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  • Author or Editor: G. Walter x
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It is suggested to carry out thermogravimetric measurements at pressures between 1 and 100 torr. In this pressure range thermal gas flow will cause only small disturbances, and the gas evolution will be much less inhibited by the surrounding gas than at higher pressures. In a thermal analysis of calcium oxalate, carried out with an apparatus containing a pressure controller, the weighing disturbances were reduced to a few micrograms.

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Abstract  

Alkali metal alkoxides can be formed by the direct reaction of alkali metals with the corresponding alcohol. Under certain conditions, however, these reactions become dangerous. One of the reasons for the instability build-up in the reaction mixture is related to the electrochemical behaviour of the heterogeneous medium. Another reason is the instability introduced by the simultaneous presence of oxygen and alkali metal atoms in the reagents. Accelerating rate calorimetry is an excellent way to determine safe working conditions for the handling of such compounds. The hazards that are encountered are discussed by means of some examples.

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Abstract  

A facility for neutron-capture γ-ray spectroscopy for analytical purposes has been developed and tested at the National Bureau of Standards reactor. The system consists of an internal beam tube with collimators, an external beam tube and irradiation station, a Compton-suppressed Ge(Li) γ-ray detection system, and a minicomputer-based data-collection and-analysis system. Detection limits have been established for many elements and errors arising from neutron self shielding, γ-ray peak overlap, neutron beam variations, and sample matrix evaluated.

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In this paper we present results from recent studies focusing on elucidation of the mechanism of visualization of simple sugars (e.g. d -(+)-glucose, d -(+)-galactose, and d -(−)-fructose) developed on glass TLC plates precoated with 3-aminopropyl chemically bonded stationary phase and then heated at elevated temperatures, a method originally developed, then recommended commercially, by Merck.Detection of the sugars under UV illumination is possible because of their substantial fluorescence; this suggests that during heating the analytes probably undergo a process which results in their structural transformation. We postulated a possible analogy with the Maillard reaction, omnipresent in innumerable living organisms.To verify our assumption we performed analysis with high-performance thin-layer chromatography (HPTLC), high-performance liquid chromatography (HPLC), and IR, UV, and fluorescence spectroscopy. All the results obtained seem to confirm the analogy between the Maillard reaction and the reaction of simple carbohydrates after development on the amino stationary phase.

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