Some trace elements in the waters,marine organisms and sediments of the Adriatic by neutron activation analysis

A number of investigations of trace elements in the waters, organisms and sediments of the Adriatic, using neutron activation analysis with radiochemical, separations are reported. These include studies of Hg in mussels from the Northern Adriatic, of Hg and Se in edible animals from the Rijeka region, and of seven elements (As, Cd, Cu, Hg, Mn, Se and Zn) in marine invertebrates from the Slovene coast. Additionally, plankton, sediment cores and water samples were taken from a grid of stations covering the whole Adriatic and analyzed for 6 to 11 of the trace elements As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Sb and Zn (Hg only in water). Generally, levels found were not indicative of pollution as compared with oceanic samples, but some evidence of locally increased levels was found, especially for Hg. The levels of eleven trace elements in three marine Intercomparison samples prepared by the IAEA Monaco Laboratory are also presented.     

The structure and variable temperature 13c nmr spectra ofμ,μ′-(1,3-dithiolatocyclohepta-4,6-diene)hexacarbonyl-diiron(I)

μ,μ′-(1,3-Dithiolatocyclohepta-4,6-diene)hexacarbonyldiiron(I) was prepared by the reaction of 2,3,4-trithiabicyclo[4,3,1]deca-6,8-diene with Fe₂(CO)₉. The carbonyls undergo rapid site exchange within each Fe(CO)₃ group but there is no exchange of carbonyls between the two different Fe(CO)₃ moieties. The novel bicyclic nature of the bridging ligand results in a short iron—iron bond distance and a long sulfur—sulfur distance as compared to other members of this class.     

Beitrag zur Kenntnis der Austauscheigenschaften von schwerl?slichen Hexacyanoferraten (II)

Zusammenfassung Verteilungskoeffizienten für Caesium, Rubidium und Kalium zwischen wäßrigen Lösungen und Zink-, Nickel-, Kobalt-, Uranyl-, Eisen-, Cadmium-, Kupfer- und Silberhexacyanoferraten(II) wurden gemessen. Silberhexacyanoferrat(II), das den höchsten Trennfaktor für das Paar Rb-Cs aufweist, wurde näher untersucht, seine Kapazität bestimmt und die Abhängigkeit der Verteilungskoeffizienten für Rb und Cs von der Konzentration der Salzsäure im Bereich von 1–10^–6m gemessen. Seine Austauscheigenschaften wurden mit denen von Ammoniumphosphormolybdat verglichen.

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Summary Distribution coefficients of caesium, rubidium and potassium between their aqueous solutions and hexacyanoferrates(II) of zinc, nickel, cobalt, uranyl, iron, cadmium, copper and silver were determined. Silver hexacyanoferrate(II) characterized by the highest separation factor for the pair rubidium-caesium was investigated in detail. Its capacity was determined as well as the dependence of the distribution coefficients of rubidium and caesium on the concentration of hydrochloric acid within the range of 1 to 10^–6 M. The ion-exchange properties of silver hexacyanoferrate(II) were also compared with those of ammonium molybdophosphate.

     

Photometrische Bestimmung von Caesium

Zusammenfassung Lösungen von Caesiumsilicowolframat in Natronlauge lassen sich nach Einstellung des pH auf 2,8–3,1 mit einer Mischung von Natriumdithionit und Natriumsulfit zu Wolframblau reduzieren, wobei die Intensität der Farbe der Konzentration von Caesium direkt proportional ist. Die Bestimmung ist einfach und in kurzer Zeit durchführbar und kann ohne Modifikation sowohl in Anwesenheit größerer Mengen von Molybdat als auch einer großen Anzahl anderer Ionen durchgeführt werden. Die Methode wurde für die Auswertung von Caesiumausbeuten bei der Trennung an Ammoniumphosphormolybdatsäulen angewendet und liefert befriedigende Resultate.

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Summary Caesium silicotungstate can be reduced to tungsten blue by dissolving the precipitate in sodium hydroxide, adjusting to pH 2.8–3.1 and adding a mixture of sodium dithionite and sodium sulphite. The intensity of colour follows Beer's law.A simple and rapid method for the determination of caesium has been developed, based on this reaction, which gives good results in pure solutions as well as in the presence of greater amounts of other ions.The method has been successfully applied to the analysis of solutions resulting after separation of caesium on ammonium phosphomolybdate columns.

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Die Verfasser danken Herrn J. Koroin für die sorgfältige Ausführung einiger flammenphotometrischer Messungen, die für den Vergleich der Resultate verwendet wurden.     

Potentiometric and volumetric determination of 6-mercaptopurine

Three methods for the determination of 6-mercaptopurine in the pure state and in tablets are described. One method is based on the reaction of this compound with silver ions, whereby an equivalent amount of nitric acid is liberated, the latter being determined potentiometrically with sodium hydroxide. The other two methods involve titration with chloramine-T, with potentiometric and visual end-point-detection. All methods afford accurate and reproducible results and can be used for routine assay of 6-mercaptopurine in tablets.     

Hypergraph polytopes

We investigate a family of polytopes introduced by E.M. Feichtner, A. Postnikov and B. Sturmfels, which were named nestohedra. The vertices of these polytopes may intuitively be understood as constructions of hypergraphs. Limit cases in this family of polytopes are, on the one end, simplices, and, on the other end, permutohedra. In between, as notable members one finds associahedra and cyclohedra. The polytopes in this family are investigated here both as abstract polytopes and as realized in Euclidean spaces of all finite dimensions. The later realizations are inspired by J.D. Stasheff ?s and S. Shnider?s realizations of associahedra. In these realizations, passing from simplices to permutohedra, via associahedra, cyclohedra and other interesting polytopes, involves truncating vertices, edges and other faces. The results presented here reformulate, systematize and extend previously obtained results, and in particular those concerning polytopes based on constructions of graphs, which were introduced by M. Carr and S.L. Devadoss.     

Self-adjunctions and matrices

It is shown that the multiplicative monoids of Temperley-Lieb algebras are isomorphic to monoids of endomorphisms in categories where an endofunctor is adjoint to itself. Such a self-adjunction is found in a category whose arrows are matrices, and the functor adjoint to itself is based on the Kronecker product of matrices. This self-adjunction underlies the orthogonal group case of Brauer's representation of the Brauer centralizer algebras.     

Education and training of Analytical chemists in Yugoslavia

Summary There are twenty chemistry departments at Yugoslavian universities and polytechnics with as many chairs of Analytical Chemistry. The individual courses show considerable differences with regard to their extent and content. The share of Analytical Chemistry is not uniform and taken as a whole not adequate. However, improvements are under way. Details of the main courses and teaching plans are given.Presented at Euroanalysis III conference. Dublin, August 20–25, 1978     

Factoriality condition of some nodal threefolds in {\mathbb{P}^4}

We prove that for n = 8, 9, 10, 11, a nodal hypersurface of degree n in is factorial if it has at most (n − 1)² − 1 nodes. The author is grateful to Ivan Cheltsov for valuable comments and suggestions.     

The degree of maps of free G-manifolds

Suppose that M and N are orientable, closed, connected manifolds with free actions of compact Lie groups G and H of the same dimension, and suppose that u : G → H is a homomorphism. We study the degree of maps f : M → N that are “equivariant up to u”. For abelian actions and for a power map such maps satisfy the condition f(λx) = λ ^r x. To Albrecht Dold and Edward Fadell