The acid-base properties of solochrome violet R. S.

Summary The acid base properties of solochrome violet R.S. has been studied with the object of testing its use as an acid base indicator or as a colorimetric reagent. The pk values of 4.35, 7.4, and 9.45 corresponding to the three steps of ionisation of the free acid were evaluated by the aid of the relation between log (acid)/(salt) and ph values obtained during the course of the potentiometric titration of the free acid with a free base. The dye has proved to be a suitable indicator in titrating some mineral and organic acids as well as a colorimetric reagent for the microdetermination of vanadium.     

Polarography as a tool in organic analysis

Summary Rapid indirect polarographic and visual micromethods have been developed for the determination of the quinone and azoxy groups by reduction with titanium(III) at pH values of 3 and 5.5, respectively. The excess of reductant is first determined polarographically followed by visual back-titration of the same solution with iron(III) using thiocyanate as indicator a drop of neutral red is added in case of the quinone function. Although the results obtained by the two finishes are of approximately the same order of accuracy (±0.46%), yet the polarographic finish proved to be of more general applicability particularly for quinones that give rise, after reduction, to a variety of colours on adding the iron(III) solution.

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Anwendung der Polarographie in der organischen AnalyseIV. Bestimmung von Chinon- und Azoxygruppen durch Reduktion mit Titan(III)

Zusammenfassung Zur schnellen Bestimmung von Chinon- und Azoxygruppen durch Reduktion mit Titan(III) bei pH 3 bzw. 5,5 werden indirekte polarographische und visuelle Mikromethoden beschrieben. Der Überschuß an Reduktionsmittel wird zunächst polarographisch und anschließend volumetrisch durch Rücktitration mit Eisen(III)-lösung bestimmt, wobei Thiocyanat (bei der Chinongruppe noch zusätzlich Neutralrot) als Indicator dient. Beide Ergebnisse weisen etwa dieselbe Genauigkeit auf (±0,46%); doch ist die polarographische Methode allgemeiner anwendbar, besonders bei Chinonen, die nach der Reduktion auf Zusatz Eisen(III) verschiedenartige Färbungen hervorrufen.

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Part III: Mikrochim. Acta 1969, 44.     

Solochrome Violett R. S. as a new colorimetric reagent

Summary The reaction between molybdenum and the sulphonic acid azo dye Solochrome Violet R.S. has proved to be a suitable one for the microdetermination of Mo amounts covering the range of 0.3 to 10 ppm in purely aqueous solutions. The variation of extinction with concentration conforms satisfactorily with Beer's law throughout the whole range. Very many cations and anions do not interfere with such a determination. Ferric iron up to 2 mg per 25 ml is completely masked with ascorbic acid.Part II: Khalifa, H., and S. W. Bishara: Z. analyt. Chem. 178, 345 (1960).     

Tulearins A, B, and C; structures and absolute configurations

The relative configuration of tulearin A (1) is determined by X-ray diffraction analysis of a cyclic carbonate derivative 2 and the absolute configuration (2R,3R,5S,8S,9S,15R,17S) from the 9-MTPA-esters 1R and 1S is determined using the modified Mosher’s method. A mechanism for the unexpected formation of carbonate 2 is suggested. Two N-phenyltriazolinedione derivatives 3 and 4 are also prepared. Two additional tulearins, B and C (5 and 6) are isolated in very small amounts and their structures are elucidated by spectroscopic means.     

Application of oxine in the polarographic analysis of organometallic compounds

Summary A procedure for the microdetermination of Cd, Mg, Zn, Mn, and Co in organometallic compounds is presented. After closed-flask combustion, the metal-oxine complex is precipitated from an ammonia-ammonium chloride buffered medium of pH 10. At this pH value oxine gives a well-defined polarographic wave. The wave height of an excessive volume of oxine is measured before and after it has been used to precipitate a known weight of the organometallic compound. The method is simple and rapid; one determination consumes 25 minutes. The average % error amounts to ± 0.53.

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Zusammenfassung Ein Verfahren zur Mikrobestimmung von Cd, Mg, Zn, Mn und Co in metallorganischen Verbindungen wurde angegeben. Nach Verbrennung im verschlossenen Kolben wird das Metall als Oxinat aus einer mit Ammoniak-Ammoniumchlorid auf pH 10 gepufferten Lösung gefällt. Bei diesem pH gibt Oxin eine gut ausgeprägte polarographische Stufe. Deren Höhe für einen Oxinüberschuß vor und nach der Fällung einer bekannten Menge metall-organischer Probe wird gemessen. Die Methode ist einfach und rasch. Eine Bestimmung dauert 25 min. Der durchschnittliche Fehler beträgt ± 0,53%.

     

Polarographic microdetermination of iron, manganese, lead, copper, bismuth, and tin in organic compounds : Application to analysis of pharmaceuticals

A micromethod for the polarographic estimation of Fe, Mn, Pb, Cu, Bi, and Sn in organometallic compounds is presented. The organic sample is decomposed using closed-flask combustion except for organotin compounds which require open-flask digestion. Pyrexglass spiral is used for mineralizing organically bound Fe, Pb, and Bi. Mixing with a flux prior to combustion is necessary for compounds containing Fe, Mn, or Bi. After combustion, a suitable supporting electrolyte is added and the cathodic reduction wave of the corresponding metal recorded. The same procedure is applied for the analysis of pharmaceuticals. The method is simple and rapid; one determination consumes less than 45 min for any of the metals reported. Results obtained are satisfactory and the average percent errors for 49 determinations are ± 0.38, ± 0.85, ± 0.42, ± 0.62, ± 0.46, and ± 0.30 for Fe, Mn, Pb, Cu, Bi, and Sn, respectively.     

Diurnal and Eleven- Year Variations of Neutron Component of Cosmic Rays

Cosmic ray ground observations are used together with the method of coupling coefficients to determine, by spectrographic method, the features of the variational primary energy spectrum of diurnal and eleven-year variations of neutron component of cosmic rays. It is found that the variational energy spectrum responsible for both types of variations can be best described by a constant spectrum up to an upper effective rigidity boundary. The upper cut-off effective rigidity boundary for the variational energy spectrum of diurnal variation was found to change from 105 GV at maximum solar activity to 15.85 GV at minimum solar activity. For Eleven-year variation, R_max was found to have a value of about 20 GV which changes slighly with solar activity due to the change of the coupling coefficients with solar activity.