DECAY KINETICS OF N, N, N', N-TETRAMETHYLBENZIDINE PHOTOCATIONS IN FROZEN MICELLAR SOLUTION OF CETYLTRIMETHYLAMMONIUM BROMIDE

Abstract—
After UV irradiation of rapidly frozen solutions of N, N, N', N' -tetramethylbenzidine (TMB) in dilute aqueous micellar cetyltrimethylammonium bromide at 80 K, the ESR signal corresponding to the TMB⁺ cation was detected indicating photoionization. This signal was monitored as a function of time at various temperatures between 80 K and 260 K. On a timescale of a few days the signal decayed to a plateau value that was stable for months. Two distinct second-order processes for the decay from the initial to the plateau value were observed: one prevailing at low temperatures with an activation energy of 0.6 kJ/mol, and one prevailing at T > 220 K with an activation energy of 13 kJ/mol. By means of spin probe investigations the latter process was shown to be connected with a local softening of the region adjacent to the micellar surface.     

The conductivity of single crystals of 9-methyladenine

The conductivity of single crystals of 9-methyladenine(6-amino-9-methyl-purine) has been determined using proton-injecting solution electrodes. The conductivities parallel and perpendicular to the (100) plane are 2.5 ± 1.9 × 10^?13/ohm-cm and 7.0 ± 2.9 × 10^?15/ohm-cm, respectively, at 295°K. The H-bonded pathways lie in the (100) planes. The conductivity is ohmic over the range of applied fields. The temperature dependence of the conductivity was determined parallel and perpendicular to the (100) planes.     

Anwendung der ascorbinometrischen Bestimmung von Hexacyanoferrat(III) zu automatischen Mikrotitrationen

Zusammenfassung Nach theoretischen Erörterungen über die Redoxpotentiale des Ascorbinsäure-Dehydroascorbinsäure-Systems und Besprechung der möglichen Reduktionsreaktionen werden Vorschriften gegeben zur ascorbinometrischen Bestimmung von Hexacyanoferrat(III), Hexacyanoferrat(II), Dichromat, Permanganat, Jodat, Bromat und Chloramin T im Mikromaßstab mit Hilfe eines automatischen Mikrotitrators.

---

Application of ascorbinometric determination of hexacyanoferrte(iii) to automatic micro-titrations

The reaction between hexacyanoferrate(III) and ascorbic acid has been applied to the ascorbinometric micro-titration of hexacyanoferrate(III), hexacyanoferrate(II), dichromate, permanganate, bromate and iodate ions as well as chloramine T. Titrations are carried out with an automatic titrimeter which records the potentiometric titration curve. Despite the small amounts of ions involved accuracy and precision of these methods are satisfactory.

     

Preparative and analytical separation of amygdalin and related compounds in injectables and tablets by reversed-phase HPLC and the effect of temperature on the separation

Previous HPLC procedures for amygdalin and related compounds in injectables and tablets were either time consuming or produced inadequate separations of D-amygdalin and its epimer. A study of the effects of temperature on the separation resulted in development of an HPLC method for amygdalin and some related compounds, using water as the mobile phase at 15 degrees C. Multimilligram quantities of amygdalin and related compounds were separated by this preparative procedure. The aqueous mobile phase allows the compounds to be recovered by simple lyophilization of the sample after elution. This permitted the carbon-13 NMR spectrum of the isolated aglyconic epimer of amygdalin to be reported for the first time. D-amygdalin, its L-mandelonitrile epimer (D-epiamygdalin), their hydrolysis products (the epimeric amides and epimeric acids), and the sugar gentiobiose were separated by the method.     

The Uncertainty of Weighing Data Obtained with Electronic Analytical Balances

Weighing is a common task in any chemical laboratory and weighing data are associated with some uncertainty, as this is common with all other working procedures and their data. This paper presents the influence factors which are part of the combined measurement uncertainty of a mass determination and their interplay, namely the technical specifications of the balance (repeatability, nonlinearity, sensitivity tolerance, and temperature coefficient of the sensitivity) and the effect of air buoyancy. Depending on the net and gross weight, the densities involved (density of air and of the weighing object in relation to the density of the reference weights) and the uncertainties of these densities the relative uncertainty of weighing data is often in the 10^–5 to 10^–4 range (10 to 100ppm). It must be kept in mind that such low values can only be obtained with simple weighing goods, i.e. in the absence of disturbances such as electrostatic charges, air drafts, evaporation, or water adsorption phenomena.     

Über einige aus dem Diacetonalkohol gewinnbare Aminolaktone

Ohne ZusammenfassungDie Untersuchung soll nach verschiedener Richtung fortgesetzt werden.     

Bemerkungen zur note des herrn philip E. B. jourdain über das prinzip der kleinsten Aktion

Ohne ZusammenfassungMath. Ann. Bd. 62, pag. 413–418