Erratum

Ohne Zusammenfassung     

Enantioseparations of non-benzenoid and oligo-Tröger’s bases by HPLC on Whelk O1 column

The separation of enantiomers of several ‘bis- and tris-Tröger’s bases’ by HPLC on commercially available chiral stationary phase Whelk O1 is described for the first time. The observed structure–enantioselectivity relationships are in agreement with the previously established molecular recognition model. For all ‘bis- and tris-Tröger’s bases’ studied, satisfactory to excellent enantioselectivities were observed.     

Simple computer solution of coupled power equations

A numerical method for solution of the coupled power equations in multimode optical fibres is presented. The method is based on the assumption that the contribution of weak mode coupling can be concentrated into discrete points along the fibre. The matrix form of the solution is derived, the accuracy of the method is briefly discussed and an example of practical results is also shown.     

Iron(III) oxide formed by decomposition of sodium jarosite as a raw material for ceramic pigments of spinel type

Iron(III) oxide prepared by the prefiring of jarosite compounds is used for the synthesis of spinel pigments, e.g. ZnFe_1–xCr_1+xO₄. The reactivity of this iron(III) oxide towards zinc oxide decreases as the temperature and duration of the precalcination are increased. The conditions of jarosite compound decomposition significantly influence the colour of the ceramic pigment of Zn-Fe-Cr type too. As concerns the processing of jarosites for the production of H₂SO₄ and Fe₂O₃, the optimal conditions of their thermal decomposition are determined.

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Zusammenfassung Mittels Vorbrennen von Jarositverbindungen erhaltenes Eisen(III)-oxid wird zur Herstellung von Spinellpigmenten, z.B. von ZnFe_1-xCn+_xO₄ verwendet. Die Reaktivität dieses Eisen (III)-oxides in der Reaktion mit Zinkoxid nimmt mit steigender Temperatur und Länge der Präkalzinierung ab. Die Bedingungen, unter denen die Zersetzung der Jarositverbindung stattfindet, bestimmen auch eindeutig den Farbton des Keramikpigmentes vom Typ Zn-Fe-Cr. Was die Verwendung dieser Jarosite für die Produktion von H₂SO₄ und Fe₂O₃ betrifft, wurden die optimalen Bedingungen für die Zersetzung ermittelt.