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991.
Summary A method is described for the C/H determination with a completely titrimetric finish. Both carbon and hydrogen are converted to an equivalent amount of carbon dioxide, which is titrated in a non-aquous medium. The procedure can be applied for the analysis of substances separated by a gas Chromatograph. The determination takes about six minutes.
Zusammenfassung Ein Verfahren zur C-H-Bestimmung wird beschrieben, bei dem die Endbestimmung volumetrisch erfolgt. Hierbei werden sowohl Kohlenstoff als auch Wasserstoff in äquivalente Mengen Kohlendioxid übergeführt und dieses durch Titration in nichtwäßrigem Medium erfaßt. Die Methode kann auch für die Analyse gaschromatographisch getrennter Substanzen benutzt werden. Eine Bestimmung ist innerhalb von 6 min beendet.相似文献
992.
The total syntheses of the ladybug alkaloids (±)-propyleine and (±)-isopropyleine are described. Evidence that the alkaloid propyleine is actually a rapidly interconverting mixture of propyleine and a previously unknown isomer isopropyleine is presented. 相似文献
993.
The influence of potassium addition on the morphological properties of Fe/MgO and Ni/MgO has been investigated: KNO3 addition to precursors results in a decrease of the reducibility and in a smaller dispersity of the metallic phase. A loss of potassium is observed at reduction temperatures in excess of 773 K. Silica-supported Ni behaves differently: silica inhibits the potassium volatilization and nickel reducibility is enhanced. This illustrates how promoter effects can be influenced by the nature of support.
Fe/MgO Ni/MgO: KNO3 . , 773 K. , : . .相似文献
994.
Fluorescence of the Xe2 continuum between 1460 and 1800 Å has been observed during excitation of Xe2 molecules with CO fourth positive bands from a microwave discharge lamp. Fluorescence spectra at different Xe and added gas pressures show that in collisions with Xe or Kr atoms, the excited Xe2 diatoms are efficiently relaxed to low vibrational levels of the 1Σu+ and 3Σu+ potentials without being quenched noticeably. With Kr the rate constant for relaxation out of the primarily excited high vibrational levels is found to be about 3×10?11 cm3 molecule?1 s?1. 相似文献
995.
A simple but rapid and accurate method for the estimation of allyl in aqueous solution has been developed, based on its oxidation with chloramine-T at room temperature, in 0.5-1.0M hydrochloric acid medium. The reaction involves a two-electron change. The effect of such variables such as pH of the medium, presence of foreign ions and perchloric or sulphuric acid on the rate of oxidation is discussed. 相似文献
996.
Treating lophine with potassium at ?50° in an inert solvent yields the radical dianion 6 of this compound. The solution being warmed to room temperature, the radical rearranges to a red diamagnetic intermediate 7. In presence of potassium then the radical dianion 3 of 2-phenyl-4,5,(9′,10′)-phenanthrimidazole is formed which has been described earlier.ESR-spectroscopical investigations show, that the spin density in the 2-phenyl ring of radical 6 vanishes. According to spin density calculations 2-phenyl residue and heterocycle are strongly distorted. 相似文献
997.
H. Kalász 《Chromatographia》1984,18(11):628-632
Summary The effect of the vapor phase and other special influences on thin-layer chromatography have been investigated. Comparisons were made of the relationships of time vs. developing distance and flow rate vs. efficiency using a planar arrangement of the thin-layer. Covering the layer facilitates the reproducibility and of the migration front but the most effective optimization step for thin-layer chromatography is provided by forced-flow of the mobile phase. It is suggested that planar chromatography with a covered sorbent layer and using a pressurised solvent stream should be calledforced-flow thin-layer chromtatography. 相似文献
998.
Nanogram amounts of mercury(II) and methylmercury in artificial sea-water containing mineral acids as preserving reagents were shown to be collected quantitatively with activated carbon. Mercury concentrated on activated carbon was determined directly by combustion, trapping on gold and electrothermal atomic-absorption spectrophotometry. The activated carbon was purified by heating at 350 degrees for 2 hr. Sulphuric acid and hydrochloric acid were purified by treatment with activated carbon. Interference from iodide was eliminated by using a carbonate buffer wash before the atomic-absorption measurement. Less than 4 ng of mercury in 200-300 ml of artificial sea-water, whether acidified or not (with sulphuric, hydrochloric or nitric acid), was satisfactorily collected with 100 mg of activated carbon. Mercury was also collected quantitatively after oxidative treatment of artificial sea-water. 相似文献
999.
1000.
C. F. Parrish G. L. Kochanny H. W. Rinn 《Journal of polymer science. Part A, Polymer chemistry》1969,7(9):2531-2535
The phase diagram of the acrylic acid–acrylamide system as determined by DTA and the supporting x-ray diffraction data are presented. This diagram shows that the system forms a 1 : 1 addition compound which decomposes above 0°C. There is also one eutectic point at a 67 mole-% acrylic acid composition. 相似文献