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991.
A rapid and accurate electrometric method for the determination of potassium ferricyanide solutions has been investigated. It consists in titrating ferricyanide solutions potentiometrically against standard AgNO3, using a silver indicator electrode in conjunction with a saturated calomel electrode connected by a KNO3 bridge. Either of the reagents may be used as the titrant. A marked change in e.m.f is observed at thc end-point corresponding to the formation and precipitation of Ag3[Fe(CN)6]. The curves have a regular form, a pronounced maximum in dE/dV occurs at the end-point and the results are very accurate and reproducible. The reaction, though simple, affords a quantitative method for the determination of ferricyanide or silver. The effect of neutral salts and ethanol on the accuracy of the end-point has been studied. 相似文献
992.
Van der Werff PM Martínez-Ferrero E Batten SR Jensen P Ruiz-Pérez C Almeida M Waerenborgh JC Cashion JD Moubaraki B Galán-Mascarós JR Martínez-Agudo JM Coronado E Murray KS 《Dalton transactions (Cambridge, England : 2003)》2005,(2):285-290
A new series of hybrid materials of type [Cp*2M][M'(dca)3] has been prepared by cation templation and structurally characterised (M = Fe(III), Co(III); M'= Mn(II), Fe(II), Co(II), Ni(II), Cd(II); dca-= N(CN)2-). The crystallographic analysis of [Cp*2Fe][Cd(dca)(3)] showed that the [Cd(dca)3]- anionic framework is of a symmetrical 3-D alpha-polonium type, containing octahedral Cd nodes and micro (1,5)-dca bridging ligands. The [Cp*2Fe]+ cations occupy the cube-like cavities within the framework. The cationic and anionic-framework sublattices remain magnetically independent and display susceptibilities, over the range 300 to 2 K, of a Curie-Weiss nature obtained by adding a S= 1/2 (Cp*2Fe+) or a S= 0 (Cp*2Co+) contribution to those of the weakly antiferromagnetically coupled frameworks of M'. These hybrid species do not show any intrinsic long-range magnetic order. The present [Cp*2Fe]M'(dca)3] series display the characteristic, unusually shaped [Cp*2Fe]+ Mossbauer line, in the range 295-5 K, assigned (below 101 K) as the sum of a narrow and a broad line. Relaxation effects were evident. The [Fe(dca)3]- compound showed superimposed low-spin Fe(III) and high-spin Fe(II) lines, the latter giving relaxation broadening effects. 相似文献
993.
Collective and self-diffusion coefficients in an ionic critical mixture: 3-methylpyridine+water+NaBr
The dynamics of concentration fluctuations of three critical samples of the 3-methylpyridine (3MP)+water+NaBr system have been measured by photon correlation spectroscopy. The collective-diffusion coefficient D shows the usual Ising behavior near the critical temperature T(c). However, as |T-T(c)| increases, the dynamic correlation length calculated from D, xi, takes values higher than the correlation length of the critical fluctuations calculated from static light scattering, xi(s). At the largest |T-T(c)| measured, xi approaches the value, xi(0,d) approximately equal to 1.13 nm, while the amplitude of xi(s) is xi(0,s)=0.38 nm. Pulsed-gradient NMR spectroscopy points out the existence of two dynamic contributions. One of them is consistent with the existence of molecular entities of hydrodynamic radius 0.31 nm, while the other one indicates the existence of aggregates rich in 3MP of radius 1.16 nm. The existence of the aggregates may explain the apparent anomalous behavior of the dynamic light scattering experiments for this system far from the critical point. 相似文献
994.
Two new semistabilized arsonium ylides have been generated and treated with carbonyl compounds. In reaction with carbonyl compounds, the carbanionic centres of both the ylides attack the carbonyl carbon to form similar cyclic intermediates. These intermediates, however, decompose to give different reaction products. The structures of the products are indicated by IR and NMR spectroscopy. 相似文献
995.
Two semi-stabilized arsonium ylides, ortho-nitrobenzylidenetriphenylarsenane and meta-nitrobenzylidenetriphenylarsenane, were prepared and treated with a range of carbonyl compounds to yield trans-olefins. In no case was an epoxide isolated. 相似文献
996.
The bis[4-aryl-3-alkylthio-1,2,4-triazol-5-yl]alkanes 4 were prepared by the action of alkyl halides on bis[4-aryl-1,2,4-triazoline-5-thione-5-yl]alkanes in aqueous sodium hydroxide (5%). The prepared sulphides 4 were oxidised to give the corresponding sulphones 5 either with acidic potassium permanganate or hydrogen peroxide. Similarly, sulphides 8 were prepared from 5-phenyl-1,3,4-oxadiazole-2-thione by reaction with different alkylhalides in alkaline medium. Mannich bases 9 from 5 -phenyl-1,3,4-oxadiazole-2-thione (7) were also prepared by stirring an equimolar solution of 6 in ethanol with formaldehyde (38%) and an amine in an ice-cold bath. All the compounds were screened for their pesticidal activities but none showed any significant activity. 相似文献
997.
Krishna C. Joshi Ram A. Misra Renuka Jain Kanti Sharma 《Journal of heterocyclic chemistry》1989,26(2):409-412
1-Trifluoroacetyl-3-dialkylaminomethyl-5-monosubstituted benzimidazoline-2-thiones have been synthesized from p-substituted anilines which were acetylated with trifluoroacetic acid. The trifluoroacetanilides were nitrated, reduced and cyclised with carbon disulphide in the presence of alcoholic potassium hydroxide and finally treated with formaldehyde and suitable secondary amines to afford the Mannich bases. The compounds were characterised by their analytical and spectral (ir, pmr, 19F and mass) data. The synthesized compounds have been screened for anti-inflammatory and analgesic activity and found to be active. 相似文献
998.
The imidazole-bridged binuclear copper(II) complex, [(Cl)2(imH)2Cu(imH)2Cu(bipy)(Cl)2] and the trinuclear copper (II) complex [(Cl)2(bipy)Cu(imH)2Cu(imH)2Cu(bipy)(Cl)2] have been synthesized by direct coupling between [Cu(imH)4(Cl)2] and [Cu(bipy)Cl2] in the appropriate stoichiometric ratios. The complexes show subnormal magnetic moments and e.p.r. spectra, characteristic of the triplet state. The antiferromagnetic coupling constant, J, has been obtained for both the complexes. 相似文献
999.
K. V. Rajagopalan Ram Prasad R. Kalyanaraman M. Sundaresan 《Journal of Thermal Analysis and Calorimetry》1991,37(10):2253-2258
The thermal constants, viz., thermal diffusivities, specific heat capacities and thermal conductivities of samples of mono- and di-calcium ferrites, prepared in the laboratory, have been obtained by laser flash method using an Ulvac-Sinku-Riko TC-3000 series instrument. The temperature range used was from 298–1100 K. All possible thermodynamic parameters associated with the heat capacity data were also calculated. 相似文献
1000.
The synthesis of both isomers of benzo[1,2]phenaleno[bc]thiophene namely, benzo[1,2]phenaleno[3,4-bc]-thiophene and benzo[1,2]phenaleno[4,3-bc]thiophene is described. 相似文献