NOPR Collection:

Catalytic current polarographic determination of traces of titanium in water after preconcentration by coflotation

Sat, 01 Apr 1995 00:00:00 GMT

Title: Catalytic current polarographic determination of traces of titanium in water after preconcentration by coflotation Authors: Basu, Bharathibai J; Rajagopalan, S R; Padma, D K Abstract: A new method is reported for the determination of trace levels of Ti(IV) in water by coflotation and polargraphy. Ti(IV) is preconcentrated and separated by coflotation using aluminium hydroxide as coprecipitant and sodium oleate as surfactant. Polarographic determination of titanium content in the froth is based on the catalytic wave of Ti(IV) in the presence of chlorate and oxalate. The effect of various cations and anions on the flotation and determination of titanium has been investigated. The method has been applied to estimation of titanium in natural fresh water samples. Page(s): 320-322

Hydrogen dissociation on Au-substituted Pt clusters

Sat, 01 Apr 1995 00:00:00 GMT

Title: Hydrogen dissociation on Au-substituted Pt clusters Authors: Khanra, Badal C Abstract: London-Eyring-Polanyi-Sato (LEPS) method has been used to study the dissociation of an H₂ molecule on Pt₁₈ and Pt₁₇Au clusters. It has been found that on Pt₁₈ cluster, dissociation at bridge site is favoured; the dissociated H atoms ultimately being chemisorbed on top sites. On the Pt₁₇Au cluster, on the other hand, dissociation at a top site is favoured when the dissociated species gets subsequently chemisorbed on bridge sites. Relevance of the work in understanding the catalytic reactions over alloy surfaces is discussed. Page(s): 249-252

Studies on the coordinated dioxygen species produced from the photoproducts of alkylcobaloximes in aqueous solution

Sat, 01 Apr 1995 00:00:00 GMT

Title: Studies on the coordinated dioxygen species produced from the photoproducts of alkylcobaloximes in aqueous solution Authors: Selvaraj, S; Natarajan, P Abstract: The reactions of' molecular oxygen with photoproduced cobaloximes(II) from the cobalt(III) complexes [CH₃Co(DH)₂Pyj, 1 and [C₂H₅Co(DH)₂Py], 2 (where DH is dimethylglyoxime and py is pyridine) have been investigated by flash photolysis methods. The reaction of cobaloxime(II) with molecular oxygen to give mononuclear superoxocobalt(IIl) species is the first step. The reactions to form the m-superoxo cobalt(III) complex from the mononuclear superoxo complex and the alkyl cobalamine( III), and the formation of the m-peroxo cobalt(III) complex directly by the reaction between mononuclear superoxo complex and the photoproduced cobalamin(II) and by the conversion of m-superoxo complex are the subsequent processes observed. The rate constants determined for these reactions are discussed based on a scheme indicating all the reactions. The results show that the reaction between the mononuclear superoxo complex and the photoproduced cobalamin to give the m-peroxo complex is faster than the reaction involving formation of the m-superoxo complex from the mononuclear superoxo complex. Page(s): 253-259

Transport properties of substituted derivatives of poly( aniline

Sat, 01 Apr 1995 00:00:00 GMT

Title: Transport properties of substituted derivatives of poly( aniline Authors: Sindhimeshram, D C; Gupta, M C Abstract: Aromatic ring and N-substituted derivatives of poly(aniline) have been synthesized by chemical peroxodisulphate oxidation method in aqueous trichloroacetic acid. UV-visible spectra of these polymers show hypsochromic shift with increase in dielectric constant of the solvent and due to substitution in the aromatic ring-.From temperature dependence of electrical conductivity, charge localization length and hopping distance are calculated and the effect of substituent and dopant on crystallinity is discussed. The introduction of substituent group either in a ring or at N-atoms produces space hinderance to internal rotation. The bulky dopant may distort or destroy the lattice and reduce the crystallinity. The temperature dependence of dielectric data and conductivity suggests that substituted derivatives of PANI are quasi ID-disordered state composed of 3D-metallic crystalline regions in 1D-localized amorphous regions. Page(s): 260-267