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891.
Résumé Une méthode d'analyse des impuretés dans l'or métallique par activation neutronique, a été mise au point. Après irradiation
de 15 heures dans un flux de 2·1014 n·cm−2·sec−1, l'échantillon d'or est traité en cellule blindée. La matrice est séparée des impuretés à analyser par des méthodes électrolytiques.
Les impuretés sont généralement séparées en 3 fractions qui sont mesurées par spectrométrie γ. Le traitement des informations
est effectué sur ordinateur IBM 360/91 moyennant un programme écrit au laboratoire. 29 éléments sont détectables par cette
méthode. 相似文献
892.
In an extension of studies of flameless atomizers for atomic-absorption spectrometry, an electrically heated tungsten-rhenium alloy wire loop was examined. Reduction of metallic salts to ground-state metal atoms was accomplished with the high temperature produced by the loop. Lead and nickel were investigated. Experimental parameters such as wavelength, slit width, atomization temperature and sheathing gas flow rate were optimized. Absolute detection limits of 6.6·10?10 and 1.2·10?10, and absolute sensitivities of 7·10?10 and 8·10?11 g of lead, were established for unenclosed and enclosed cells, respectively. The interferences of twenty cations and sixteen anions were studied; foreign cations generally enhanced the lead absorption by retarding its vaporization, allowing the slow detection system to respond more efficiently. Nickel was investigated as a representative less volatile metal; an absolute detection limit of 1.6·10?9 and an absolute sensitivity of 9·10?10 g of nickel were established. 相似文献
893.
Summary A new, simple, and selective test is described for the detection of nitrite ion with isoperthiocyanic acid (I) as the reagent. The test is based on the reaction of a 5% solution ofI with the nitrite ion solution, a deep orange precipitate being formed. Conversely, the test can be used in the identification ofI itself. Presumably, the coloured product is 3-hydroxy-5-thione-1, 2, 4-dithiazole, formed by the action of nitrous acid (producedin situ by the action of sulphuric acid and nitrite) on the 3-amino group ofI. The limit of detection is 300g of NO2
– in a drop (0.05 ml). Most anions (including IO3
–) do not interfere. Only I–, thiourea, and hydrogen peroxide interfere; S2O3
2– interferes only when present in large amounts.
Zusammenfassung Ein neuer, einfacher und selektiver Nachweis von Nitrit mit Isoperthio cyansäure (I) wurde beschrieben. Er beruht auf der Umsetzung einer 5% igen Lösung von I mit Nitritlösung, wobei ein tief orange gefärbter Niederschlag entsteht. Umgekehrt kann die Reaktion auch zum Nachweis von I dienen. Vermutlich handelt es sich bei dem gefarbten Produkt um 3-Hydroxy-5-thion-1, 2, 4-dithiazol, das durch Einwirkung der salpetrigen Säure auf die 3-Aminogruppe von I entsteht. Die Erfassungsgrenze betragt 300g NO2 –im Tropfen (0,05 ml). Die meisten Anionen (inklusive JO3 –) stören nicht. Nur J–, Thioharnstoff und H2O2 stören; Thiosulfat stört nur in großen Mengen.相似文献
894.
Kordes and Nolte are of the opinion that, on melting, Na2W2O7 dissociates according to the reaction whereas Gelsing et al. assume a dissociation into Na+ ions and a mixture of chains of WO4 tetrahedra (WO, W2O, W3O, etc.). In the present paper it is demonstrated that a dissociation according to the ideas of Gelsing et al. can excellently explain the cryometric results found by Kordes and Nolte themselves. The dissociation scheme proposed by Gelsing et al., is even more likely than that proposed by Kordes and Nolte when the results of surface tension measurements reported by Gossink and Stevels are taken into account. 相似文献
895.
A. V. Kazymov L. P. Shchelkina N. G. Kabirova A. F. Vompe 《Chemistry of Heterocyclic Compounds》1971,7(11):1452-1455
Several new polymethine dyes of the cyanine and merocyanine series with 1-methyl-1H-imidazo [4,5-b]pyridine residues were synthesized, and their colors were studied. Replacement of the benzimidazole residue in the cyanine dyes by a l-methyl-1H-imidazo[4,5-b]-pyridine residue leads to deepening of the dye color.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1561–1565, November, 1971. 相似文献
896.
The formation constants, log K(mab), for the reactions MA + B right harpoon over left harpoon MAB [where M = Cu(II), Ni, Zn or Cd, A = terdentate ligand and B = bidentate or terdentate ligand] have been determined. Potentiometric evidence is presented for the stepwise addition of the secondary ligand B to the 1:1 metal iminodiacetate (MA). The formation constants and the free energies of formation (DeltaG) have been calculated at 25 +/- 1 degrees and mu = 0.10. The order in terms of secondary ligands has been found to be ASPA > Gly > Aln and Gly > Aln > ASPA with iminodiacetic and nitrilotriacetic acid as primary ligands respectively (ASPA = aspartic acid, Gly = glycine, Aln = dl-alanine). The plot of log K(mab) against log k(mb)(2) shows a linear relationship between the formation constants of the ternary and 1:2 M(II)secondary ligand complexes. 相似文献
897.
G. A. Veinberg E. M. Belevich É. Ya. Lukevits 《Chemistry of Heterocyclic Compounds》1982,18(5):489-491
The oxidation of 6--[(hexahydro-1H-azepin-1-yl)methyleneamino]penicillanic acid with potassium periodate or m-chloroperbenzoic acid leads to the corresponding sulfoxide. Its structure was proved by alternative synthesis by splitting out the N-phenylacetyl group from the benzylpenicillin sulfoxide and condensation of the 6-aminopenicillanic acid sulfoxide with N-formylhexamethyleneimine dibutylacetal.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 649–651, May, 1982. 相似文献
898.
Conclusions The acid chlorides of thiophosphorous and thiophosphonous acids react with trimethylsilyi cyanide to give the corresponding trivalent phosphorus thiocyanides, which give the-cyanoalkyl esters of phosphorus thioacids when reacted with carbonyl compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 939–940, April, 1982. 相似文献
899.
Spectrophotometric investigation of the reaction of eriochrome cyanin RC and magnesium and aluminium
The reaction of magnesium or aluminium ions with Eriochrome Cyanin RC in alkaline medium leads to formation of a complex of type ML. The molar absorptivities of the complexes are 1.90 +/- 0.14 x 10(3)1. mole(-1).cm(-1) at 570 nm for the magnesium complex and 3.87 +/- 0.04 x 10(4) at 555 nm for the aluminium complex. The conditional stability constants of the complexes were determined at various pH values, and hence the overall formation constants, which were found to be log beta(111) = 8.65 +/- 0.06 for MgOHL, log beta(121) = 22.29 +/- 0.05 for AlH(2)L, log beta(111) = 18.25 +/- 0.14 for AlHL, and log beta(101) = 13.66 +/- 0.01 for AlL. 相似文献
900.
Impurities contained in nuclear graphites have been determined so far individually. A method of systematic analysis is described
which permits to determine about twenty impurities in one sample, such as the following elements: Ag, Se, Hg, Sb, Cu, Fe,
Ga, Co, Cd, Zn, In, Zr, Cr, Sc, Ba, Ca, Na, K, Rb, and Cs. Brief mention is made of methods used for the determination of
all rare earth metals, Si, S and P, as well as the elements which can be determined without chemical separation, such as Cl,
Mn, V.
Determination quantitative des impuretes des graphites nucleaires par les methodes de radioactivation analyse systematique相似文献