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排序方式: 共有1182条查询结果,搜索用时 15 毫秒
131.
I. S. El-Yamani E. N. Abd El-Messieh 《Journal of Radioanalytical and Nuclear Chemistry》1989,129(2):435-442
The distribution of beryllium between aqueous sulfuric acid/potassium iodide solutions and organic phases of tributyl phosphate is described. The dependence of extraction on the pH of the aqueous phase, metal and extractant concentration, diluent type and organic additive, has been investigated. Extraction mechanism is discussed on the basis of results obtained. A method for the separation and determination of beryllium, in a mixture of beryllium and aluminium (with other contaminants) is outlined. 相似文献
132.
A series of fused and spiro pyrazolones, isoxazolines, pyrimidines, β‐lactams, and thiazolidinones incorporating 4‐amino‐2‐methyl‐5,10‐dioxo‐1,5,10,11‐tetrahydrobenz[g]quinoline 3‐carbonitrile 1 and 4‐amino‐2‐methyl‐5,6,11‐trioxo‐1,4,4a,5,6,11,12,12a‐octahydro‐1,12‐diazanaphthacene 3‐carbonitrile 2. 7,8a‐c, 15,16a‐c, 19,20a‐d, 21,22a‐d , have been synthesised by cyclocondensation addition reaction and cycloaddition reaction of hydrazines, hydroxylamine, urea, thiourea, monochloroacetyl chloride and mercaptoacetic acid with the synthesised 15,16a‐c and 17,18a‐c . 相似文献
133.
5-[p-(R-Sulfonyl)phenylazo]-1,10-o-phenanthroline (L) and its octahedral complexes of the type [Ni(R2dtp)2(L)] (where R2dtp = diethyl-or dipropyldithiophosphate) with the core NiN2S4 have been prepared and characterized by spectral, magnetic, and thermogravimetric methods. The thermal decomposition mechanism
of the compounds was proposed and the kinetic parameters of decomposition were calculated making use of the Coats—Redfern
and Horowitz—Metzger equations. 相似文献
134.
S.H. Mohamed A.M. Abd El-Rahman L. Pichon 《Journal of Physics and Chemistry of Solids》2006,67(11):2351-2357
ZnO thin films were prepared by thermal oxidation of metallic Zn films and nitrided by an inductively coupled rf plasma. The effects of successive plasma processing cyclic times on structural and optical properties as well as electrical resistivity were examined by different characterization techniques. A small amount of nitrogen was detected at the film-substrate interface. The grain size decreased slightly as the treatment time increased. The surface roughness of examined films increased while the thickness decreased with increasing plasma treatment time. The electrical resistivity decreased about four orders of magnitude when the sample nitrided for 15 min. However, the transmittance increased as the plasma treatment time increased. The optical band gap increased from 2.76 to 3.02 eV with increasing plasma treatment time from 0 to 15 min. 相似文献
135.
136.
R. A. Brown Razak Abd. Samad Bin Yahya 《Journal of Polymer Science.Polymer Physics》1985,23(3):451-459
Measurements of thermal diffusivities of peroxide-cured and sulfur-cured rubbers, over the range 0–100°C and 0–75 phr of carbon, are described. They are based on the asymptotic time dependences of heating and cooling curves, recorded following quenching of the samples into baths at various temperatures. The diffusivities are shown to depend linearly on both temperature and carbon content, to reasonable accuracies over the ranges studied. Some theory bearing on measurement techniques is presented. 相似文献
137.
R.M. Saleh J.M. Abd El Kader A.A. El Hosary A.M. Shams El Din 《Journal of Electroanalytical Chemistry》1975,62(1):297-310
The dissolution of Cu in solutions of HNO3 of different concentrations has been studied by the thermometric method. Starting from the initial temperature, Ti, the temperature—time curves exhibit an induction period followed by a rapid rise in temperature to a maximum value, Tm, attained t min after the start of the reaction. Tm increases and t decreases with increase of the acid concentration, M. ΔT (i.e.Tm ? Ti) and the reaction number (R.N. = (Tm ? Ti)/t) vary with M according to: ΔT = k(M ? M0) and R.N. = A1Mn, where k, M0, A1 and n are constants.The effect of varying concentrations of HCl, H2SO4 and H3PO4 on the R.N. of Cu in 3.5 M HNO3 was examined. Small amounts of these acids lower the R.N. (inhibition) due to the displacement of an active species on the surface of the metal by the anion of the acid. Larger additions of the acids accelerate dissolution. The concentration at which the added acid changes from corrosion-inhibitor to accelerator varies as HCl < H2SO4 < H3PO4. This sequence is considered to parallel the strength of adsorption of the respective anions. The results of experiments with salt additions confirm this view; all salts act only as dissolution-retardants. Calculations pertaining to the effect of the various ions on the R.N. support the conclusion that the dissolution of Cu in HNO3 is autocatalytic in nature, and depends on the [H+]/[NO3?] ratio.Cu does not dissolve in air-free, cold HCl. Attack takes place, however, in the presence of KNO3. Under these conditions attack is of the pitting- rather than the general type. The temperature rises suddenly after an incubation period, which decreases in length with increase of the amount of the added salt.Proof of the involvement of HNO2 in the autocatalytic cycle of Cu dissolution in HNO3 is obtained from the results of urea additions to the solution. 相似文献
138.
A. A. Abd El Raheem M. Z. El Sabban M. M. Dokhana 《Fresenius' Journal of Analytical Chemistry》1962,188(2):96-109
Summary Solochrome Fast Navy 2R has been found to be a suitable colorimetric reagent for the determination of copper, manganese and zinc either in pure solutions or in mixtures. The range of determination varies between 0.5–4 g/25 ml. Study of the effect of time, temperature, pH on the determination was carried out. The molecular ratio of the dyemetal complex was investigated using the slope ratio method.Tables for the various determination are given and show that the experimental errors are of satisfactory order. Good results were obtained by the use of EDTA, cyanide or thioglycollic acid to mask the various interfering cations.
Zusammenfassung Solochrome Fast Navy 2R wird zur colorimetrischen Bestimmung von Kupfer, Mangan und Zink in reinen Lösungen oder in Mischungen empfohlen. Die erfaßbaren Mengen liegen im Bereich zwischen 0,5 und 4 g/25 ml. Die Genauigkeit der Ergebnisse ist befriedigend. Der Einfluß der Zeit, der Temperatur und des pH-Wertes sowie das Molverhältnis im Metall-Farbstoff-Komplex wurden untersucht. Verschiedene störende Kationen konnten erfolgreich mit ÄDTA, Cyanid oder Thioglykolsäure maskiert werden.相似文献
139.
Summary The reactions of Omega Chrome Black Blue G with a large number of cations is studied. This study has shown in many cases high sensitivity limits of detection of metals. It also showed that this dye can be used as an indicator for EDTA titrations of zinc, cadmium, manganese and lead. It is also a suitable indicator for the step wise titration of calcium and magnesium in blood serum and water. 相似文献
140.
Abd el Sadek el Meligy Mahmoud Ahmed el Sherbini 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1959,10(5):474-477
Zusammenfassung Die Absorptionsbanden der Alkalihalogenidkristalle werden auf Elektronen zurückgeführt, die an leeren Gitterstellen eingefangen sind. Als Feld wird ein bei kleinen Distanzen horizontal abgeschnittenes Coulomb-Feld angesetzt. Die Eigenwerte werden im ganzen Energiebereich aus einer genauen Reihenentwicklung der Lösungen der Schrödinger-Gleichung bestimmt. 相似文献