Convolution potential sweep voltammetry: Part IV. Homogeneous follow-up chemical reactions

The application of Convolution Potential Sweep Voltammetry to mechanism analysis and rate determination in electrochemical processes involving homogeneous chemical reaction is discussed. The formal analysis of the transition between pure diffusion control and pure kinetic condition is treated in the case of a first order follow-up reaction. The practical applicability of the method is then tested on the reductive pinacolization of acetophenone in acetonitrile using as operational parameters the sweep rate, the initial concentration and the water content of the medium.     

Nanotomography in the chemical, biological and materials sciences

Nanotomography is a technique of growing importance in the investigation of the shape, size, distribution and elemental composition of a wide variety of materials that are of central interest to investigators in the physical and biological sciences. Nanospatial factors often hold the key to a deeper understanding of the properties of matter at the nanoscale level. With recent advances in tomography, it is possible to achieve experimental resolution in the nanometre range, and to determine with elemental specificity the three-dimensional distribution of materials. This critical review deals principally with electron tomography, but it also outlines the power and future potential of transmission X-ray tomography, and alludes to other related techniques.     

The publication speed of information in bibliographic chemical databases.

The quality of bibliographic databases depends very much on the reliably fast follow-up of the pertinent literature. We have studied this quality feature of two important chemical bibliographic databases: Chemical Abstracts (CA) and Analytical Abstracts (AA). The follow-up rate (speed of information) of these databases has been determined with respect to 10 core journals in analytical chemistry. On the average the performance of Chemical Abstracts has been good over the past decade, while the formerly poor performance of Analytical Abstracts has improved considerably. Some quite unexpected nonuniformities can, however, still be detected in the publication time distributions of both databases.     

The learning machine in quantitative chemical analysis: Part 2. Potentiometric titrations of mixtures of three bases

Computer-calculated curves for the titration of mixtures of one strong base and two weak bases are used in the training and testing of a linear learning machine. The results indicate that multicategory classifiers can be calculated from a computer-generated training set of titration curves in which a random error of ±0.01 unit in the pH values is introduced. The relative error in the predictions for concentrations of bases not included in the training set was of the orderof ± 1% for concentration ratios up to 10:1 when δpK_b for the weak bases exceeded 1 pK unit and for K_b1 ? 5 × 10^-4 and K_b2 ? 10^-9. Calculation of the first derivative of the volume of titrant versus pH curves as a preprocessing step was necessary to obtain this accuracy for the weak bases, whereas the volume of titrant versus pH curves had to be used directly in the determination of the strong base. Predictions of concentrations of actual samples were in agreement with the computer-calculated results.     

Part IV. Review and evaluation of spark source mass spectrometry as an analytical method

Summary The analytical features and most important fields of application of spark source mass spectrometry are described with respect to the trace analysis of highpurity materials and the multielement analysis of technical alloys, geochemical and cosmochemical, biological and radioactive materials, as well as in environmental analysis. Comparisons are made to other analytical methods. The distribution of the method as well as opportunities for contract analysis are indicated and developmental tendencies discussed.

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Überblick und Bewertung der Funken-Massenspektrometrie als Analysenmethode

Zusammenfassung Die Analyseneigenschaften und wichtigsten Einsatzgebiete der Funken-Massenspektrometrie zur Spurenanalyse an hochreinen Materialien und zur Multielementanalyse an technischen Legierungen, geo- und kosmochemischen, biologischen und radioaktiven Materialien sowie in der Umweltanalytik werden beschrieben. Vergleiche zu anderen Analysenverfahren werden gegeben. Die Verbreitung der Methode sowie Möglichkeiten der Auftragsanalytik werden angegeben und Entwicklungstendenzen diskutiert.

     

Data-, knowledge- and method-bases in chemical sciences I. BAQOR-database for equilibrium constants in aquo-organic media

BAQOR is a computer readable database for equilibrium constants in presence of different percentages of water miscible cosolvents. The present version with user friendly software in dBase III+ contains 740 records and runs on any IBM compatible PC. The physico-chemical properties of binary and ternary water-cosolvent mixtures, the equilibrium constants of proton- and metal-ligand complexes are retrievable through pop-up menus. Specific searches by metal-, ligand-, solvent-, and stoichiometry-wise and their combinations is possible. Several display modes-monitor, file and hard copy-are available for the numerical fields as well as for literature citation.     

Isotopic shifts in chemical exchange systems,IV

A separation factor of 0.94±0.02 for²²Na and²⁴Na has been obtained in a system consisting of a Li⁺ loaded cation exchange resin and a methanol solution. The ratio of the Na-isotopes was determined by measurement of the -rays in a precision arrangement.     

Congresses,conferences, symposia,consultations, and seminars in the field of chemical sciences held with participation of the russian academy of sciences

Information

Congresses, conferences, symposia, consultations, and seminars in the field of chemical sciences held with participation of the russian academy of sciencesVI International Frumkin Symposium Fundamental Aspects of Electrochemistry*     

DFT-based chemical reactivity indices in the Hartree-Fock method. II. Fukui function, chemical potential, and hardness

A derivation of the density-functional-theory- (DFT) based reactivity indices in the ensemble unrestricted Hartree-Fock (eUHF) method is presented. The comparison between the properties of the reactivity indices evaluated in one and two sets of spin-orbital approach of the eUHF and hyper-unrestricted Hartree-Fock (UHF) methods are shown. All approaches give similar Fukui function irrespective of methodology used, but significantly differ for the global indices, containing important chemical information, and so their interpretation in terms of DFT- based indices can be questionable. The calculation scheme for the indices using the first- and second-order coupled perturbed eHF equations is proposed. A method for the identification of the spinorbitals involved in the change of the total number of electrons is included. The illustrative examples (water and hydrogen cyanide) show that the ground-state (GS) properties of the (Z +/- 1)-electron systems can be predicted from the GS properties of the Z-electron systems with an accuracy comparable with the UHF calculations. The relaxation effect, important for the HCN system in which a change in the symmetry of the highest-occupied spin-orbital occurs, is effectively predicted.     

Effects of quaternary ammonium bases on valence-saturated but coordination-unsaturated chelates: Part IV. Extraction of some divalent metal 8-hydroxyquinolinates

The effect of zephiramine on the chelate formation and extraction of some divalent metals with oxine is reported. In the presence of zephiramine, the non-extractable 1:2 zinc— and cadmium—oxine chelates as well as the extractable 1:2 nickel— and manganese—oxine chelates become highly coordinated ternary complexes, M(Q)₃ (zeph), which are easily extracted into 1,2-dichloroethane. Copper is easily extracted into 1,2-dichloroethane as Cu(Q)₂, which is not affected by zephiramine.     

Information resources in chemistry and related sciences: Publishing houses, electronic libraries, information networks, search and retrieval systems, databases, and catalogues

Data on changes in the status of many scientific journals are systematized. Newly organized journals, cessation of issues, journals incorporated into others, and merged and split journals are mentioned. Information is collected about a large number of scientific publishers which have made a significant contribution to the printed and electronic output and electronic libraries, information networks, search and retrieval systems, databases, and catalogs of scientific literature in chemistry and related sciences, including their web sites.     

Many-body effects in electrochemisorption: Part IV. Multi-boson formalism

Several channels provided by many-body couplings — both fermion-fermion and fermion-boson — for the evolution of the chemisorption system are discussed. This provides an opportunity of a systematic study of the effects of correlations reflected through the intricate pole structure of the absorbate Green functions. The results of Newns, Anda and others in the context of chemisorption are generalized.     

Similarity and representation in chemical knowledge practices

This paper argues for the theoretical and practical validity of similarity as a useful epistemological tool in scientific knowledge generation, specifically in chemistry. Classical analyses of similarity in philosophy of science do not account for the concept’s practical significance in scientific activities. We recur to examples from chemistry to counter the claim of authors like Quine or Goodman to the effect that similarity must be excluded from scientific practices (as well as their philosophical analysis). In conclusion we argue that more recent conceptualizations of the notion of similarity, particularly Giere’s one, are appropriate for a philosophical analysis that considers scientific practices on equal terms with scientific theory.     

Transfusion-transmitted diseases. Current status and future directions.

Blood transfusion is associated with a number of potential risks, including the transmission of infectious diseases. Although a zero-risk blood supply may never be attainable, much effort is directed toward the identification of blood donors with evidence of transmissible infectious agents. This article summarizes the current knowledge of transfusion-transmitted diseases. In addition, possible future directions in decreasing the incidence of such diseases are discussed.     

Nucleophilic displacement of aromatic fluorine. Part IV. Quinolinoquinolines and benzochromenoquinolines

The title compounds were obtained by facile intramolecular nucleophilic displacement of aromatic fluorine from 4-(2-fluorophenyl)quinolines bearing substituents such as a carboxamide, carboxaldehyde, carboxaldoxime or a hydroxymethyl group in the 3-position.