Polarographie des periodates applications analytiques

The polarography of periodates is described and that of hypoiodites is outlined. The first is applied to the determination of traces of iodates in periodates and conversely; in addition, it allows the micro determination of potassium by the method of willard and BOYLE to be adapted to the polarograph, giving a rapid and sensitive method. Possible applications of the second to the determination of hypoiodites in solution and to similar unstable systems in general are given.     

Dosages Polarographiques du Cobalt et du fer a l'aide de nouvelles solutions de,base au trilon

After stressing the necessity of finding new base solutions for use in polarography, the authors show that Trilon B strongly displaces the reduction potentials of numerous elements.Owing to its ready transformation to the trivalent state cobalt can be determined without preliminary separation, in presence of an excess of most other metals, because it is then reduced at a very much lower negative potential (the step is at about 0.2 v) than in the usual divalent form (for which E$\text{1}\text{2}$, is always greater than I v). The method is applied to the analysis of steels.After complexing by Trilon B small amounts of iron can similarly be determined in the presence of an excess of other metals. The method is applied to the determination of small amounts of iron in brasses and “pure” metals.     

Sur quelques étalons de pH faciles à préparer

Résumé L'étalonnage des électrodes de verre, dans la pratique courante, est grandement facilité par l'emploi de solutions tampons étalons préparées rapidement en dissolvant, à saturation, des sels purs. Au bitartrate préconisé parLingane, nous ajoutons le carbonate de lithium, et le borax (dont le coefficient de température est inférieur à celui du borax non saturé), utilisables en milieu alcalin.

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Summary The standardization of glass electrodes in routine practice is greatly facilitated by the use of buffer solutions which are rapidly prepared by dissolving pure salts to the saturation point. To bitartrate, recommended byLingane, we add lithium carbonate, and borax (whose temperature coefficient is less than that of unsaturated borax). These can be employed in alkaline surroundings.

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Zusammenfassung Die Eichung von Glaselektroden für die laufende Praxis wird wesentlich vereinfacht durch die Verwendung von Standard-Puffer-Lösungen, die durch Sättigung mit reinen Salzen rasch herstellbar sind. Dem vonLingane vorgeschlagenen Bitartrat setzen wir Lithiumcarbonat und Borax zu (dessen Temperaturkoeffizient geringer ist als in nicht gesättigten Boraxlösungen). Diese Pufferlösung eignet sich für das alkalische Gebiet.

     

Ueber die Zusammensetzung des hydratischen Schwefelzinks

Ohne Zusammenfassung     

Zur Bestimmung des Chroms als Chromoxyd

Ohne Zusammenfassung     

A Layered Tin Bismuth Selenide with Three Different Building Blocks that Account for an Extremely Large Lattice Parameter of 283 Å

The layered compound Sn_2.8(4)Bi_20.2(4)Se₂₇ exhibits an extraordinarily long-periodic 150R stacking sequence. The crystal structure contains three different building blocks, which form upon the addition of Sn to a Bi-rich bismuth selenide. Sn-doped Bi₂ double (“2”) layers similar to those in elemental bismuth, Sn_0.3Bi_1.7Se₃ quintuple (“5”) layers and Sn_0.4Bi_2.6Se₄ septuple (“7”) layers are arranged in a 7525757525|7525757525|7525757525 sequence, which corresponds to a structure with a=4.1819(4) and c=282.64(6) Å in space group R m. The structure of a microcrystal was determined using microfocused synchrotron radiation and refined as a formally commensurately modulated structure in (3+1)D superspace (superspace group R m(00γ)00), with a trivial basic structure that contains just one atom. The stacking sequence as well as the cation distribution are confirmed by aberration-corrected scanning transmission electron microscopy (STEM) in combination with chemical mapping by X-ray spectroscopy with atomic resolution. Stacking faults are not typical but have been observed occasionally.     

The physical significance of the mixed dynamic form factor

We show that the mixed dynamic form factor for inelastic scattering of fast electrons in crystals is closely related to the density matrix of the probe electron and to that of the scatterer. With this insight it is possible to calculate both energy filtered diffraction patterns and energy spectroscopic high-resolution images. As an example we discuss the Si-K and -L edges.     

Bestimmung des Bleies als Schwefelblei

Ohne Zusammenfassung