Über die Einwirkung von Ammoniak auf Anthragallol

Ohne ZusammenfassungDiese Untersuchung ist vor mehr als Jahresfrist infolge Eintrittes in die chemische Praxis abgebrochen worden. Äussere Verhältnisse machen die Vollendung der begonnenen Versuche auch weiterhin unmöglich und sehe ich mich desshalb veranlasst, meine Beobachtungen zu veröffentlichen.     

Application of a digital signal processor to Fourier-transform infrared spectroscopy

Summary The application of a digital signal processor (DSP) to Fourier-transform infrared spectroscopy is described, which allows for near real-time display of the transformed interferograms as spectra.     

Simultane Ionen-Chromatographie von Kationen und Anionen mit Komplexonen als Elutionsmittel und selektiver UV-Detektion

Summary The complexones EDTA, DCTA and EGTA were investigated as eluting agents at various pH-values for the simultaneous separation of 9 cations and 6 anions using ion chromatography on a silica gel based anion exchanger (Nucleosil 10-Anion II). 1,2-Diaminocyclohexanetetraacetic acid (DCTA) proved to be the best eluting agent. UV spectrophotometry was used for both direct and indirect detection of the anions and anionic metal complexes and a detailed study was carried out with respect to selectivity of detection. This was facilitated by referring to the UV absorption spectra of the anions and metal complexes involved. By choice of a suitable wavelength between 203 and 270 nm and taking into account pH effects, a number of selective determinations were possible. Examples include Pb and Cu in the presence of excess of Ca and Mg as well as nitrate, nitrite and bromide in a large excess of chloride and sulphate. Some examples of detection limits are (g/l) nitrate 2, Fe(III) 3, Cu 9 and Pb 12 (sample volume 20 l, direct UV-detection). The Chromatographie behaviour of Fe(II) and Fe(III) was studied and discussed. Drinking water was analysed for chloride, nitrate and sulphate as well as Ca and Mg using DCTA in the eluent. Complete analyses can be carried out in less than 15 min.

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Herrn Prof. Dr. R. Neeb zum 60. Geburtstag gewidmet     

Beiträge zur Chemie der Pyrrolpigmente, 19. Mitt.: Die elektrochemische Oxidation von Pyrromethenonen und Pyrromethenen (Gallenpigment-Partialstrukturen)

The electrochemical oxidation of arylmethylene-pyrrolinones, pyrromethenones and pyrromethenes as representative bile pigment partial structure models was investigated by means of a rotating disc platinum electrode using acetonitrile as the solvent. Two different oxidation reactions were found. The first reaction being a reversible one-electron oxidation with compounds of the arylmethylene-pyrrolinone series and pyrromethenones which are unsubstituted in position 5 of the pyrrole ring. A two step reaction (the first one reversible, the second irreversible) on the other hand was found to be typical for pyrromethenones bearing a methyl group in this position.Through protonation the first step is at a higher potential, whereas the second one is lowered and becomes reversible. The resulting oxidation pattern can be interpreted analogous to the oxidation of hydroquinones in aprotic solvents.The geometrical isomers of a pyrromethenone were oxidized at appr. the same potential, but there is a strong dependence of the potential of the first oxidation step on the substitution: a higher degree of alkylation favours oxidation by lowering the oxidation potential.

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Mit 1 Abbildung     

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Book reviews

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Notices bibliographiques

     

Applications of capillary electrophoresis in element speciation analysis of plant and food extracts

The performance of a new separation technique for metal-speciation — capillary electrophoresis (CE) — is presented. Polyhydroxy compounds such as polyphenols and organic tanning agents can be determined in the g/L range. Certain complexes of these compounds with iron (III) ions may also be directly or indirectly verified. The work has shown that it is possible to determine certain complexes existing in beverages (tea and coffee) by decomplexation with chelating agents (CDTA). The ligands released can be separated by CE and identified by their migration time and UV/VIS absorption spectra.     

Local Borel summability of Euclidean 311-1311-1311-1a simple proof via differential flow equations

It is shown how the differential flow equation (or, equivalently, the continous renormalization group) method can be employed to give an astonishingly easy proof of the local Borel summability of the renormalized perturbative Euclidean massive ₄ ⁴ .Supported by NSF grant # DMS-9100383     

Two-photon spectroscopy of the low-lying singlet states of naphthalene and acenaphthene

Two-photon excitation spectra of naphthalene and acenaphthene have been measured up to 50000 cm^?1. In naphthalene. three two-photon allowed states are observed for which the symmetry assignment is confirmed by polarization. The corre- sponding transitions are also seen in acenaphthene. The experimental data are in excellent agreement with theoretical predictions.