Die Bestimmung von Derivaten der Kohlensäure über eine saure Verseifung

Zusammenfassung Durch Hydrolyse in siedender, hochkonzentrierter Phosphorsäure läßt sich anscheinend aus allen Kohlensäurederivaten quantitativ Kohlendioxid abspalten. Dieses wird nach Reinigung und Trocknung gravimetrisch bestimmt. Folgende Verbindungen wurden analysiert: lineare und cyklische Harnstoffe, Thioharnstoffe, Urethane, Carbamate, Kohlensäureester, Phenylisocyanat, Melamin, Guanidin, Cyanursäure und Dicyandiamid. Die Anwendung verschiedener Phosphorsäurekonzentrationen erlaubt auch selektive Bestimmungen.

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The determination of derivatives of carbonic acid via an acidic hydrolysis

Summary Hydrolysis in boiling highly concentrated phosphoric acid seemingly results in the quantitative splitting off of carbon dioxide from all derivatives of carbonic acid. The latter is determined gravimetrically after purification and drying. The following compounds were analyzed: linear and cyclic ureas, thioureas, urethanes, carbamates, esters of carbonic acid, phenylisocyanate, melamine, guanidine, cyanuric acid, dicyandiamide. The use of various concentrations of phosphoric acid permits selective determinations.

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Herrn Prof. Dr.B. Timm zum 60. Geburtstag gewidmet.     

Massenspektrometrische untersuchungen zur elementaranalyse organischer verbindungen—III: Verbrennungsvorgänge im leeren rohr

A measuring system is described which permits study of all stages of combustion processes as functions of carrier gas, temperature, residence time and tube filling. The organic sample is fed at constant speed into a stream of carrier gas. The mixture reaches the combustion chamber within a few milliseconds via a transfer capillary. With the help of a viscous inlet system, a sample of the resulting reaction products is taken and fed into a mass spectrometer. Reaction time and temperature can be adjusted within wide ranges or varied continuously. A plot of the extent of reaction of the various combustion products against temperature at a chosen reaction time yields an oxidation-thermogram which gives a clear picture of the combustion process. It is evident from thermograms of selected compounds that the samples decompose in the presence of oxygen at appreciably lower temperatures than in inert gas. The primary step of the decomposition is “oxidative pyrolysis” which often leads to other products than “inert pyrolysis”. The intermediate products found are partly structurally specific and, especially with nitrogen-containing samples, are numerous and long-lived (for example, carbon monoxide, nitric oxide, cyanogen, hydrocyanic acid, cyanic acid and methyl cyanate). The notorious “difficult combustibility” is largely due to the fact that carbon monoxide, cyanic and hydrocyanic acids undergo complete combustion only at very high temperature. The combustion properties of the “empty tube” can be improved noticeably by a filling of quartz wool and markedly by partly filling with platinum wool.     

Conformationally Controlled Odor Perception in ‘Steroid-type’ Scent Molecules

A series of compounds possessing a ‘Steroid-type’ scent and related to 4-(4′-t-butylcyclohexyl)-4-methyl-2-pentanones ( 1 and 2 ) has been synthesized. The odor of these compounds has been found to be dependent on their conformation; only when the molecule can assume a steroid-like shape there is an interaction with the odor chemoreceptor.     

Atomabsorptions-Flammenphotometrie im Einstrahlverfahren mit Kompensation der von Flamme und Hintergrundstrahler verursachten Schwankungen

Zusammenfassung Es wird gezeigt, daß auch im Einstrahlverfahren sogar extrem starke Schwankungen der Betriebsparameter der Flamme (Brenngas- und Preßluftdruck, Probendurchsatz) aus dem Meßergebnis weitgehend eliminiert werden können, wenn hinreichend oft Zwischeneichungen vorgenommen werden. Auf die gleiche Weise kann man selbstverständlich auch zeitliche Änderungen der Emission des Hintergrundstrahlers ausschalten. Für die Voruntersuchungen wurde ein aus handelsüblichen Bauteilen zusammengestelltes Gerät benutzt, welches mehr als 15 Zwischeneichungen pro Minute zuläßt. Dabei zeigte sich unter anderem, daß eine Änderung des Probendurchsatzes um den Faktor 10 (innerhalb 1 min) eine Änderung des Extinktionswertes der Probe um den Faktor 4 (also 400%) zur Folge hat. Dagegen beträgt in dieser Meßreihe die größte beobachtete Abweichung einer Einzelmessung des Extinktionsverhältnisses Analysenlösung/Eichlösung vom Mittelwert nur 22%. Abschließend wird ein in der Entwicklung befindliches und weitgehend automatisiertes Gerät vorgeschlagen, welches wesentlich bessere Ergebnisse erwarten läßt.

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Summary It is shown that even for atomic-absorption analyses with a single-beam instrument, the values measured will be essentially independent on large fluctuations in the operating conditions of the flame (gas pressures and sample flow rate), if the standard measurement made after every sample measurement is repeated often enough. Naturally, with the same technique the variation of emission from the discharge lamp will also not affect the analytical results. For the first experiments an instrument composed of commercially available components was used. It allowed the sample solution and standard solution to be alternately aspirated more than 15 times per minute. It was observed that the extinction value for the sample solution changed by a factor of 4 (that is 400%) when the sample flow rate changed by a factor of 10 (within a minute). On the other hand, in this series of measurements the gratest deviation observed between a single value for the ratio of sample solution extinction/standard solution extinction and the average value amounted to only 22%. Finally, an essentially automatic instrument being developed is proposed. With this instrument considerably better results can be expected.

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Herrn Prof. Dr. R. Herrmann möchte ich auch an dieser Stelle meinen Dank aussprechen für sein reges Interesse am Fortgang der Arbeit und für die kritische Durchsicht des Manuskriptes. Fräulein B. Gutsche danke ich für die Mitarbeit bei der Durchführung und Auswertung der Messungen.     

Production of indigotin in submerged culture using morchella nov. ES-1

A new strain of the fungusMorchella nov. ES-1 (ATCC 20951) that produces blue pigment in submerged culture has been isolated. The blue pigment was extracted by chloroform or ethyl acetate treatment. The crude extract when chromatographed yielded three fractions; a blue one has been identified by mass spectrometry as indigotin. Fermentation studies using enriched media revealed that maximum accumulation of indigotin in culture was approx 24 mg/L in 168 h.     

Strikte Konvexität für Variationsprobleme auf demn-dimensionalen Torus

We consider a variational problem with an integrandF:R ⁿ ×R×R ⁿ →R that isZ-periodic in the firstn+1 variables and satisfies certain growth-conditions. By a recent result of Moser, there exist for every α∈R ⁿ minimal solutionsu:R ⁿ →R minimising ƒF(x, u(x), u _x (x)) dx with respect to compactly supported variations ofu and such that sup |u(x)-αx|<∞. Given such a minimal solutionu we define the average action (whereB _r is ther-ball around 0∈R ⁿ ) and show thatM(α) is indeed independent of the minimal solutionu satisfying sup |u(x)-αx|<∞. We prove that this average actionM(α) is strictly convex in α.      

Fractional noise

Fractional noiseN(t),t 0, is a stochastic process for every , and is defined as the fractional derivative or fractional integral of white noise. For = 1 we recover Brownian motion and for = 1/2 we findf ^–1-noise. For 1/2 1, a superposition of fractional noise is related to the fractional diffusion equation.     

Differential operators on homogeneous spaces. I

Summary In this paper, we extend recent work of one of us [Br] to investigate an old problem of the other one [B2]. Given a connected semisimple complex Lie-groupG with Lie-algebrag, we study the representation of the enveloping algebra of by global differential operators on a complete homogeneous spaceX=G/P. It turns out that the kernelI _x of _X is the annihilator of a generalizedVerma-module. On the other hand, we study the associated graded ideal grI _x , and relate it to the geometry of a generalizedSpringer-resolution, that is a map of the cotangent-bundle ofX onto a nilpotent variety in , as studied e.g. in [BM1]. We prove, for instance, that grI _x is prime if and only if _X is birational with normal image. In general, we show that is prime. Equivalently, the associated variety ofI _x in is irreducible: In fact, it is the closure of theRichardson-orbit determined byP. For the homogeneous spaceY=G/(P, P), we prove that the analogous idealI _y has for associated variety the closure of theDixmier-sheet determined byP. From this main result, we derive as a corollary, that for any module induced from a finitedimensional LieP-module the associated variety of the annihilator is irreducible, proving an old conjecture [B2], 2.5. Finally, we give some applications to the study of associated varieties of primitive ideals.