Caesium salts of titanium,zirconium and thorium cyanoferrates(II)

The synthesis of cyanoferrates of quadrivalent metals and the sorption of caesium ions by these materials have been studied. It has been found that the compositions of the compounds and their properties are strongly influenced by the degree of hydrolysis of the metal. These is no sorption of caesium by Zr⁴⁺ and Th⁴⁺ cyanoferrates, while the compounds of oxygencontaining bivalent complex cations exhibit behaviour similar to that of the other bivalent metals. The sorption of caesium by (TiO)₂R is govermed by an ion-exchange mechanism; with (ZrO)₂R changes occur in the crystal lattice, and (ThO)₂R exhibits a low affinity towards caesium.     

Die Anwendung von Silikagel in der anorganischen Analyse. Trennung und Bestimmung kleiner Zirkonium-Mengen

Zusammenfassung Die Bedingungen der quantitativen Sorption von Zirkonium an einer Silikagelsäule wurden untersucht. Die Vollständigkeit der Sorption wurde in Abhängigkeit vom ph, der Durchflußgeschwindigkeit und dem Volumen der Waschflüssigkeit untersucht. In 1- bis 1,2-n HCl oder HNO₃ ist die Sorption sehr selektiv, Zirkonium kann von einer Reihe von Begleitelementen getrennt werden. Der Einfluß einiger Anionen auf die Vollständigkeit der Zirkoniumelution aus der Säule wurde untersucht. Nach einer statischen Methode wurde die Kapazität des verwendeten Silikagels bestimmt. Die erzielten Ergebnisse wurden zur Bestimmung kleiner Zirkoniummengen in mineralischen Rohstoffen verwendet.

---

Summary The conditions for quantitative Sorption of zirconium on a silica gel column were studied. The completeness of the sorption was studied in relation to ph, the rate of flow, and the volume of the wash liquid. The sorption is very selective in 1–1.2N HCl or HNO₃. Zirconium may be separated from a number of accompanying elements. The influence of several anions on the completeness of the zirconium elution from the column was investigated. The capacity of the silica gel employed was determined by a statistical method. The results obtained were employed for determining-small quantities of zirconium in mineral raw materials.

---

Résumé On a étudié les conditions de sorption quantitative du zirconium sur colonne de silicagel. On a examiné l'influence du ph, de la vitesse d'écoulement et du volume de liquide de lavage sur la sorption. Celle-ci se montre très sélective dans l'acide chlorhydrique 1 à 1,2N ou dans l'acide nitrique et le zirconium peut être séparé d'avec une série d'éléments qui l'accompagnent. On a étudié l'influence de quelques anions sur l'élution du zirconium de la colonne. On a déterminé la capacité du silicagel employé d'après une méthode statistique. On a utilisé les résultats obtenus pour doser de petites quantités de zirconium dans les matières premières minérales.

---

---

Herrn Prof. Dr. Ing.M. Jureek zum 60. Geburtstag gewidmet.     

Separation of trace amounts of titanium by the sorption of the titanium peroxocomplex on silica gel

Summary The possibility of the analytical use of the sorption of titanium peroxocomplex on silica gel for the determination of trace amounts of titanium was studied. The exchange capacity of silica gel in dependence on the time and the composition of the titanium peroxocomplex sorbed were described. A simple and very efficient separation procedure has been developed for the determination of traces of titanium in various waters and water-soluble salts.     

Affinities of insoluble hexacyanoferrates(II) for alkali metals and ammonium

The affinities of insoluble ferrocyanides of bivalent manganese, iron and cadmium for sodium potassium, rubidium, caesium and ammonium have been studied. It has been found that the affinities of the univalent cations for the ferrocyanides generally increase in the usual order Na<K<NH₄<Rb<Cs. Comparing the results with those previously obtained, the affinity towards formation of double ferrocyanides with univalent cations generally follows the order Cd ∼ Mn >Co>Fe(II)>Ni>Zn>Cu>Fe(III). The precipitation isotherms of the systems are presented and the relationship between the affinities and some other properties of the transition metal ferrocyanides is discussed.     

Optimal control existence results for general discrete systems

General existence theorems for discrete optimal control problems are derived. It is assumed that dynamical equations of the system, as well as all control and state constraints, depend on the finite history of the system. All results are formulated in a general way in regular topological spaces. To prove such theorems, some basic concepts and results of the theory of the so-called multivalued mappings are necessary which are briefly summarized. The imposed assumptions are general enough to be of practical interest. The reported results thus include and generalize all known cases which are met in the discrete optimal control theory. Practical importance of the obtained results is illustrated on the so-called multiproduct inventory problem which is treated in the detail. Using the derived results we are able to show that under usual assumptions the inventory problem has an optimal solution.     

Thermal analysis of ternary gypsum-based binders stored in different environments

Although gypsum belongs to the low-energy environmentally friendly binders, its wider applications in building constructions are limited due to the negative effect of moisture on its mechanical properties. When calcined gypsum (CaSO₄·1/2H₂O) transforms into its hydrated form (CaSO₄·2H₂O), it is partially soluble in water and it has a relatively low strength. This problem can be resolved when gypsum is used as a part of binary or ternary binders. In this paper, a system consisting of calcined gypsum, lime, and silica fume is presented as a functional solution for a wider utilization of gypsum in wet environments. For this purpose, the newly designed materials were stored in different environments (laboratory conditions in air or water) up to 182 days. The effect of silica fume on the hydration process and the growth of the main products is evaluated by using differential scanning calorimetry and thermogravimetry in the temperature range from 25 to 1000 °C with a heating rate of 5 °C min^?1 in an argon atmosphere. The carbonation level of studied materials is also evaluated. Besides this, the information about the thermal stability of studied materials is provided. These results are supported by evolved gas analysis, X-ray diffraction, and scanning electron microscopy. The basic physical and mechanical properties are determined to provide more detailed information about the behavior of the designed materials under various conditions at selected days of hydration. The addition of silica fume to the gypsum–lime system activates the pozzolanic reaction of the analyzed pastes, which is proved by the presence of the CSH phase and by the consumption of portlandite in the mixtures. Wet environment speeds up the hydration processes and prevents samples from carbonation.     

Oxidation of hydroxynaphthalenes by means of Co(III) acetate

1,4-Dihydroxynaphthalene can be quantitatively oxidized to 1,4-naphthoquinone with Co(III) acetate in glacial acetic acid. Analytical determination can be carried out both directly potentiometrically, as well as indirectly using excess of the oxidant and back titrating the unconsumed amount of the reagent with Fe(II) sulfate.     

Design,synthesis and anti-mycobacterial evaluation of some new <Emphasis Type="Italic">N</Emphasis>-phenylpyrazine-2-carboxamides

N-Phenylpyrazine-2-carboxamides (anilides of pyrazinoic acids with simple substituents in various positions) were previously shown to possess significant biological activities in vitro, markedly anti-mycobacterial and photosynthesis-inhibiting activity. Based on structure-activity relationships (SAR) extracted from previously published series, 25 new anilides of non-substituted pyrazinoic acid (POA), 5-CH₃-POA, 6-Cl-POA, 5-tert-butyl-POA and 5-tert-butyl-6-Cl-POA were designed and synthesised. The phenyl part was substituted with simple hydrophobic substituents chosen from methyl and halogens. 5-tert-Butyl-N-(5-fluoro-2-methylphenyl)pyrazine-2-carboxamide (9), N-(3-chloro-4-methylphenyl)-5-methylpyrazine-2-carboxamide (12), 6-chloro-N-(3-chloro-4-methylphenyl)pyrazine-2-carboxamide (13) and 6-chloro-N-(5-iodo-2-methylphenyl)pyrazine-2-carboxamide (18) possessed whole cell anti-mycobacterial activity in vitro against Mycobacterium tuberculosis H37Rv with minimum inhibitory concentration (MIC) of around 10 μM. Importantly, no cytotoxicity in the HepG2 model was detected in vitro at the concentrations tested and the estimated IC50 values were in hundreds of μM, indicating promising selectivity. N-(3-Chloro-4-methylphenyl)pyrazine-2-carboxamide (11) and N-(4-chloro-2-iodophenyl)pyrazine-2-carboxamide (21) exerted significant activity against Mycobacterium kansasii with MIC 12.6 μM and 8.7 μM, respectively. No activity was detected against Mycobacterium avium. SAR were in accordance with those observed for the derivatives previously published.