolecular 1,5-hydrogen abstraction by alkoxy radicals and formation of δ-bromohydrins. A novel and simple procedure for obtaining tetrahydrofurans from alcohols by way of the hypochlorite reaction, using silver or mercuric salts and chlorine, is described.     

Spectral and electrochemical study of coordination molecules Cu4OX6L4: 3-Methylpyridine and 4-Methylpyridine Cu4OBrnCl(6−n)L4 complexes

The tetranuclear Cu₄OBr_nCl_(6-n)L₄ complexes, where L = 3-methylpyridine (3-Mepy), 4-methylpyridine (4-Mepy) and n=0–6 with trigonal bipyramidal coordination of copper(II) were prepared and their infrared and electronic absorption spectra as well as cyclic voltammograms in nitromethane solutions were measured. The polyhedra in Cu₄OBr_nCl_(6−n) (3-Mepy)₄ molecules are less distorted comparing with those of 4-Mepy analogues as indicated by infrared Cu₄O absorptions, far infrared Cu—Br, Cu—Cl, and Cu—N absorptions, d—d bands in electronic spectra and potentials, measured by cyclic voltammetry. The 3-Mepy complexes exhibit strong single infrared Cu₄O absorptions, while for related 4-Mepy complexes doubly split Cu₄O bands were observed. Two strongly overlapped d—d bands in electronic absorption spectra of the 3-and 4-Mepy complexes in nitromethane were resolved by Gaussian fitting. The 4-Mepy ligand produces slightly stronger ligand field than its 3-Mepy analogue. The maxima of high-energy d—d bands are in a linear correlation with the number of bromide ligands. The correlations for corresponding low-energy bands are considerably deviated from linearity. The halfwave potentials of the complexes in nitromethane correlate with both the number of bromides and the data of electronic absorption spectra suggesting that the reducing electron at the electrode process enters the half-filled d _{z 2} orbital of the copper(II) atom. The origin of a difference between the 3-and 4-Mepy complexes in their spectral and electrochemical properties is also discussed.     

Comparison of the Temperature Effect on the π∗←n and π∗←π Electronic Transition Bands of NO<Subscript>3</Subscript><Superscript>−</Superscript>(aq)

The effect of temperature on the π∗←π transition band in the UV absorption spectrum of NO₃⁻(aq) centered at ≈200 nm was studied in the temperature range 10–70 ^∘C. The observed temperature independence of this band was in contrast to the significant influence of temperature on the nitrate π∗←n transition reported recently by us. However, taking into account the electronic states involved in both the transitions, it was concluded that this finding was in accordance with our previous assumption that interconversion between spectrally distinct (with respect to π∗←n band) nitrate species included the rupture/formation of hydrogen bond(s) in the hydration shell of the nitrate ion.